Sea Lamprey Control Research Articles

Acute Toxicity of the Lampricide 4-Nitro-3-(trifluoromethyl)phenol to the Mussel (Obovaria subrotunda), Its Host (Percina maculata), and a Surrogate Mussel Species (Obovaria olivaria).

The risk of lampricide applications (such as 4-nitro-3-[trifluoromethyl]phenol [TFM]) to nontarget fauna continues to be a concern within the Great Lakes Fishery Commission Sea Lamprey Control Program, especially among imperiled aquatic species-such as native freshwater mussels. The Grand River (Ohio, USA) is routinely treated for larval sea lampreys (Petromyzon marinus), and this river contains populations of the federally threatened mussel Obovaria subrotunda. Given this spatial overlap, information on the sensitivity of O. subrotunda to TFM is needed. Our objectives were to assess the toxicity of TFM to (1) adult Obovaria olivaria (a surrogate for O. subrotunda), (2) glochidial larvae of O. olivaria and O. subrotunda, (3) juveniles of O. olivaria and O. subrotunda, and (4) adult Percina maculata (host for O. subrotunda glochidia). In acute toxicity tests, TFM was not toxic to glochidia and adult mussels at exposure concentrations that exceed typical treatment rates. Although significant dose-response relationships were observed in hosts and juveniles, survival was ≥95% (Percina maculata), ≥93% (O. olivaria), and ≥74% (O. subrotunda) at typical treatment rates. However, the steep slope of these dose-response relationships indicates that an approximately 20% difference in the treatment level can result in nearly an order of magnitude difference in survival. Collectively, these data indicate that routine sea lamprey control operations are unlikely to acutely affect these species or their host. However, given that many mussel species are long-lived (30-100 years), the risks posed by lampricide treatments in the Great Lakes would be further informed by research on the potential long-term effects of lampricides on imperiled species. Environ Toxicol Chem 2024;43:1423-1430. Published 2024. This article is a U.S. Government work and is in the public domain in the USA.

Seasonal differences in larval sea lamprey (Petromyzon marinus) sensitivity to the pesticide TFM

Invasive sea lamprey (Petromyzon marinus) are controlled in the Great Lakes with 4-nitro-3-(trifluoromethyl)phenol (commonly 3-trifluoromethyl-4-nitrophenol or TFM). The proper amount of TFM must be applied during treatments to effectively kill larval sea lamprey while minimizing impacts to non-target species. In this study, bioassay tests were conducted in May, July, and September in a portable test trailer at six larval sea lamprey infested rivers in Michigan to determine potential seasonal changes in sensitivity of larval sea lamprey to TFM. Larvae greater than 60 mm were collected from each stream and exposed for 12 h in TFM-treated stream water using two independent continuous-flow diluter systems. A suite of water chemistries and larval physiological parameters were collected during the tests and modeled as potential predictors of seasonal changes in the sensitivity of larval sea lamprey to TFM. The observed minimum lethal concentrations to larval sea lamprey were 0–40% lower (May), 8% lower–59% higher (July), and 49–117% higher (September) than sea lamprey control personnel treatment prediction charts. Water temperature, liver glycogen content, and time of year were strongly associated with seasonal differences in TFM sensitivity, offering sea lamprey control personnel more exact predictions to limit potential residual lamprey surviving future treatments.

Differences in the transcriptome response in the gills of sea lamprey acutely exposed to 3-trifluoromethyl-4-nitrophenol (TFM), niclosamide or a TFM:niclosamide mixture

Sea lamprey (Petromyzon marinus) control in the Laurentian Great Lakes of North America makes use of two pesticides: 3-trifluoromethyl-4-nitrophenol (TFM) and niclosamide, which are often co-applied. Sea lamprey appear to be vulnerable to these agents resulting from a lack of detoxification responses with evidence suggesting that lampricide mixtures produce a synergistic effect. However, there is a lack of information pertaining to the physiological responses of sea lamprey to niclosamide and TFM:niclosamide mixtures. Here, we characterized the transcriptomic responses of the sea lamprey to TFM, niclosamide, and a TFM:niclosamide (1.5 %) mixture in the gill. Along with a control, larval sea lamprey were exposed to each treatment for 6 h, after which gill tissues were extracted for measuring whole-transcriptome responses using RNA sequencing. Differential gene expression patterns were summarized, which included identifying the broad roles of genes and common expression patterns among the treatments. While niclosamide treatment resulted in no differentially expressed genes, TFM- and mixture-treated fish had several differentially expressed genes that were associated with the cell cycle, DNA damage, metabolism, immune function, and detoxification. However, there was no common differential expression among treatments. For the first time, we characterized the transcriptomic response of sea lamprey to niclosamide and a TFM:niclosamide mixture and identified that these agents impact mRNA transcript abundance of genes associated with the cell cycle and cellular death, and immune function, which are likely mediated through mitochondrial dysregulation. These results may help to inform the production of more targeted and effective lampricides in sea lamprey control efforts.

Transcriptomic impacts and potential routes of detoxification in a lampricide-tolerant teleost exposed to TFM and niclosamide

Sea lamprey (Petromyzon marinus) control in the Laurentian Great Lakes of North America often relies on the application of 3-trifluoromethyl-4-nitrophenol (TFM) and niclosamide mixtures to kill larval sea lamprey. Selectivity of TFM against lampreys appears to be due to differential detoxification ability in these jawless fishes compared to bony fishes, particularly teleosts. However, the proximate mechanisms of tolerance to the TFM and niclosamide mixture and the mechanisms of niclosamide toxicity on its own are poorly understood, especially among non-target fishes. Here, we used RNA sequencing to identify specific mRNA transcripts and functional processes that responded to niclosamide or a TFM:niclosamide mixture in bluegill (Lepomis macrochirus). Bluegill were exposed to niclosamide or TFM:niclosamide mixture, along with a time-matched control group, and gill and liver tissues were sampled at 6, 12, and 24 h. We summarized the whole-transcriptome patterns through gene ontology (GO) term enrichment and through differential expression of detoxification genes. The niclosamide treatment resulted in an upregulation of several transcripts associated with detoxification (cyp, ugt, sult, gst), which may help explain the relatively high detoxification capacity in bluegill. Conversely, the TFM:niclosamide mixture resulted in an enrichment of processes related to arrested cell cycle and growth, and cell death alongside a diverse detoxification gene response. Detoxification of both lampricides likely involves the use of phase I and II biotransformation genes. Our findings strongly suggest that the unusually high tolerance of bluegill to lampricides is due to these animals having an inherently high capacity and flexible detoxification response to such compounds.

Behavioral and reproductive effects of the lampricides TFM and TFM:1% Niclosamide on native freshwater mussels

The lampricides TFM (3-trifluoromethyl-4′-nitrophenol) and Niclosamide (NIC, 2′, 5-dichloro-4′-nitrosalicylanilide) are used to control sea lamprey populations in the Great Lakes and associated tributaries. Niclosamide is often used as an additive to TFM to reduce the amount of TFM required to control sea lamprey. Concern is growing over the risk that lampricide treatments pose to native freshwater mussels residing in streams. Our objectives were to determine the acute toxicity of TFM and TFM:NIC to free glochidia (removed from the marsupial gills), compare the relative toxicity of TFM and TFM:NIC between free glochidia and brooded glochidia (within the marsupial gills), determine if glochidia age influences toxicity, and assess if exposure of gravid mussels to TFM and TFM:NIC alters behavior and reproduction. Three acute toxicity tests (2:TFM, 1:TFM : NIC) were conducted with glochidia and adults of the plain pocketbook mussel (Lampsilis cardium). In tests with glochidia, viability did not differ across TFM and TFM : NIC concentrations that encompassed typical stream treatments. Glochidia age influenced toxicity as glochidia obtained later in the brooding season were less viable than glochidia obtained earlier in the brooding season. Exposure of adults to elevated concentrations of lampricides often resulted in behavioral effects, but rarely affected reproductive endpoints. Because mussels are long-lived (30 to 100 y), even intermittent and short duration exposures may cumulatively affect mussels over their lifetime. The risks posed by lampricide treatments in the Great Lakes would be further informed by research on the sublethal effects of lampricides, particularly effects on non-target organisms such as mussels.

A 90-year record of lake whitefish Coregonus clupeaformis abundances in Michigan waters of the upper Laurentian Great Lakes

Fishery managers throughout the upper Laurentian Great Lakes are currently faced with a two-decade decline in abundance and harvest of lake whitefish Coregonus clupeaformis stocks. We used multivariate auto-regressive state-space (MARSS) models to develop long-term (90-year; 1929–2018) time-series of lake whitefish relative abundance based on commercial catch-per-effort (CPE) data for 13 statistical districts in State of Michigan waters, including 1836 and 1842 Treaty ceded waters, of Lakes Superior, Michigan, and Huron. CPE time-series were used to estimate historical baseline conditions, which were compared to more recent conditions, specifically with reference to select regulatory, environmental, and ecological conditions in each lake and fishing intensity. Population growth rates suggested that lake whitefish stocks responded: (1) negatively to high levels of harvest and expansion of sea lamprey Petromyzon marinus populations during the early-1900s; (2) positively to commercial fishery regulation and sea lamprey control during the late-1950s and early-1960s; and (3) negatively to establishment of dreissenid mussels Dreissena spp. in Lakes Michigan and Huron by 2005 and the recent period of low productivity in all three lakes since the mid- to late-2000s. When placed in a historical context, the most recent (2011–2018) lake whitefish abundances are low, intermediate, and high in 31 %, 46 %, and 23 % of all districts examined. Although environmental and ecological conditions likely drove recent declines, correlation analysis suggested that higher levels of fishing intensity were associated with greater district-specific declines in abundance during the last two decades (1999–2016), a period characterized by lower overall productivity and limited recruitment in most lake whitefish stocks.

Variation in the Transcriptome Response and Detoxification Gene Diversity Drives Pesticide Tolerance in Fishes.

Pesticides are critical for invasive species management but often have negative effects on nontarget native biota. Tolerance to pesticides should have an evolutionary basis, but this is poorly understood. Invasive sea lamprey (Petromyzon marinus) populations in North America have been controlled with a pesticide lethal to them at lower concentrations than native fishes. We addressed how interspecific variation in gene expression and detoxification gene diversity confer differential pesticide sensitivity in two fish species. We exposed sea lamprey and bluegill (Lepomis macrochirus), a tolerant native species, to 3-trifluoromethyl-4-nitrophenol (TFM), a pesticide commonly used in sea lamprey control. We then used whole-transcriptome sequencing of gill and liver to characterize the cellular response in both species. Comparatively, bluegill exhibited a larger number of detoxification genes expressed and a larger number of responsive transcripts overall, which likely contributes to greater tolerance to TFM. Understanding the genetic and physiological basis for pesticide tolerance is crucial for managing invasive species.

Forecasting suppression of invasive sea lamprey in Lake Superior

Abstract Resource managers frequently are tasked with mitigating or reversing adverse effects of invasive species through management policies and actions. In Lake Superior, of the Laurentian Great Lakes, invasive sea lamprey populations are suppressed to protect valuable fish stocks. However, the relationship between choice of long‐term control strategy and the future chance of achieving the suppression target is unclear. Using a 60+ year time series of suppression effort and monitoring data from 50 assessment sites located on Lake Superior tributaries, we developed a Bayesian state‐space model to forecast the probability of suppressing lamprey below the suppression target. With annual application of lampricide (i.e. lamprey‐specific pesticide) at historical mean levels, we forecasted a 15% chance of achieving the Lake Superior sea lamprey suppression target in 2040. Increasing lampricide effort and/or supplementing lampricide control with age‐1 recruitment reduction increased suppression chance. Annual application of the maximum historical lampricide effort resulted in a 50% predicted chance of achieving the target, annual application of the mean historic lampricide effort plus a 40% reduction in recruitment resulted in a 54% chance, and the maximum amount of effort considered (maximum historic lampricide and 60% reduction in recruitment) resulted in a 94% chance. Policy implications. We developed a simulation model from a robust, long‐term monitoring dataset that improves understanding of why long‐term sea lamprey suppression objectives have been difficult to achieve in Lake Superior. Furthermore, the model provides a means to gauge efficacy of sea lamprey control policy and action scenarios based on forecasted chance of achieving the suppression target. Creating processes for iteratively refining our forecasting model with stakeholder and technical‐expert input and integration with a decision analysis framework could strengthen the link between ecological knowledge obtained from long‐term monitoring and invasive sea lamprey management.

Estimation of lake-scale stock-recruitment models for Great Lakes sea lampreys

Understanding recruitment dynamics is an essential part of effective fisheries management, whether the focus is on conservation, harvest policy development, or invasive species control. We developed a model that estimates lake-wide Ricker stock-recruitment relations for invasive sea lampreys (Petromyzon marinus) in each of the five Laurentian Great Lakes to inform future control efforts. We fit adult-to-adult models, taking advantage of a long time series of lake-wide, adult, sea lamprey abundance estimates. We incorporated proportional contributions at age for the stock as well as additional explanatory variables sea lamprey weight, as a surrogate for fecundity, and lampricide quantity applied, as a surrogate for anthropogenic mortality, to explain residual recruitment variability. The best model incorporated equal cohort contributions from the adult stock (that matured 5, 6, and 7 years prior to recruitment), a single productivity parameter (α) common to all five lakes, lake-specific carrying capacity parameters (βj), and coefficients for sea lamprey weight and lampricide quantity applied. The precision of the estimated Ricker parameters compared favorably to those estimated by adult-to-larva models, a promising development in the pursuit of sea lamprey recruitment prediction. The model should be useful to fisheries managers in the Great Lakes wishing to consider various recruitment overfishing strategies in the control of invasive sea lampreys, reaffirming that even models built on a single life stage can inform our understanding of ecological interactions and explorative management scenarios.

Reversible disruptions to energy supply and acid-base balance in larval sea lamprey exposed to the pesticide: Niclosamide (2',5-dichloro-4'-nitrosalicylanilide).

Since the 1960s, chemical control of larval sea lamprey has been achieved using the pesticides 3-trifluoromethyl-4-nitrophenol (TFM) and niclosamide (Bayluscide®). Much more potent, niclosamide is often used as an adjuvant for TFM, and on its own to treat lentic habitats, rivers with high discharge and currents, and for population surveys. Yet, little is known about its mode of action or physiological effects on sea lamprey. Like TFM, niclosamide is thought to impair mitochondrial ATP production by uncoupling oxidative phosphorylation. We therefore tested the hypothesis that niclosamide would result in metabolic perturbations and disturbances to acid-base balance in larval lamprey due to their need to balance ATP supply with ATP demands. When larval sea lamprey were exposed to the nominal 9-h niclosamide LC50 (0.11mg L-1) over 9h, it resulted in significant decreases in brain, phosphocreatine (35 %) and glycogen (50 %), accompanied by a 5-fold increase in lactate. In carcass, there were 25-30 % decreases in glycogen, corresponding increases in pyruvate and lactate, and a pronounced 0.5 unit decrease in intracellular pH. Calculation of the NAD+/NADH ratio in the carcass indicated that neither oxygen delivery nor the flux of reducing equivalents through the mitochondrial electron transport chain were impaired by niclosamide, supporting the hypothesis that niclosamide interferes with mitochondrial ATP production by uncoupling oxidative phosphorylation. Thus, greater reliance on glycogen, characterized by higher rates of glycolysis, temporarily mitigates the corresponding shortfall in ATP supply caused by niclosamide. Notably, all lamprey that survived niclosamide exposure readily restored ATP, phosphocreatine, glycogen and acid-base balance after recovery in niclosamide-free water. This resilience suggests that sea lamprey that survive or escape niclosamide treatment could compromise sea lamprey control efforts by subsequently completing their larval stage and developing into parasitic juvenile sea lamprey that could ultimately threaten Great Lake's fisheries populations.

Setting and tracking suppression targets for sea lampreys in the Great Lakes

In response to invasive species, the course of action taken by management agencies often evolves over a range of options from a do-nothing approach to suppression to complete eradication. As a case study of suppression targets, we explore the history of approaches used by the Great Lakes Fishery Commission in response to the invasion of the Laurentian Great Lakes by sea lampreys (Petromyzon marinus). With the early realization that eradication was not possible using available techniques, focus shifted to suppression of sea lampreys to support fish community objectives for the lakes. As a surrogate for damage to the fishery, a suppression target was defined for the maximum acceptable marking rate, indicated by the average number of sea lamprey wounds observed on every 100 large lake trout (Salvelinus namaycush) surveyed. Historic marking rates were used to delineate time periods of acceptable sea lamprey predation levels as an approximate measure of sea lamprey-induced mortality. A second target, independent of lake trout population status, was based on the average sea lamprey abundance estimated during the specified time periods. These intuitive targets have served as suppression benchmarks for the Sea Lamprey Control Program in the Great Lakes, allowing decision makers to gauge progress towards targets, refine control strategies and prioritize geographic areas for increased control effort. Here we document the development and subsequent changes to targets, summarize the methods used to implement these changes, and provide considerations for the future.

100 years of sea lampreys above Niagara Falls: A reflection on what happened and what we learned

In the one hundred years since sea lampreys (Petromyzon marinus) were discovered in Lake Erie, the species completed its invasion throughout the Great Lakes basin, contributed to the downfall of the commercial fishing industry, and served as a catalyst for the development of the collaborative fishery management regime that exists today. The sea lamprey invasion simultaneously caused wide-spread devastation while giving rise to a collective realization that the health of the Great Lakes would require ongoing cooperation among governments, scientists, and users of the resource. Since its inception, the effort to control sea lampreys in the Great Lakes has been defined by a “shoot for the moon” mentality. The desperation of communities directly harmed by the sea lamprey invasion, coupled with the determination and unyielding commitment to science by those tasked with addressing the problem, led to the formation of the only reported successful aquatic vertebrate invasive species control program at an ecosystem scale.

The relationship between thermal physiology and lampricide sensitivity in larval sea lamprey (Petromyzon marinus)

The sensitivity of larval sea lamprey (Petromyzon marinus) to the lampricide 3-trifluoromethyl-4-nitrophenol (TFM) varies with season, with highest sensitivity in spring and tolerance increasing by 2- to 3-fold in the mid-late summer. Until recently, the physiological basis for these differences was unresolved. Using previously published and unpublished findings, we illustrate how the acute toxicity of TFM (12-h LC50, 12-h LC99.9) changes with season in two populations of larval sea lamprey collected through the spring, summer and fall from Deer Creek and the Au Sable River, Michigan, U.S.A. Our findings reveal that the greater TFM tolerance of larval sea lamprey in the summer is most closely related to increases in water temperature. Although the energy reserves (glycogen, lipid) and body condition of larval sea lamprey may be lower in the spring after overwintering, these physiological indices have little impact on TFM sensitivity. We therefore conclude that water temperature, rather than energy stores or body condition, explains the greater tolerance of sea lamprey to TFM in the summer. We propose that as water temperature increases through the spring and summer, and approaches the thermal optima of larval sea lamprey, their metabolic rate and capacity to detoxify TFM increases, which slows the rate at which TFM accumulates in the body, despite concurrent increases in TFM uptake rate. We therefore recommend that water temperature be considered when planning and executing lampricide applications to mitigate temperature-induced increases in sea lamprey tolerance to TFM that could undermine sea lamprey control efforts in the Great Lakes.

Next-generation lampricides: a three-stage process to develop improved control tools for invasive sea lamprey

Successful integrated management of the invasive predatory sea lamprey (Petromyzon marinus) in the Laurentian Great Lakes of North America is owed largely to the long history of beneficial use of two lampricides: 3-trifluoromethyl-4-nitrophenol (TFM) and 2′,5-dichloro-4′-nitrosalicylanilide (niclosamide). Ensuring continued successful sea lamprey control necessitates consideration of possible next-generation lampricides to supplement or replace current lampricides. This review identifies fifteen hallmarks of success for current lampricides to be used as design criteria in a search for next-generation lampricides. A three-stage research approach is outlined. Targeted research using omics, computer modelling, and high-throughput technology to define molecular mechanisms and high probability molecular targets for sea lamprey selective toxic action is crucial to prioritizing chemical candidates. Targeted delivery or identifying synergists to existing or new lampricides can provide increased efficiency and reduced environmental impact. Ultimate development of next-generation lampricides will rely on traditional toxicity testing methodologies to ensure safety and regulatory compliance.

Targeted lampricide treatment strategies for sea lamprey suppression in the Great Lakes: 2008–2018

The invasive sea lamprey, Petromyzon marinus, continues to be a persistent threat to the Great Lakes fishery. Beginning in 2008, the Great Lakes Fishery Commission’s resources for controlling sea lamprey were increased and directed toward maintaining sea lamprey populations at or below target levels utilizing experimental lampricide treatment strategies. The Commission’s Sea Lamprey Control Program executed five targeted treatment strategies in the Great Lakes from 2008 to 2018. These strategies focused on killing large numbers of sea lamprey larvae prior to metamorphosis. Strategies included consecutive lampricide stream treatments (streams treated twice within three years), comprehensive treatment of specific geographic regions, and increased treatment effort toward the most productive sea lamprey streams. Determining the effect of individual strategies proved challenging and results were mixed; yet, the additional treatment effort expended in the upper Great Lakes appears to have contributed to overall declines in the index of adult sea lamprey abundance. The complete effect this additional treatment effort has on sea lamprey populations may be revealed through future assessments.

A seasonal electric barrier blocks invasive adult sea lamprey (Petromyzon marinus) and reduces production of larvae

Sea lamprey (Petromyzon marinus) control is achieved in the Laurentian Great Lakes by applying lamprey-specific pesticides (lampricides) to habitats containing larval sea lamprey. Lampricide treatments cost less and are more effective in watersheds where dams block adult sea lamprey migration and limit larval distribution relative to watersheds with no barriers to migration. However, dams impound water and can block movement of valued fishes, outcomes that are untenable for some stakeholders. Here, a seasonal and non-physical barrier of pulsed direct electrical current was tested to block adult sea lamprey while also monitoring the movement and mortality of non-target fish species. The electric barrier was operated in the Black Mallard River, a tributary to northern Lake Huron, March through August 2016–2018. The electric field blocked adult sea lamprey; 1056 adult sea lamprey were captured downstream of the electric field and two were captured upstream of the electric barrier over the three-year study. In 2018, larval sea lamprey abundance upstream of the barrier was about 50% less than historical averages, and genetic analysis found that roughly 98% of larvae upstream of the barrier were spawned in years prior to barrier installation. When the barrier was electrified, non-target fish species were blocked, and a small percentage (<3%) were killed. This study demonstrated that a seasonally deployed electric barrier can reduce the abundanceoflarval sea lamprey upstream without impounding water, but effects on the movements and survival of other fish species remain a concern.

An adaptive management implementation framework for evaluating supplemental sea lamprey (Petromyzon marinus) controls in the Laurentian Great Lakes

Invasive sea lamprey (Petromyzon marinus) populations in the Laurentian Great Lakes Basin have been suppressed for over 60 years primarily by migration barriers and lamprey-specific pesticides. Improving control outcomes by supplementing barriers and pesticides with additional control strategies has been a long-standing objective of managers and stakeholders, but progress towards this objective has been limited. We developed an adaptive management implementation framework and applied it to this objective. The framework consists of a set of adaptive management implementation goals (develop effective monitoring practices, develop effective participatory process, and conduct management experiments), a set of aspirational targets hypothesized to be related to Sea Lamprey Control Program adaptive capacity (multi-level political and social organization, creation of safe-to-fail decision making arenas, and effective use of multi-criteria decision analysis), and a feedback loop linking adaptive capacity and progress towards adaptive management implementation goals. Progress towards improving sea lamprey control outcomes by integrating supplemental control strategy into the Sea Lamprey Control Program may be possible through adaptive management implementation.

Prioritizing lampricide treatments in Great Lakes tributaries and lentic areas during 2000–2017

The sea lamprey (Petromyzon marinus) is an invasive species in the Laurentian Great Lakes which requires control to protect valuable fisheries. The Sea Lamprey Control Program (program) uses chemical methods (lampricides) each year to treat infested streams, but limited resources only allow control agents to target 100–125 streams annually. To provide the most cost-effective use of these resources, the program began using the Empiric Stream Treatment Ranking (ESTR) system in 2000 as a decision support tool for selecting streams for treatment. Following a comprehensive review of larval assessment techniques in 2002, the program transitioned from a labor-intensive quantitative technique to a more rapid catch-per-unit-effort based approach. Staff resources were re-allocated to lampricide control, allowing for treatment of more streams annually. Beginning in 2009, stream selection shifted to cost-per-kill of large larvae (>100 mm) and incorporated expert opinion along with targeted treatment strategies. This resulted in a greater number of treatments on an annual basis overall as well as increased treatment frequency for many individual streams. The average adult sea lamprey index decreased by 26% and lake trout wounding rates decreased by 21% across the Great Lakes basin during 2010 to 2017 when compared to 2000 to 2009. Recommended improvements to the stream selection model include: leveraging historic data and expert knowledge to identify streams for treatment, refining the accuracy of the ESTR decision tool, incorporating supplemental and alternative control methods into the treatment selection process, and identifying areas to improve larval assessment techniques that guide and evaluate lampricide control efforts.

A case history of sea lamprey (Petromyzon marinus) abundance and control in Lake Huron: 2000–2019

Beginning with the first lampricide treatments of Lake Huron streams in 1960, applying lampricides and maintaining barriers to migration in Lake Huron tributaries continue to be the primary methods of controlling sea lampreys (Petromyzon marinus). In years leading up to the new millennium, sea lamprey abundance in Lake Huron remained at high levels, yet well below the pre-control adult abundance estimate of 700,000 adults. Two decades later, a variety of sea lamprey control strategies have been developed and employed to further reduce sea lamprey abundance in Lake Huron. In recent years, record low numbers have been achieved and continue to be at or near target levels for sea lamprey abundance. The St. Marys River continues to be one of the largest producers of sea lampreys to Lake Huron and additional actions have been taken to address this challenge. Controlling larval abundance in the St. Marys River along with increasing lampricide treatments throughout the basin and focusing on the largest sea lamprey producing streams have contributed to the decline in sea lamprey abundance. Lake trout (Salvelinus namaycush) restoration efforts along with increased sea lamprey control has facilitated natural reproduction and increase in wild stocks across the basin. The fish community objective for sea lampreys in Lake Huron has not been entirely met and efforts to achieve this objective are ongoing.

Sea lamprey control in the Great Lakes: A Tribal/First Nations Representative’s perspective

Sea lamprey control has been a dominant feature in the Great Lakes since the Great Lakes Fishery Commission (GLFC) formation in 1955. Review and recommendations on the sea lamprey control program are undertaken by a Sea Lamprey International Symposium (SLIS) held every twenty years beginning in 1979. In the forty-year history of the SLIS, this is the first paper on Indigenous perspectives in the published outputs and is an important inaugural step for the SLIS. However, one singular paper does not represent the viewpoints of the many independent Indigenous communities of the Great Lakes area. Willingness to understand the Indigenous perspective is the first step toward trust responsibility obligations and consultation with Tribes in the U.S. and engagement with First Nations in Canada. Indigenous peoples’ belief systems can include kinship ties between human and nature. In turn, this dictates respectful relationships toward all life forms. As such sea lamprey (Petromyzon marinus) can be considered a life form to merit respect which can be incongruent with contemporary sea lamprey control strategies. Perhaps it is time to consider future reviews of sea lamprey control within an Indigenous context and knowledge framework to assist in an equitable and sustainable future for the Great Lakes.