Pacific Lamprey

The StreamNet Library has been asked to merge a number of bibliographies on Pacific Lamprey (Entosphenus tridentatus) into one full, annotated bibliography. If you would like to contribute your bibliography to the project, please contact Lenora at oftl ‘at’

We now have a bibliography on Zotero under username katzen0466.


Clemens, B. J., van de Wetering, S., Sower, S. A., & Schreck, C. B. (2013). Maturation characteristics and life-history strategies of the Pacific lamprey, Entosphenus tridentatus. Canadian Journal of Zoology, 91(11), 775–788. doi:10.1139/cjz-2013-0114
Keefer, M. L., Caudill, C. C., Clabough, T. S., Jepson, M. A., Johnson, E. L., Peery, C. A., … Moser, M. L. (2013). Fishway passage bottleneck identification and prioritization: a case study of Pacific lamprey at Bonneville Dam. Canadian Journal of Fisheries and Aquatic Sciences, 70(10), 1551–1565. doi:10.1139/cjfas-2013-0164

Abstract: Fishways designed for salmonids often restrict passage by non-salmonids, and effective tools are needed both to identify passage problems for nontarget species and to inform remediation planning. In this case study, we used migration histories from 2170 radio-tagged adult Pacific lamprey (Entosphenus tridentatus) to identify locations of poor passage (bottlenecks) at a large, multifishway dam. Over 10 years, 49%% of tagged lamprey that entered fishways failed to pass the dam. Models accounting for repeated attempts by individual lamprey indicated successful passage strongly depended on attempted passage route. Success also varied with time of fishway entry, water temperature, and lamprey body size. Most failed passage attempts terminated in lower fishway segments, but extensive seasonal shifts in bottleneck locations were detected. Ranking metrics helped prioritize bottlenecks and identified sites where structural or operational modifications should improve lamprey passage. Our integration of spatially int..., Les passes migratoires conçues pour les salmonidés restreignent souvent le passage d’autres poissons, et des outils efficaces sont nécessaires pour cerner les problèmes associés au passage d’espèces non visées et éclairer la planification de mesures correctives. Dans la présente étude de cas, nous avons utilisé les historiques de migration de 2170 lamproies du Pacifique (Entosphenus tridentatus) adultes munies de radio-émetteurs pour cerner les lieux de passage difficiles (goulots d’étranglement) à un important barrage comptant plusieurs passes. Sur une période de 10 ans, 49 %% des lamproies munies d’émetteurs qui entraient dans ces passes ne réussissaient pas à remonter le barrage. Des modèles tenant compte de tentatives multiples par les mêmes lamproies ont indiqué que le succès du passage dépendait fortement de la voie de passage employée. Le taux de succès variait également selon le moment de l’entrée dans la passe, la température de l’eau et la taille du corps de la lamproie. La plupart des tentatives...

Christiansen, H. E., Gee, L. P., & Mesa, M. G. (2013). Anesthesia of Juvenile Pacific Lampreys with MS-222, BENZOAK, AQUI-S 20E, and Aquacalm. North American Journal of Fisheries Management, 33(2), 269–276. doi:10.1080/02755947.2012.754807

Abstract: Abstract Effective anesthetics are a critical component of safe and humane fish handling procedures. We tested three concentrations each of four anesthetics—Finquel (tricaine methanesulfonate, herein referred to as MS-222), BENZOAK (20%% benzocaine), AQUI-S 20E (10%% eugenol), and Aquacalm (metomidate hydrochloride)—for efficacy and safety in metamorphosed, outmigrating juvenile Pacific Lampreys Entosphenus tridentatus. The anesthetics MS-222 (100 mg/L) and BENZOAK (60 mg/L) were the most effective for anesthetizing juvenile Pacific Lampreys to a handleable state with minimal irritation to the fish. Fish anesthetized with BENZOAK also had lower rates of fungal infection than those exposed to MS-222, AQUI-S 20E, or no anesthetic. Exposure to AQUI-S 20E irritated juvenile Pacific Lampreys, causing them to leap or climb out of the anesthetic solution, and Aquacalm anesthetized fish to a handleable state too slowly and incompletely for effective use with routine handling procedures. Our results indicate that MS-222 and BENZOAK are effective anesthetics for juvenile Pacific Lampreys, but field studies are needed to determine whether exposure to MS-222 increases risk of fungal infection in juvenile Pacific Lampreys released to the wild. Received August 28, 2012; accepted November 26, 2012

Murauskas, J. G., Orlov, A. M., & Siwicke, K. A. (2013). Relationships between the Abundance of Pacific Lamprey in the Columbia River and Their Common Hosts in the Marine Environment. Transactions of the American Fisheries Society, 142(1), 143–155. doi:10.1080/00028487.2012.730113

Abstract: Abstract The returns of Pacific Lamprey Entosphenus tridentatus to the Columbia River over the past decade have declined significantly compared with the peak returns of the 1950s and 1960s, with no quantifiable mechanisms identified. To determine if the abundance of documented host species in the marine environment is related to adult returns of Pacific Lamprey, we examined stock assessment data, commercial fishery statistics, and counts of adult fish at Bonneville Dam between 1997 and 2010. Significant positive correlations were observed between lamprey returns and abundance indices of Pacific Hake Merluccius productus, Walleye Pollock Theragra chalcogramma, Pacific Cod Gadus macrocephalus, Chinook Salmon Oncorhynchus tshawytscha, and Pacific Herring Clupea pallasii throughout the U.S. Pacific Northwest. Commercial landings of these species in Washington and Oregon were also significantly and strongly correlated to lamprey returns, with the exception of Walleye Pollock. Several of these fisheries have demonstrated significant reductions in mean landings since the 1950s and 1960s, and adult lamprey returns have declined proportionally. We further examined large-scale and regional indices of oceanic productivity as a potential underlying mechanism. Multiple regression techniques indicated that host abundance was the principal factor in predicting lamprey returns, though inclusion of oceanic conditions increased the precision of the model. These results represent the first established relationship to recent trends of Pacific Lamprey returns to the Columbia River and indicate that spawning escapement is primarily a function of conditions experienced during the predatory phase of the life cycle. We hypothesize that Pacific Lamprey abundance in the Columbia River is cyclical in nature, but limited by availability of several host species over a potentially vast geographic range. Biologists and resource managers should reassess the relatively overlooked marine ecology of Pacific Lamprey. Received April 16, 2012; accepted September 7, 2012

Hess, J. E., Campbell, N. R., Close, D. A., Docker, M. F., & Narum, S. R. (2013). Population genomics of Pacific lamprey: adaptive variation in a highly dispersive species. MEC Molecular Ecology, 22(11), 2898–2916.

Abstract: Unlike most anadromous fishes that have evolved strict homing behaviour, Pacific lamprey (Entosphenus tridentatus) seem to lack philopatry as evidenced by minimal population structure across the species range. Yet unexplained findings of within-region population genetic heterogeneity coupled with the morphological and behavioural diversity described for the species suggest that adaptive genetic variation underlying fitness traits may be responsible. We employed restriction site-associated DNA sequencing to genotype 4439 quality filtered single nucleotide polymorphism (SNP) loci for 518 individuals collected across a broad geographical area including British Columbia, Washington, Oregon and California. A subset of putatively neutral markers (N = 4068) identified a significant amount of variation among three broad populations: northern British Columbia, Columbia River/southern coast and ‘dwarf’ adults (FCT = 0.02, P ? 0.001). Additionally, 162 SNPs were identified as adaptive through outlier tests, and inclusion of these markers revealed a signal of adaptive variation related to geography and life history. The majority of the 162 adaptive SNPs were not independent and formed four groups of linked loci. Analyses with matsam software found that 42 of these outlier SNPs were significantly associated with geography, run timing and dwarf life history, and 27 of these 42 SNPs aligned with known genes or highly conserved genomic regions using the genome browser available for sea lamprey. This study provides both neutral and adaptive context for observed genetic divergence among collections and thus reconciles previous findings of population genetic heterogeneity within a species that displays extensive gene flow.

Moser, M. L., Jackson, A. D., Tsuzaki, T., & Kemp, P. S. (2013). Do surgically implanted radio transmitters alter the climbing ability of adult Pacific lamprey, Lampetra tridentata? FME Fisheries Management and Ecology, 20(4), 374–376.
Grantham, T. E. (2013). USE OF HYDRAULIC MODELLING TO ASSESS PASSAGE FLOW CONNECTIVITY FOR SALMON IN STREAMS. RRA River Research and Applications, 29(2), 250–267.

Abstract: The maintenance of hydrologic connectivity in river networks has become an important principle for guiding management and conservation planning for threatened salmon populations, yet our understanding of how fish movement is impaired by spatial and temporal variation in connectivity remains limited. In this study, a two-dimensional hydraulic modelling approach is presented to evaluate flow connectivity in relation to passage requirements of adult steelhead trout (Oncorhynchus mykiss) in coastal California streams. High-resolution topographic data of stream reaches with distinct channel morphology were collected using terrestrial light detection and ranging surveys and linked with water surface measurements to calibrate hydraulic model simulations. Quantitative metrics of longitudinal flow connectivity were developed to assess fish passage suitability in relation to stream discharge. Measured flow data from the 2008-2009 winter season and simulated long-term records indicated that suitable passage flows occur with relatively low frequency and duration at all sites, suggesting that instream flow protections for fish passage are warranted. Results from the hydraulic modelling simulations were then compared with two alternative methods for assessing passage flows. A regional formula used by the State of California to identify minimum instream flow needs provided conservative estimates of passage flow requirements, whereas an approach based on riffle crest water depths underestimated flow needs. The hydraulic modelling approach appears well suited for simulating flows for fish passage studies and may be particularly useful for testing alternative environmental flow assessment methods and evaluating habitat-flow relationships in stream reaches of importance, such as critical habitat for threatened fish species. Copyright © 2011 John Wiley & Sons, Ltd.

Keefer, M. L., Boggs, C. T., Peery, C. A., & Caudill, C. C. (2013). Factors affecting dam passage and upstream distribution of adult Pacific lamprey in the interior Columbia River basin. EFF Ecology of Freshwater Fish, 22(1), 1–10.

Abstract: Low dam passage rates of adult Pacific lamprey (Entosphenus tridentatus) during upstream spawning migration have been implicated in the species' steep decline in the interior Columbia River basin. In this 2000-2010 study, we used radiotelemetry to evaluate potential predictors of lamprey passage success at McNary Dam, located ~469 river kilometres (rkm) from the Pacific Ocean. The tagged population included 276 lampreys collected at McNary Dam and 53 collected at Bonneville Dam (rkm 235) that migrated to McNary Dam. McNary Dam passage efficiency was similar for the two samples, with multiyear estimates of 0.65 and 0.75, respectively. Larger-bodied lampreys and those with earlier migration timing were more likely to return to McNary Dam after release, to pass the dam and to be detected upstream from McNary reservoir. Far more lampreys entered the upper Columbia River than the Snake River, suggesting that environmental cues (e.g., water discharge, temperature) or conspecific cues (e.g., pheromone concentrations) affect lamprey distribution above this large confluence. Overall, results indicate that Pacific lamprey passage success at barriers depends on a combination of individual lamprey traits plus seasonal and site-specific effects on behaviour.


Clemens, B. J., Sower, S. A., van de Wetering, S., & Schreck, C. B. (2012). Incidence of male intersex in adult Pacific lamprey (Entosphenus tridentatus), with a brief discussion of intersex vs. hermaphroditism in lampreys (Petromyzontiformes). Canadian Journal of Zoology, 90(9), 1201–1206. doi:10.1139/z2012-085

Abstract: We report the incidence of male intersex in adult Pacific lamprey (Entosphenus tridentatus (Richardson, 1836)) during their pre-spawning migration in fresh water. Although “hermaphrodites” have been suggested in other adult lampreys, this is the first detailed description and discussion of this phenomenon. A total of 0.5%% of our adult Pacific lamprey from Willamette Falls (2 out of 427 adults) were intersex, with oocytes in the testes. This phenomenon was identifiable only by histological examination. The testes of the intersex males were immature, in the beginning stages of meiosis. One intersex male possessed primary growth or perinucleolar stage oocytes loosely interspersed throughout the testes, and the other possessed at least 6 mid-vitellogenic oocytes (0.6 mm, mean long diameter) separate from the testes. Because premetamorphic lamprey can possess both female and male gonial cells, we hypothesize that intersex is a remnant larval trait and that these fish failed to fully develop into males during m..., Nous rendons compte de l’incidence d’intersexualité chez des mâles adultes de lamproie du Pacifique (Entosphenus tridentatus (Richardson, 1836)) durant leur migration en eau douce précédant le frai. Bien que la présence « d’hermaphrodites » ait été suggérée chez d’autres lamproies adultes, il s’agit des premières description et discussion détaillées de ce phénomène. Au total, 0,5 %% des lamproies du Pacifique adultes de Willamette Falls recensées (2 individus sur 427 adultes) étaient intersexuelles, présentant des oocytes dans les testicules. Ce phénomène n’est observable que par un examen histologique. Les testicules des mâles intersexuels étaient immatures, aux stades initiaux de la méiose. Un mâle intersexuel possédait des oocytes au stade de croissance primaire ou périnucléolaire disséminés çà et là dans les testicules et l’autre possédait au moins six oocytes à des stades intermédiaires de la vitellogénèse (diamètre long moyen de 0,6 mm) séparés des testicules. Étant donné que la lamproie prémétamorph...

Taylor, E. B., Harris, L. N., Spice, E. K., & Docker, M. F. (2012). Microsatellite DNA analysis of parapatric lamprey (Entosphenus spp.) populations: implications for evolution, taxonomy, and conservation of a Canadian endemic. Canadian Journal of Zoology, 90(3), 291–303. doi:10.1139/z11-135

Abstract: Parapatric freshwater and anadromous parasitic lampreys (Petromyzontiformes) from southwestern Vancouver Island, British Columbia, have been described as distinct taxa (Vancouver lamprey (Entosphenus macrostomus (Beamish, 1982)) and Pacific lamprey (Entosphenus tridentatus (Richardson, 1836)), respectively), using morphology, life history, and physiology. We tested for genetic differentiation at microsatellite DNA loci between these taxa and similar freshwater parasitic lampreys from two other lakes. The number of alleles and expected heterozygosity averaged 3.8 and 0.50, respectively, across loci and populations, and anadromous populations were more variable than freshwater populations. Population subdivision was moderate (FST = 0.096, P < 0.001) and 3%% of the total variation was found between taxa and 1.7%% was found among populations within taxa (both P < 0.001). Parapatric freshwater and anadromous parasitic lampreys separated by a maximum of 40 km were more distinct (mean FST = 0.042) than were anadro..., Des lamproies parasites (Pétromyzontiformes) parapatriques, dulcicoles et anadromes, du sud-ouest de l’île de Vancouver, Colombie-Britannique, ont été décrites comme des taxons différents, soit respectivement, la lamproie à grand disque (Entosphenus macrostomus (Beamish, 1982)) et la lamproie du Pacifique (Entosphenus tridentatus (Richardson, 1836)), d’après leur morphologie, leur cycle biologique et leur physiologie. Nous avons vérifié la différenciation génétique à des locus microsatellites d’ADN entre ces taxons et d’autres lamproies parasites d’eau douce semblables provenant de deux autres lacs. Le nombre d’allèles et l’hétérozygotie attendue sont en moyenne respectivement de 3,8 et de 0,50, pour l’ensemble des locus et des populations; les populations anadromes sont plus variables que les populations d’eau douce. La subdivision de la population est moyenne (FST = 0,096, P < 0,001); 3 %% de la variation totale se retrouve entre les taxons et 1,7 %% entre les populations à l’intérieur des taxons (P < 0,0...

Mueller, R., Arntzen, E., Nabelek, M., Miller, B., Klett, K., & Harnish, R. (2012). Laboratory Testing of a Modified Electroshocking System Designed for Deepwater Juvenile Lamprey Sampling. Transactions of the American Fisheries Society, 141(3), 841–845. doi:10.1080/00028487.2012.675908

Abstract: Abstract A submersible sled with the ability to electroshock and detect larval lampreys via an optical camera was developed to sample deepwater rearing habitats (>1 m). Three trials, each with 10 juvenile western brook lampreys Lampetra richardsoni (70–150 mm), were conducted in a laboratory setting to determine the effective shocking area and detection efficiency of the device. Electroshock was delivered for 30 s, and lamprey responses were observed. The detection efficiency ranged from 40%% to 70%% for the three trials (mean detection efficiency = 60%%). Mean postshock emergence time was 4.4 s, and the maximum was 13 s. The device detected juvenile western brook lampreys without the need to transport them to the surface, thereby increasing sampling volume per unit time and reducing the potential for injury caused by handling. The system was developed to determine juvenile lamprey presence in regions where backpack electrofishers are unable to survey due to water depth. Received July 18, 2011; accepted December 21, 2011

Rose, B. P., & Mesa, M. G. (2012). Effectiveness of Common Fish Screen Materials to Protect Lamprey Ammocoetes. North American Journal of Fisheries Management, 32(3), 597–603. doi:10.1080/02755947.2012.678965

Abstract: Abstract Understanding the effects of irrigation diversions on populations of Pacific lamprey Lampetra tridentata in the Columbia River basin is needed for their recovery. We tested the effectiveness of five common fish screen materials for excluding lamprey ammocoetes: interlock (IL), vertical bar (VB), perforated plate (PP), and 12-gauge and 14-gauge wire cloth (WC12) and (WC14). When fish (28–153 mm) were exposed for 60 min to screen panels perpendicular to an approach velocity of 12 cm/s in a recirculating flume, the percentage of ammocoetes entrained (i.e., passed through the screen) was 26%% for the IL, 18%% for the PP, 33%% for the VB, 62%% for the WC14, and 65%% for the WC12 screens. For all screens, most fish were entrained within the first 15–20 min. Fish length significantly influenced entrainment, with the PP, VB, and IL screens preventing fish greater than 50–65 mm from entrainment and the WC14 and WC12 screens preventing entrainment of fish greater than 90–110 mm. Fish of all sizes repeatedly became impinged (i.e., contacting the screen for more than 1 s) on the screens, with the frequency of impingement events increasing during the first 5 min and becoming relatively stable thereafter. Impingement ranges were highest on the IL screen (36–62%%), lowest on the WC14 and WC12 screens (13–31%%), and intermediate on the PP and VB screens (23–54%%). However, the WC14 and WC12 screens had fewer and larger fish remaining as time elapsed because so many were entrained. For all screen types, injuries were rare and minor, and no fish died after overnight posttest holding. Our results indicate that wire cloth screens should be replaced, where practical, with perforated plate, vertical bar, or interlocking bar screens to reduce lamprey entrainment at water diversions. Received October 26, 2011; accepted March 14, 2012

Clabough, T. S., Keefer, M. L., Caudill, C. C., Johnson, E. L., & Peery, C. A. (2012). Use of Night Video to Enumerate Adult Pacific Lamprey Passage at Hydroelectric Dams: Challenges and Opportunities to Improve Escapement Estimates. North American Journal of Fisheries Management, 32(4), 687–695. doi:10.1080/02755947.2012.690820

Abstract: Abstract Reliable estimates of adult Pacific lamprey Entosphenus tridentatus escapement are critically needed to improve management of this declining and ecologically important species. The longest time series of Pacific lamprey counts are from count stations at Columbia River basin dams designed to enumerate adult salmonids during the day, but many Pacific lamprey pass at night. To estimate their total escapement, we used video to monitor nighttime lamprey passage in combination with daytime counts at two count stations at Bonneville Dam and two at The Dalles Dam in 2007–2008. We examined relationships among day and night counts and evaluated the potential for using expansion factors to estimate total escapement from past and future daytime count data. As expected, daytime counts systematically underestimated total lamprey passage, and day and night counts were positively correlated in most comparisons. Unexpectedly, ratios of night: day counts varied widely among sites and years because patterns of upstream and downstream movements past count stations varied. We highlight challenges associated with enumerating cryptic and nocturnal species, such as Pacific lamprey, the potential impact of species-specific behaviors on enumeration efforts, and the importance of appropriate count station location and structure for video monitoring of fish passage. Received August 9, 2011; accepted April 27, 2012

Jackson, A., & Moser, M. (2012). Low-Elevation Dams Are Impediments to Adult Pacific Lamprey Spawning Migration in the Umatilla River, Oregon. North American Journal of Fisheries Management, 32(3), 548–556. doi:10.1080/02755947.2012.675950

Abstract: Abstract Due to tribal concerns over the recent decline of Pacific lamprey Lampetra tridentata, a restoration program was initiated to establish a self-sustaining, harvestable lamprey population within the ceded lands of the Confederated Tribes of the Umatilla Indian Reservation in Oregon. We hypothesized that low returns of adult lampreys to spawning areas in the Umatilla River were caused by loss of habitat connectivity in this watershed. We conducted a study to determine whether the ubiquitous, low-elevation irrigation diversion dams in the main-stem Umatilla River were obstacles to adult lamprey spawning migration. Radiotelemetry was used to assess lamprey passage efficiency at seven dams located within the lowest 55-km reach of the Umatilla River. During this 4-year study, we tracked 217 adult Pacific lampreys that were implanted with radio transmitters and released downstream from the dams. Logistic regression analysis indicated that dam design, fish size, and temperature had the greatest effects on passage efficiency. Poor performance (<30%% fitted passage probability) was recorded at the two lowest dams in the system and resulted in limited escapement to upper sites. During the study, one dam was breached, after which passage efficiency there immediately improved from 32%% to 81%%. In addition, water augmentation actions at Three Mile Falls Dam apparently contributed to improved mean passage efficiency of migratory-phase fish (from 17%% to 50%%). Thus, actions to improve adult lamprey access to historical spawning areas are feasible and are key to successful restoration of this species. Received June 29, 2011; accepted February 13, 2012

Mesa, M. G., Copeland, E. S., Christiansen, H. E., Gregg, J. L., Roon, S. R., & Hershberger, P. K. (2012). Survival and Growth of Juvenile Pacific Lampreys Tagged with Passive Integrated Transponders (PIT) in Freshwater and Seawater. Transactions of the American Fisheries Society, 141(5), 1260–1268. doi:10.1080/00028487.2012.686951

Abstract: Abstract Tagging methods are needed for both adult and juvenile life stages of Pacific lampreys Lampetra tridentata to better understand their biology and factors contributing to their decline. We developed a safe and efficient technique for tagging juvenile Pacific lampreys with passive integrated transponder (PIT) tags. We tested the short-term survival of PIT-tagged juvenile lampreys in freshwater at four temperatures (9, 12, 15, and 18°C) and their long-term growth and survival in seawater. For both experiments there was little to no tag loss, and juvenile lampreys in freshwater showed high survival at all temperatures at 7 d (95–100%%) and 14 d (88–100%%) posttagging. Prolonged holding (40 d) resulted in significantly lower survival (28–79%%) at warmer temperatures (12–18°C). For juvenile lampreys tagged in freshwater and then transitioned to seawater, survival was 97%% for tagged fish until day 94, and at the end of 6 months, survival was about 58%% for both tagged and control fish. About half of the tagged and control fish that survived in seawater grew, but there was no difference in growth between the two groups. In freshwater, but not in seawater, most fish that died had an aquatic fungal infection. In both experiments, survival increased with increasing fish length at tagging. Our results indicate that tags similar in size to a 9-mm PIT tag are a feasible option for tagging metamorphosed juvenile lampreys migrating downstream and that when fungal infections are mitigated—as in seawater—long-term (at least 6 months) survival of tagged juvenile lampreys is high. Received October 31, 2011; accepted April 16, 2012

Johnson, E. L., Caudill, C. C., Keefer, M. L., Clabough, T. S., Peery, C. A., Jepson, M. A., & Moser, M. L. (2012). Movement of Radio-Tagged Adult Pacific Lampreys during a Large-Scale Fishway Velocity Experiment. Transactions of the American Fisheries Society, 141(3), 571–579. doi:10.1080/00028487.2012.683468

Abstract: Abstract Optimization of fishways to pass multiple species is challenging because life history, swimming ability, and behavior often differ among species. For example, high fishway water velocities designed to attract adult Pacific salmon Oncorhynchus spp. at Columbia River dams inhibit fishway entrance and passage success of adult Pacific lampreys Lampetra tridentata, a species of conservation concern. We tested whether reduced water velocities (?1.2 m/s, 0.15 m of head) at Bonneville Dam fishway openings improved entrance efficiency and other passage metrics for radio-tagged Pacific lampreys compared with control velocities (>1.98 m/s, 0.46 m of head) and near-zero (“standby”) velocities. Lamprey entrance efficiencies were significantly higher in the reduced-velocity treatment (26–29%%) than in the control (13–20%%) or standby (5–9%%) treatment. In some years, significantly more Pacific lampreys passed through fishway collection channels and transition pools and reached the fish ladder during reduced-velocity treatment conditions, indicating that benefits extended beyond fishway entrances. However, overall passage efficiency at the dam was relatively unchanged, suggesting that additional passage bottlenecks for Pacific lampreys exist upstream from fishway entrances. The experiment demonstrated how operational changes can improve passage performance and how exploiting behavioral differences among species can improve multispecies management. Received January 6, 2011; accepted November 22, 2011

Jolley, J. C., Silver, G. S., & Whitesel, T. A. (2012). Occupancy and Detection of Larval Pacific Lampreys and Lampetra spp. in a Large River: the Lower Willamette River. Transactions of the American Fisheries Society, 141(2), 305–312. doi:10.1080/00028487.2012.662201

Abstract: Abstract Pacific lampreys Entosphenus tridentatus (formerly Lampetra tridentata) are declining in the Columbia River basin, and the use of large, main-stem river habitats by larvae of this species is unknown. We used a deepwater electrofisher to explore occupancy, detection, and habitat use of larval Pacific lampreys and larval Lampetra spp. in the lower Willamette River, Oregon. We used a generalized random tessellation stratified approach to select sampling quadrats (30 × 30 m) in a random, spatially balanced order. Pacific lampreys, Lampetra spp., and unidentified lampreys were found in the Willamette River; larvae were detected in all areas except the Multnomah Channel. We calculated reach- and quadrat-specific detection probabilities and the amount of sampling effort required for 80%% confidence that larval lampreys were in fact absent when they were not detected. Lampreys were detected in a variety of areas (although relatively low numbers were collected), including shallow, nearshore areas; midchannel areas (depth up to 16 m); and anthropogenically affected areas. Detection probabilities (i.e., in occupied areas) were 0.07 (reach) and 0.23 (quadrat). The sampling effort required for 80%% confidence that lampreys were absent when undetected was 20 quadrats (in the lower Willamette River reach) and 6 subquadrats (within a quadrat). Differences in lamprey detection by depth were not observed. A variety of sizes was collected (20–144 mm total length), indicating the likely occurrence of multiple ages of larvae. Our study identifies how the occurrence of larval Pacific lampreys can be quantified with statistical rigor in a large river (i.e., larger than fourth order [1:100,000 scale]). The effect of channel management activities on larval lampreys should be considered in efforts to conserve these important species. Received March 9, 2011; accepted August 19, 2011

Smith, D. M., Welsh, S. A., & Turk, P. J. (2012). Available benthic habitat type may influence predation risk in larval lampreys. EFF Ecology of Freshwater Fish, 21(1), 160–163.
Ward, D. L., Clemens, B. J., Clugston, D., Jackson, Aaron D, Moser, M. L., & Peery, C., Statler, David P. (2012). Translocating Adult Pacific Lamprey within the Columbia River Basin: State of the Science. Fisheries Fisheries, 37(8), 351–361.
SPICE, E. K., GOODMAN, D. H., REID, S. B., & DOCKER, M. F. (2012). Neither philopatric nor panmictic: microsatellite and mtDNA evidence suggests lack of natal homing but limits to dispersal in Pacific lamprey. MEC Molecular Ecology, 21(12), 2916–2930.

Abstract: Most species with lengthy migrations display some degree of natal homing; some (e.g. migratory birds and anadromous salmonids) show spectacular feats of homing. However, studies of the sea lamprey (Petromyzon marinus) indicate that this anadromous species locates spawning habitat based on pheromonal cues from larvae rather than through philopatry. Previous genetic studies in the anadromous Pacific lamprey (Entosphenus tridentatus) have both supported and rejected the hypothesis of natal homing. To resolve this, we used nine microsatellite loci to examine the population structure in 965 Pacific lamprey from 20 locations from central British Columbia to southern California and supplemented this analysis with mitochondrial DNA restriction fragment length polymorphism analysis on a subset of 530 lamprey. Microsatellite analysis revealed (i) relatively low but often statistically significant genetic differentiation among locations (97%% pairwise FST values were <0.04 but 73.7%% were significant); and (ii) weak but significant isolation by distance (r²?=?0.0565, P?=?0.0450) but no geographic clustering of samples. The few moderate FST values involved comparisons with sites that were geographically distant or far upstream. The mtDNA analysis—although providing less resolution among sites (only 4.7%%FST values were significant)—was broadly consistent with the microsatellite results: (i) the southernmost site and some sites tributary to the Salish Sea were genetically distinct; and (ii) southern sites showed higher haplotype and private haplotype richness. These results are inconsistent with philopatry, suggesting that anadromous lampreys are unusual among species with long migrations, but suggest that limited dispersal at sea precludes panmixia in this species.


Renaud, C. B., & Food and Agriculture Organization of the United Nations. (2011). Lampreys of the world: an annotated and illustrated catalogue of lamprey species known to date. Rome: Food and Agriculture Organization of the United Nations. (Download)
Mesa, M. G., Magie, R. J., Copeland, E. S., & Christiansen, H. E. (2011). Surgical wound healing in radio-tagged adult Pacific lamprey Entosphenus tridentatus held on different substrata. JFB Journal of Fish Biology, 79(4), 1068–1075.

Abstract: Radio-tagged adult Pacific lamprey Entosphenus tridentatus held in a raceway with Plexiglas-lined walls and bottom healed more slowly and retained sutures longer than fish held in an all-concrete raceway or one with Plexiglas walls and a cobble-lined bottom. On all substrata, healing depended on when sutures were lost, and fish that lost their sutures in <14 days post-surgery healed faster than those that kept sutures longer. Long-term suture retention led to tissue trauma, infection and poor survival.

KEEFER, M. L., PEERY, C. A., LEE, S. R., DAIGLE, W. R., JOHNSON, E. L., & MOSER, M. L. (2011). Behaviour of adult Pacific lamprey in near-field flow and fishway design experiments. FME Fisheries Management and Ecology, 18(3), 177–189.

Abstract: Abstract? An experimental fishway was used to examine adult Pacific lamprey, Lampetra tridentata (Gairdner), behaviour in a series of attraction and passage-performance tests. Among all experiments, lamprey oriented to the fishway floor and walls and were attracted to both ambient and concentrated flow. When confronted with high-velocity areas (vertical-slot and submerged-orifice weirs), many lamprey failed to pass upstream. However, lamprey were able to find and take advantage of low-velocity refuges when they were provided. Lamprey climbed shallow- and steep-angled ramps when attraction cues were sufficient and other passage routes were restricted. The combined results demonstrated the passage challenges that fishways designed and operated for salmonids present to non-salmonid species. They also highlight the importance of evaluating trade-offs between fishway attraction and passage efficiency. The experiments were integrated with tagging studies and development of lamprey-specific passage structures, a research combination that provided an effective template for fishway performance evaluations.

Lampman, R. T. (2011). Passage, migration behavior, and autoecology of adult Pacific lamprey at Winchester Dam and within the North Umpqua River Basin, Oregon, USA. Corvallis, Or.: Oregon State University. Retrieved from

Abstract: The extensive reduction in adult Pacific lamprey (Entosphenus tridentatus) counts at many hydroelectric dams in the northwestern USA signals a substantial decline in lamprey numbers across the entire region in the past 40 to 50 years. Among the many potential causes of this decline, obstruction of migration routes has likely played a substantial role. Within the North Umpqua River basin in southwest Oregon, USA, I focused on the following three research goals: 1) to describe the passage efficiency and migration routes of adult Pacific lamprey at Winchester Dam; 2) to evaluate the seasonal movement patterns of adult Pacific lamprey and their use of holding habitat at Winchester Dam in relation to temperature conditions; and 3) to portray the diversity of upstream migratory behaviors of adult Pacific lamprey and the environmental factors that influence these behaviors. This radio telemetry study was conducted between March 2009 and August 2011 with a combination of fixed stations and manual tracking. Passage efficiency was low in both years (8%% and 19%%, respectively), and all tagged lamprey that successfully passed the dam used routes other than the fish ladder. Lamprey that migrated early within the run and those with relatively small tags had higher passage rates and traveled further than the other groups of lamprey. Lamprey released above of the dam or those that passed the dam on their own distributed themselves widely in the upstream environment, suggesting that the dam deterred their upstream migration. Using mark-recapture data for the two years, the adult Pacific lamprey population upstream of Winchester Dam was estimated at 960 (95%% C.I. [188, 4760]) in 2009 and 556 (95%% C.I. [110, 2798]) in 2010, which was considerably lower than historical counts at the dam (between 14,532-46,785 in 1965-1971). Most tagged lamprey that did not pass the dam remained at the base of the dam at the end of the summer migration (63%% in 2009 and 67%% in 2010). Types of habitat most frequently used by lamprey downstream from the dam included the dam surface (wooden structures with crevices), interface zones between fast and slow water, and highway bridge pilings. The lamprey movement changed considerably between August and September, and the frequency of movements decreased sharply during this period. Tagged lamprey were detected using thermal refuges immediately downstream of the dam that were 0.4 to 2.8 C° colder than the mean river temperature at the dam, and this temperature differential increased as the season progressed. Lamprey may be seeking overwintering habitat associated with hyporheic exchange flows at the dam towards the end of the summer season after their display of heightened activity early in the summer. Ninety-five percent of the overall upstream migration took place during the first spring/summer period, and only small-scale upstream movements were observed during the winter and second spring/summer (4%% and 1%%, respectively). The rate of upstream migration (median) was the fastest during the initial migration phase and was 1.9 km/day (ranging from 0.3 to 11.0 km/day) for tagged lamprey released above Winchester Dam. During winter, 71%% of the lamprey remained in the same location where they initiated holding. Multiple regression analysis indicated that the total upstream distance traveled by individual lamprey was most strongly related to presence/absence of Winchester Dam, relative tag size, and water temperature and photoperiod conditions at release. The presence of Winchester Dam, large relative tag size, and high water temperature / short photoperiod conditions at release significantly reduced upstream migration distance.

Yun, S.-S., Wildbill, Andrew J, Siefkes, M. J., Moser, M. L., Dittman, A. H., Corbett, S. C., Li, W., Close, David A, & MacLatchy, D. L. (2011). Identification of putative migratory pheromones from Pacific lamprey ( Lampetra tridentata). Canadian Journal of Fisheries and Aquatic Sciences, 68(12), 2194–2203.

Abstract: Pacific lamprey, Lampetra tridentata, has declined precipitously throughout their range in the Columbia River basin of North America. Tribal Nations and Federal and State agencies are engaged in efforts to restore these fish. Understanding whether Pacific lamprey emit and detect migratory pheromones is particularly important for these restoration efforts. Using behavioural assays, we demonstrated that migratory adult Pacific lamprey are attracted to odors emanating from their larval conspecifics. We then identified putative pheromones released by larval Pacific lamprey. Chemical analysis of the conditioned water from larval lamprey using liquid chromatography - mass spectrometry (LC-MS) revealed that the Pacific lamprey can release petromyzonamine disulfate (PADS), petromyzosterol disulfate (PSDS), and petromyzonol sulfate (PZS). Electro-olfactogram studies further demonstrated that adult Pacific lamprey can smell those bile acid compounds. Our data strongly indicate that the Pacific lamprey employ a chemical communication system mediated by a mixture of bile acids, as evidenced by pheromonal functions of the bile acid compounds in guiding migratory adult sea lamprey to the spawning streams. Comprehensive understanding of the chemical communications involved in lamprey migratory behavior may lead to improved scientific approaches for restoration efforts.

MOSER, M. L., KEEFER, M. L., PENNINGTON, H. T., OGDEN, D. A., & SIMONSON, J. E. (2011). Development of Pacific lamprey fishways at a hydropower dam. FME Fisheries Management and Ecology, 18(3), 190–200.

Abstract: Abstract? Traditional fishways do not accommodate the passage needs of all migrating species. In the north-western United States, structures designed to aid adult Pacific lamprey, Lampetra tridentata (Gairdner), passage are critically needed. The structures described here were fabricated in modular units and installed at Bonneville Dam on the Columbia River (235?km). They featured a series of aluminium ramps interspersed with rest boxes that prevented lamprey from moving back downstream. The effects of various design changes and structure operation (water volume delivered) were assessed using lamprey counts and passive integrated transponder detections. Up to 40%% of the lamprey entered the structures and 90-100%% of these passed through to the exit. Lowering water volume pumped to the structures had little effect on lamprey performance, but passage improved when a 3.8-m-long, steep (40°) ramp was replaced with two, 1.4-m-long, 45° ramps. Pacific lamprey ascended the 8- to 9-m-high structures and entered the dam forebay in less than 1?h. The success of these prototypes was attributed to site selection and attention to lamprey-specific performance.


Keefer, M. L., Daigle, W. R., Peery, C. A., Pennington, H. T., Lee, S. R., & Moser, M. L. (2010). Testing Adult Pacific Lamprey Performance at Structural Challenges in Fishways. North American Journal of Fisheries Management, 30(2), 376–385. doi:10.1577/M09-099.1

Abstract: Abstract Adult Pacific lampreys Lampetra tridentata migrate through areas of difficult passage and high water velocity by attaching their oral discs to substrate and then releasing and bursting upstream. In fishways at dams, this burst-and-attach behavior can be ineffective, particularly where suitable attachment surfaces are unavailable. We used an experimental fishway to test performance of adult Pacific lampreys when confronted with a series of structural challenges. These included vertical steps near fishway weir orifices, squared versus rounded orifice entrances, and floor-mounted metal grates. All experimental challenges simulated common existing structures in weir-and-orifice fishways at Columbia and Snake River dams. Most experiments were paired with field evaluations of radio-tagged Pacific lampreys or video observations of untagged individuals in situ. Field and experimental results consistently indicated that the structural challenges reduced passage efficiency and lengthened passage times. Improving Pacific lamprey passage may be facilitated by removing or modifying vertical steps and other sharp-edged corners and by providing adequate attachment surfaces. Such accommodations should be especially beneficial in areas with high water velocity. The findings demonstrate how fish morphology and behavior should be explicitly considered in the design or retrofitting of fish passage structures.

The ecological and cultural importance of a species at risk of extinction, Pacific lamprey. (2010). American Fisheries Society. Retrieved from

Abstract: The cultural and ecological values of Pacific lamprey (Lampetra tridentata) have not been understood by Euro-Americans and thus their great decline has almost gone unnoticed except by Native Americans, who elevated the issue and initiated research to restore its populations, at least in the Columbia Basin. They regard Pacific lamprey as a highly valued resource and as a result ksuyas (lamprey) has become one of their cultural icons. Ksuyas are harvested to this day as a subsistence food by various tribes along the Pacific coast and are highly regarded for their cultural value. Interestingly, our review suggests that the Pacific lamprey plays an important role in the food web, may have acted as a buffer for salmon from predators, and may have been an important source of marine nutrients to oligotrophic watersheds. This is very different from the Euro- American perception that lampreys are pests. We suggest that cultural biases affected management policies. 10.1577/1548-8446


Keefer, M. L., Moser, M. L., Boggs, C. T., Daigle, W. R., & Peery, C. A. (2009). Effects of Body Size and River Environment on the Upstream Migration of Adult Pacific Lampreys. North American Journal of Fisheries Management, 29(5), 1214–1224. doi:10.1577/M08-239.1

Abstract: Abstract Dams in the Columbia River basin present significant obstacles to declining populations of anadromous Pacific lampreys Lampetra tridentata. Mitigation efforts have focused on fine-scale improvements in passage at individual dams, but there is an increasing need for basinwide estimates of survival and escapement. We developed a half-duplex passive integrated transponder (PIT) tag monitoring array at five Columbia and Snake River dams to evaluate adult lamprey migrations. We tagged 3,598 lampreys over 3 years and calculated the rates of main-stem escapement through 15 river reaches. From these data, we assessed the relative effects of lamprey size, river discharge, water temperature, and migration timing on upstream passage. The results indicated high attrition as lampreys progressed upstream. In each year, about one-half of the fish passed one dam, 28–33%% passed two dams, 17–19%% passed three dams, 4–5%% passed four dams, and about 1%% passed the first dam on the Snake River (five dams and >300 km upstream from their release sites). In most reaches, upstream passage was strongly size dependent, the largest lampreys being two to four times more likely to pass than the smallest fish. Lamprey size was more predictive of passage than were the river discharge, temperature, or migration timing variables. These findings suggest that adult Pacific lamprey migration is affected by physiological constraints and that effective mitigation for the difficult passage conditions at dams should include size-related considerations.

Robinson, T. C., Sorensen, Peter W, Bayer, J. M., & Seelye, J. G. (2009). Olfactory Sensitivity of Pacific Lampreys to Lamprey Bile Acids. Transactions of the American Fisheries Society, 138(1), 144–152.

Abstract: AbstractPacific lampreys Lampetra tridentata are in decline throughout much of their historical range in the Columbia River basin. In support of restoration efforts, we tested whether larval and adult lamprey bile acids serve as migratory and spawning pheromones in adult Pacific lampreys, as they do in sea lampreys Petromyzon marinus. The olfactory sensitivity of adult Pacific lampreys to lamprey bile acids was measured by electro-olfactogram recording from the time of their capture in the spring until their spawning in June of the following year. As controls, we tested L-arginine and a non-lamprey bile acid, taurolithocholic acid 3-sulfate (TLS). Migrating adult Pacific lampreys were highly sensitive to petromyzonol sulfate (a component of the sea lamprey migratory pheromone) and 3-keto petromyzonol sulfate (a component of the sea lamprey sex pheromone) when first captured. This sensitivity persisted throughout their long migratory and overwinter holding period before declining to nearly unmeasurable levels by the time of spawning. The absolute magnitudes of adult Pacific lamprey responses to lamprey bile acids were smaller than those of the sea lamprey, and unlike the sea lamprey, the Pacific lamprey did not appear to detect TLS. No sexual dimorphism was noted in olfactory sensitivity. Thus, Pacific lampreys are broadly similar to sea lampreys in showing sensitivity to the major lamprey bile acids but apparently differ in having a longer period of sensitivity to those acids. The potential utility of bile acid-like pheromones in the restoration of Pacific lampreys warrants their further investigation in this species.

Biology and Conservation of Lampreys in North America, B., Larry R (Ed.). (2009). Biology, management, and conservation of lampreys in North America. Bethesda, Md.: American Fisheries Society.

Abstract: "Lampreys represent an ancient lineage extending back to the ostracoderms and are one of the most successful groups of living fishes. Perhaps best known for feeding on and killing bony fishes valued by humans, such as salmonids, lampreys exhibit a variety of fascinating life histories. Most lamprey species have lost the adult predatory stage of the life cycle and metamorphose, spawn, and die in the same stream in which they were spawned. Unfortunately, the bad reputation of predatory lampreys and the inconspicuous nature of small non-predaceous lampreys have resulted in their importance and special requirements in aquatic ecosystems being ignored. The impetus for this book was a petition to list four species of lamprey under the U.S. Endangered Species Act, which was denied in 2004 because of insufficient information. This decision energized many biologists to gather the scattered existing information on lampreys and to begin new research. This book presents new scientific as well as traditional (indigenous) knowledge of lampreys, while demonstrating their fascinating nature. Readers interested in learning about lampreys will find not only a wealth of new information but also extensive citations of existing information in each chapter"--Publisher's description.

LUCAS, M. C., BUBB, D. H., & JANG, M.-H., HA, KYONG, MASTERS, JEROME E. G. (2009). Availability of and access to critical habitats in regulated rivers: effects of low-head barriers on threatened lampreys. FWB Freshwater Biology, 54(3), 621–634.

Abstract: 1.?Conservation of freshwater animal populations requires their access to, as well as sufficient availability of, critical habitats, such as those for reproduction. Abundant small-scale barriers may cause extensive fragmentation of freshwater habitat but, by comparison to larger structures their effects are rarely considered by catchment managers. The relationship between the distribution of, and access to, spawning habitat in a regulated river, characterized by abundant small barriers, was examined for river lamprey Lampetra fluviatilis, a threatened migratory fish.
2.?Telemetry of adult lamprey in the River Derwent, North East England was used to quantify upriver migration and access to spawning habitat, together with surveys of spawning habitat availability and spawning activity between 2002 and 2007.
3.?Access in to the Derwent appeared severely restricted by a tidal barrage, beyond which lamprey migrated rapidly in unobstructed reaches. Of all lamprey tagged in the lower 4?km of river, or ascending the barrage, 64%% and 17%% passed the first and second weirs respectively, with high flows crucial for this. Although over 98%% of lamprey spawning habitat occurred more than 51?km upstream, on average just 1.8%% of river lamprey spawners were recorded there.
4.?In order to protect or rehabilitate species or species assemblages, greater attention needs to be paid to the relative spatial distribution of low-head barriers and the resultant availability of key habitats within individual catchments. This is particularly important given the renewed emphasis internationally on low-head hydropower solutions as a source of renewable energy, and the rapid growth in numbers of low-head barriers in many catchments.

Silver, G. S., Luzier, C. W., & Whitesel, T. A. (2009). Detection and Longevity of Uncured and Cured Visible Implant Elastomer Tags in Larval Pacific Lampreys. North American Journal of Fisheries Management, 29(5), 1496–1501.

Abstract: AbstractStudies of the biology, ecology, and status of the Pacific lamprey Lampetra tridentata may require effective means of tagging larval Pacific lampreys. However, few assessments of the methods suitable for tagging larval Pacific lampreys have been conducted. We evaluated the performance of visible implant elastomer (VIE) tags in larval Pacific lampreys, specifically testing the effects of elastomer treatment (uncured versus cured VIE) and inspection light source (ambient light versus blue light-emitting diode [LED] flashlight) on tag detection in 40 larvae. Through day 251 after tagging, tag detection was 100%% for both uncured and cured VIE tags observed under ambient light and blue LED light. Longevity of uncured VIE tags was assessed in a second cohort of 32 VIE-tagged larval Pacific lampreys over a 2-year captive rearing period. Percent VIE tag detection was 91%% for red tags, 90%% for orange tags, and 64%% for green tags through day 699 after tagging. This study affirms that both uncured and cured VIE tags can be effectively used to tag larval Pacific lampreys. Tagging with uncured VIE is a convenient and economical alternative to cured VIE tagging, particularly when tagging over protracted periods or small sample sizes.

Clemens, B. J., Van De Wetering, S., Kaufman, J., Holt, R. A., & Schreck, C. B. (2009). Do summer temperatures trigger spring maturation in Pacific lamprey, Entosphenus tridentatus? EFF Ecology of Freshwater Fish, 18(3), 418–426.

Abstract: Abstract?-? Pacific lamprey, Entosphenus tridentatus, return to streams and use somatic energy to fuel maturation. Body size decreases, the lamprey mature, spawn, and then die. We predicted that warm, summer temperatures (>20?°C) would accentuate shrinkage in body size, and expedite sexual maturation and subsequent death. We compared fish reared in the laboratory at diel fluctuating temperatures of 20-24?°C (mean?=?21.8?°C) with fish reared at cooler temperatures (13.6?°C). The results confirmed our predictions. Lamprey from the warm water group showed significantly greater proportional decreases in body weight following the summer temperature treatments than fish from the cool water group. A greater proportion of warm water fish sexually matured (100%%) and died (97%%) the following spring than cool water fish (53%% sexually mature, 61%% died). Females tended to mature and die earlier than males, most obviously in the warm water group.

United States, Department of Energy, United States, Bonneville Power Administration, United States, Department of Energy, & Office of Scientific and Technical Information. (2009). Evaluate Status of Pacific Lamprey in the Clearwater River and Salmon River Drainages, Idaho, 2009 Technical Report. Washington, D.C.; Oak Ridge, Tenn.: United States. Dept. of Energy ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy. Retrieved from

Abstract: Pacific lamprey Lampetra tridentata have received little attention in fishery science until recently, even though abundance has declined significantly along with other anadromous fish species in Idaho. Pacific lamprey in Idaho have to navigate over eight lower Snake River and Columbia River hydroelectric facilities for migration downstream as juveniles to the Pacific Ocean and again as adults migrating upstream to their freshwater spawning grounds in Idaho. The number of adult Pacific lamprey annually entering the Snake River basin at Ice Harbor Dam has declined from an average of over 18,000 during 1962-1969 to fewer than 600 during 1998-2006. Based on potential accessible streams and adult escapement over Lower Granite Dam on the lower Snake River, we estimate that no more than 200 Pacific lamprey adult spawners annually utilize the Clearwater River drainage in Idaho for spawning. We utilized electrofishing in 2000-2006 to capture, enumerate, and obtain biological information regarding rearing Pacific lamprey ammocoetes and macropthalmia to determine the distribution and status of the species in the Clearwater River drainage, Idaho. Present distribution in the Clearwater River drainage is limited to the lower sections of the Lochsa and Selway rivers, the Middle Fork Clearwater River, the mainstem Clearwater River, the South Fork Clearwater River, and the lower 7.5 km of the Red River. In 2006, younger age classes were absent from the Red River.


Reinhardt, U. G., Eidietis, L., Friedl, S. E., & Moser, M. L. (2008). Pacific lamprey climbing behavior. Canadian Journal of Zoology, 86(11), 1264–1272. doi:10.1139/Z08-112

Abstract: New lamprey-friendly fishways feature inclined ramps that facilitate passage of Pacific lampreys (Lampetra tridentata (Richardson, 1836)) over Bonneville Dam on the Columbia River, USA. We observed the lampreys moving against water at two flow volumes and on two ramps of 45° and 18° angles relative to horizontal. We documented climbing movements using high-speed video (125 frames/s). Lampreys advanced on the ramps by repeated cycles of attaching to the ramps by their sucker mouths (resting phase), bending their bodies into a W shape (stage II), and then, rapidly straightening the body to propel themselves up the ramp, with simultaneous brief (20–140 ms) release of suction (stage III). We inferred that lampreys were using burst swimming to propel themselves up the ramp, because we observed inflection points in the body curvature traveling toward the posterior of the body and the center of mass moving up, during stage III. This climbing behavior is not described for any other fish species. Vertical motion, ..., De nouvelles passes à poissons plus accessibles aux lamproies du Pacifique (Lampetra tridentata (Richardson, 1836)) au barrage Bonneville sur le Columbia, É.-U., comportent des rampes qui facilitent leur passage. Nous avons observé les lamproies se déplacer à contre-courant à deux débits différents sur deux rampes inclinées à des angles de 45º et de 18º par rapport à l’horizontale. Nous avons observé les ascensions à l’aide de vidéo haute vitesse (125 images/s). Les lamproies progressent sur les rampes au cours de cycles répétés de fixation sur la rampe à l’aide de leur ventouse buccale (phase de repos), de repliement du corps en forme de W (étape II) et ensuite de redressement rapide du corps pour se propulser vers l’avant sur la rampe, en relâchant brièvement (20–140 ms) la succion (étape III). Nous déduisons que les lamproies utilisent la nage par poussée pour se faire avancer sur la rampe, parce que nous avons observé que des points d’inflexion dans la courbure du corps se propagent vers l’arrière et ...

Cochran, P. A., Bloom, D. D., & Wagner, R. J. (2008). Alternative Reproductive Behaviors in Lampreys and Their Signifcance. Journal of Freshwater Ecology, 23(3), 437–444. doi:10.1080/02705060.2008.9664221

Abstract: ABSTRACT A typical lamprey mating involves a female attaching to a stone near the upstream end of the nest A male then attaches to the back of the female's head and wraps his body around hers. Both vibrate vigorously as gametes are released. In some cases, a second male, the satellite, circles about the urogenital area of a mating pair at the moment of gamete release in what has been interpreted as an attempt to gain fertilizations. Analysis of videotapes of spawning Lampetra appendix in the North Branch Whitewater River in Minnesota (Mississippi River drainage) and Jambo Creek in eastern Wisconsin (Great Lakes drainage) revealed that at both sites at least 50%% of matings in nests with at least three lampreys included a satellite male. Nest associations involving more that one lamprey species in the same nest are known to involve many combinations of species, but especially relevant are cases involving closely related parasitic and nonparasitic species. For example, we have observed nonparasitic Ichthyomyzon gagei and parasitic Ichthyomyzon castaneus spawning in the same nests and have observed a male I. gagei attached to a female I. castaneus. Conventional wisdom is that the size difference between parasitic and nonparasitic lampreys prevents successful mating, but a combination of interspecific nest association and satellite male behavior could conceivably permit gene flow between paired nonparasitic and parasitic forms. This combination is displayed by at least some Lampetra species.

Lin, B., Zhang, Z., Wang, Y., Currens, K. P., Spidle, A., Yamazaki, Y., & Close, D. A. (2008). Amplified Fragment Length Polymorphism Assessment of Genetic Diversity in Pacific Lampreys. North American Journal of Fisheries Management, 28(4), 1182–1193. doi:10.1577/M07-035.1

Abstract: Abstract This study is the first to document genetic differences among Pacific lampreys Lampetra tridentata across much of their range. We examined collections of migrating adult Pacific lampreys from the Naka River, Japan; Moose River, Alaska; and six Pacific Northwest locations (North Fork Toutle, Willamette, Deschutes, John Day, Rogue, and Klamath rivers) based on variation at 180 polymorphic loci among the 556 amplified fragment length polymorphism loci generated by seven primer combinations. Despite the large geographical distances separating the samples, the different collections were characterized by a high proportion of shared bands, which indicated significant levels of historical gene flow across the range of the species. Analysis of molecular variance across three geographical regions—the Pacific Northwest, Alaska, and Japan—showed divergence among samples (genetic differentiation index FST = 0.106, P < 0.001) and significant differences among regions (regional differentiation FRT = 0.014; P < 0.001), among Pacific Northwest collections (population differentiation FSR = 0.092; P < 0.001), and within collections. Over this extent of the species' range, genetic divergence tended to follow a pattern of isolation by distance, which suggested that allelic diversity may have been maintained by stepping stone patterns of dispersal. This pattern did not occur within the Pacific Northwest: among the six collections, all pairwise FST comparisons were statistically significant and ranged from 0.037 to 0.182, but the differences corresponded to no obvious geographical pattern.

Moser, M. L., Pennington, H. T., & Roos, J. M. (2008). Grating Size Needed to Protect Adult Pacific Lampreys in the Columbia River Basin. North American Journal of Fisheries Management, 28(2), 557–562. doi:10.1577/M07-126.1

Abstract: Abstract Adult Pacific lampreys Lampetra tridentata routinely pass through picketed leads and diffuser gratings at lower Columbia River hydropower dams and enter areas where they can be delayed, injured, or killed. We assessed the bar spacing needed to exclude adult lampreys that enter the fishways at Bonneville Dam (river kilometer (rkm) 235). The experimental fish used (n = 242) ranged from 53 to 79 cm in total length and from 282 to 800 g in weight. All were able to swim through a 2.5-cm vertical gap, 47%% passed through a 2.2-cm gap, and none passed through a gap of 1.9 cm or less. In dewatering simulations, none of the additional 50 Pacific lampreys tested were able to pass through a 1.9-cm diffuser grating, while 86%% were able to pass through a traditional 2.5-cm grating. Based on these results, we conclude that bar spacing of 1.9 cm or less is needed to exclude most adult Pacific lampreys in the Columbia River drainage. An initial field test of the 1.9-cm grating at John Day Dam (rkm 347) confirmed these results.

McGree, M., Whitesel, T. A., & Stone, J. (2008). Larval Metamorphosis of Individual Pacific Lampreys Reared in Captivity. Transactions of the American Fisheries Society, 137(6), 1866–1878. doi:10.1577/T07-206.1

Abstract: Abstract This study is one of the first to follow individual Pacific lampreys Lampetra tridentata through the process of metamorphosis. Readily observable external changes were described for 13 individual Pacific lampreys undergoing metamorphosis. Changes occurred to the mouth, eyes, and branchial region from July to at least November. During metamorphosis, Pacific lampreys also exhibited asymmetric growth, including an increase in snout depth, that had not previously been reported in the literature. The order of the morphological changes and the patterns of asymmetric growth in the Pacific lamprey closely matched those reported for another Lampetra species, the American brook lamprey L. appendix, but exhibited unexpected variations from those reported in other species of lampreys. Excepting one catastrophic event, under captive rearing conditions 96.4%% of the ammocoetes survived and the maximum growth rates of 0.040-0.071 mm/d were within the range of those estimated for ammocoetes rearing naturally in stream environments. Supplemental feeding improved larval growth but did not influence the incidence of metamorphosis in captively reared animals. To develop effective conservation strategies for Pacific lampreys in the Columbia River basin, it would be prudent to consider that metamorphosis, a time when the animals are relatively vulnerable, may last from July to December.

Goodman, D. H., Reid, S. B., Docker, M. F., Haas, G. R., & Kinziger, A. P. (2008). Mitochondrial DNA evidence for high levels of gene flow among populations of a widely distributed anadromous lamprey Entosphenus tridentatus (Petromyzontidae). JFB Journal of Fish Biology, 72(2), 400–417.

Abstract: Mitochondrial DNA variation among 1246 individuals of Pacific lamprey (Entosphenus tridentatus) from 81 populations spanning 2600 km from the Skeena River, British Columbia, to the Ventura River, California, was surveyed using five restriction enzymes. A total of 29 composite haplotypes was detected in two gene fragments (ND2 and ND5). The three most common haplotypes, occurring in 91%% of all samples, were present at similar frequencies in all regions. Samples were divided into six biogeographic regions based on sample distribution and geographical landmarks to assess geographic genetic structure. Analysis of molecular variance indicated that 99%% of the genetic variation was explained by variability within drainages. The lack of geographical population structure is likely related to a life-history pattern that includes a prolonged larval freshwater stage, migration to oceanic feeding and return to fresh water to spawn. The lack of strong natal homing apparently promotes gene flow among drainages and regions.

Gilvear, D. ., Sutherland, P., & Higgins, T. (2008). An assessment of the use of remote sensing to map habitat features important to sustaining lamprey populations. AQC Aquatic Conservation: Marine and Freshwater Ecosystems, 18(6), 807–818.

Abstract: Copyright © 2007 John Wiley & Sons, Ltd.:
This study describes the use of colour aerial photography and Airborne Thematic Mapper (ATM) multispectral imagery (420-1050?nm) to map gravel-bed river habitats important to sustaining river lamprey (Lampetra fluviatilis) — an aquatic species with high conservation interest in Europe. The accuracy of the remote sensing approach was assessed by comparing the output from automated mapping of physical habitat features using image analysis and GIS and habitat maps derived from field survey.
Unsupervised classification of the aerial photography and ATM imagery mapped hydraulic habitat such as pools and riffles with overall accuracies of 57%% and 65.5%% respectively. Submerged sand and silt deposits, which are important to river lamprey ammocoetes could not be identified on the imagery by simple unsupervised or supervised classification. They could be mapped indirectly, however, by association between their presence and morphological attributes such as backwaters and embayments in the bank profile detectable on the imagery. Remotely determining the likely presence and location of lamprey ammocoete habitat can be useful in planning detailed electrofishing campaigns to estimate lamprey densities, to assess conservation status and any change over time, and to determine the need for restoration strategies.
The results suggest that on rivers wider than 20?m without a continuous wooded riparian fringe, and where there is good quality imagery, it is possible to automate mapping of physical habitat features important to many river species with high nature conservation interest. As a result organizations charged with monitoring and conserving river species should consider investing in airborne imagery covering river systems of high conservation value.


Meeuwig, M. H., Puls, A. L., & Bayer, J. M. (2007). Survival and Tag Retention of Pacific Lamprey Larvae and Macrophthalmia Marked with Coded Wire Tags. North American Journal of Fisheries Management, 27(1), 96–102. doi:10.1577/M06-074.1

Abstract: Abstract We examined the survival, tag retention, and growth of Pacific lamprey Lampetra tridentata larvae and macrophthalmia marked with standard-length decimal coded wire tags and exposed to two levels of handling stress. The survival of marked individuals did not differ from that of unmarked individuals at either life stage for the duration of the experiment (56 d). Tag retention was 100%% for all treatment combinations except larvae that were handled frequently (93 ± 3%%). The majority of tag loss occurred within 28 d of marking, and no tag loss was observed between 42 and 56 d after marking. The individuals that lost tags were among the smallest marked, and a logistic regression model indicated a relationship between larva length and the probability of tag retention. Size of larvae (length and mass) and macrophthalmia (mass) decreased over the duration of the experiment; however, changes in size were systematic among treatment combinations, indicating that factors other than tagging or handling affected growth. These data indicate that coded wire tags may be useful for field-based studies of Pacific lamprey larvae and macrophthalmia.


Hardisty, M. W. (2006). Lampreys: life without jaws. Tresaith, Cardigan, Ceregidion: Forrest. (Download)
Brun, C. V., Graham, J. C., United States, Bonneville Power Administration, United States, Department of Energy, … United States. Bonneville Power Administration. (2006). Determining Lamprey Species Composition, Larval Distribution, and Adult Abundance in the Deschutes River, Oregon, Subbasin; 2005-2006 Annual Report. Portland, Ore.; Oak Ridge, Tenn.: United States. Bonneville Power Administration ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy. Retrieved from

Abstract: Information about lamprey species composition, distribution, life history, abundance, habitat requirements, and exploitation in the lower Deschutes River Subbasin is extremely limited. During 2002, we began a multi-year study to assess the status of lamprey in the Deschutes River subbasin. The objectives of this project are to determine ammocoete (larval lamprey) distribution and associated habitats; Lampretra species composition; numbers of emigrants; adult escapement and harvest rates at Sherars Falls. This report describes the preliminary results of data collected during 2005. We continued documenting ammocoete (larval) habitat selection by surveying four perennial eastside tributaries to the Deschutes River (Warm Springs River, Badger, Beaver and Shitike creeks) within the known ammocoete distribution. The results of 2003-2005 sampling indicate that positive relationships exist between: presence of wood (P = <0.001), depositional area (P = <0.001), flow (P = <0.001), and fine substrate (P = <0.001). Out-migrants numbers were not estimated during 2005 due to our inability to recapture marked larvae. In Shitike Creek, ammocoete and microphthalmia out-migration peaked during November 2005. In the Warm Spring River, out-migration peaked for ammocoetes in April 2006 and December 2005 for microphthalmia. Samples of ammocoetes from each stream were retained in a permanent collection of future analysis. An escapement estimate was generated for adult Pacific lamprey in the lower Deschutes River using a two event mark-recapture experiment during run year 2005. A modified Peterson model was used to estimate the adult population of Pacific lamprey at 3,895 with an estimated escapement of 2,881 during 2005 (95%% CI= 2,847; M = 143; C = 1,027 R = 37). A tribal creel was also conducted from mid-June through August. We estimated tribal harvest to be approximately 1,015 adult lamprey during 2005 (95%% CI= +/- 74).

Mueller, R. P., Moursund, R. A., & Bleich, M. D. (2006). Tagging Juvenile Pacific Lamprey with Passive Integrated Transponders: Methodology, Short-Term Mortality, and Influence on Swimming Performance. North American Journal of Fisheries Management, 26(2), 361–366. doi:10.1577/M05-017.1

Abstract: Abstract This study was conducted to determine the feasibility (i.e., efficiency and nonintrusiveness) of tagging juvenile Pacific lampreys Lampetra tridentata with passive integrated transponder (PIT) tags and to determine any associated impacts on survivorship and swimming ability. Juvenile Pacific lampreys were obtained from the John Day Dam fish collection facility and tests were conducted at the Pacific Northwest National Laboratory in 2001 and 2002. A new PIT-tagging procedure was used to inject 12-mm tags 5 mm posterior to the gill openings. Lampreys were allowed to recover for 3–4 d following surgery before postmortality and swimming tests were conducted. The PIT tagging procedure during 2001 did not include a suture, and 2.6%% of the tags were shed after 40 d. During 2002 a single suture was used to close the opening after inserting a tag, and no tag shedding was observed. Overall short-term mortality rates for lampreys 120–155 mm (total length) held for 40 d at 8°C was 2.2%% for tagged and 2.7%% for untagged fish. Mortality increased significantly when tagged and untagged groups were held in warmer (19–23°C) river water: 50%% for tagged and 60%% for untagged animals. Lengths did not significantly affect survival for either the tagged or untagged group held in warm water. A fungal infection was observed to be the cause of death when water temperature increased. Swimming tests to determine any adverse effects due to tag insertion showed no significant difference (P = 0.12) between tagged and untagged lampreys for mean burst speed; however, maximum burst speeds were significantly lower for the PIT-tagged group.

Stone, J., McGree, M., & Whitesel, T. A. (2006). Detection of Uncured Visible Implant Elastomer Tags in Larval Pacific Lampreys. North American Journal of Fisheries Management, 26(1), 142–146. doi:10.1577/M05-046.1

Abstract: Abstract Lampreys in the Columbia River basin are a conservation concern, and understanding their status is a priority among managers. Many population assessment techniques depend on the ability to tag fish so that these tags are retained for the duration of the study with minimal effect on survival. There are several methods for tagging small fishes in streams, including passive integrated transponders, coded wire tags, and visible implant elastomer (VIE) tags. Of these, VIE tags have not been extensively tested on larval or juvenile lampreys. We evaluated the performance of uncured VIE tags on ammocoetes of Pacific lampreys Lampetra tridentata in a laboratory experiment to determine tag detection and the influences of color and tag position on detection. Additionally, we examined the effects of transformation (ammocoete to macrophthalmia) on tag detection. Though survival was not specifically tested, 0 of the 84 lampreys died as a result of tagging. Tag detection was 87%% after 168 d in lampreys that did not transform; in those that did transform, however, tag detection was reduced to 38%%. Tag position did not affect detection, but red and orange tags were detected more consistently than green tags. Overall, uncured VIE tags can be used effectively to tag larval lampreys; however, studies that depend on long-term tag detection either should be conducted at a time when lampreys are not expected to transform or should only use ammocoetes that are not likely to transform during the study.

Pacific Northwest National Laboratory (PNNL), R., WA (US). (2006). Swimming behaviour of juvenile Pacific lamprey, Lampetra tridentata. Environmental Biology of Fishes, 75(2):167-171, 75(2).

Abstract: Actively migrating juvenile Pacific lamprey (Lampetra tridentata Richardson, 1836) were collected from hydroelectric bypass facilities in the Columbia River and transferred to the laboratory to study their diel movement patterns and swimming ability. Volitional movement of lamprey was restricted mainly to night, with 94%% of all swimming activity occurring during the 12-hr dark period. Burst speed of juvenile lamprey ranged from 56 to 94 cm/s with a mean of 71 ±5 cm/s or an average speed of 5.2 body lengths (BL)/s. Sustained swim speed for 5-min test intervals ranged from 0 to 46 cm/s with a median of 23 cm/s. Critical swimming speed was 36.0±10.0 cm/s and 2.4±0.6 BL/s. There was no significant relationship between fish length and critical swimming speed. Overall swimming performance of juvenile Pacific lamprey is low compared to that of most anadromous teleosts. Their poor swimming ability provides a challenge during the freshwater migration interval to the Pacific Ocean.

Brumo, A. F. (2006). Spawning, larval recruitment, and early life survival of Pacific lampreys in the South Fork Coquille River, Oregon.

Abstract: Recently, there has been concern over the decline of the Pacific lamprey, Lampetra tridentata, in the northwestern United States. However, effective management has been impeded by data gaps in basic biology, especially in the early life stages. Consequently, in 2004 and 2005 I examined reproductive ecology, larval recruitment, and lamprey monitoring methods in the South Fork Coquille River, a coastal Oregon stream. In Chapter 2 I monitored spawning populations at large (9.2 km) and small (focal area) scales. Relationships between adult counts at the two spatial scales and adult and redd counts at the large scale were analyzed. Weekly adult, redd, and carcass counts and tagging were also used to describe spawning and residence times, movement, size, and sex of mature adults. Large-scale adult and redd counts were highly correlated (2004, r2 = 0.867; P = 0.0069; 2005, r2 = 0.877; P = 0.0002); as were large-scale and focal area adult counts over both years combined (r2 = 0.690, P = 0.0001) and in 2004 (r2 = 0.753, P = 0.0250), but not in 2005 when densities were much lower (r2 = 0.065, P = 0.5069). Average residence time in spawning areas was less than a week for males and shorter for females, since >90%% of recaptured fish were male. Two-thirds of dead fish (2:1) were male, versus only one-half of live fish (1:1), indicating additional sex-specific differences in postspawning behavior. No seasonal or spatial patterns in sex ratio or adult length were detected. Both adult and redd counts have inherent errors related to observer variability, movement during surveys, night spawning, and variable visibility due to weather and flow. To make adult and redd counts more useful for population monitoring their errors need to be better quantified and their relevance to life-cycle dynamics better understood. In Chapter 3 I monitored intra-annual cohorts of spawning adults and emergent larvae at a single spawning area to examine annual and seasonal patterns of spawning, larval recruitment, and early life survival. In 2004 spawning occurred from April 6???June 3 (59 d) and larval emergence occurred from May 6???June 28 (54 d). In 2005 both spawning and emergence were later and more protracted, from April 25???July 3 (70 d) and May 15???July 25 (71 d), respectively. Over both years, larval recruitment was highly variable and only marginally correlated with spawning stock (r2 = 0.149, P = 0.0512). Survival until larval emergence was significantly related to spawning stock size, discharge during spawning, and their interaction. Survival generally declined with increasing spawning stock and decreasing discharge, both apparently related to negative density-dependent effects, which resulted in highly variable early life survival. For example, in April 2004, 65%% of larvae were produced by 28%% of spawners, while in May, 35%% of larvae were produced by 70%% of spawners. Egg predation by speckled dace, Rhinichthys osculus, increased with temperature, but contrary to expectations, had no detectable effect on survival until emergence. This study provided justification for a multi-life stage approach to monitoring Pacific lamprey populations and understanding their dynamics. Application of this approach can provide insight into density-dependent survival and the roles of biotic and abiotic factors in larval production. Applied to the South Fork Coquille, Pacific lamprey larval production appeared to have an upper limit related, in part, to spawner density.

Cochnauer, T., & Putnam, S., Claire, Christopher W. (2006). Evaluate status of pacific lamprey in the Clearwater River drainage, Idaho: annual report 2005. Portland, Or.: Bonneville Power Administration, Environment, Fish and Wildlife.
Meeuwig, M. H., Bayer, J. M., & Reiche, R. A. (2006). Morphometric discrimination of early life stage Lampetra tridentata and L. richardsoni (Petromyzonidae) from the Columbia River Basin. JMOR Journal of Morphology, 267(5), 623–633.

Abstract: The effectiveness of morphometric and meristic characteristics for taxonomic discrimination of Lampetra tridentata and L. richardsoni (Petromyzonidae) during embryological, prolarval, and early larval stages (i.e., age class 1) were examined. Mean chorion diameter increased with time from fertilization to hatch and was significantly greater for L. tridentata than for L. richardsoni at 1, 8, and 15 days postfertilization. Lampetra tridentata larvae had significantly more trunk myomeres than L. richardsoni; however, trunk myomere numbers were highly variable within species and deviated from previously published data. Multivariate examinations of prolarval and larval L. tridentata (7.2-11.0 mm; standard length) and L. richardsoni (6.6-10.8 mm) were conducted based on standard length and truss element lengths established from eight homologous landmarks. Principal components analysis indicated allometric relationships among the morphometric characteristics examined. Changes in body shape were indicated by groupings of morphometric characteristics associated with body regions (e.g., oral hood, branchial region, trunk region, and tail region). Discriminant function analysis using morphometric characteristics was successful in classifying a large proportion (>94.7%%) of the lampreys sampled. J. Morphol. © 2006 Wiley-Liss, Inc.


Meeuwig, M. H., & Bayer, J. M. (2005). Morphology and Aging Precision of Statoliths from Larvae of Columbia River Basin Lampreys. North American Journal of Fisheries Management, 25(1), 38–48. doi:10.1577/M03-184.1

Abstract: Abstract The general morphology and precision associated with age determination of statoliths from larval Pacific lampreys Lampetra tridentata and western brook lampreys L. richardsoni found within the Columbia River basin were examined. Significant positive correlations were observed between the size of left and right statoliths from individuals. Principal components analysis indicated an allometric relationship between lamprey length and statolith size as well as a potential species grouping based on these measurements. Discriminant analysis was able to correctly classify more than 94%% of Pacific lampreys and 92%% of western brook lampreys based on lamprey length and statolith size, and Pacific lamprey statoliths tended to be larger than western brook lamprey statoliths for lampreys of a given size. Reader bias in age estimates of statoliths was greater for older lampreys. Multiple independent age readings of both statoliths from individual lampreys indicated that the overall average percent error was 16.7%% for Pacific lampreys and 33.0%% for western brook lampreys. Within-individual average percent error ranged from 5.1%% to 20.1%% among species and readers. Within-reader average percent error ranged from 6.4%% to 17.8%% among species and readers. The average percent error observed in this study was greater than that observed in studies of other species of lampreys; however, statoliths that were ambiguous or difficult to read were not excluded from this study. In general, the modal separation of age-groups observed in length-frequency distributions for lampreys is poor, as seen in this study; therefore, statolith-based ages may verify or provide better estimates of population age structure. These data demonstrate that estimates of precision are necessary before management actions founded on statolith-based age structure determination are implemented.

Meeuwig, M. H., Bayer, J. M., & Seelye, J. G. (2005). Effects of Temperature on Survival and Development of Early Life Stage Pacific and Western Brook Lampreys. Transactions of the American Fisheries Society, 134(1), 19–27. doi:10.1577/FT03-206.1

Abstract: Abstract We examined the effects of temperature (10, 14, 18, and 22°C) on survival and development of Pacific lampreys Lampetra tridentata and western brook lampreys L. richardsoni during embryological and early larval stages. The temperature for zero development was estimated for each species, and the response to temperature was measured as the proportion of individuals surviving to hatch, surviving to the larval stage, and exhibiting abnormalities at the larval stage (i.e., malformations of the body). The estimated temperature for zero development was 4.85°C for Pacific lampreys and 4.97°C for western brook lampreys. Survival was greatest at 18°C, followed by 14, 10, and 22°C, significant differences being observed between 22°C and the other temperatures. Overall survival was significantly greater for western brook lampreys than for Pacific lampreys; however, the overall difference in proportion of individuals surviving was only 0.02. Overall survival significantly decreased from the time of hatch (proportion surviving = 0.85) to the larval stage (0.82; i.e., during the free-embryo stage). The proportion of individuals exhibiting abnormalities at the larval stage was greatest at 22°C, followed by 18, 10, and 14°C, significant differences being observed between 22°C and the other temperatures. These data provide baseline information on the thermal requirements of early life stage Pacific and western brook lampreys and will aid in assessment and prediction of suitable spawning and rearing habitats for these species.

Stone, J., Barndt, Scott. (2005). Spatial Distribution and Habitat Use of Pacific Lamprey (Lampetra tridentata) Ammocoetes in a Western Washington Stream. Journal of Freshwater Ecology, 20(1), 171–185.

Abstract: ABSTRACTWe investigated the spatial distribution and habitat associations of Pacific lamprey (Lampetra tridentata) ammocoetes in a southwest Washington stream. The ammocoetes exhibited a highly aggregated, non-random spatial distribution pattern. Conductivity, dissolved oxygen, and gradient influenced ammocoete distribution at the large scale (across 50 m reaches), whereas wetted width, percent fines, canopy density, and velocity influenced distribution at the small scale (1 m2 quadrats). We observed optimum water depths of 70 cm and current velocities of 0 to 10 cm/sec. In general, ammocoetes preferred fine substrates though larger ammocoetes were found at low densities in large gravel substrates. Our findings illustrate the importance of slow water environments for the rearing stage of Pacific lamprey. Restoration activities should be designed to restore watershed function and process in a way that naturally allows systems to retain these critical habitats. Additionally, when considering ammocoete habitat use and distribution, it is important to take into account the scale of the observations.

Yamazaki, Y., Fukutomi, Norio, Oda, Norio, Shibukawa, Koichi, Niimura, Yasuo, Iwata, Akihisa. (2005). Occurrence of larval Pacific lamprey Entosphenus tridentatus from Japan, detected by random amplified polymorphic DNA (RAPD) analysis. Ichthyological Research, 52(3), 297–301.

Abstract: Species identifications of the Pacific lamprey Entosphenus tridentatus from four other Japanese lampreys, Lethenteron japonicum, L. kessleri, and two undescribed Lethenteron species (L. sp. N and L. sp. S), were carried out on the basis of random amplified polymorphic DNA (RAPD) using the polymerase chain reaction (PCR) method. Of 65 RAPD loci, seven loci possessing species-specific fragments were obtained for E. tridentatus. Based on these RAPD loci, four larval individuals of E. tridentatus from the Naka River (eastern Honshu Island, Japan) were recognized in 2001 and 2002. The existence of larval individuals of E. tridentatus, as well as spawning adults previously reported from the same river, indicated the possibility of residence in that species.


Kearn, G. C. (2004). Leeches, lice and lampreys: a natural history of skin and gill parasites of fishes. Dordrecht: Springer. (Download)
Torgersen, C. E., & Close, D. A. (2004). Influence of habitat heterogeneity on the distribution of larval Pacific lamprey (Lampetra tridentata) at two spatial scales. Freshwater Biology, 49(5), 614–630.

Abstract: 1. Spatial patterns in channel morphology and substratum composition at small (1-10 metres) and large scales (1-10 kilometres) were analysed to determine the influence of habitat heterogeneity on the distribution and abundance of larval lamprey. 2. We used a nested sampling design and multiple logistic regression to evaluate spatial heterogeneity in the abundance of larval Pacific lamprey, Lampetra tridentata, and habitat in 30 sites (each composed of twelve 1-m2 quadrat samples) distributed throughout a 55-km section of the Middle Fork John Day River, OR, U.SA. Statistical models predicting the relative abundance of larvae both among sites (large scale) and among samples (small scale) were ranked using Akaike's Information Criterion (AIC) to identify the ‘best approximating’ models from a set of a priori candidate models determined from the literature on larval lamprey habitat associations. 3. Stream habitat variables predicted patterns in larval abundance but played different roles at different spatial scales. The abundance of larvae at large scales was positively associated with water depth and open riparian canopy, whereas patchiness in larval occurrence at small scales was associated with low water velocity, channel-unit morphology (pool habitats), and the availability of habitat suitable for burrowing. 4. Habitat variables explained variation in larval abundance at large and small scales, but locational factors, such as longitudinal position (river km) and sample location within the channel unit, explained additional variation in the logistic regression model. The results emphasise the need for spatially explicit analysis, both in examining fish habitat relationships and in developing conservation plans for declining fish populations.

Meeuwig, M. H., Bayer, J. M., Reiche, R. A., United States, & Bonneville Power Administration. (2004). Identification of Larval Pacific Lampreys (Lampetra tridentata), River Lampreys (L. ayresi), and Western Brook Lampreys (L. richardsoni) and Thermal Requirements of Early Life History Stages of Lampreys, Annual Report 2002-2004. Portland, Or.: Bonneville Power Administration.
United States, Department of Energy, United States, Bonneville Power Administration, United States, Department of Energy, & Office of Scientific and Technical Information. (2004). Identification of Larval Pacific Lampreys (Lampetra tridentata), River Lampreys (L. ayresi), and Western Brook Lampreys (L. richardsoni) and Thermal Requirements of Early Life History Stages of Lampreys, Annual Report 2002-2003. Washington, D.C.; Oak Ridge, Tenn.: United States. Dept. of Energy ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy. Retrieved from

Abstract: Two fundamental aspects of lamprey biology were examined to provide tools for population assessment and determination of critical habitat needs of Columbia River Basin (CRB) lampreys (the Pacific lamprey, Lampetra tridentata, and the western brook lamprey, L. richardsoni). We evaluated the usefulness of current diagnostic characteristics for identification of larval lampreys (i.e., pigment patterns) and collected material for development of meristic and morphometric descriptions of early life stage CRB lampreys, and we determined the effects of temperature on survival and development of early life stage CRB lampreys. Thirty-one larval lampreys were collected from locations throughout the CRB and transported to the Columbia River Research Laboratory. Lampreys were sampled at six-week intervals at which time they were identified to the species level based on current diagnostic characteristics. Sampling was repeated until lampreys metamorphosed, at which time species identification was validated based on dentition, or until they died, at which time they were preserved for genetic examination. These lampreys were sampled 30 times with two individuals metamorphosing, both of which were consistently identified, and subsequently validated, as Pacific lampreys. Of the remaining lampreys, only one was inconsistently identified (Pacific lamprey in 83%% of the sampling events and western brook lamprey in 17%% of the sampling events). These data suggest that pigmentation patterns do not change appreciably through time. In 2001 and 2002 we artificially spawned Pacific and western brook lampreys in the laboratory to provide material for meristic and morphometric descriptions. We collected, digitized, preserved, and measured the mean chorion diameter of Pacific and western brook lamprey embryos. Embryos ranged in development from 1 d post fertilization to just prior to hatch, and were incubated at 14 C. Mean chorion diameter was greater and more variable for Pacific lampreys (mean ± SD; 1.468 ± 0.107 mm, N = 320) than for western brook lampreys (1.237 ± 0.064 mm, N = 280). An unpaired t-test showed that the difference in mean chorion diameter between species was highly significant (t = 32.788, df = 528.62, P < 0.0001). For larvae, we collected, digitized, and preserved 156 individuals from each species. Eight homologous landmarks defining a two-cell truss network with two appended triangles were selected for morphometric analyses and species discrimination. A full model discriminant analysis correctly classified 92%% of the Pacific lampreys and 93%% of the western brook lampreys in a classification data set. When applied to a test data set, the classification functions correctly classified 91%% of the Pacific lampreys and 85%% of the western brook lampreys. A backward elimination discriminant analysis removed four variables from the full model, and the reduced model correctly classified 91%% of the Pacific lampreys and 93%% of the western brook lampreys in a classification data set. The reduced model classification functions correctly classified 91%% of the Pacific lampreys and 85%% of the western brook lampreys in a test data set. In 2001 and 2002 Pacific and western brook lampreys were artificially spawned and resulting progeny were reared in the laboratory at 10 C, 14 C, 18 C, and 22 C. The estimated temperature for zero development was 4.85 C for Pacific and 4.97 C for western brook lampreys. Survival was greatest at 18 C followed by 14 C, 10 C, and 22 C, with significant differences observed between 22 C and other temperatures. Overall survival was significantly greater for western brook than for Pacific lampreys, although the difference in proportion of individuals surviving was only 0.02. Survival to hatch was significantly greater than survival to the larval stage with a difference of only 0.03. The proportion of individuals exhibiting abnormalities at the larval stage was greatest at 22 C followed by 18 C, 10 C, and 14 C, with significant differences observed between 22 C and other temperatures.

Cochnauer, T., Claire, C. W., United States, Bonneville Power Administration, & Environment, F. and W. (2004). Evaluate status of pacific lamprey in the Clearwater River drainage, Idaho annual report 2003. Portland, Or.: Bonneville Power Administration, Environment, Fish and Wildlife. Retrieved from


Close, D. A., Fitzpatrick, M. S., Lorion, C. M., Li, H. W., & Schreck, C. B. (2003). Effects of Intraperitoneally Implanted Radio Transmitters on the Swimming Performance and Physiology of Pacific Lamprey. North American Journal of Fisheries Management, 23(4), 1184–1192. doi:10.1577/MO2-057

Abstract: Abstract Information on movement patterns and behaviors of Pacific lampreys Lampetra tridentata at Columbia River hydroelectric projects is needed to determine effects of the dams on survival. Radiotelemetry provides a good method for gaining knowledge about Pacific lamprey behavior at the dams; however, one of the assumptions of a radiotelemetry experiment is that tagged individuals are representative of untagged individuals. Therefore, we undertook an assessment of the swimming performance and physiological effects of surgical implantation of radio transmitters into the peritoneal cavities of Pacific lamprey. We measured concentrations of plasma glucose, ventilation rate, and swimming performance at short-term and long-term intervals following the surgical implantation of radio transmitters in Pacific lamprey. We found no short-term difference in glucose levels between tagged (3.4-g tags) and control lampreys, suggesting tagging is no more stressful than handling. Plasma levels of glucose in Pacific lampreys implanted with 7.4-g transmitters were greater at 3 and 24 h postsurgery compared with controls; however, these differences disappeared at 96 h. Ventilation rates of tagged (7.4 g) and control lampreys did not differ at 1, 24, and 168 h after surgeries. Swimming performance of Pacific lampreys implanted with 7.4-g transmitters was impaired immediately after surgery; however, swimming was not compromised at 1 and 7 d after surgery. In the long term (i.e., 4 months postimplantation), plasma glucose levels in lampreys implanted with 3.4-g transmitters did not differ from control or sham lampreys, whereas those implanted with 10.0 g transmitters had higher plasma glucose than intact controls. Adult lampreys implanted with 7.4-g transmitters remained statistically indistinct from controls at 30, 60, 90, and 180 d after surgery. Of the control and 7.4-g tagged lampreys, 22%% matured and developed secondary sexual characteristics with loose eggs or flowing milt by the end of March. We found 100%% survival rate with our tagged fish in all experiments. These results indicate that radio tags weighing 7.4 g or less that are surgically implanted in adult Pacific lamprey can meet the core assumption of radiotelemetry, provided precautions are taken to ensure adequate time for recovery from surgery.

Mesa, M. G., Bayer, J. M., & Seelye, J. G. (2003). Swimming Performance and Physiological Responses to Exhaustive Exercise in Radio-Tagged and Untagged Pacific Lampreys. Transactions of the American Fisheries Society, 132(3), 483–492. doi:10.1577/1548-8659(2003)132<0483:SPAPRT>2.0.CO;2

Abstract: Abstract Populations of Pacific lamprey Lampetra tridentata have declined in the Columbia River basin. One factor that may have contributed to this reduction in population size is an excessive use of energy by adult lampreys as they negotiate fishways at dams during spawning migrations. To gain an understanding of the performance capacity of Pacific lampreys, we estimated the critical swimming speed (U crit) and documented physiological responses of radio-tagged and untagged adult lampreys exercised to exhaustion. The mean (±SD) U crit of untagged lampreys was 86.2 ± 7.5 cm/s at 15°C, whereas the U crit for radio-tagged lampreys was 81.5 ± 7.0 cm/s, a speed that was significantly lower than that of untagged fish. The physiological responses of tagged and untagged lampreys subjected to exhaustive exercise included decreases in blood pH of 0.3–0.5 units, a 40%% decrease in muscle glycogen levels, a 22%% increase in hematocrit for untagged fish only, and a 4- to 5-fold increase in muscle and a 40- to 100-fold increase in plasma lactate concentrations. These physiological changes were significant compared with resting control fish and usually returned to resting levels by 1–4 h after fatigue. Our estimates of U crit for Pacific lampreys are the first quantitative measures of their swimming performance and suggest that these fish may have difficulty negotiating fishways at dams on the Columbia River, which can have water velocities approaching 2 m/s. Our physiological results indicate that tagged and untagged Pacific lampreys show similar metabolic dysfunction after exhaustive exercise but recover quickly from a single exposure to such a stressor.

White, J. L., & Harvey, B. C. (2003). Basin-scale Patterns in the Drift of Embryonic and Larval Fishes and Lamprey Ammocoetes in two Coastal Rivers. Environmental Biology of Fishes, 67(4), 369–378.
Meeuwig, M. H., United States, Department of Energy, United States, Bonneville Power Administration, United States, … Bonneville Power Administration. (2003). Identification of Larval Pacific Lampreys (Lampetra Tridentata), River Lampreys (L. Ayresi) and Western Brook Lampreys (L. Richardson) and Thermal Requirements of Early Life History Stages of Lampreys Annual Report 2002. Washington, D.C; Oak Ridge, Tenn.: United States. Dept. of Energy ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy. Retrieved from

Abstract: Two fundamental aspects of lamprey biology were examined to provide tools for population assessment and determination of critical habitat needs of Columbia River Basin lampreys (the Pacific lamprey, Lampetra tridentata, and the western brook lamprey, L. richardsoni). In particular: (1) we examined the usefulness of current diagnostic characteristics in identification of larval lampreys, specifically pigmentation patterns, and collected material for development of meristic and morphometric descriptions of early life stages of lampreys, and (2) we examined the effects of temperature on survival and development of early life stages of Columbia River Basin lampreys.

United States, Department of Energy, United States, Bonneville Power Administration, United States, Department of Energy, & Office of Scientific and Technical Information. (2003). Evaluate Status of Pacific Lamprey in the Clearwater River Drainage, Idaho, Annual Report 2002. Washington, D.C.; Oak Ridge, Tenn.: United States. Dept. of Energy ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy. Retrieved from

Abstract: In 2002 Idaho Department of Fish and Game continued investigation into the status of Pacific lamprey populations in Idaho's Clearwater River drainage. Trapping, electrofishing, and spawning ground redd surveys were used to determine Pacific lamprey distribution, life history strategies, and habitat requirements in the South Fork Clearwater River, Lochsa River, Selway River, and Middle Fork Clearwater River subbasins. Five-hundred forty-one ammocoetes were captured electroshocking 70 sites in the South Fork Clearwater River, Lochsa River, Selway River, Middle Fork Clearwater River, Clearwater River, and their tributaries in 2002. Habitat utilization surveys in Red River support previous work indicating Pacific lamprey ammocoete densities are greater in lateral scour pool habitats compared to riffles and rapids. Presence-absence survey findings in 2002 augmented 2000 and 2001 indicating Pacific lamprey macrothalmia and ammocoetes are not numerous or widely distributed. Pacific lamprey distribution was confined to the lower reaches of Red River below rkm 8.0, the South Fork Clearwater River, Lochsa River (Ginger Creek to mouth), Selway River (Race Creek to mouth), Middle Fork Clearwater River, and the Clearwater River (downstream to Potlatch River).

Claire, C. W. (2003). Pacific lamprey larvae life history, distribution, and habitat utilization in the South Fork Clearwater River drainage, Idaho.


Moser, M. L., Ocker, P. A., Stuehrenberg, L. C., & Bjornn, T. C. (2002). Passage Efficiency of Adult Pacific Lampreys at Hydropower Dams on the Lower Columbia River, USA. Transactions of the American Fisheries Society, 131(5), 956–965. doi:10.1577/1548-8659(2002)131<0956:PEOAPL>2.0.CO;2

Abstract: Abstract Hydropower dams in the lower Columbia River may contribute to declines in the populations of anadromous Pacific lamprey Lampetra tridentata by limiting access to historical spawning locations. To identify obstacles to migration, we documented the movements of radio-tagged adult Pacific lampreys in specific areas of fishways (entrances, collection channels, transition areas, ladders, and counting stations) at the first three dams they encounter as they move upstream (Bonneville, The Dalles, and John Day). From 1997 to 2000, 147-299 radio-tagged lampreys were released downstream from Bonneville Dam. In 1997 and 2000, we also moved 50 radio-tagged lampreys each year to positions upstream from Bonneville Dam to assess the passage success of fish that had not passed through an entire fishway (i.e., “naive fish”). The passage efficiency of lampreys at Bonneville Dam was 38-47%%, and the median time required to pass over the dam ranged from 4.4 to 5.7 d. In contrast, 50-82%% of the lampreys passed over The Dalles Dam in each year, and passage times ranged from 2.0 to 4.0 d. Passage efficiency was lowest at John Day Dam, but that estimate was based on relatively few fish. After entering the fishways, lampreys had the greatest difficulty (1) negotiating collection channels and transition areas that lacked attachment sites and (2) passing through the Bonneville Dam counting stations. Unexpectedly high passage success was documented in the ladders, where maximum current velocities could exceed 2.4 m/s. We found no evidence that lampreys released downstream from Bonneville Dam had higher passage success at The Dalles Dam than naive fish. In each year up to 60%% of the lampreys made multiple entrances at the fishways, indicating that lampreys persistently attempted to pass upstream. Dams in the lower Columbia River impede adult Pacific lamprey migration, and only 3%% of the fish we tagged reached areas above John Day Dam.

Moser, M. L., Bjornn, T. C., Stuehrenberg, L. C., Cavender, W., McCarthy, S. G., Geological Survey (U.S.), … Pacific States Marine Fisheries Commission. (2002). Radiotelemetry investigations of adult Pacific lamprey migration behavior: evaluation of modifications to improve passage at Bonneville Dam, 2000. Seattle, Wash.: Fish Ecology Division, Northwest Fisheries Science Center, National Marine Fisheries Service.
Kostow, K., Oregon, & Fish Division. (2002). Oregon lampreys natural history, status, and problem analysis. [Salem, Or.]: Oregon Dept. of Fish and Wildlife, [Fish Division. Retrieved from
United States, Bonneville Power Administration, United States, Department of Energy, & Office of Scientific and Technical Information. (2002). Ecological and Cultural Importance of a Species at Risk of Extinction, Pacific Lamprey, 1964-2002 Technical Report. Portland, Ore.; Oak Ridge, Tenn.: United States. Bonneville Power Administration ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy. Retrieved from

Abstract: The cultural and ecological values of Pacific lamprey (Lampetra tridentata) have not been understood by Euro-Americans and thus their great decline has almost gone unnoticed except by Native Americans, who elevated the issue and initiated research to restore its populations, at least in the Columbia Basin. They regard Pacific lamprey as a highly valued resource and as a result ksuyas (lamprey) has become one of their cultural icons. Ksuyas are harvested to this day as a subsistence food by various tribes along the Pacific coast and are highly regarded for their cultural value. Interestingly, our review suggests that the Pacific lamprey plays an important role in the food web, may have acted as a buffer for salmon from predators, and may have been an important source of marine nutrients to oligotrophic watersheds. This is very different from the Euro-American perception that lampreys are pests. We suggest that cultural biases affected management policies.

Close, D. A., United States, Bonneville Power Administration, & Environment, F., and Wildlife. (2002). Pacific lamprey research and restoration project: annual report 2001. Pendleton, Or.; Portland, Or.: Confederated Tribes of the Umatilla Indian Reservation, Dept. of Natural Resources, Fisheries Program ; Bonneville Power Administration, Environment, Fish and Wildlife Dept.
Close, D. A., United States, Bonneville Power Administration, & Environment, F., and Wildlife. (2002). Pacific lamprey research and restoration project: annual report 2000. Pendleton, Or.; Portland, Or.: Confederated Tribes of the Umatilla Indian Reservation, Dept. of Natural Resources, Fisheries Program ; Bonneville Power Administration, Environment, Fish and Wildlife Dept.
Cochnauer, T., Claire, C. W., United States, Bonneville Power Administration, & Environment, F. and W. (2002). Evaluate status of pacific lamprey in the Clearwater River drainage, Idaho annual report 2001. Portland, Or.: Bonneville Power Administration, Environment, Fish and Wildlife. Retrieved from


Stone, J., Sundlov, T., Barndt, S., & Coley, T. (2001). Evaluate Habitat Use and Population Dynamics of Lampreys in Cedar Creek. CreateSpace Independent Publishing Platform. (Download)
Moursund, R. A., Dauble, D. D., Degerman, T. M., Mueller, R. P., & Pacific Northwest National Laboratory (U.S.). (2001). Effects of dam passage on juvenile Pacific lamprey (Lampetra tridentata). Richland, Wash.: Pacific Northwest National Laboratory.
United States, Bonneville Power Administration, United States, Department of Energy, United States, Department of Energy, & Office of Scientific and Technical Information. (2001). Upstream Migration of Pacific Lampreys in the John Day River Behavior, Timing, and Habitat Use. Washington, D.C; Oak Ridge, Tenn.: United States. Dept. of Energy ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy. Retrieved from

Abstract: Historic accounts and recent observations of Pacific lampreys (Lampetra tridentata) at mainstem Columbia River dams indicate the number of Pacific lampreys migrating upriver has decreased dramatically over the last 60 years. Consequently, state, federal, and tribal governments have recently expressed concern for this species. Little is known about the biological and ecological characteristics of habitats suitable for upstream migrating Pacific lampreys. If rehabilitation efforts are to be done effectively and efficiently, we must gain knowledge of factors limiting survival and reproduction of Pacific lampreys. From data gathered in the first year of this project, we can for the first time, describe the timing, extent, and patterns of movements for Pacific lampreys. We have tested methods and gained information that will allow us to refine our objectives and approach in future work. Knowledge of behavior, timing, and the resulting quantification of habitat use will provide a means to assess the suitability of overwintering and spawning habitats and allow the establishment of goals for recovery projects. Further research is necessary, including multiple years of data collection, tracking of movement patterns through the spawning season, and more rigorously examining habitat use.

Vella, J. J., Bjornn, T. C., Geological Survey (U.S.), Biological Resource Division, Northwest Fisheries Science Center (U.S.), Fish Ecology Division, … Portland District. (2001). Migration patterns of Pacific lamprey (Lampetra tridentata) in the lower Columbia River, 1997: report of research. Seattle, Wash.: Fish Ecology Division, Northwest Fisheries Science Center, National Marine Fisheries Service.
Ocker, P. A., Bjornn, T. C., Tolotti, K. R., Geological Survey (U.S.), Biological Resource Division, Northwest Fisheries Science Center (U.S.), … Portland District. (2001). Monitoring adult Pacific lamprey (Lampetra tridentata) migration behavior in the lower Columbia River using radiotelemetry, 1998-1999: report of research. Seattle, Wash.: Fish Ecology Division, Northwest Fisheries Science Center, National Marine Fisheries Service.
United States, Bonneville Power Administration, United States, Department of Energy, United States, Department of Energy, & Office of Scientific and Technical Information. (2001). Pacific Lamprey Research and Restoration Project Annual Report 1999. Washington, D.C; Oak Ridge, Tenn.: United States. Dept. of Energy ; Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy. Retrieved from

Abstract: This report summarizes results of research activities conducted from 1996 through 1999. The findings in these chapters represent the efforts of the Confederated Tribes of the Umatilla Indian Reservation (CTUIR) and collaborative efforts among other researchers working on Pacific lampreys (Lampetra tridentata) under this project. The findings in these chapters will help management and recovery of Pacific lampreys in the Columbia River Basin. Traditional Ecological Knowledge (TEK) of Pacific lampreys from tribal members within the Confederated Tribes of the Umatilla Indian Reservation was useful in gaining baseline life history information. Tribal members described harvesting two types of lampreys from spring through fall, the short brown type and the long dark type. Lamprey spawning distribution was from the mouth to the headwaters in the Umatilla River. Larval lampreys were observed in the mud and sand areas of the river. Tribal members observed major declines in lampreys within the Columbia River basin. Larval Pacific lampreys were distributed throughout the John Day River basin. Larval distribution in the other subbasins was patchy and limited to the lower reaches of the streams. Larval densities were highly variable in the Middle Fork John Day and North Fork John Day rivers, as opposed to the Main stem John Day River. Larval lengths varied little in the Middle Fork John Day and North Fork John Day rivers, but were highly variable in the Main stem John Day River. Larval abundance decreased as we moved upstream in the Columbia and Snake rivers. In addition, we found strong evidence for lack of larval recruitment as distance increased from the mouth of the Columbia River. We identified clinical indicators of stress in adult Pacific lampreys. Plasma glucose became elevated soon after acute stress and remained elevated for one week. Plasma lactate also became elevated by 30 minutes; however, it decreased to resting levels by one hour after application of the stressor. Muscle lactate was shown to have an inverse relationship with glucose. Muscle lactate levels decreased by 4 hours and remained depressed for two days. Plasma chloride ions decreased by one hour, then returned to resting levels by 8 hours, decreased again at 24 hours, and then recovered by 48 hours. The steroid cortisol was not found in the plasma of Pacific lampreys. Our study suggests plasma glucose, lactate, chloride ions, and muscle lactate can be used as clinical indicators of stress in Pacific lampreys.

Cochnauer, T., & Claire, C. W. (2001). Evaluate status of pacific lamprey in the Clearwater River drainage, Idaho: annual report 2000. Portland, Or.: Bonneville Power Administration, Environment, Fish and Wildlife.
Case, Shawn D. 2001. “Contributions to the Life History of Adult Pacific Lamprey.” Bulletin of the Southern California Acadmy of Sciences 100 (2): 74–85.

Abstract: Data on the relative abundance, seasonal timing, and size at entry into freshwater of upstream migrants were collected on a population of Pacific lamprey inhabiting the Santa Clara River. In addition, spent lamprey were also collected and provided information on the length, decrease in body length between entry into freshwater and spawning the following year, and the potential timing of spawning.


United States, Independent Scientific Review Panel, & Coutant, C. C. (2000). Review of the Confederated Tribes of the Umatilla Indian Reservation’s “Restoration plan for Pacific lampreys (Lamptera tridentata) in the Umatilla River, Oregon.” Portland, Or.: Northwest Power Planning Council. Retrieved from


Docker, M. F., Youson, J. H., Beamish, R. J., & Devlin, R. H. (1999). Phylogeny of the lamprey genus Lampetra inferred from mitochondrial cytochrome b and ND3 gene sequences. Canadian Journal of Fisheries and Aquatic Sciences, 56(12), 2340–2349. doi:10.1139/f99-171

Abstract: Mitochrondrial DNA analysis resolved many previously unanswered questions concerning the phylogeny of the lamprey genus Lampetra (comprising the subgenera Entosphenus, Lethenteron, and Lampetra). A total of 735 base pairs were sequenced from the cytochrome b and NADH dehydrogenase subunit 3 (ND3) genes in 11 lamprey species. With the exception of L. (E.) hubbsi from California, species of the Entosphenus subgenus formed a tight-knit clade that was very distinct from the other two subgenera. Lampetra hubbsi clustered with species of the Lampetra subgenus from the west coast of North America (L. ayresii and L. richardsoni) whereas species of the Lampetra subgenus from Atlantic drainages, namely the North American L . aepyptera and European L. fluviatilis, formed a third cluster. A fourth cluster included two species from the Lethenteron subgenus (L. japonica and L. appendix). Inclusion of published data from a third Lethenteron species, L. zanandreai, showed it to group with the L. (L.) fluviatilis lineage ..., L'analyse de l'ADN mitochrondial a permis de répondre à bon nombre de questions relativement à la phylogénie du genre de lamproie Lampetra (englobant les sous-genres Entosphenus, Lethenteron et Lampetra). On a déterminé la séquence d'un total de 735 paires de bases des gènes pour la cytochrome b et la sous-unité 3 de la NADH déshydrogénase (ND3) chez 11 espèces de lamproie. À l'exception de L. (E. ) hubbsi de la Californie, les espèces du sous-genre Enthosphenus formaient un clade cohérent très distinct de ceux des deux autres sous-genres. Lampetra hubbsi se rapprochait des espèces du sous-genre Lampetra de la côte ouest de l'Amérique du Nord (L. ayresii et L. richardsoni) tandis que les espèces du sous-genre Lampetra des bassins de l'Atlantique, à savoir L. aepyptera de l'Amérique du Nord et L. fluviatilis de l'Europe formaient un troisième groupe. Un quatrième groupe englobait deux espèces du sous-genre Lethenteron (L. japonica et L. appendix). L'ajout de données publiées pour une troisième espèce de Le...

Vella, J. J., Bjornn, T. C., Stuehrenberg, L. C., Idaho Cooperative Fish and Wildlife Research Unit, Northwest Fisheries Science Center (U.S.), Fish Ecology Division, … Portland District. (1999). Radiotelemetry of Pacific lamprey (Lampetra tridentata) in the lower Columbia River, 1996. Seattle, Wash.: Fish Ecology Division, Northwest Fisheries Science Center, National Marine Fisheries Service.
Jackson, A. D., United States, Bonneville Power Administration, & Division of Fish and Wildlife. (1999). Pacific lamprey research and restoration: annual report 1997. Portland, Or.: Bonneville Power Administration.


Close, D. A., Fitzpatrick, M. S., Hatch, D. R., Jackson, A. D., Kissner, P. D., Li, H. W., … Environment, F., and Wildlife. (1998). Pacific lamprey research and restoration: annual report 1996. Portland, Or.: Bonneville Power Administration.


Whyte, J. N. C., Beamish, R. J., Ginther, N. G., & Neville, C.-E. (1993). Nutritional Condition of the Pacific Lamprey (Lampetra tridentata) Deprived of Food for Periods of Up to Two Years. Canadian Journal of Fisheries and Aquatic Sciences, 50(3), 591–599. doi:10.1139/f93-068

Abstract: The anadromous parasitic Pacific lamprey (Lampetra tridentata) does not feed during metamorphosis or its spawning migration. To assess the utilization of body reserves, we compared the compositions of an adult lamprey held for 2?yr without food, recently metamorphosed lampreys, and lampreys starved for 6?mo. Moisture was higher and soluble ash and lipid levels were lower in tissue of the 2-yr-starved than in metamorphosed lampreys (2.67 and 3.39?kj?g?1, respectively). Fatty acid profiles of 2-yr-starved and metamorphosed lampreys were qualitatively similar except for the presence of 15:0 in the latter. Substantially lower levels of 14:0 and 16:1 n7 and higher levels of polyunsaturated fatty acids occurred in starved lampreys. Changes in composition of lampreys starved for 6?mo were similar to changes between the 2-yr-starved and metamorphosed lampreys. Maintenance energy in a normalized 1-g lamprey starved for 6?mo was derived from catabolism of 71%% lipid and 29%% protein; total loss was 2.56?kJ or 49%% of ..., La lamproie du Pacifique parasite anadrome (Lampetra tridentata) ne s'alimente pas durant sa métamorphose ni durant sa migration de frai. Pour évaluer ses réserves corporelles, nous avons comparé la constitution de lamproies adultes privées de nourriture pendant 2 ans, des lamproies récemment métamorphosées et des lamproies privées de nourriture pendant 6?mo. La teneur en eau était plus élevée et la concentration de cendres solubles et de lipide étaient plus faibles dans les tissus des lamproies privées pendant 2 ans que dans ceux des lamproies récemment métamorphosées (respectivement 2,67 et 3,39?kJ?g?1). Les profils des acides gras chez les lamproies privées pendant 2 ans et les lamproies récemment métamorphosées étaient semblables du point de vue qualitatif, sauf pour ce qui est de la présence d'acides 15 : 0 chez ces dernières; chez les lamproies privées d'aliments, on a observé des concentrations d'acide 14 : 0 et 16 : 1n7 substantiellement plus faibles et des concentrations d'acides gras polyinsatur...


Beamish, R. J., & Levings, C. D. (1991). Abundance and Freshwater Migrations of the Anadromous Parasitic Lamprey, Lampetra tridentate, in a Tributary of the Fraser River, British Columbia. Canadian Journal of Fisheries and Aquatic Sciences, 48(7), 1250–1263. doi:10.1139/f91-151

Abstract: The migration of young adult Lampetra tridentata out of the Nicola River during 1984–85 through 1987–88 was estimated to be approximately 176?000,19?000,90?000, and 102?000; at the same time, approximately 749?000, 909?000, 920?000, and 605?000 large ammocoetes, age 4 and 5 yr, left the river. Migration of young adults started in September, with the largest number migrating from mid-March to mid-May. Ammocoetes behaved similarly except that movement continued throughout the year. Most young adults metamorphosed at age 4 or 5 and were age 5 or 6 when they migrated to sea. It was not determined when lamprey from the Nicola River reached salt water; however, L. tridentata entered the Strait of Georgia from the Fraser River from March until July. Maturing adults first returned to the Nicola River from the ocean in August when water levels in the river were at their lowest. This is the first estimate of abundance of young adult L. tridentata in any river in the Fraser River drainage. The very large number of y..., Selon nos estimations, environ 176?000, 19?000, 90?000 et 102?000 jeunes Lampetra tridentata de stade adulte sont sortis de la rivière Nicola de 1984–1985 à 1987–1988; durant la même période, il est aussi parti environ 749?000, 909?000, 920?000 et 605?000 grands ammocètes de 4 et 5 ans. La migration des jeunes adultes a commencé en septembre; les plus gros contingents ont migré de la mi-mars à la mi-mai. Il en a été de même pour les ammocètes, sauf que leur migration s'est poursuivie toute l'année. La plupart des jeunes adultes se sont métamorphosés à 4 ou 5 ans et avaient 5 ou 6 ans lorsqu'ils ont migré vers l'océan. Nous n'avons pas déterminé quand les lamproies de la rivière Nicola arrivent en eau salée; nous savons néanmoins que L. tridentata est entré au détroit de Géorgie, arrivant du Fraser, de mars jusqu'à juillet. Les adultes en maturation ont commencé à migrer de l'océan jusqu'à la Nicola en août, lorsque le niveau de l'eau de la rivière était au plus bas. C'est la première fois que l'on estime ...


Beamish, R. J., & Northcote, T. G. (1989). Extinction of a Population of Anadromous Parasitic Lamprey, Lampetra tridentata, Upstream of an Impassable Dam. Canadian Journal of Fisheries and Aquatic Sciences, 46(3), 420–425. doi:10.1139/f89-056

Abstract: The construction of dams on the outlet of Elsie Lake, in British Columbia, prevented young adult Pacific lamprey (Lampetra tridentata) from going to sea and adult lamprey from spawning above the dams. This resulted in a high incidence of lamprey attacks on resident trout that was initially interpreted as indicating that the lamprey population was landlocked. This study showed that a landlocked population of lamprey was not established. The attacks on fish occurred for only a brief period each year. Attacks on trout stopped approximately 7?yr after dam construction. Because this was the average estimated age when ammocoetes metamorphosed and scarred fish or ammocoetes were no longer found, we concluded that metamorphosed lamprey were unable to survive to maturity. The inability to establish a landlocked population indicated that the transition from an anadromous parasitic life history type to a freshwater parasitic life history type did not occur as quickly or as easily as previously suggested. The study a..., La construction de digues à l'exutoire du lac Elsie, Colombie-Britannique, a empêché de jeunes lamproies adultes du Pacifique (Lampetra tridentata) d'atteindre la mer et des lamproies adultes d'aller se reproduire en amont des digues. Cela s'est traduit par une fréquence élevée d'attaques de lamproies contre des truites résidentes, ce qui a été interprété initialement comme le signe que la population de l'endroit était devenue une population de lac. Cette étude montre qu'une telle population ne s'est pas établie. Les attaques sur les poissons se produisaient durant une brève période chaque année. Les attaques contre les truites ont cessé au bout de 7 an environ après la construction des digues. Puisque sept ans constituent l'âge moyen estimé de la métamorphose de ces ammocètes et que des poissons portant des cicatrices ou des ammocètes n'étaient plus trouvés passé cette période, il a été conclu que les lamproies métamorphosés n'avaient pas pu survivre jusqu'à maturité. L'inaptitude à constituer une popula...


Clarke, W. C., & Beamish, R. J. (1988). Response of Recently Metamorphosed Anadromous Parasitic Lamprey (Lampetra tridentata) to Confinement in Fresh Water. Canadian Journal of Fisheries and Aquatic Sciences, 45(1), 42–47. doi:10.1139/f88-006

Abstract: Recently metamorphosed Lampetra tridentata were collected from six rivers in British Columbia in early autumn and held in fresh water in the laboratory at ambient temperature and simulated natural photoperiod. Ability to survive in fresh water varied considerably among populations, ranging from the Babine River population which did not survive beyond February to the Chemainus River population which survived until July. Associated with the onset of mortality was a decrease in plasma sodium concentrations. Plasma sodium concentrations in individual lampreys were correlated with condition factor, indicating that osmoregulatory failure may have resulted from depletion of body energy reserves. In a separate experiment, postmetamorphic lamprey sampled from two rivers fed poorly in fresh water and feeding did not prolong their survival. We conclude that confinement of L. tridentata in fresh water does not easily result in the formation of landlocked populations., Des Lampetra tridentata récemment métamorphosées ont été capturées dans six rivières de la Colombie-Britannique au début de l'automne et gardées en laboratoire dans les conditions suivantes : eau douce, température ambiante et photopériode simulant la photopériode naturelle. La capacité de survie en eau douce a varié considérablement selon les populations, les extrêmes étant la population de la rivière Babine qui n'a pas survécu après février et la population de la rivière Chemainus qui a survécu jusqu'en juillet. Le début de la mortalité coïncidait avec une baisse du taux de sodium pfasmatique. Les taux de sodium plasmatique chez les lamproies individuelles étaient corrélés avec le coefficient de conditions, ce qui indique que l'insuffisance de l'osmorégulation pourrait résulter de l'épuisement des réserves énergétiques de l'organisme. Dans une autre expérience, des lamproics métamorphosées provenant de deux rivières s'alimentaient peu en eau douce et l'alimentation n'a pas prolongé leur survie. On concl...

Beamish, F. W. H., & Medland, T. E. (1988). Age Determination for Lampreys. Transactions of the American Fisheries Society, 117(1), 63–71. doi:10.1577/1548-8659(1988)117<0063:ADFL>2.3.CO;2

Abstract: Abstract Age structures of several populations of parasitic and nonparasitic lampreys were estimated from statolith band number and length-frequency distributions. In larval populations of the parasitic sea lamprey Petromyzon marinus and nonparasitic American brook lamprey Lampetra appendix, which display strong seasonal patterns ofgrowth, one narrow dark band or annulus and one broad opaque band was produced each winter and summer, respectively. The formation of an annulus during slow growth was validated in two populations of sea lampreys with a chemical tissue marker, oxytetracycline. Length-frequency distributions required large samples to identify age groups, and the older age groups within a population were often difficult to distinguish because of overlap in size ranges. Thus, the assignment of age to an individual from its total length was likely to be imprecise unless that individual's length was close to the modal length of an age group. Some discrepancies in the assignment of population age structure were noted between the two methods. Annuli were not recognizable in the statoliths of larvae or adults from a population of southern brook lamprey Ichthyomyzon gagei that displayed an even growth rate throughout the year, thus making length-frequency distribution analysis the only alternative.


Beamish, R. J. (1987). Evidence that Parasitic and Nonparasitic Life History Types are Produced by One Population of Lamprey. Canadian Journal of Fisheries and Aquatic Sciences, 44(10), 1779–1782. doi:10.1139/f87-219

Abstract: A population of lamprey in a small stream on Vancouver Island, British Columbia, Canada, was shown to contain the nonparasitic Lampetra richardsoni and a parasitic variety., L'auteur montre que la population de lamproies d'un petit cours d'eau de l'île de Vancouver (Colombie-Britannique) se compose de l'espèce non parasite Lampetra richardsoni et d'une variété parasite.

Russell, J. E., Beamish, F. W. H., & Beamish, R. J. (1987). Lentic Spawning by the Pacific Lamprey, Lampetra tridentata. Canadian Journal of Fisheries and Aquatic Sciences, 44(2), 476–478. doi:10.1139/f87-057

Abstract: Anadromous Pacific lamprey, Lampetra tridentata, typically construct nests and reproduce in lotic environments. In the summer of 1984, Pacific lamprey were observed spawning in shallow lentic water in two regions of the Babine Lake system, British Columbia. Nests were subject to wave action but an obvious unidirectional flow was not observed., La lamproie du Pacifique anadrome, Lampetra tridentata, construit généralement un nid et se reproduit en milieu lotique. À l'été 1984, on a observé des lamproies du Pacifique frayant en milieu lentique peu profond dans deux régions du système du lac Babine (Colombie-Britannique). Les nids étaient soumis à l'action des vagues quoiqu'un courant unidirectionnel n'ait pas été observé.


Lemons, D. E., & Crawshaw, L. I. (1985). Responses to rapid temperature change in the Pacific lamprey (Lampetra tridentata). Canadian Journal of Zoology, 63(5), 1027–1032. doi:10.1139/z85-154

Abstract: Some aspects of the thermal biology of the Pacific lamprey (Lampetra tridentata) were studied by making rapid changes in the ambient water temperature (Ta). Calorimetric studies were conducted to determine the rate of ensuing changes in mean body temperature and various deep body temperatures. Cardiovascular–respiratory alterations were evaluated in an experimental flow-through apparatus in which Ta could be rapidly shifted while changes in ventilation frequency (fV) and heart rate (fH) were recorded. Immediately following a step increase in Ta, the change in of a 0.21-kg lamprey was 33%% complete in 33?s and 67%% complete in 127?s. Deep dorsal muscle temperature changed much more slowly, being 33%% complete in 87?s and 67%% complete in 225?s. During rapid shifts in Ta, fV and fH changed at a significantly greater rate than would be predicted taking into account the change in and the resultant Q10 effects on metabolism. This effect persisted when the of the water was held at 600?Torr (1?Torr?=?133.322?Pa). A ..., Certains aspects de la thermobiologie de la lamproie Lampetra tridentata ont été étudiés à la suite de brusques changements de la température de l'eau du milieu (Ta) : des examens calorimétriques ont servi à déterminer la vitesse des changements de la température moyenne du corps et des températures ponctuelles profondes consécutifs à ces variations de la température du milieu. Les variations cardiovasculaires–respiratoires ont été évaluées dans un appareil à courant continu dans lequel Ta pouvait être changée rapidement et les changements dans la fréquence respiratoire (fV) et le rythme cardiaque (fH) pouvaient être enregistrés. Immédiatement après une augmentation brusque de Ta, le changement de chez une lamproie de 0,21?kg atteint 33%% de son amplitude maximale après 33?s, et 67%% après 127?s. La température du muscle dorsal profond change beaucoup plus lentement, puisque ce changement atteint 33%% de son amplitude après 87?s et 67%% après 225?s. Lorsque la température Ta change brusquement, fV et fH chang...


Farlinger, S. P., & Beamish, R. J. (1984). Recent Colonization of a Major Salmon-Producing Lake in British Columbia by Pacific Lamprey (Lampetra tridentata). Canadian Journal of Fisheries and Aquatic Sciences, 41(2), 278–285. doi:10.1139/f84-032

Abstract: Pacific lamprey (Lampetra tridentata) were first observed in Babine Lake, the largest natural lake wholly contained in British Columbia, in 1963 and are currently found along approximately 15%% of the length of the lake near the outlet. The number of spawning adults in 1982 was estimated to be 7281. Since Babine Lake is a major nursery area for sockeye salmon (Oncorhynchus nerka), the colonization of this lake by a parasitic lamprey is of concern, particularly if the species can become nonanadromous. The colonization may be beneficial if a commercial fishery can be sustained and if the species does not begin to feed in freshwater. The reason for the recent colonization is unknown but it coincides with increased human manipulation of fishes and habitat, including the removal of a major rock slide, 65?km downstream of the lake., La lamproie du Pacifique (Lampetra tridentata) a été observée pour la première fois dans le lac Babine, le plus grand lac compris entièrement dans les limites de la Colombie-Britannique, en 1963 et on la trouve actuellement sur environ 15%% de la longueur du lac, près de l'émissaire. En 1982, on estimait à 7281 le nombre d'adultes reproducteurs. Comme le lac Babine est une importante région d'alevinage du saumon nerka (Oncorhynchus nerka), la colonisation de ce lac par une lamproie parasite n'est pas sans causer d'inquiétudes, surtout si elle devenait non anadrome. Par ailleurs, si la lamproie pouvait être exploitée commercialement de façon soutenue et qu'elle ne commence pas à se nourrir en eau douce, la colonisation par cette espèce pourrait être avantageuse. On ignore la raison de cette récente colonisation, mais elle coïncide avec une manipulation accrue des poissons et de l'habitat par l'homme, dont l'enlèvement d'un important éboulis de roches à 65?km en aval du lac.


Mallatt, J. (1983). Laboratory growth of larval lampreys (Lampetra (Entosphenus) tridentata Richardson) at different food concentrations and animal densities. JFB Journal of Fish Biology, 22(3), 293–301.

Abstract: Lampreys are important research animals. This study investigates some of the Parameters important for culturing the Suspension feeding larvae: food concentration, temperature and crowding. Large larvae (Lampetra (Entosphenus) tridentata Richardson) were used, weigh-ing from l·5 to 3·0 g (wet). Two food types were employed: suspended yeast cells (Saccharo-myces cerevisiae, 0-20 mg1 - (dry), or, in a few tests, a fine particulate fish food, Liquifry® (Interpet LTD, 0-13 mg l-1). At both 14 and 4°C, yeast could sustain weight increases comparable to those in nature: >6%% month-1 for up to 6 months, the duration of the study. In a single lest, a vitamin Supplement failed to improve growth on yeast. Growth-was fastest at 14°C (+41%% month-1, max. weight increase), although also substantial at 4°C (+11%% month-1, max). Growth could not be sustained at 20°C, due perhaps to difficulty in removing products of food decay from the aquaria. Food level being constant, growth rate varied inversely with animal density. It is suggested that larval lampreys release a growth-inhibiting substance into the sand which they inhabit. Overall, the best growth was obtained at 14° C, with <0·05g of animal (wet weight) - aquarium water and average daily yeast concentrations between 4 and 13 mg -. Liquifry was associated with lowered growth rates when present continually above 4 mg (dry weight) - (14° C), although growth did occur at lower concentrations.


Richards, J. E., Beamish, R. J., & Beamish, F. W. H. (1982). Descriptions and Keys for Ammocoetes of Lampreys from British Columbia, Canada. Canadian Journal of Fisheries and Aquatic Sciences, 39(11), 1484–1495. doi:10.1139/f82-200

Abstract: Characters useful for the identification of ammocoetes of lampreys found in British Columbia were verified by rearing ammocoetes through metamorphosis to specifically identifiable adults. We developed a key that employs new as well as some previously published features. We showed that published descriptions previously thought to be characteristic of species are unreliable for taxonomy. Counts of trunk myomeres and body proportions were not useful for separating species.Key words: ammocoetes, taxonomy, identification criteria, En élevant des ammocètes jusqu'au stade adulte identifiable, en passant par la métamorphose, il a été possible de vérifier les caractères taxonomiques des ammocètes de lamproies rencontrées en Colombie-Britannique. Nous avons préparé une clé reposant sur des caractères à la fois nouveaux et déjà publiés. Nous démontrons que des diagnoses jadis considérées comme étant caractéristiques de l'espèce ne sont pas fiables en taxonomie. Les comptages de myomères du tronc et les proportions du corps ne permettent pas de séparer les espèces.


Larsen, L. O. (1980). Physiology of Adult Lampreys, with Special Regard to Natural Starvation, Reproduction, and Death after Spawning. Canadian Journal of Fisheries and Aquatic Sciences, 37(11), 1762–1779. doi:10.1139/f80-221

Abstract: In this review I have attempted to define (1) how the genetic program responsible for migration, sexual maturation, and death after spawning is implemented via the endocrine system, and (2) to what extent environmental factors influence the implementation of the genetic program. The time of upstream migration and the body size at migration may vary enormously (e.g. in Lampetra fluviatilis). Whether the differences reflect different genetic backgrounds in different populations or different environmental conditions in previous stages is unknown. Migration is correlated with lack of food intake, loss of marine osmoregulatory capacity, and atrophy of the intestine. The possible endocrine control of this phase is not clear. Development of secondary sex characters, final maturation of the gonads, spermiation, and ovulation seem to depend on a gonadotropic factor secreted by the pro- and meso-adenohypophysis, but gonadotropin is not as important as in higher vertebrates. Increases in day length or in temperature..., Le compte rendu qui suit tente de définir (1) la manière dont le programme génétique responsable de la migration, de la maturation sexuelle et de la mort après la fraie est exécuté par le biais du système endocrinien, et (2) jusqu'à quel point les facteurs de l'environnement influent sur l'exécution de ce programme. Il peut y avoir de grandes variations de l'époque de migration vers l'amont et de la taille au moment de cette migration (e.g. chez Lampetra fluviatilis). On ignore si ces différences reflètent des variations dans la constitution génétique des diverses populations ou dans les conditions ambiantes à des stades antérieurs. Il y a relation entre migration et jeûne, perte de capacité osmorégulatrice en mer et atrophie de l'intestin. Le contrôle endocrinien de cette phase n'est pas clair. Le développement des caractères sexuels secondaires, la maturation finale des gonades ainsi que la sécrétion de la laitance et l'ovulation semblent dépendre d'un facteur gonadotrope sécrété par la pro- et la méso-...

Potter, I. C. (1980). Ecology of Larval and Metamorphosing Lampreys. Canadian Journal of Fisheries and Aquatic Sciences, 37(11), 1641–1657. doi:10.1139/f80-212

Abstract: Ammocoetes are relatively sedentary burrowing animals. Movement is related to water discharge, temperature, and season, and occurs predominantly downstream and at night. Growth is asymptotic and seasonal. At the end of larval life, the ammocoete ceases to increase markedly in length and starts to accumulate lipid. Length–frequency curves and data on kidney growth indicate that, in relatively stable and productive sites, ammocoetes of long established populations of the landlocked and anadromous sea lamprey take ~?5?yr to reach metamorphosing length. Many animals probably enter transformation within a further 3?yr. information from an isolated population in the Big Garlic River and from other tributaries of lakes Superior and Michigan, some of which had been treated with larvicide, shows that the onset of metamorphosis can be highly variable and is apparently related to the growth rates and size of larvae. A short larval life is usually associated with a fast growth rate of ammocoetes, as is sometimes foun..., Les ammocètes sont des animaux fouisseurs relativement sédentaires. Leurs mouvements sont affectés par le débit d'eau, la température et la saison, et se produisent surtout vers l'aval et la nuit. La croissance est asymptotique et saisonnière. À la fin de leur phase larvaire, les ammocètes cessent presque complètement de croître et commencent à accumuler des lipides. Les courbes de fréquence de longueur et les données sur la croissance du rein indiquent que, à des endroits relativement stables et productifs, les ammocètes de populations établies de longue date de grandes lamproies marines cantonnées en eau douce et anadromes prennent environ 5 ans pour atteindre la longueur de métamorphose. Pour plusieurs sujets, la métamorphose sera retardée d'une période allant jusqu'à 3 ans. Des observations faites sur une population isolée de la rivière Big Garlic et dans d'autres tributaires des lacs Supérieur et Michigan, dont certains avaient été traités à un larvicide, démontrent que le début de la métamorphose pe...

Lewis, S. V. (1980). Respiration of Lampreys. Canadian Journal of Fisheries and Aquatic Sciences, 37(11), 1711–1722. doi:10.1139/f80-217

Abstract: In lampreys, though the gross morphology of the branchial chamber and the method of ventilating the gills are radically different from that found in gnathostomes, the total gill area of larval (1462–2717?mm2?g?1) and adult (1402–2337?mm2?g?1) lampreys, the ultrastructure of the gills, and the thickness of the water–blood barrier are similar to active teleosts. The standard rates of oxygen consumption of ammocoetes are low, values for medium-sized Ichthyomyzon hubbsi ranging from 18.1??L?g?1?h?1 at 3.5 °C to 90.1??L?g?1?h?1 at 22.5 °C. The consumption rates increase during metamorphosis rising in Lampetra fluviatilis held at 10 °C from 29.3 to 60.4??L?g?1?h?1, and at the same time a circadian rhythm of consumption develops; maximum rates occur in the dark. Adult lampreys have consumption rates ranging from 66.1??L?g?1?h?1 in L. fluviatilis to 36.9??L?g?1?h?1 in Petromyzon marinus, and Q10's in the temperature range 5–15 °C are from 1.6 to 4.83. Sexually mature males of L. planeri and L. fluviatilis have hi..., Bien que la morphologie macroscopique de la chambre branchiale et la méthode de ventilation des branchies des lamproies soient radicalement différentes de celles des gnathostomes, la superficie totale des branchies des larves (1462–2717?mm2?g?1) et des lamproies adultes (1402–2337?mm2?g?1) ainsi que la structure fine des branchies et l'épaisseur de la barrière eau–sang sont semblables à celles des téléostéens actifs. Les taux normaux de consommation d'oxygène des ammocètes sont faibles, les valeurs chez Ichthyomyzon hubbsi de taille moyenne s'étalant de 18,1??L?g?1?h?1 à 3,5 °C à 90,1??L?g?1?h?1 à 22,5 °C. Les taux de consommation augmentent durant la métamorphose, passant, chez Lampetra fluviatilis maintenue à 10 °C, de 29,3 à 60,4??L?g?1?h?1, alors qu'en même temps s'établit un rythme circadien de consommation; les taux maximaux se produisent à la noirceur. Les lamproies adultes ont des taux de consommation allant de 66,1??L?g?1?h?1 chez L. fluviatilis à 36,9??L?g?1?h?1 chez Petromyzon marinus, et les Q...

Bailey, Reeve M. 1980. “Comments on the Classification and Nomenclature of Lampreys — An Alternative View.” Canadian Journal of Fisheries and Aquatic Sciences 37 (11) (November): 1626–1629. doi:10.1139/f80-209.


Vladykov, V. D., & Kott, E. (1979). A new parasitic species of the holarctic lamprey genus Entosphenus Gill, 1862 (Petromyzonidae) from Klamath River, in California and Oregon. Canadian Journal of Zoology, 57(4), 808–823. doi:10.1139/z79-100

Abstract: A new parasitic lamprey is described from 29 metamorphosed specimens in feeding stage. The holotype (No. NMC 75-1550) is deposited in the National Museum of Natural Sciences. Ottawa, Canada. It is easily separable by its functional intestinal tract and strong dentition from the three nonparasitic species: Entosphenus folletti, E. hubbsi, and E. lethophagus. From the parasitic E. tridentatus it is distinguishable by (1) fewer myomeres, (2) greater disc length, (3) smaller eye diameter, (4) differences in dentition, and (5) differences in number and morphology of velar tentacles. From another parasitic species, E. minimus, it differs by (1) larger size, (2) greater disc length, (3) smaller eye length, (4) stronger dentition, and (5) differences in velar tentacle number., On décrit ici une nouvelle espèce parasite de lamproie en se basant sur l'étude de 29 individus metamorphosés au stade actif de nutrition. L'holotype (No. NMC 75-1550) se trouve au Musée National des Sciences Naturelles à Ottawa. Canada, Son tube digestif fonctionnel et sa forte dentition permettent de séparer facilement cette espèce des trois autres espèces non-parasites : Entosphenus folletti, E. hubbsi et E. lethophagus. Elle se distingue également de l'espèce parasite E. tridentatus par (1) un nombre inférieur de myomères, (2) un disque plus grand, (3) un diamètre plus petit de l'œil, (4) des différences dans la dentition et (5) des différences dans le nombre et la morphologie des tentacules vélaires. Elle diffère aussi d'une autre espèce parasite E. minimus par (1) une plus grande taille, (2) un disque plus grand, (3) un œil plus petit, (4) une dentition plus forte et (5) des différences dans le nombre de tentacules vélaires.

Hammond, R. J. (1979). Larval biology of the Pacific lamprey, Entosphenus tridentatus (Gairdner), of the Potlatch River, Idaho.


Starke, G. M. (n.d.). Pacific lamprey (Lampetra tridentata) passage patterns past Bonneville Dam and incidental observations of lamprey at the Portland District Columbia River dams in 1993. US Army Corps of Engineers, Portland District. (Download)
Close, D. A. (n.d.). Pacific lamprey research and restoration project: Annual report 1998. Bonneville Power Administration, Division of Fish and Wildlife. (Download)
Close, D. A. (n.d.). Status report of the Pacific lamprey (lampetra tridentata) in the Columbia River Basin. Bonneville Power Administration. (Download)
Williams, I. V. (n.d.). Lamprey parasitism on Fraser River sockeye and pink salmon during 1967, (International Pacific Salmon Fisheries Commission. Progress report no. 18). (Download)


Kan, T. T. (1975). Systematics, variation, distribution, and biology of lampreys of the genus Lampetra in Oregon.

Abstract: Based on the number of velar tentacles and the form of longitudinal lingual laminae found in Lampetra (Entosphenus) t. tridentata and its closely related forms, the taxon Entosphenus should not be considered as a genus as commonly adopted, but, along with the taxa Lethenteron and Lampetra, should be regarded as a subgenus of the genus Lampetra. The genus Lampetra is distinct for various reasons, including particularly the character that no cusps are present in the area distal to the lateral circumorals. Six nominal species, belonging to the subgenera Entosphenus and Lampetra, have been known to occur in four of the seven major drainage systems of Oregon. The anadromous L. (E.) t.tridentata, is widespread in the Columbia River and Coastal drainage systems, occurring in most streams with access to the ocean regardless of distance to the ocean, as long as suitable spawning grounds and ammocoete habitats are present. Morphometrics and dentitional features vary little over its geographical range. The number of trunk myomeres and the adult body size vary appreciably so that two categories of regional forms, coastal and inland, may be recognized. The coastal forms are generally smaller and have fewer trunk myomeres compared to those of the larger inland forms. The spawning migration begins from the late spring to late summer for the coastal forms but may occur much earlier for the inland forms. The adult body size appears to be positively correlated with absolute fecundity, but is negatively correlated with relative fecundity. Duration of the larval period is from four to six years. Metamorphosis usually takes place in the fall. Macrophthalmia are known to enter the ocean over a long period, those descending coastal streams enter salt water in the late fall and early winter, whereas the peak of emigration from inland streams is in the early spring. Duration of its marine parasitic phase appears to be from 20 to 40 months. The small landlocked L. (E.) t. kawiaga n. subsp., found only in the Klamath and Goose Lake drainage systems in southern Oregon and northern California, differs from t. tridentata in body size and various meristic and morphometric characters. Its lacustrine parasitic phase is about 12 months long. L. (E.) lethophaga, the nonparasitic derivative of tridentata, occurs in the Klamath and probably also the Goose Lake drainage system. It is characterized by an extension of the larval phase and by a greatly reduced post-larval period. The presumably extinct L. (E.) minima, a parasitic derivative of tridentata, found formerly only in Miller Lake, Oregon, possessed a number of characters that were concomitants of dwarfism, the distinctive feature of the species. Relationships and evolution among the subgenus Entosphenus were discussed. Distributional records of L. ayresii and L. richardsoni of the subgenus Lampetra in Oregon were given. Evidence indicates that a complex of clinal races, including L. pacifica Vladykov, 1973, may exist in the latter species.

Bose, K S, and R H Sarma. 1975. “Delineation of the Intimate Details of the Backbone Conformation of Pyridine Nucleotide Coenzymes in Aqueous Solution.” Biochemical and Biophysical Research Communications 66 (4) (October 27): 1173–1179. (Download)
Bose, K S, and R H Sarma. 1975. “Delineation of the Intimate Details of the Backbone Conformation of Pyridine Nucleotide Coenzymes in Aqueous Solution.” Biochemical and Biophysical Research Communications 66 (4) (October 27): 1173–1179. (Download)


Vladykov, V. D. (1973). Lampetra pacifica, a New Nonparasitic Species of Lamprey (Petromyzontidae) from Oregon and California. Journal of the Fisheries Research Board of Canada, 30(2), 205–213. doi:10.1139/f73-037

Abstract: A new nonparasitic species of Petromyzontidae, Lampetra pacifica, from streams of Oregon and California is described and illustrated. This species is distinguishable from Lampetra richardsoni, its nearest relative, by fewer myomeres, body proportions, pronounced pigmentation inside the buccal cavity, patterns of pigmentation of the head and tail, and geographical distribution. The description is based on an examination of 233 specimens (43 transformed individuals and 190 ammocoetes)., Cet article, accompagné de photographies, décrit une espèce nouvelle de lamproies non parasites, Lampetra pacifica, trouvées dans les ruisseaux d’Oregon et de Californie. Cette espèce se distingue de Lampetra richardsoni, son congénère le plus rapproché, par les myomères moins nombreux, les proportions du corps, la pigmentation foncée très prononcée de l’infundibulum buccal, la pigmentation restreinte de la tête et de la queue et la répartition géographique. La description est basée sur une étude de 233 spécimens (43 individus transformés et 190 ammocètes).


Hardisty, M. W. (1971). The biology of lampreys. London, New York: Academic Press.


Pletcher, F. T. (1963). The life history and distribution of lampreys in the salmon and certain other rivers in British Columbia, Canada.


A List of Common and Scientific Names of the Better Known Fishes of the United States and Canada. (1948). Transactions of the American Fisheries Society, 75(1), 353–397. doi:10.1577/00028487.1948.10493257


Confederated Tribes of the Umatilla Indian Reservation in Oregon, Columbia River Inter-Tribal Fish Commission, Oregon Cooperative Fishery Research Unit, United States, Bonneville Power Administration, & Environment, F., and Wildlife. (0000 uu). Pacific lamprey research and restoration annual report. Pacific lamprey research and restoration annual report.

Entries from the following sources are already entered:

Claire, C. Pacific lamprey larvae life history, distribution, and habitat utilization in the south fork Clearwater River drainage, Idaho (2003 Thesis)