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Ecosystem managers confronted with newly invasive species may respond with a program of suppression or eradication. Suppression of an invasive species refers to management of a species such that its effect on other biota in the local ecosystem is acceptable. Eradication is the removal of all individuals of a species from a defined region. We examine the cost and benefit trade-offs between suppression and eradication of Laurentian Great Lakes sea lampreys (Petromyzon marinus) based on discussions at the 3rd Sea Lamprey International Symposium (held in 2019). Substantial effort has been expended annually since the 1960s to suppress sea lampreys in the Great Lakes basin. Choosing between suppression and eradication is a value judgement, ideally made jointly by scientists, decision-makers, stakeholders, and society. Successful large-scale eradications have been limited to a small number of cases for which the cost to human society justified and supported the long-term commitment necessary for success. The greatest challenge to successful eradication of sea lampreys from the Great Lakes may be a suitable social, political, legal, and institutional environment. Preparations could be made now for a transition in which public pushback on current control methods (pesticide applications and barriers to fish passage) leads to more extensive use of an alternative control method, such as genetic control.

Eradication has been achieved for many vertebrate pest control programs, primarily on small, isolated islands, but has never been considered a practical goal for invasive sea lampreys in the Laurentian Great Lakes. Our objective was to examine evidence relevant to the feasibility of setting eradication as a management goal for Great Lakes sea lampreys. Bomford and O'Brien (1995) listed six conditions for successful eradication of a vertebrate pest; here we examine evidence that these conditions are likely to be met for Great Lakes sea lampreys, with a focus on the first condition: that removal of the pest through control can exceed their rate of replenishment. We analyzed two data sets – one empirical and one synthetic – to estimate stock-recruitment relationships and calculate the exploitation rate necessary for extinction. The empirical data set included the effect of existing lampricide control and suggested an exploitation rate of 59%, in addition to lampricide control, would be sufficient for eventual eradication. The synthetic data set, derived from a simulation of stream-level recruitment dynamics in the absence of lampricide control, suggested that an overall exploitation rate of 90% would be sufficient. We suggest that both of these targets could be achieved. Meeting the other conditions will depend on the scale of the eradication effort, and on development of an exploitation strategy, such as genetic biocontrol, that can target sea lampreys in presently invulnerable habitats. Overall, we concluded that eradication of sea lampreys from the Great Lakes should not be dismissed as a prospective goal.

From 2000 to 2019, sea lamprey control in Lake Erie focused primarily on deploying lampricides and completing important barrier and dam renovation projects in tributaries including the Big Creek barrier, and Harpersfield and Dunnville dams. The number of Lake Erie stream treatments doubled during 2000–2019 compared to 1986–1999 due to changes in larval assessment and stream selection protocols. Despite increased lampricide use and few infested tributaries relative to other Great Lakes, achieving program targets for Lake Erie has been challenging, but progress has been made. The St. Clair River is a potential significant source of sea lampreys to Lake Erie harboring an estimated 920,000 larvae; however, to date, no lampricide treatments have occurred. In 1986, sea lamprey control began in Lake Erie primarily to restore lake trout. Prior to control efforts, sea lamprey induced mortality on lake trout was too high to allow the establishment of adult lake trout stocks necessary to achieve fishery program goals. Sea lamprey marks on adult lake trout declined dramatically in Lake Erie following sea lamprey control. State and provincial agencies have prioritized stocking the Seneca strain of lake trout, thought to be more resistant to sea lamprey attacks. This change in stocking strategy, coupled with more aggressive sea lamprey control, has contributed to increasing adult lake trout survival. Protecting species at risk in Lake Erie adds to the challenges faced by the sea lamprey control program, but productive collaboration has proven an effective strategy in dealing with the increasing complexity of sea lamprey control.

Barriers and pesticides have been used in streams to control sea lamprey in the Laurentian Great Lakes for nearly 70 years. Considerable effort has been spent to develop additional control measures, but much less effort has gone toward identifying how or where additional control measures might be cost-effectively integrated into the sea lamprey control program. We use a management strategy evaluation model in Lake Michigan to identify the stream types that would be most suitable for deploying traps to remove adults prior to spawning and estimate the likely impact on adult sea lamprey abundance in subsequent years under several trapping scenarios relative to status quo abundance. The greatest reduction in lake-wide adult sea lamprey abundance predicted by the model resulted when removing adult sea lampreys from streams that are difficult for control program personnel to treat with lampricide because lampricide applications would be required less frequently. Additionally, targeting streams which experience regular sea lamprey recruitment and streams with low adult sea lamprey density should result in reduced lake-wide abundance if trapping costs are relatively low or removal is high. Our results provide direction on where to trap and why, and indicate that trapping may be a valuable part of an integrated sea lamprey control approach advancing the goals of the Great Lakes Fishery Commission.

Sea lampreys attack fish, killing some and leaving marks on others. Great Lakes fishery managers rely on observed marking rates to assess the success of the sea lamprey control program and estimate sea lamprey-induced mortality of lake trout. Because marking rates are only observed on survivors of sea lamprey attacks, they may not provide a reliable index of actual attack or mortality rates. To investigate the effect of survivor bias, we developed a simulation model representing a single season (June–December) of sea lamprey attacks. Simulated attack rates varied with month and lake trout size; simulated pierce and lethality rates varied with month alone. Surveyed marking rates were represented by simulated survivors in October; true rates were calculated from all simulated lake trout (dead and alive) in December. Simulation results were subsetted to include only those within the range of marking rates actually observed in the Great Lakes. Type A (piercing) marking rates were a good index of the sea lamprey attack rate and the sea lamprey-induced mortality rate if annual lethality rates were relatively constant. Type B (non-piercing) marking rates were a good index of the sea lamprey attack rate and the sea lamprey-induced mortality rate if annual pierce rates were relatively constant. Due to the uncertainty surrounding the pierce and lethality rates, we recommend that sea lamprey abundance information be incorporated in existing lake trout statistical catch-at-age models via a functional response component relating sea lamprey feeding to lake trout abundance, if possible.

The lampricides 3-trifluoromethyl-4-nitrophemol (TFM) and niclosamide have been used for over 60 years to control the invasive sea lamprey (Petromyzon marinus) population in the Laurentian Great Lakes. In this review, we summarize these findings in the context of the mode of action of both lampricides, with a focus on: (1) the physiology of uptake, bodily distribution and mode of action, detoxification, and excretion of lampricides in lamprey and non-target fishes, (2) the development of an Adverse Outcome Pathway for TFM and niclosamide, and (3) the identification of novel avenues for future research that can be further explored to ensure continuous suppression of the sea lamprey population in the Great Lakes. We explored how research on the mode of action of lampricides has provided novel insights into the gill microenvironment and how this impacts lampricide toxicity; described new information on mitochondria and tissue physiology; and discussed how the activity of enzymes that are involved in detoxification pathways impacts the response of fishes to xenobiotics. Considering the information that has been generated over the years on sea lamprey and bony fish physiology from studying the mode of action of lampricides, here we propose an Adverse Outcome Pathway for TFM and niclosamide and identify novel avenues for research on the short and long-term effects of lampricide applications, either alone or in combination. Lastly, we discuss how the differences in physiology between sea lampreys and non-target fishes can be further exploited to ensure continuous suppression of the sea lamprey population in the Great Lakes.

Sea lampreys (Petromyzon marinus) invaded the Great Lakes in the early twentieth century and caused considerable economic and ecological harm. People who fished the Great Lakes suffered crippling losses and successfully lobbied elected officials in Canada and the United States to create a sea lamprey control program which the Great Lakes Fishery Commission implements under the 1954 Convention on Great Lakes Fisheries. The control program relies on two primary methods: chemical lampricides and physical barriers. Sea lamprey control has been a tremendous success; although the urgency to act is apparent to certain publics and although control methods are deemed by professionals to be safe and effective, continued public advocacy for and acceptance of the control program is not ensured. Many people in the control program are concerned that the urgency to act is not commensurate with the risk sea lampreys continue to pose and that societal acceptance of the primary control methods could wane. This commentary reflects on issues of “shifting baselines” (changes in perceived risk) and the “social license to operate” (trust in authorities to make responsible decisions regarding current and planned control methods) and suggests a course to better understand these issues. Improved understanding of these issues will inform communication efforts for all involved in the control program. Moreover, the case examined here is potentially relevant and informative for other environmentally related actions where there may be erosion of the social license.

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.

Lake sturgeon, a species of conservation concern, can be affected by sea lamprey control activities in the Great Lakes basin. Specifically, age-0 lake sturgeon are sensitive to the pesticides used to kill larval stage sea lampreys; and, as tributary spawners, barriers that restrict access to habitat for adult sea lampreys can also restrict access to spawning lake sturgeon habitat. Conversely, lake sturgeon are also potentially prey for juvenile sea lampreys, so they benefit from control measures that reduce sea lamprey abundance. Over the past 20 years research has defined conditions under which treatments to control sea lampreys, such as high tributary alkalinity levels, are of highest risk for age-0 lake sturgeon mortality. Adult lake sturgeon are likely to survive a sea lamprey attack, and adult wounding rates vary through time and space across the Great Lakes basin and in Lake Champlain. Juvenile lake sturgeon are at higher risk of mortality from a sea lamprey attack, yet rarely display wounds. There are mitigation measures, including treating tributaries later in the year, capturing and holding age-0 lake sturgeon prior to treatment in high-risk tributaries, maximizing the time between treatments, and providing passage for spawning lake sturgeon above sea lamprey barriers that can minimize risks to lake sturgeon populations. As such, we believe that there remains room for both a robust sea lamprey control program moving forward in concert with lake sturgeon rehabilitation across the Great Lakes basin.

With carbon dioxide (CO2) levels rising dramatically, climate change threatens marine environments. Due to increasing CO2 concentrations in the ocean, pH levels are expected to drop by 0.4 units by the end of the century. There is an urgent need to understand the impact of ocean acidification on chemical-ecological processes. To date, the extent and mechanisms by which the decreasing ocean pH influences chemical communication are unclear. Combining behaviour assays with computational chemistry, we explore the function of the predator related cue 2-phenylethylamine (PEA) for hermit crabs (Pagurus bernhardus) in current and end-of-the-century oceanic pH. Living in intertidal environments, hermit crabs face large pH fluctuations in their current habitat in addition to climate-change related ocean acidification. We demonstrate that the dietary predator cue PEA for mammals and sea lampreys is an attractant for hermit crabs, with the potency of the cue increasing with decreasing pH levels. In order to explain this increased potency, we assess changes to PEA’s conformational and charge-related properties as one potential mechanistic pathway. Using quantum chemical calculations validated by NMR spectroscopy, we characterise the different protonation states of PEA in water. We show how protonation of PEA could affect receptor-ligand binding, using a possible model receptor for PEA (human TAAR1). Investigating potential mechanisms of pH-dependent effects on olfactory perception of PEA and the respective behavioural response, our study advances the understanding of how ocean acidification interferes with the sense of smell and thereby might impact essential ecological interactions in marine ecosystems.

We used high-performance liquid chromatography (HPLC) methods to quantify aspartate, GABA, and glutamine levels in the spinal cord of larval sea lampreys following a complete spinal cord injury. Mature larval sea lampreys recover spontaneously from a complete spinal cord transection and the changes in neurotransmitter systems after spinal cord injury might be related to their amazing regenerative capabilities. The data presented here show the concentration of the aminoacidergic neurotransmitters GABA (and its precursor glutamine) and aspartate in the spinal cord of control (non-injured) and 2-, 4-, and 10-week post-lesion animals. Statistical analyses showed that GABA and aspartate levels significantly increase in the spinal cord four weeks after a complete spinal cord injury and that glutamine levels decrease 10 weeks after injury as compared to controls. These data might be of interest to those studying the role of neurotransmitters and neuromodulators in recovery from spinal cord injury in vertebrates.

Locomotion occurs sporadically and needs to be started, maintained, and stopped. The neural substrate underlying the activation of locomotion is partly known, but little is known about mechanisms involved in termination of locomotion. Recently, reticulospinal neurons (stop cells) were found to play a crucial role in stopping locomotion in the lamprey: their activation halts ongoing locomotion and their inactivation slows down the termination process. Intracellular recordings of these cells revealed a distinct activity pattern, with a burst of action potentials at the beginning of a locomotor bout and one at the end (termination burst). The termination burst was shown to be time linked to the end of locomotion, but the mechanisms by which it is triggered have remained unknown. We studied this in larval sea lampreys (Petromyzon marinus; the sex of the animals was not taken into account). We found that the mesencephalic locomotor region (MLR), which is known to initiate and control locomotion, stops ongoing locomotion by providing synaptic inputs that trigger the termination burst in stop cells. When locomotion is elicited by MLR stimulation, a second MLR stimulation stops the locomotor bout if it is of lower intensity than the initial stimulation. This occurs for MLR-induced, sensory-evoked, and spontaneous locomotion. Furthermore, we show that glutamatergic and, most likely, monosynaptic projections from the MLR activate stop cells during locomotion. Therefore, activation of the MLR not only initiates locomotion, but can also control the end of a locomotor bout. These results provide new insights onto the neural mechanisms responsible for stopping locomotion.SIGNIFICANCE STATEMENTThe mesencephalic locomotor region (MLR) is a brainstem region well known to initiate and control locomotion. Since its discovery in cats in the 1960s, the MLR has been identified in all vertebrate species tested from lampreys to humans. We now demonstrate that stimulation of the MLR not only activates locomotion, but can also stop it. This is achieved through a descending glutamatergic signal, most likely monosynaptic, from the MLR to the reticular formation that activates reticulospinal stop cells. Together, our findings have uncovered a neural mechanism for stopping locomotion and bring new insights into the function of the MLR.

Following traumatic spinal cord injury, most mammalian species are unable to achieve substantial neuronal regeneration and often experience loss of locomotor function. In contrast, larval sea lampreys (Petromyzon marinus) spontaneously recover normal swimming behaviors by 10-12 weeks post-injury, which is supported by robust regeneration of spinal axons. While recovery of swimming behavior is well established, the lamprey's ability to recover more complex behaviors, such as burrowing, is unknown. Here we evaluated the lamprey's ability to burrow into a sand substrate over the typical time course of functional recovery (1-11 weeks post-injury). Compared to uninjured control lampreys, which burrow rapidly and completely, spinal-transected animals did not attempt burrowing until 2 weeks post-injury; and they often did not succeed in fully covering their entire body in the sand. Burrowing behavior gradually improved over post-injury time, with most animals burrowing partially or completely by 9-11 weeks post-injury. Burrowing behavior has two components: the initial component that resembles swimming with propagated body undulations and the final component that pulls the tail under the sand. While the duration of the initial component did not differ between control and spinal-transected animals across the entire recovery period, the duration of the final component in spinal-transected animals was significantly longer at all time points measured. These data indicate that, after spinal cord injury, lampreys are able to recover burrowing behaviors, though some deficits persist.

[Graphic][1] Sea lampreys are masters of transformation. These ancient fish begin life as tiny worm-like creatures that bury in sandy riverbeds and filter food particles out of the water. However, after years of sedentary existence, lampreys undergo a dramatic metamorphosis; just like

Escape swimming is a crucial behavior by which undulatory swimmers evade potential threats. The hydrodynamics of escape swimming have not been well studied, particularly for anguilliform swimmers, such as the sea lamprey Petromyzon marinus. For this study, we compared the kinematics and hydrodynamics of larval sea lampreys with those of lampreys accelerating from rest during escape swimming. We used experimentally derived velocity fields to calculate pressure fields and distributions of thrust and drag along the body. Lampreys initiated acceleration from rest with the formation of a high-amplitude body bend at approximately one-quarter body length posterior to the head. This deep body bend produced two high-pressure regions from which the majority of thrust for acceleration was derived. In contrast, steady swimming was characterized by shallower body bends and negative-pressure-derived thrust, which was strongest near the tail. The distinct mechanisms used for steady swimming and acceleration from rest may reflect the differing demands of the two behaviors. High-pressure-based mechanisms, such as the one used for acceleration from rest, could also be important for low-speed maneuvering during which drag-based turning mechanisms are less effective. The design of swimming robots may benefit from the incorporation of such insights from unsteady swimming.

We tested the efficacy of a vertically oriented field of pulsed direct current (VEPDC) created by an array of vertical electrodes for guiding downstream-moving juvenile Sea Lampreys Petromyzon marinus to a bypass channel in an artificial flume at water velocities of 10–50 cm/s. Sea Lampreys were more likely to be captured in the bypass channel than in other sections of the flume regardless of electric field status (on or off) or water velocity. Additionally, Sea Lampreys were more likely to be captured in the bypass channel when the VEPDC was active; however, an interaction between the effects of VEPDC and water velocity was observed, as the likelihood of capture decreased with increases in water velocity. The distribution of Sea Lampreys shifted from right to left across the width of the flume toward the bypass channel when the VEPDC was active at water velocities less than 25 cm/s. The VEPDC appeared to have no effect on Sea Lamprey distribution in the flume at water velocities greater than 25 cm/s. We also conducted separate tests to determine the threshold at which Sea Lampreys would become paralyzed. Individuals were paralyzed at a mean power density of 37.0 µW/cm3. Future research should investigate the ability of juvenile Sea Lampreys to detect electric fields and their specific behavioral responses to electric field characteristics so as to optimize the use of this technology as a nonphysical guidance tool across variable water velocities. Received April 26, 2016; accepted November 1, 2016 Published online February 13, 2017

The growth rate of larval lampreys (ammocoetes) is of critical importance for scientists and managers seeking to better understand, control, and protect lamprey populations. To date, measurements of ammocoete growth have often relied upon indirect methods (e.g., length frequency), but direct measurements of growth rate in wild populations are rare. Lamprey ammocoetes in three streams were individually marked with visible implant elastomer and were subsequently recaptured. Ammocoete growth was variable among sites and among sample events (from –0.035 to 0.18 mm/d; from –0.0022 to 0.012 g/d), and maturation to the juvenile or adult stage was estimated to take 4–10 years, with some animals possibly requiring more time. American Brook Lampreys Lethenteron appendix grew 0.13 mm/d or 0.0055 g/d on average, whereas the growth of Sea Lampreys Petromyzon marinus was variable, with ammocoetes experiencing significantly higher mean growth at one site (0.12 mm/d; 0.0025 g/d) than at the other site (0.032 mm/d; 0.00039 g/d). These estimates provide support for the generally long growth periods of ammocoetes but also suggest that variability plays a wider role even within populations. The variability in growth rate may provide ammocoetes with a highly flexible life history, allowing them to exploit habitats under a variety of conditions potentially encountered during development. Received June 16, 2016; accepted October 12, 2016 Published online December 12, 2016

Species-specific monitoring activities represent fundamental tools for natural resource management and conservation but require techniques that target species-specific traits or markers. Sea lamprey, a destructive invasive species in the Laurentian Great Lakes and conservation target in North America and Europe, is among very few fishes that possess and use oral suction, yet suction has not been exploited for sea lamprey control or conservation. Knowledge of specific characteristics of sea lamprey suction (e.g., amplitude, duration, and pattern of suction events; hereafter ‘suction dynamics’) may be useful to develop devices that detect, record, and respond to the presence of sea lamprey at a given place and time. Previous observations were limited to adult sea lampreys in static water. In this study, pressure sensing panels were constructed and used to measure oral suction pressures and describe suction dynamics of juvenile and adult sea lampreys at multiple locations within the mouth and in static and flowing water. Suction dynamics were largely consistent with previous descriptions, but more variation was observed. For adult sea lampreys, suction pressures ranged from –0.6 kPa to –26 kPa with 20 s to 200 s between pumps at rest, and increased to –8 kPa to –70 kPa when lampreys were manually disengaged. An array of sensors indicated that suction pressure distribution was largely uniform across the mouths of both juvenile and adult lampreys; but some apparent variation was attributed to obstruction of sensing portal holes by teeth. Suction pressure did not differ between static and flowing water when water velocity was lower than 0.45 m/s. Such information may inform design of new systems to monitor behavior, distribution and abundance of lampreys.

Adult sea lamprey (Petromyzon marinus) abundance in Lake Erie has remained above targets set by fishery managers since 2005, possibly due to increased recruitment in the St. Clair-Detroit River System (SCDRS). Sea lamprey recruitment in the SCDRS poses an enormous challenge to sea lamprey control and assessment in Lake Erie because the SCDRS contains no dams to facilitate capture and discharge is at least an order of magnitude larger in the SCDRS than most other sea lamprey-producing tributaries in the Great Lakes. As a first step toward understanding population size, spatial distribution, and spawning habitat of adult sea lampreys in the SCDRS, we used acoustic telemetry to determine where sea lampreys ceased migration (due to spawning, death, or both) among major regions of the SCDRS. All tagged sea lampreys released in the lower Detroit River (N = 27) moved upstream through the Detroit River and entered Lake St. Clair. After entering Lake St. Clair, sea lampreys entered the St. Clair River (N = 22), Thames River (N = 1), or were not detected again (N = 4). Many sea lampreys (10 of 27) were last observed moving downstream (“fallback”) but we were unable to determine if those movements occurred before or after spawning, or while sea lampreys were dead or alive. Regardless of whether estimates of locations where sea lampreys ceased migration were based on the most upstream region occupied or final region occupied, most sea lampreys ceased migration in the St. Clair River or Lake St. Clair. Results suggest that spawning and rearing in the St. Clair River could be an important determinant of sea lamprey recruitment in the SCDRS and may direct future assessment and control activities in that system.

The effects of coded wire tagging Sea Lamprey Petromyzon marinus larvae from a known-aged stream-dwelling population were assessed. Tagged larvae were significantly shorter on average than untagged larvae from 3 to 18 months after tagging. However, 30 months after tagging, the length distribution of tagged and untagged larvae did not differ and tagged Sea Lampreys were in better condition (i.e., higher condition factor) and more likely to have undergone metamorphosis than the untagged population. The reason why tagged larvae were more likely to metamorphose is not clear, but the increased likelihood of metamorphosis could have been a compensatory response to the period of slower growth after tagging. Slower growth after tagging was consistent across larval size-classes, so handling and displacement from quality habitat during the early part of the growing season was likely the cause rather than the tag burden. The tag effects observed in this study, if caused by displacement and handling, may be m...

The spinal locomotor networks controlling swimming behavior in larval and adult lampreys may have some important differences. As an initial step in comparing the locomotor systems in lampreys, in larval animals the relative timing of locomotor movements and muscle burst activity were determined and compared to those previously published for adults. In addition, the kinematics for free swimming in larval and adult lampreys was compared in detail for the first time. First, for swimming in larval animals, the neuromechanical phase lag between the onsets or terminations of muscle burst activity and maximum concave curvature of the body increased with increasing distance along the body, similar to that previously shown in adults. Second, in larval lampreys, but not adults, absolute swimming speed (U; mm s(-1)) increased with animal length (L). In contrast, normalized swimming speed (U'; body lengths [bl] s(-1)) did not increase with L in larval or adult animals. In both larval and adult lampreys, U' and normalized wave speed (V') increased with increasing tail-beat frequency. Wavelength and mechanical phase lag did not vary significantly with tail-beat frequency but were significantly different in larval and adult animals. Swimming in larval animals was characterized by a smaller U/V ratio, Froude efficiency, and Strouhal number than in adults, suggesting less efficient swimming for larval animals. In addition, during swimming in larval lampreys, normalized lateral head movements were larger and normalized lateral tail movements were smaller than for adults. Finally, larval animals had proportionally smaller lateral surface areas of the caudal body and fin areas than adults. These differences are well suited for larval sea lampreys that spend most of the time buried in mud/sand, in which swimming efficiency is not critical, compared to adults that would experience significant selection pressure to evolve higher-efficiency swimming to catch up to and attach to fish for feeding as well as engage in long-distance migration during spawning. Finally, the differences in swim efficiency for larval and adult lampreys are compared to other animals employing the anguilliform mode of swimming.

Sea lampreys (Petromyzon marinus L., 1758) are nocturnal, so experiments evaluating their behaviour to chemosensory cues have typically been conducted at night. However, given the brief timeframe each year that adult P. marinus are available for experimentation, we investigated whether P. marinus exposed to a 12 h shifted diurnal cycle (reversed photoperiod) could be tested in a darkened arena during the day and show the same response to chemosensory cues as natural photoperiod P. marinus that were tested during the night. Ten replicates of 10 P. marinus, from each photoperiod, were exposed to deionized water (negative control), 2-phenylethylamine hydrochloride (PEA HCl, putative predator cue), or P. marinus whole-body extract (conspecific alarm cue). All P. marinus demonstrated a significant avoidance response to both cues. No significant differences were found in avoidance to PEA HCl between photoperiods. Avoidance of P. marinus whole-body extract was significantly stronger in natural compared with reversed photoperiod P. marinus. The use of reversed photoperiod subjects is suitable for examining the presence or absence of avoidance in response to novel chemosensory alarm cues, or the change in the magnitude of antipredator response. Studies investigating the natural magnitude of antipredator response should use natural photoperiod experimental subjects.

Invasive sea lampreys have had substantial negative ecological and economic impacts on the Laurentian Great Lakes region. Control efforts, such as lampricide application and barriers, have resulted in a reduction in number of sea lampreys in the Great Lakes. Due to environmental and non-target impacts of existing control mechanisms, coupled with the fact that no non-physical barrier is completely effective at stopping fish movement, there is a critical need to develop novel control technologies to assist with the control and suppression of sea lamprey populations. Recent work has indicated that carbon dioxide gas (CO 2 ) applied to water will influence the movement and behavior of fishes, providing the potential for CO 2 to act as a non-physical barrier that can exclude fish from a target area. To date, the effectiveness of CO 2 at influencing the movement and behavior of sea lampreys has not been explored. The current study showed that CO 2 applied to water will result in behavioral agitation for both adult and transformer sea lampreys, and will eventually result in equilibrium loss. More importantly, both adult and transformer sea lampreys will ‘choose’ to avoid water with CO 2 concentrations of 85 and 160 mg/L (respectively). Together, results from this study suggest that CO 2 applied to water has the potential to act as a non-physical barrier to deter the movement of free-swimming lamprey in the wild. Carbon dioxide gas can be integrated with existing control technologies to act as a novel barrier technology and augment existing control strategies for sea lampreys.

Allocating resources between the gathering of information to guide management actions and implementing those actions presents an inherent tradeoff. This tradeoff is evident for control of the Sea Lamprey Petromyzon marinus in the St. Marys River, connecting Lakes Huron and Superior and a major source of parasitic Sea Lampreys to Lake Huron and northern Lake Michigan. Larval Sea Lampreys in the St. Marys River are controlled through the application of Bayluscide, which is applied to areas of high larval density. Bayluscide applications are guided with an annual deepwater electrofishing survey to estimate larval Sea Lamprey density at relatively fine spatial scales. We took a resampling approach to describe the effect of sampling intensity on the success of the larval Sea Lamprey management program and explicitly incorporated the economic tradeoff between assessment and control efforts to maximize numbers of larvae killed in the St. Marys River. When no tradeoff between assessment and control was in...

Invasive sea lampreys (Petromyzon marinus) in the Laurentian Great Lakes are the target of binational control. Trapping of adults could be used for control if trap success was higher. At a hydro-generating station on the St. Marys River, we tested whether the probability of trap entry is low (0.2–0.3) because (i) lampreys spend insufficient time near traps to find and enter the trap, (ii) high discharge at trap sites makes attractant flow from traps difficult to detect or trap openings difficult to reach, and (iii) conspecifics impede trap entry. Discharge at the site was manipulated nightly, and the behaviour of lampreys at trap openings was video-recorded. Odds of a lamprey reaching a trap opening and entering the trap were 3.4 and 1.6 times higher, respectively, with every second spent at a trap. The probability of reaching a trap was not lower on nights when discharge was high or when conspecifics were present at the trap opening. Improved trap entry will require manipulation of stimuli other than discharge that affect the time spent at traps.

The St. Marys River (SMR) historically has been a major producer of sea lampreys (Petromyzon marinus) in the Laurentian Great Lakes. In the early 2000s, a decision analysis (DA) project was conducted to evaluate sea lamprey control policies for the SMR; this project suggested that an integrated policy of trapping, sterile male releases, and Bayluscide treatment was the most cost-effective policy. Further, it concluded that formal assessment of larval sea lamprey abundance and distribution in the SMR would be valuable for future evaluation of control strategies. We updated this earlier analysis, adding information from annual larval assessments conducted since 1999 and evaluating additional control policies. Bayluscide treatments continued to be critical for sea lamprey control, but high recruitment compensation minimized the effectiveness of trapping and sterile male release under current feasible ranges. Because Bayluscide control is costly, development of strategies to enhance trapping success remains a priority. This study illustrates benefits of an adaptive management cycle, wherein models inform decisions, are updated based on learning achieved from those decisions, and ultimately inform future decisions.

We examined how attack frequency by sea lampreys on fishes in Lake Ontario varied in response to sea lamprey abundance and preferred host abundance (lake trout > 433 mm). For this analysis we used two gill net assessment surveys, one angler creel survey, three salmonid spawning run datasets, one adult sea lamprey assessment, and a bottom trawl assessment of dead lake trout. The frequency of fresh sea lamprey marks observed on lake trout from assessment surveys was strongly related to the frequency of sea lamprey attacks observed on salmon and trout from the creel survey and spawning migrations. Attack frequencies on all salmonids examined were related to the ratio between the abundances of adult sea lampreys and lake trout. Reanalysis of the susceptibility to sea lamprey attack for lake trout strains stocked into Lake Ontario reaffirmed that Lake Superior strain lake trout were among the most and Seneca Lake strain among the least susceptible and that Lewis Lake strain lake trout were even more susceptible than the Superior strain. Seasonal attack frequencies indicated that as the number of observed sea lamprey attacks decreased during June–September, the ratio of healing to fresh marks also decreased. Simulation of the ratios of healing to fresh marks indicated that increased lethality of attacks by growing sea lampreys contributed to the decline in the ratios and supported laboratory studies about wound healing duration.

SummaryVertebrate rod photoreceptors are thought to have evolved from cone photoreceptors only after the divergence of the jawed and jawless fishes, but this idea is questioned by new evidence that the short ‘cones’ of jawless sea lampreys are physiologically equivalent to rods.

Sea lampreys (Petromyzon marinus L., 1758) invaded the Great Lakes early in the 20th century and have caused economic and ecological damage to native fish species. The integrated sea lamprey control program involves low-head barrier dams, lampricides, and trapping. The search for low cost and less toxic alternatives to lampricides could involve the use of repellents in the form of chemical alarm cues. The objective of this study was to determine whether larval sea lamprey showed a behavioural response when exposed to damage-released chemical alarm cues by increasing their swimming time, rate of direction changes, or rate of escape attempts in an artificial stream channel experiment. Larval sea lampreys were exposed to conspecific larval sea lamprey extract, heterospecific swordtail (Xiphophorus hellerii Heckel, 1848) extract, or a distilled water control. The larvae increased their rate of escape attempts after exposure to both swordtail and larval lamprey extracts and their rate of direction changes after exposure to sea lamprey extract. However, larvae did not increase their swimming time in response to any experimental stimuli. This is the first study to suggest that larval sea lamprey respond to potential chemosensory risk assessment cues.

The origin of populations of the landlocked Sea Lamprey Petromyzon marinus in Lakes Champlain and Ontario, whether by artificial canals or by natural colonization following the last ice age, is controversial, in part because the related history and ecology had been poorly documented. This situation favored a native classification for the populations in both lakes based mainly on genetics. A native classification for the Lake Champlain population was predicated on either of two erroneous dates of first record, 1841 and 1894, whereas the correct date, 1929, was much more recent and strongly supports a nonnative classification. The detection of the Sea Lamprey in Lake Champlain occurred shortly after the opening in 1916 of the Champlain Barge Canal, which opened the upper Hudson River to fish passage. The case for a native Lake Ontario population did not account for a watershed breach in 1863 between the Susquehanna River, where the Sea Lamprey had been common, and the Lake Ontario drainage. Shortly ...

Larval Sea Lampreys Petromyzon marinus live burrowed in stream bottoms and then metamorphose into their parasitic stage. Among larvae that metamorphose in a given year (i.e., parasitic cohort), autumn out-migrants (October–December) to the Laurentian Great Lakes can feed on fish for up to 6 months longer than spring out-migrants (March–May), which overwinter in streams without feeding. We evaluated whether the season of out-migration affected growth or survival of newly metamorphosed Sea Lampreys in Lake Huron. Newly metamorphosed individuals (n = 2,718) from three parasitic cohorts were netted during their out-migration from Black Mallard Creek, Michigan, to Lake Huron during autumn 1997 through spring 2000; each out-migrant was injected with a sequentially numbered coded wire tag and was released back into the creek. After up to 18 months of feeding in the Great Lakes, 224 (8.2%) Sea Lampreys were recaptured (in 1999–2001) as upstream-migrating adults in tributaries to Lakes Huron and Michigan. ...

We determined whole-fish total mercury (Hg) concentrations of 40 male and 40 female adult sea lampreys (Petromyzon marinus) captured in the Cheboygan River, a tributary to Lake Huron, during May 2011. In addition, bioenergetics modeling was used to explore the effects of sex-related differences in activity and resting (standard) metabolic rate (SMR) on mercury accumulation. The grand mean for Hg concentrations was 519 ng/g (standard error of the mean=46 ng/g). On average, males were 16% higher in Hg concentration than females. Bioenergetics modeling results indicated that 14% higher activity and SMR in males would account for this observed sex difference in Hg concentrations. We concluded that the higher Hg concentration in males was most likely due to higher rate of energy expenditure in males, stemming from greater activity and SMR. Our findings have implications for estimating the effects of sea lamprey populations on mercury cycling within ecosystems, as well as for the proposed opening of sea lamprey fisheries. Eventually, our results may prove useful in improving control of sea lamprey, a pest responsible for substantial damage to fisheries in lakes where it is not native.

This study tested the hypothesis that sea lampreys (Petromyzon marinus L., 1758) undergo a reduction in the photosensitivity of photoreceptors in the tail after metamorphosing from burrow-dwelling, filter-feeding larval sea lampreys (ammocoetes) into open-water, parasitic juvenile phase animals that attach themselves to and feed on the blood of marine and freshwater fishes. Using a photo-illumination apparatus, ammocoetes and juvenile sea lampreys were exposed to white light at an intensity of 10 lx and the photokinetic response (time to movement) was measured in individual animals. The median latency of the response of juvenile lampreys was 5.4 times longer (i.e., slower response time) than observed in ammocoetes, and only 61% of the juvenile animals responded to the light compared with 95% of ammocoetes. It is concluded that the greater photosensitivity of tail photoreceptors in ammocoetes helps ensure that the animals are totally concealed from potential predators while burrowing. Decreased photosensitivity following metamorphosis is likely related to the transition to an open water, parasitic life style in which tail photoreception would have little selective advantage.