Larval Pacific Lamprey Research Articles

Upper temperature limit of larval Pacific lamprey Entosphenus tridentatus: implications for conservation in a warming climate

Climate models suggest that by 2100, maximum temperatures where many larval Pacific lamprey, Entosphenus tridentatus, rear now may approach 27–31 °C. Little information exists on whether larval Pacific lamprey can tolerate these temperatures. We used acclimated chronic exposure (ACE) and direct acute exposure (DAE) experiments to determine the water temperature that is lethal to larval Pacific lamprey and whether sublethal water temperatures influence larval burrowing behavior. After 30 days in ACE experiments, all larvae survived in temperatures averaging ≤ 27.7 °C, no larvae survived in temperatures averaging ≥ 30.7 °C and the ultimate upper incipient lethal temperature (UILT) was estimated to be 29.2 °C. After seven days in DAE experiments, all larvae survived in 27.1 °C, only larvae acclimated to 23.3 °C survived in 29.1 °C, and no larvae survived in temperatures ≥ 30.6 °C. Using a time to death analysis, estimates of the UILTs ranged from 27.5 to 30.2 °C and the ultimate UILT was estimated to be > 28.3 °C. Using a percent mortality analysis, estimates of the ultimate UILT were not definitive but indicated it may be > 30.2 °C. To burrow, larvae reared for 30 days at temperatures averaging 26.9–27.7 °C exhibited more total time, active time, and stops than those reared for 30 days at temperatures averaging 22.3–23.9 °C. Our findings suggest that larval Pacific lamprey may be resilient to the most likely temperature increase scenarios predicted by climate models. However, they may be vulnerable to the high-temperature increase scenarios and, relatively high but sublethal temperatures may impact the behavior, and ultimately survival, of larval Pacific lamprey.

Rapid development of larval Pacific lamprey Entosphenus tridentatus in southern populations provides adaptive benefits for uncertain flow regimes

Rapid development of larval Pacific lamprey Entosphenus tridentatus in southern populations provides adaptive benefits for uncertain flow regimes

Whose Kids Did You Eat? Genetic Identification of Species and Parents of Larval Lampreys in Fish Predator Guts

AbstractThe Pacific Lamprey Entosphenus tridentatus is an important species both ecologically and culturally, but their population numbers and range have declined severely in the past several decades in the Columbia Basin. In freshwater ecosystems, larval lampreys are candidate prey species for many fish predators, but little is known regarding the magnitude of predation they currently experience. Predation on larval Pacific Lampreys may be substantially underestimated by morphological gut content analysis because their soft bodies are quickly digested and leave no hard evidence, such as bones and scales. We conducted an experimental predation study and analyzed larval Pacific Lampreys in the gut contents of predators’ digestive tracts via both morphological and molecular methods. Whereas most consumed larval lampreys (67–100%) were morphologically unidentifiable within two nights, genetic species identification rates using four single nucleotide polymorphisms from stomachs were high (83%). The single nucleotide polymorphisms optimized for parentage in Pacific Lamprey also successfully identified the parents of four out of five Pacific Lampreys with complete genotypes. When a genetic baseline of candidate parents is available, this molecular technique using parentage‐based tagging offers a novel method for determining precise characteristics of predation behavior in field studies, including the ages and natal origins of larvae being consumed.

Using a Customized Portable Deepwater Electrofisher to Assess Larval Lamprey Populations in Irrigation Canals

AbstractWater diversions are very common in agricultural landscapes, providing water to irrigate a diverse range of crops. Larval Pacific Lamprey Entosphenus tridentatus are vulnerable to entrainment during the irrigation withdrawals and can be exposed to desiccation or predation during dewatering at the end of the irrigation season. A customized portable deepwater electrofishing system was deployed to determine larval lamprey densities at two large scaled irrigation diversion canals located on the Yakima River in eastern Washington. The system components can be easily transported to a remote survey site due the number of components and minimal total weight. The surveys were conducted in the fall during the dewatering period in 2015 and 2017, and the densities for larval lampreys ranged from 0.8 to 8.8 fish/m2 at the Sunnyside Canal and 4.2 fish/m2 at the Wapato Canal (2015 only). Our results indicate that the use of the deepwater electroshocking system was effective at determining larval lamprey presence and densities in hard‐to‐sample irrigation canals.

Evaluation of effluent waste water from salmonid culture as a potential food and water supply for culturing larval Pacific lamprey Entosphenus tridentatus

The Pacific lamprey is an iconic native fish of great importance to the ecosystem and indigenous cultures in the U.S. Pacific Northwest. Pacific lamprey populations have declined in abundance from historic levels, and conservation aquaculture has been proposed as a technique to restore these populations. The present research focused on expanding the culture methods for larval lamprey. The larvae filter feed and cohabitate with juvenile salmonids in the wild, therefore the effluent water from rearing salmonids may be a viable source of water and food for culturing lamprey. This approach could be a sustainable method for raising lamprey at existing salmonid hatcheries. A nine week trial investigated the effects of rearing in effluent water from salmonid culture on the growth, survival, proximate composition, and fatty acid profile of larval lamprey. This trial also explored the potential of this rearing strategy to improve the water quality by removing nutrients from the effluent. The trial included three treatments testing the use of the effluent from steelhead trout (Oncorhynchus mykiss), a conventional lamprey diet (control diet), or both combined as a means for rearing lamprey. A fourth treatment where lamprey were excluded served as a water quality control to test the effect of lamprey presence on effluent quality. Lamprey survival was not affected by treatment. Lamprey reared solely on the effluent waste matched the survival and growth of fish fed the conventional diet. Lamprey fed the combination treatment grew faster than the conventional diet fed fish. Whole body lipid levels were elevated in lamprey from the combination treatment relative to the conventional diet fed lamprey. Crude protein in the whole bodies of effluent fed lamprey was low compared to fish from either of the treatments where the conventional diet was fed. Lamprey offered the effluent nutrients were high in saturated fats relative to the control fed fish, which reflected the lipid profile of this diet. However, lamprey from the combination treatment were lower in long chain polyunsaturated fatty acids relative to the control or the effluent treatment lamprey. There was no measureable improvement in water quality due to the presence of lamprey, though lamprey were able to sequester approximately 1.3% of the effluent dry matter as lamprey biomass. Overall, it appears the larval stage of lamprey can be effectively reared on salmonid effluent, and this method provides superior growth when used in combination with a conventional lamprey diet.

Comparison of stable isotope ratios in larval Pacific lamprey tissues and their nutritional sources when reared on a mixed diet

Aquaculture of larval lampreys (ammocoetes), to help recover and maintain threatened populations, is increasingly viewed as an important management tool. Ammocoetes are filter-feeders that remain burrowed in fine grain substrates for the majority of their lives, making it difficult to determine how well diets are being supplied and in what proportions various foods are utilized. Stable isotope analysis offers the ability to distinguish which foods are being incorporated into animal biomass. While muscle tissue is most commonly used for stable isotope analysis, other tissues could also be collected to avoid lethal sampling (e.g., blood) or to provide insight into condition (e.g., liver). Muscle, red blood cells (RBC), plasma, liver, and notochord were collected from Pacific lamprey (Entosphenus tridentatus) larvae raised in the laboratory on a varied diet; δ2H, δ13C, δ15N, δ18O and δ34S were measured in food sources, animal tissues, and lipid-extracted muscle. Tissues were generally isotopically similar to one another except in a few notable cases. The δ2H of notochord was more enriched than any other tissue and the δ15N and δ34S of RBC were elevated over muscle. The δ18O of all tissues was predicted from source water, allowing this isotope ratio to provide information about regional origin of lampreys. A stable isotope mixing model found that larval biomass, even when ammocoetes were supplied with various diet items, was still primarily dependent on aquatic sediments. Therefore, the burrowing medium supplied to ammocoetes in aquaculture facilities is likely to have a strong impact on growth rate and may benefit from the inclusion of more labile organic material or feed that specifically enriches the aquatic sediment.

Pacific lamprey recolonization of a Pacific Northwest river following dam removal

AbstractRecolonization of Pacific lampreys Entosphenus tridentatus into historically used freshwater habitats in the United States Pacific Northwest was evaluated in the White Salmon River basin after removal of Condit Dam. Pacific lamprey population declines are of concern, and passage barrier removal is often recommended for conservation. Condit Dam on the White Salmon River in Washington was a complete barrier to fish migrating upstream for nearly 100 years, was breached in 2011, and was removed by 2012. Distribution of larval Pacific lampreys was estimated before and after removal of Condit Dam using either backpack or deepwater electrofishing. Larval detection probabilities were calculated for the basin, and sample efforts were refined to ensure at least 80% confidence that larvae were absent when not detected. Pacific lampreys were not present upstream of Condit Dam before it was removed but were present in areas downstream of the dam. After dam removal, Pacific lamprey larvae were collected upstream of the former dam site from four reaches of the mainstem White Salmon River, indicating a recent recolonization event. Pacific lampreys were absent from the river mouth area before the dam was removed but were found in newly created habitat at the mouth after dam removal. Pacific lampreys naturally recolonized the White Salmon River basin within a few years after dam removal. Removing dams and providing passage opportunity can allow Pacific lampreys to distribute into vacant areas and may help reverse population declines.

Low Mortality of Larval Lampreys from Electrofishing, Suction-pumping, Anesthesia, and Handling

Abstract Native lamprey populations are declining worldwide. In the Pacific Northwest focus on conservation and management of these ecologically and culturally important species has increased. Concern has emerged regarding the effects of sampling and handling of lamprey, with little to no attention given to the larval lifestage. We monitored the survival of larval Pacific Lamprey Entosphenus tridentatus and Lampetra spp. after backpack electrofishing, deepwater electrofishing and suction-pumping, anesthesia, and handling. We performed survival trials on wild-caught lamprey (n = 15 larvae in each trial) collected from the Clackamas River drainage in Oregon, USA, coupled with control group trials from lamprey sourced from a hatchery (n = 10 larvae). Short-term (96 h) survival was >98% with only one observed mortality. Delayed mortality (1 wk) was observed for four individuals that had fungus; two of those were positive for the bacteria Aeromonas hyrdrophila. We recorded blood hematocrit as a secondary measure of stress. The baseline, nonstressed larvae hematocrit levels did not differ from those of fish that had undergone stress through electrofishing, suction-pumping, and handling without anesthesia. Electrofishing, suction-pumping, and anesthesia showed no short-term negative effects on larval lamprey although potential long-term effects remain unstudied. These techniques appear to provide efficient and relatively safe methods for collecting and surveying larval lamprey.

Estimation of occupancy, density, and abundance of larval lampreys in tributary river mouths upstream of dams on the Columbia River, Washington and Oregon

We estimated occupancy, density, and abundance of larval Pacific lamprey (Entosphenus tridentatus) and Lampetra spp. in tributary river mouths to impounded portions of the Columbia River, Washington and Oregon, using count data from deepwater electrofishing. Count data were analyzed by Bayesian methods using zero-inflated N-mixture models modified to include our experimentally derived estimate of capture probability of 0.70 (95% CI: 0.63–0.77). Lampetra spp. were only collected in river mouths in Bonneville Reservoir, while Pacific lamprey were also captured from river mouths in The Dalles and John Day reservoirs. In occupied river mouths, mean densities were commonly 0.2–0.3·m−2, but ranged from 0.18 to 1.72·m−2for Pacific lamprey and 0.24 to 1.72·m−2for Lampetra spp. Although there was spatial overlap, estimated density peaked in the Klickitat River mouth (556 600 larvae) for Pacific lamprey and in the Wind River mouth (544 800 larvae) for Lampetra spp. Our study demonstrates considerable larval rearing in river mouths to impounded portions of the Columbia River; however, information on survival is needed to evaluate the contribution of this production to population growth and conservation.

Sample Sizes Needed to Describe Length-Frequency of Small-Bodied Fishes: An Example Using Larval Pacific Lamprey

Abstract The ability to describe the length distribution of a fish population requires sampling an adequate number of individuals, but collecting more fish than needed is inefficient. While fisheries managers have assessed sample size requirements for many sport fishes, these requirements are not routinely described for small-bodied fishes (i.e., maximum length ≤200 mm), particularly larval lampreys. To improve the efficiency of data collection for these fishes, we used resampling analyses to asses sample size requirements for accurately describing length distributions of larval (freshwater-dwelling) Pacific lamprey Entosphenus tridentatus, an anadromous fish native to western North America (total length 60–156 mm). We found that the highest increases in accuracy occurred with sample sizes <50, and that we needed sample sizes of 40 to 130 to describe length frequency with 95% confidence, depending on length interval used for performing length-frequency analyses. From these results, we recommend collecting 100 individuals if using 5-mm length intervals to examine length frequency of larval lamprey. These findings can also be used to estimate the relative accuracy of sample sizes in existing assessments and develop and refine monitoring programs for larval lampreys and other small-bodied fishes.

Feeding and Growth of Larval Pacific Lamprey Reared in Captivity

AbstractPacific Lampreys Entosphenus tridentatus are declining in the Columbia River basin as well as in much of their broader range. To mitigate for reductions in abundance, strategies such as hatchery propagation and captive rearing of lamprey larvae are currently being considered. We conducted a series of experiments using captive larval Pacific Lampreys at Eagle Creek National Fish Hatchery to investigate the effect of different food types and different food concentrations on the growth of larvae. In our first experiment, we evaluated the growth of larvae (TL range, 59–145 mm) given four different food types (algae, leaves, yeast–larval fish food, and salmon carcass analogs) and a control group that was not fed. Assimilation of food types was evaluated by tracking unique stable isotope signatures of δ13C and δ15N within larval tissues. Results from experiment 1 indicated that lampreys fed a diet of salmon carcass analog or algae had positive growth (up to 0.16 mm/d and 42% proportional change in length) over approximately 6 months. Isotopic analyses of larval tissues showed unique signatures that matched those of their specific food treatment. Based on the results of experiment 1, we conducted a second experiment to evaluate the growth of larvae fed four different quantities of salmon carcass analog. Results from this experiment indicated larval growth rate increased with increasing rations of food, but positive growth was observed in all feeding treatments. The highest dose of salmon carcass analog resulted in the highest growth (up to 0.15 mm/d and 36% proportional change in length) over 6 months. We successfully reared larval Pacific Lampreys in captivity with minimal mortality and positive growth, which highlights the potential to use captive rearing and propagation as a conservation tool for this ecologically and culturally important species.

Evaluation of Methods to Measure Condition in Pacific Northwest Larval Lampreys

Pacific lamprey (Entosphenus tridentatus) populations are declining and western brook lamprey (Lampetra richardsoni) status is unknown in the Pacific Northwest. Accurate measures of fish condition are a basic requirement to monitor health and status of fish populations. Fulton's condition factor has traditionally been used to assess condition of larval lamprey but alternative field-based and laboratory-based measures have not been assessed. We compared condition factor, body density, and lipid content of sympatric larval Pacific lamprey and western brook lamprey in 2010 and 2011 from two rivers of the Pacific Northwest. Condition factor was higher for Pacific lamprey than it was for western brook lamprey. All measures were variable and correlations among condition indices were weak. Body density and lipid content were higher in western brook lamprey in one year suggesting the possibility of increased energy requirements of metamorphosis to a nontrophic adult stage. The body density technique was onerous and likely has little field-based practicality. Body density and lipid content had a negative relationship as increased lipids leads to a more buoyant and less dense fish. Condition factor did not appear to be a good predictor of lipid content in our study and a suite of complex factors, including lipid dynamics prior to metamorphosis and nutritional resources, may underlie these results. This study provides one of the few empirical datasets on sympatric lampreys with different life history strategies.

Development of diets for the intensive culture of Pacific lamprey

The Pacific lamprey Entosphenus tridentatus is an ancestral species of critical importance to the ecosystem and indigenous cultures in the Pacific Northwest. Conservation aquaculture has been proposed as a potential technique to restore Pacific lamprey populations. Intensive culture methods and diets for this species have not been developed. A sixteen week feeding trial tested the effects of seven diet treatments on the survival, growth, fatty acid profile and whole body lipid content of Pacific lamprey ammocoetes. Dietary treatments were: active dry yeast, yeast plus fish oil emulsion, micro-algae, micro-algae plus fish oil emulsion, yeast with micro-algae, yeast with micro-algae plus fish oil emulsion and yeast with larval fish diet. Each diet was offered to five replicate tanks stocked with 20 ammocoetes that were 51 days post hatch. Survival during the trial was not affected by diet. The greatest length and weight increases were in fish fed diets containing yeast. Growth decreased as the amount of algae in the diet was increased. Lipid retention was significantly higher in fish fed yeast with larval fish diet relative to the other treatments. Feed conversion ratio was lowest in fish fed diets containing yeast. Whole body fatty acid profiles tended to reflect the fatty acid profile of the diet. Percentages of 20:5n-3 and 22:6n-3 were significantly higher in fish fed diets containing fish oil emulsion. Overall, yeast with larval fish diet provided the best growth performance in larval Pacific lamprey.

Reconnaissance of contaminants in larval Pacific lamprey (Entosphenus tridentatus) tissues and habitats in the Columbia River Basin, Oregon and Washington, USA

Pacific lampreys (Entosphenus tridentatus) have resided in the Columbia River Basin for millennia and have great ecological and cultural importance. The role of habitat contamination in the recent decline of the species has rarely been studied and was the main objective of this effort. A wide range of contaminants (115 analytes) was measured in sediments and tissues at 27 sites across a large geographic area of diverse land use. This is the largest dataset of contaminants in habitats and tissues of Pacific lamprey in North America and the first study to compare contaminant bioburden during the larval life stage and the anadromous, adult portion of the life cycle. Bioaccumulation of pesticides, flame retardants, and mercury was observed at many sites. Based on available data, contaminants are accumulating in larval Pacific lamprey at levels that are likely detrimental to organism health and may be contributing to the decline of the species.

Role of large‐ and fine‐scale variables in predicting catch rates of larval Pacific lamprey in the Willamette Basin, Oregon

AbstractPacific lamprey Entosphenus tridentatus is an anadromous fish native to the Pacific Northwest of the USA. That has declined substantially over the last 40 years. Effective conservation of this species will require an understanding of the habitat requirements for each life history stage. Because its life cycle contains extended freshwater rearing (3–8 years), the larval stage may be a critical factor limiting abundance of Pacific lamprey. The objective of our study was to estimate the influence of barriers and habitat characteristics on the catch‐per‐unit‐effort (CPUE) of larval Pacific lamprey in the Willamette River Basin, Oregon, USA. We sampled lampreys at multiple locations in wadeable streams throughout the basin in 2011–13 and used an information theoretic approach to examine the relative influence of fine‐ and large‐scale predictors of CPUE. Pacific lamprey was observed across the basin, but its relative abundance appeared to be limited by the presence of natural and artificial barriers in some sub‐basins. Lower velocity habitats such as off‐channel areas and pools contained higher densities of larval lamprey; mean Pacific lamprey CPUE in off‐channel habitats was 4 and 32 times greater than in pools and riffles respectively. Restoration and conservation strategies that improve fish passage, enhance natural hydrologic and depositional processes and increase habitat heterogeneity will likely benefit larval Pacific lamprey.

Occupancy and Detection of Larval Pacific Lampreys and Lampetra spp. in a Large River: the Lower Willamette River

AbstractPacific 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.

Identification of putative migratory pheromones from Pacific lamprey (Lampetra tridentata)

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.

Swimming Performance of Larval Pacific Lamprey (Lampetra tridentata)

Abstract Laboratory experiments were conducted to measure the prolonged-sustained and burst swimming speeds of wild larval (ammocoete) Pacific lamprey (Lampetra tridentate). Prolonged-sustained speeds were measured using an annular variable speed swimming chamber and burst speeds were determined using a swimming raceway and digital video analysis. During prolonged-sustained swimming experiments, the mean length of time lamprey (72 – 143 mm TL) were able to swim in the chamber ranged from 43.0 min when exposed to a velocity of 10 cm/s, to 0.4 min when exposed to 50 cm/s. The burst swimming speeds of lamprey tended to increase as length increased from 107 to 150 mm TL, and ranged from 33.3 to 75.0 cm/s. Our estimates of the overall swimming performance of this life-stage are the first reported for this species, and can provide important information when developing approach velocities and infrastructure to improve lamprey passage while minimizing entrainment loss.

Detection and Longevity of Uncured and Cured Visible Implant Elastomer Tags in Larval Pacific Lampreys

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.

Detection of Uncured Visible Implant Elastomer Tags in Larval Pacific Lampreys

AbstractLampreys 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.