Discriminating natal origin of spawning adult sea lamprey (Petromyzon marinus) in Lake Champlain using statolith elemental signatures

Sea lamprey (Petromyzon marinus) is a nuisance species in the Great Lakes and Lake Champlain. Information about tributary contributions to the spawning adult phase is critical for appropriate allocation of efforts to control this species. We examined the accuracy of statolith elemental composition to identify the natal origin (i.e., individual rivers or clusters of rivers) of 33 known-origin adults from the Lake Champlain basin. To do so, we first established natal origin chemical signatures using the statoliths of 238 larvae from the same basin. Using laser-ablation inductively coupled plasma mass spectrometry, the 238 larvae originating from 12 streams and one delta were discriminated with a classification accuracy of 57% (range: 25–80%) and 70% (range: 29–80%) when individual streams and groups of streams were considered respectively, highlighting the potential of statolith microchemistry to identify natal origins. However, the assignment of natal origin for adults was overwhelmingly incorrect. Using a maximum likelihood procedure, 88% of the adults were assigned to a cluster of three streams and one delta, while only 3% of these individuals were known to originate from this particular cluster. More research is required to understand the low classification accuracy of sea lamprey adults and validate the use of statolith microchemistry to identify sea lamprey natal origin.     

Development and Evaluation of a New Predictive Model for Metamorphosis of Great Lakes Larval Sea Lamprey (Petromyzon marinus) Populations

Accurate forecasts of the number of larval sea lamprey (Petromyzon marinus) within a stream that will enter into metamorphosis are critical to currently used methods for allocating lampricide treatments among streams in the Great Lakes basin. To improve our ability to predict metamorphosis we used a mark-recapture technique, involving the marking of individual larval lamprey with sequentially coded wire tags, to combine information regarding individual and stream level parameters collected in year t, with direct observations of metamorphic outcome of lamprey recaptured in year t+1. We used these data to fit predictive models of metamorphosis. The best model demonstrated excellent predictive capabilities and highlighted the importance of weight, age, larval density, stream temperature and geographic location in determining when individual lamprey are likely to transform. While this model was informative, it required data whose measures are not practical to obtain routinely during the larval sea lamprey assessment program. A second model, limited to data inputs that can be easily obtained, was developed and included length of larvae the fall prior to metamorphosis, stream latitude and longitude, drainage area, average larval density in type-2 habitat, and stream lamprey production category (a measure of the regularity with which treatments are required). This model accurately predicted metamorphosis 20% more often than current models of metamorphosis; however, we recommend further validation on an independent set of streams before adoption by the Great Lakes Fishery Commission for ranking streams.     

Factors affecting recruitment dynamics of Great Lakes sea lamprey (Petromyzon marinus) populations

Knowledge of stock–recruitment dynamics is as important for control of pest species such as the sea lamprey (Petromyzon marinus) as it is for sustainable harvest management of exploited fish species. A better understanding of spatial and temporal variation in recruitment of pest populations may inform managers on where and when to effectively apply different control methods. Sea lamprey stock–recruitment data combined from streams across the Great Lakes basin into a Ricker stock–recruitment model indicated both compensation (density-dependent survival) and a large amount of density-independent recruitment variation. We evaluated the use of a mixed-effects model to look at common year effects and stream-level variables that could affect productivity and growing season length, with the objective of identifying factors that may explain this density-independent variation in recruitment. After selecting the “best model”, we tested factors that might affect recruitment variation, using a Great Lakes dataset comprising 97 stream–years. Lake Superior tributaries, streams with larger numbers of lamprey competitors, and streams regularly requiring lampricide treatment showed significantly higher recruitment. Alkalinity and thermal regulation did not affect the observed recruitment pattern among streams. In four long-term study streams we observed significant variation among streams, tested as a fixed effect, but no evidence suggested a common pattern of variation among years. Differences in recruitment among streams were consistent with evidence of quality of spawning and larval habitat among streams. Our findings suggest that management models should account for differences in recruitment dynamics among sea lamprey-producing streams, but not common year effects.     

Evaluating the growth potential of sea lampreys (Petromyzon marinus) feeding on siscowet lake trout (Salvelinus namaycush) in Lake Superior

Differences in the preferred thermal habitat of Lake Superior lake trout morphotypes create alternative growth scenarios for parasitic sea lamprey (Petromyzon marinus) attached to lake trout hosts. Siscowet lake trout (Salvelinus namaycush) inhabit deep, consistently cold water (4-6 °C) and are more abundant than lean lake trout (Salvelinus namaycush) which occupy temperatures between 8 and 12 °C during summer thermal stratification. Using bioenergetics models we contrasted the growth potential of sea lampreys attached to siscowet and lean lake trout to determine how host temperature influences the growth and ultimate size of adult sea lamprey. Sea lampreys simulated under the thermal regime of siscowets are capable of reaching sizes within the range of adult sea lamprey sizes observed in Lake Superior tributaries. High lamprey wounding rates on siscowets suggest siscowets are important lamprey hosts. In addition, siscowets have higher survival rates from lamprey attacks than those observed for lean lake trout which raises the prospect that siscowets serve as a buffer to predation on more commercially desirable hosts such as lean lake trout, and could serve to subsidize lamprey growth.     

Impact of the Alga Cladophora on the Survival of E. coli, Salmonella, and Shigella in Laboratory Microcosm

E. coli is an indicator of recent fecal contamination of freshwater beaches around the Great Lakes region. Elevated concentrations indicate that a fecal contamination has occurred, and that the risk for contact with fecal pathogenic organisms is heightened. The green algae, Cladophora, harbors populations of E. coli and potentially allows for prolonged survival and even replication of the bacterium in the lake environment. If presence of Cladophora mats on beaches is associated with persistence of E. coli in beach water, then E. coli would be a useful indicator organism only if pathogens also were able to survive and persist in the algae. This study utilized lab microcosms to study the persistence of E. coli, and of the fecal pathogens, Salmonella and Shigella, in lake water with and without the presence of Cladophora. E. coli was able to persist for extended periods in the presence of Cladophora (attached to algal mats for 45 days). Salmonella and Shigella, however, were unable to persist for this time period while in the presence of Cladophora (Salmonella attached to Cladophora was detectable for 10 days and Shigella was detectable for only 2 days). These data imply that E. coli is able to survive in the presence of Cladophora for greater times than are the fecal pathogens and that E. coli may not be an appropriate indicator organism for beaches with accumulations of algal material.     

Consistent individual differences in sea lamprey (Petromyzon marinus) behaviour: Implications for control via trapping

We tested if consistent individual differences (CIDs) in the behaviour of sea lamprey (Petromyzon marinus) from the Laurentian Great Lakes could influence their vulnerability to trapping. The sea lamprey is invasive in the Upper Laurentian Great Lakes and the target of a binational control program. Trapping could be used for control if trapping efficiency is unbiased and effective. Our test involved comparing the behaviour of sea lamprey collected in the field from a trap (n = 42) at a barrier and electrofished (n = 9) downstream of the barrier. We quantified each individual's latency to exit an enclosure (a measure of exploration), proportion of time spent moving (a measure of general activity), and change in activity in response to a putative predator cue (a measure of boldness). CIDs were detected for each behaviour measured (intraclass correlations: 0.3–0.5). CIDs in behaviour also differed between trapped individuals and those collected downstream using electrofishing, irrespective of size, sex, and maturity status. Trapped individuals decreased their activity in response to a putative predator cue, while individuals collected using electrofishing increased their activity in response to the cue. Trapped individuals also tended to spend a greater proportion of time moving than individuals sampled downstream of the trap. However, the two samples of lamprey did not differ significantly in time taken to exit an enclosure. The behavioural differences between sea lamprey sampled from a trap and those sampled downstream of the trap suggest that CIDs in behaviour can influence an individual's vulnerability to trapping.     

Shifting status and distribution of range margin chorus frog (Pseudacris) populations in eastern Great Lakes watersheds

Contiguous with their range across major rivers into Canada, two different species of chorus frogs are now thought to inhabit the Great Lakes watersheds of New York. Pseudacris triseriata is found along the western Lake Ontario and Lake Erie plains while P. maculata (tentatively a new frog species in NY) inhabits the lowlands of eastern Lake Ontario and the St. Lawrence River. Both species are on their extreme range margins in NY. In 2010 we detected distributional declines of both putative chorus frog species based on a broad survey following standardized occupancy detection protocols. Causes are unclear but could relate to reforestation and urbanization of formerly more extensive agricultural lands, climate change, pathogenic fungal outbreaks and/or the contaminant effects of intensive agriculture. On the other hand, the prior overestimation of ranges because of misidentification may have inflated earlier perceived distributions (positive survey bias) because false positives are problematical for this cryptic frog. At broad geographical scales, chorus frog (meta)populations are highly dynamic and are likely shifting their ranges in response to rapidly changing overall environmental conditions in the northeastern U.S. and Canada.     

Trends in Diporeia populations across the Laurentian Great Lakes, 1997-2009

Benthic communities in the Laurentian Great Lakes have been in a state of flux since the arrival of dreissenid mussels, with the most dramatic changes occurring in population densities of the amphipod Diporeia. In response, the US EPA initiated an annual benthic macroinvertebrate monitoring program on all five Great Lakes in 1997. Although historically the dominant benthic invertebrate in all the lakes, no Diporeia have been found in Lake Erie during the first 13 years of our study, confirming that Diporeia is now effectively absent from that lake. Populations have almost entirely disappeared from our shallow (< 90 m) sites in lakes Ontario, Huron, and Michigan. In Lake Ontario, three of our four deep (> 90 m) sites still supported Diporeia populations in 2009, with densities at those sites ranging between 96 and 198/m². In Lake Michigan, populations were still found at six of our seven deep sites in 2009, with densities ranging from 57 to 1409/m². Densities of Diporeia in 2009 at the four deep sites in Lake Huron were somewhat lower than those in Lake Michigan, ranging from 191 to 720/m². Interannual changes in population size in Lake Huron and Lake Michigan have shown a degree of synchrony across most sites, with periods of rapid decline (1997-2000, 2003-2004) alternating with periods of little change or even increase (2001-2002, 2005-2009). There has been no evidence of directional trends at any sites in Lake Superior, although substantial interannual variability was seen.     

Escherichia coli toxin and attachment genes in sand at Great Lakes recreational beaches

The United States Environmental Protection Agency recommends density thresholds for the fecal indicator organism Escherichia coli in order to ensure the safety of recreational waters. A number of studies published over the past ten years indicate that E. coli is encountered frequently in sand at recreational beaches. While a majority of the sand-associated E. coli may be commensal or environmental strains, the potential for pathogenic strains of E. coli to be present exists. Therefore, the aim of this study was to assess the presence of attachment and virulence genes associated with enteropathogenic and enterohemorrhagic strains of E. coli (EPEC and EHEC) in populations of E. coli recovered from swash zone sand from seven recreational beaches along Lake Huron and Lake St. Clair in eastern Michigan, USA. Genes coding for attachment proteins in EPEC and EHEC were very prevalent in sand E. coli, but genes coding for toxin genes were uncommon. The paucity of genes associated with E. coli toxins suggests that the EPEC and EHEC pathotypes are not common in sand; however, the high prevalence of genes associated with attachment in E. coli pathotypes suggests that these genes are being retained within the beach sand E. coli population.     

Spatial and temporal variation in the distribution of burrowing mayfly nymphs (Ephemeroptera: Hexagenia limbata and H. rigida) in western Lake Erie

In the early 1990s, burrowing mayfly species reappeared in sediments of the western basin of Lake Erie after an absence of over 30 years due to episodic hypoxia at the sediment–water interface. Long-term monitoring of adult mayflies at shoreline areas had revealed that Hexagenia rigida was more abundant than Hexagenia limbata during the initial recolonization period, but was gradually replaced by H. limbata. We hypothesized that this shift in dominance would be confirmed by the distribution and abundance of nymphs. We identified nymphs collected each spring throughout western Lake Erie from 1997 to 2004. The relative abundances of H. rigida and H. limbata nymphs exhibited the same temporal sequence as adults. Furthermore, the number of sites in the western basin in which H. rigida occurred decreased as the occurrence frequency of H. limbata increased. H. limbata were dominant in the basin by 2004. Hexagenia limbata nymphs persisted in the center-most part of the basin, whereas H. rigida did not, possibly due to differences in tolerance to hypoxia. There were no significant differences in body size between the two populations. Differences in dispersal distance from source populations and the timing and success of egg hatching likely accounted for the initial colonizing success of H. rigida, but the differential ability of H. limbata eggs to overwinter in sediments and possible tolerance of nymphs to hypoxia has possibly led to its current dominance in the western basin.     

Investigation of viruses in Diporeia spp. from the Laurentian Great Lakes and Owasco Lake as potential stressors of declining populations

The benthic amphipod Diporeia is an ecologically and biogeochemically important constituent of deep freshwater lakes in North America. The proliferation of dreissenid mussels in the mid-1990s coincided with a sharp decrease in Diporeia populations in several Laurentian Great Lakes; however the ultimate cause and mechanisms of their decline are still unknown. Here we examined the composition of DNA viruses associated with Diporeia collected from populations of Lake Michigan that had declined and stable populations in Lake Superior and Owasco Lake (Finger Lake in central New York State). Viral metagenomic libraries from Owasco Lake and Lake Superior were comprised primarily of bacteriophages, which may infect bacteria within the amphipod microbiome. In contrast, the metagenomic library from Lake Michigan contained well-represented ssDNA circular viral genomes. The prevalence and viral load of one putative Type V ssDNA circular virus (LM29173) that recruited almost 30% of total viral sequence reads in the Lake Michigan library was analyzed by quantitative PCR. The prevalence of LM29173 was over two orders of magnitude greater in Lake Michigan compared to the other two lakes. Although further research is necessary to establish the pathology and epidemiological extent of viral-Diporeia interactions, our data suggest that viruses may be numerically significant constituents of the Diporeia microbiome, and if pathogenic some of these viruses may be a stressor of Great Lakes Diporeia populations. Our data further indicate that special attention should be given to the circovirus that was prevalent in the declining Michigan population but uncommon in the other two lakes.     

Acoustical conditioning and retention in the common carp (Cyprinus carpio)

Classical acoustic conditioning was investigated with the common carp (Cyprinus carpio) to determine its potential as a management tool for this invasive species. Groups of five juvenile carp were trained to associate a 400 Hz pure tone stimulus with a food reward in small laboratory tanks (≤ 1000 L). Following three days of training, the majority of fish showed a consistent and rapid (< 30 s) ability to localize the sound. All groups (n = 5) displayed retention without subsequent reinforcement for at least four months, and three groups maintained the conditioned behavior after 5 months. Additional trials were conducted in a 24,000 L outdoor pool to mimic more natural conditions. Carp again displayed relatively short learning curves and high accuracy (84.4%) in localizing the sound source. These findings indicate that carp are readily conditioned to an acoustic signal and are able to retain this behavior for months, suggesting that acoustical conditioning may be used as a management strategy in which the movement of wild carp can be manipulated for trapping and removal within a lake system.     

Stock assessment and fishery management of Henicorhynchus spp., Cyclocheilichthys enoplos and Channa micropeltes in Tonle Sap Great Lake,Cambodia

Tonle Sap Great Lake, in the lower Mekong River basin, contributes 60% of Cambodia's inland fisheries catch. There are four types of fisheries, including the middle-scale fishery. The major species comprising the middle-scale fishery are Henicorhynchus spp. (16%), a small-bodied fish caught mainly with small-mesh nets, and Cyclocheilichthys enoplos (13%), and Channa micropeltes (7%) which are caught with a variety of gear. Here we apply the Schaefer surplus production model to the middle-scale fisheries using monitoring data collected between 1995 and 1999. Model simulations determined that the maximum sustainable yield (F_MSY) for Henicorhynchus spp., was obtained with the use of 47,206 gillnets (mesh size < 50 mm) and 4269 and 1605 fishing boats for C. enoplos and C. microplestes, respectively. Over 1995–1999, there was a strong trend of increase in fishing effort and decrease of catch-per-unit-effort in the waters of Pursat, Siem Riep and Kampong Chnnang provinces. These provinces have large population centres located close to the fishing grounds; fishing in these areas should be more strictly regulated.     

Evaluating Sampling Strategies for Larval Cisco (Coregonus artedi)

To improve our ability to assess larval cisco (Coregonus artedi) populations in Lake Superior, we conducted a study to compare several sampling strategies. First, we compared density estimates of larval cisco concurrently captured in surface waters with a 2 × 1-m paired neuston net and a 0.5-m (diameter) conical net. Density estimates obtained from the two gear types were not significantly different, suggesting that the conical net is a reasonable alternative to the more cumbersome and costly neuston net. Next, we assessed the effect of tow pattern (sinusoidal versus straight tows) to examine if propeller wash affected larval density. We found no effect of propeller wash on the catchability of larval cisco. Given the availability of global positioning systems, we recommend sampling larval cisco using straight tows to simplify protocols and facilitate straightforward measurements of volume filtered. Finally, we investigated potential trends in larval cisco density estimates by sampling four time periods during the light period of a day at individual sites. Our results indicate no significant trends in larval density estimates during the day. We conclude estimates of larval cisco density across space are not confounded by time at a daily timescale. Well-designed, cost effective surveys of larval cisco abundance will help to further our understanding of this important Great Lakes forage species.     

Predation by fallfish (Semotilus corporalis) on Pacific salmon eggs in the Salmon River,New York

Fallfish (Semotilus corporalis) are the largest native cyprinid in the northeastern United States and are the most abundant native species in the Salmon River, New York. The Salmon River is a high-quality spawning and nursery river for Pacific salmon (Oncorhynchus spp.) migrating from Lake Ontario. Because of the large number of Pacific salmon spawning in the river in the fall extensive redd superimposition occurs resulting in salmonid eggs being available on the substrate. We examined the fall diet of 647 fallfish in 2007 and 2008 to determine the extent of predation on Pacific salmon eggs. The contribution of eggs in the diet significantly increased once fallfish attained a size of 100 mm total length. The largest size category of fallfish examined (≥ 150 mm) had the highest proportion (86.1%) of salmon eggs in their diet. The contribution of zooplankton and chironomids in the diet of fallfish decreased with fish size. Except for the two largest groups of fallfish examined (i.e., 100–149 mm and ≥ 150 mm) diet overlap among size groups was low. The high contribution in the diet during the fall and high caloric value of Pacific salmon eggs could increase growth and survival of this species in the Salmon River.     

Coexistence of the native benthic amphipod Diporeia spp. and exotic dreissenid mussels in the New York Finger Lakes

Populations of the benthic amphipod Diporeia spp. have sharply declined since the early 1990s in all North America's Great Lakes except Lake Superior. The onset and continued decline coincides with the invasion of these lakes by zebra (Dreissena polymorpha) and quagga (Dreissena rostriformis bugensis) mussels and the spread of quagga mussels to deep habitats. The six deepest Finger Lakes of central New York (Seneca, Cayuga, Skaneateles, Canandaigua, Keuka, and Owasco) have historically been Diporeia habitat and have had dreissenids for more than a decade. These lakes represent a wide range of trophic state, maximum depth, and dreissenid invasion history. We hypothesized that Diporeia abundance would be negatively impacted by dreissenid mussel expansion in the Finger Lakes. During 2006–2010, we sampled Diporeia and mussel populations in these six lakes. Diporeia was present in all six lakes, and was abundant (2000/m²) in Owasco Lake that has only zebra mussels and in Cayuga and Seneca Lakes that have had zebra and quagga mussels since 1994. Diporeia abundance was lowest (1000/m²) in Skaneateles, Canandaigua, and Keuka Lakes where quagga mussels have recently expanded. Productivity indicators explained much of the variability of Diporeia abundance. The persistence of Diporeia with quagga mussels in these lakes may be because of available alternative food resources. Fatty acid tracers indicate that Diporeia from Owasco Lake, the lake without quagga mussels, utilize diatoms, but Diporeia from Cayuga Lake that coexist with abundant quagga mussels also use food resources associated with terrestrial detritus that cannot be intercepted by dreissenids.     

The discovery of the nonindigenous,mottled fingernail clam, Eupera cubensis (Prime, 1865) (Bivalvia: Sphaeriidae) in the Chicago Sanitary and Ship Canal (Illinois River Drainage), Cook County,Illinois

The nonindigenous mottled fingernail clam, Eupera cubensis is reported from the Upper Mississippi River Basin for the first time. This record represents a significant northern range expansion for the species in the United States. It appears to be presently confined to a 35-km stretch of the Chicago Sanitary and Ship Canal (CSSC), an artificial waterway that connects the Mississippi River drainage to the Great Lakes. Although the introduction of this species to the Great Lakes basin poses uncertain risks to the general aquatic community, the immediate effects of Eupera cubensis on the fauna of the CSSC are expected to be minimal.     

Fall diet and bathymetric distribution of deepwater sculpin (Myoxocephalus thompsonii) in Lake Huron

Deepwater sculpin Myoxocephalus thompsonii are an important component of Great Lake's offshore benthic food webs. Recent declines in deepwater sculpin abundance and changes in bathymetric distribution may be associated with changes in the deepwater food web of Lake Huron, particularly, decreased abundance of benthic invertebrates such as Diporeia. To assess how deepwater sculpins have responded to recent changes, we examined a fifteen-year time series of spatial and temporal patterns in abundance as well as the diets of fish collected in bottom trawls during fall of 2003, 2004, and 2005. During 1992–2007, deepwater sculpin abundance declined on a lake-wide scale but the decline in abundance at shallower depths and in the southern portion of Lake Huron was more pronounced. Of the 534 fish examined for diet analysis, 97% had food in the stomach. Mysis, Diporeia, and Chironomidae were consumed frequently, while sphaerid clams, ostracods, fish eggs, and small fish were found in only low numbers. We found an inverse relationship between prevalence of Mysis and Diporeia in diets that reflected geographic and temporal trends in abundance of these invertebrates in Lake Huron. Because deepwater sculpins are an important trophic link in offshore benthic food webs, declines in population abundance and changes in distribution may cascade throughout the food web and impede fish community restoration goals.     

Occurrence of the Great Lake's most recent invader, Hemimysis anomala, in the diet of fishes in southeastern Lake Ontario

The Ponto-Caspian mysid, Hemimysis anomala, was first observed in southeastern Lake Ontario in May 2006. During July and August 2007, gill nets were fished in 6 to 8 m of water at two locations of known Hemimysis colonization in southeastern Lake Ontario to determine if fish that consume macroinvertebrates were beginning to include this new invasive mysid in their diets. Of nine fish species captured in August, September, and October 2007, three species had consumed Hemimysis: alewife (Alosa pseudoharengus), rock bass (Ambloplites rupestris), and yellow perch (Perca flavescens); and six species had not: round goby Apollonia melanostoma, smallmouth bass Micropterus dolomieu, spottail shiner Notropis hudsonius, gizzard shad Dorosoma cepedianum, white perch Morone americana and log perch Percina caprodes. Diets of alewives from all samples were composed predominantly of Hemimysis (69.6% -100% frequency of occurrence, 46.0%–74.5% dry weight diet composition). Two of 6 rock bass stomachs sampled in August contained ≥ 98.9% Hemimysis (10 and 40 individuals each) and one of 61 yellow perch stomachs sampled in September contained 10.0% Hemimysis (6 individuals) and 90.0% fish. While Hemimysis were observed only sparsely in the diet of most nearshore fish, their predominance in alewife diets and their omnivorous feeding behavior indicated that they have the potential to alter energy flow in Great Lakes' foodwebs.     

The Invasive New Zealand Mud Snail (Potamopyrgus antipodarum) in Lake Erie

The New Zealand mud snail (Potamopyrgus antipodarum) is an invasive species in Europe, Japan, Australia, and North America. In the western United States it is a species of special concern where population densities in some rivers and streams are very large (∼300,000 per m²) and considerable ecological effects of its presence have been reported. Much less about the effects of this species is known in the Great Lakes, where the snail was found in Lake Ontario and the St. Lawrence River in 1991. Here we report the occurrence of the snail in Lake Erie. Two P. antipodarum were collected in 18 m deep water (sampling range 5–18 m) in Lake Erie off shore of Presque Isle State Park near Erie, Pennsylvania in the summer of 2005 and others were collected off of Sturgeon Point in Lake Erie (sampling range 5–20 m) south of Buffalo, NY and in the central basin of Lake Erie (18 m) in 2006. This finding demonstrates that this species continues to expand its range in the Great Lakes. The range expansion increases the likelihood that it may become established in rivers and streams emptying into the Great Lakes where higher densities and greater ecological damage may result.