Sources and Sinks of Escherichia coli in Benthic and Pelagic Fish

Escherichia coli and fecal coliform bacteria were isolated from five benthic and four pelagic fish species to determine their role in the fecal contamination of recreational waters. All fish were collected during fall 2006 from Southworth Marsh in the Duluth-Superior Harbor, a public beach that is commonly posted to minimize water contact due to high E. coli levels. Although fecal coliform bacteria were isolated from each fish species, they were only isolated from 66% and 72% of the individual benthic and pelagic fish, respectively. While 42% of the fecal coliforms from benthic fish were E. coli, only 4% of these bacteria from pelagic fish were E. coli. Cluster analysis showed different fish species harbored identical strains of E. coli and some fish contained multiple E. coli strains. The potential source for 65% of the E. coli isolates obtained from fish were identified by using the HFERP DNA fingerprinting method and libraries of E. coli DNA fingerprints from warm-blooded animals and environmental isolates collected in the area. The E. coli strains whose source could be identified were most similar to strains isolated from sediments, Canada geese, mallard ducks, and wastewater. None of the fish E. coli had DNA fingerprints matching those from any water or beach sand isolates. Although our results demonstrate that benthic fish contain E. coli, it may be more appropriate to consider these fish as a vector of E. coli from other sources, rather than a new source of E. coli contamination in aquatic environments.     

Composite Analysis for Escherichia coli at Coastal Beaches

At some coastal beaches, concentrations of fecal-indicator bacteria can differ substantially between multiple points at the same beach at the same time. Because of this spatial variability, the recreational water quality at beaches is sometimes determined by stratifying a beach into several areas and collecting a sample from each area to analyze for the concentration of fecal-indicator bacteria. The average concentration of bacteria from those points is often used to compare to the recreational standard for advisory postings. Alternatively, if funds are limited, a single sample is collected to represent the beach. Compositing the samples collected from each section of the beach may yield equally accurate data as averaging concentrations from multiple points, at a reduced cost. In the study described herein, water samples were collected at multiple points from three Lake Erie beaches and analyzed for Escherichia coli on modified mTEC agar (EPA Method 1603). From the multiple-point samples, a composite sample (n =116) was formed at each beach by combining equal aliquots of well-mixed water from each point. Results from this study indicate that E. coli concentrations from the arithmetic average of multiple-point samples and from composited samples are not significantly different (t = 1.59, p = 0.1139) and yield similar measures of recreational water quality; additionally, composite samples could result in a significant cost savings.     

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.     

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.     

A model laboratory system to study the synergistic interaction and growth of environmental Escherichia coli with macrophytic green algae

Escherichia coli, an important fecal indicator bacterium, is known to persist and reproduce in association with Cladophora and other macrophytic algae and environmental substrates. Recent increases in the growth of Cladophora and other macrophytic algae in many of the Laurentian Great Lakes result in the accumulation of large amounts of algal biomass along the shoreline and on beaches. While the Cladophora–E. coli association may pose substantial public health risks, detailed laboratory-based studies have not been done to investigate the bases of the interaction. This is due, in large part, to past inabilities to culture many macrophytic algae under near axenic conditions. Here we describe the development and experimental use of laboratory microcosms to study the synergistic interaction and growth of the green alga Pithophora, a close relative of Cladophora, with environmental E. coli. In the absence of exogenous organic carbon supply, the E. coli population attached to algal filaments increased approximately three orders of magnitude within 72 h of inoculation. Growth of E. coli on Pithophora appeared to be limited by dissolved nitrogen with a concentration of ≥ 66 μg/mL N allowing maximal bacterial growth. In contrast, an environmental strain of Salmonella did not grow under identical conditions in the microcosms, suggesting that this bacterium requires additional growth factors not provided by Cladophora. Since the alga can be maintained in the laboratory for long periods of time, this system allows for further experimentation and understanding of macroalga–microbe interactions.     

A short-term look at potential changes in Lake Michigan slimy sculpin diets

Diporeia hoyi and Mysis relicta are the most important prey items of slimy sculpins (Cottus cognatus) in the Great Lakes. Slimy sculpins were collected from dreissenid-infested bottoms off seven Lake Michigan ports at depths of 27–73 m in fall 2003 to study their lake-wide diets. Relatively large dreissenid biomass occurred at depths of 37- and 46-m. Quagga mussels (Dreissena bugnesis) composed at least 50% of dreissenid biomass at Manistique, Saugatuck, and Sturgeon Bay. Mysis accounted for 82% of the sculpin diet by dry weight at eastern Lake Michigan while Diporeia composed 54–69% of the diet at western Lake Michigan and dominated the diets of slimy sculpins at all sites deeper than 46 m. In northern Lake Michigan, this diet study in new sites showed that slimy sculpin consumed more prey with low energy contents, especially chironomids, than Mysis and Diporeia in shallow sites (depth <55 m). We recommend diet studies on sedentary benthic fishes to be conducted along perimeters of the Great Lakes to observe changes in their diets that may be impacted by changing benthic macroinvertebrate communities.     

Microbial Concentrations in Sand and their Effect on Beach Water in Door County,Wisconsin

The seasonal variations and patterns of Escherichia coli in Wisconsin's coastal waters have been closely studied in recent years due to increased beach monitoring activities. Patterns of distribution of the indicator organism, E. coli, in the sand at these beaches are now being investigated as a source of E. coli to adjacent beach water. This project investigates the concentrations of E. coli in beach sand, and the relationship between these sand-microbe concentrations and concentrations of microbes in the corresponding beach water. Weekly sampling of upshore, swash, and submerged sand at six beaches provided numbers of the indicator bacteria in each beach's sand substrate for two consecutive summers. Overall concentrations of E. coli were highest in the swash sand of the beach, with the highest numbers seen in the summer months and lowest numbers in the winter months. Each location had very different concentrations of E. coli in the beach sand from 1,800 CFU/100 g to 21,670 CFU/100 g sand. Each location had a very different relationship between the indicator organism found in the beach sand and that found in the beach water. These data suggest that sand may be a reservoir for E. coli at some locations, and another source of contamination that should be considered in beach monitoring programs. However, elevated levels of E. coli in beach sand were not universal and varied greatly from location to location.     

Lyngbya wollei in western Lake Erie

We report on the emergence of the potentially toxic filamentous cyanobacterium, Lyngbya wollei as a nuisance species in western Lake Erie. The first indication of heavy L. wollei growth along the lake bottom occurred in September 2006, when a storm deposited large mats of L. wollei in coves along the south shore of Maumee Bay. These mats remained intact over winter and new growth was observed along the margins in April 2007. Mats ranged in thickness from 0.2 to 1.2 m and we estimated that one 100-m stretch of shoreline along the southern shore of Maumee Bay was covered with approximately 200 metric tons of L. wollei. Nearshore surveys conducted in July 2008 revealed greatest benthic L. wollei biomass (591 g/m² ± 361 g/m² fresh weight) in Maumee Bay at depth contours between 1.5 and 3.5 m corresponding to benthic irradiance of approximately 4.0–0.05% of surface irradiance and sand/crushed dreissenid mussel shell-type substrate. A shoreline survey indicated a generally decreasing prevalence of shoreline L. wollei mats with distance from Maumee Bay. Surveys of nearshore benthic areas outside of Maumee Bay revealed substantial L. wollei beds north along the Michigan shoreline, but very little L wollei growth to the east along the Ohio shoreline.     

Recent increases in the large glacial-relict calanoid Limnocalanus macrurus in Lake Michigan

Since 2004, population density of the large hypolimnetic calanoid Limnocalanus macrurus Sars. has increased dramatically in Lake Michigan. The average summer biomass of this species between 2004 and 2006 was roughly three times that of the period 1984–2003, and at levels unprecedented in our 22-year dataset, making L. macrurus the dominant zooplankter in the lake in terms of biomass. These increases have been accentuated by coincident population declines of the main daphnid, Daphnia mendotae, in the lake with the result that in 2006, L. macrurus accounted for 75% and 50% of the large (> 0.9 mm) crustacean biomass in the northern and southern basins of Lake Michigan, respectively. The increases in L. macrurus populations have closely coincided with equally dramatic increases in summer water clarity. Recent extinction coefficients are among the lowest recorded for the lake, and deepening light penetration has permitted increases in the size of the deep chlorophyll layer. In addition, planktivorous fish populations have declined coincidently with the increases in L. macrurus. It seems likely that an increase in sub-epilimnetic production has resulted in increased food resources for the deep-living L. macrurus, while low planktivore abundances have reduced predation loss, permitting L. macrurus to respond to these increases in sub-epilimnetic production.     

The establishment of the nuisance cyanobacteria Lyngbya wollei in Lake St. Clair and its potential to harbor fecal indicator bacteria

Lyngbya wollei is a filamentous cyanobacterium which forms large nuisance mats and has infested eastern and southeastern U.S. Lakes and reservoirs for over 100 years. Lyngbya was recently identified in the Great Lakes system in the St. Lawrence River, and Western Lake Erie. Here we report on large deposits of L. wollei washing onshore at a popular recreational beach in Lake Saint Clair, part of the Great Lakes system. The amount of L. wollei deposited on shore was quantified and evaluated for the presence of fecal indicator bacteria (FIB). High concentrations of Escherichia coli, enterococci and Clostridium perfringens were found in the L. wollei in nearshore waters. The densities of E. coli (MPN), enterococci (MPN) and C. perfringens (CFU) attached to L. wollei averaged 3.5, 3.2 and 3.2 log/g, respectively. In contrast, nearshore waters contained nearly 10 times less FIB, averaging 2.6, 2.4 and 2.6 log/100 ml of E. coli (MPN), enterococci (MPN) and C. perfringens (CFU), respectively. DNA fingerprint analysis was used to examine the population structure of E. coli isolates obtained from L. wollei mats. The L. wollei-borne E. coli strains were genetically diverse, suggesting a causal relationship between E. coli and L. wollei. Results from this study indicate that in addition to the macroalga such as Cladophora, cyanobacteria like L. wollei also harbor FIB, potentially impacting water quality and human health in the Great Lakes.     

Spatial and temporal variations of persistent organic pollutants impacted by episodic sediment resuspension in southern Lake Michigan

The impacts of large-scale, episodic sediment resuspension on the cycling of polychlorinated biphenyl congeners (PCBs) were examined using a spatially coordinated air and water sampling strategy conducted in southern Lake Michigan in the late winters of 1998, 1999, and 2000. We found no significant temporal changes in gas phase, dissolved phase, or suspended sediment PCB concentrations despite large-scale seasonal storms occurring before and after sampling campaigns. Only gas phase and suspended sediment PCBs varied spatially. Higher total suspended material (TSM) concentrations and fraction organic carbon (f_oc) were measured at sampling stations located in the near-shore region of southern Lake Michigan than at open-water sampling stations. Gas phase concentrations (ΣPCB_g) were higher in the west (0.436 ± 0.200 ng/m³, n = 11) and south (0.408 ± 0.286 ng/m³, n = 5) than the east (0.214 ± 0.082 ng/m³, n = 10) and central (0.253 ± 0.145 ng/m³, n = 8) regions of southern Lake Michigan. Dissolved phase concentrations (ΣPCB_d) averaged 0.18 ± 0.024 ng/L (n = 52); suspended sediment concentrations (ΣPCB_s) accounted for between 4% and 72% (23 ± 4%, n = 52) of the total ΣPCB concentrations (ΣPCB_T = ΣPCB_d + ΣPCB_s). Despite no consistent temporal variations in both dissolved phase or suspended sediment ΣPCB concentrations, there were temporal and spatial variations in the distribution shift between phases that can be linked to sediment resuspension, not a state of equilibrium. Specifically, our analysis suggests sediment resuspension results in preferential sorption of heavier, more chlorinated PCB congeners.     

The Great Lakes Cladophora Model: Development,testing, and application to Lake Michigan

A recent review of the Great Lakes Water Quality Agreement has concluded that while controls on phosphorus inputs to Lake Michigan achieved the desired effect in offshore waters, the nearshore region continues to suffer from elevated phosphorus levels. Failure to achieve trophic state goals in the nearshore is manifested in nuisance growth of Cladophora and attendant impacts on property owners, utilities, and the public health and welfare. This study focuses on a site in Lake Michigan near Milwaukee, Wisconsin, where nuisance growth of Cladophora and associated beach fouling occur regularly. A mechanistic model simulating Cladophora growth, suitable for guiding nutrient management in the Great Lakes nearshore, is presented. The model represents an update of the Canale and Auer framework, reflecting current understandings of Cladophora ecology and offering a user-friendly interface making the software more widely available to decision makers. This Great Lakes Cladophora Model (GLCM) is first validated for the Auer/Canale data set collected in 1979 at a site on Lake Huron and then for a data set developed in 2006 for a site on Lake Michigan. Model performance under the strikingly different forcing conditions (depth, light, phosphorus levels) characteristic of these two sites affirms the widespread applicability of the tool. The GLCM is then extended to examine the impacts of ecosystem perturbation (dreissenid colonization) on Cladophora growth and to future approaches to monitoring and management.     

Spatial genetic structure and recruitment dynamics of burbot (Lota lota) in Eastern Lake Michigan and Michigan tributaries

Burbot (Lota lota) are the only freshwater member of the Cod like (Lotidae) family that have a circumpolar distribution and occupy the widest geographic distribution of all Laurentian Great Lakes fish species. Information regarding burbot spatial genetic structure and recruitment dynamics is critical for the development of effective management strategies. Although burbot are a species of conservation concern throughout their range, little demographic or behavioral information exists. We estimated levels of genetic diversity within, and the degree of spatial population structure between samples collected from Lake Michigan and tributaries of the Manistee River, MI. Measures of genetic diversity across 10 microsatellite loci were moderately high. Disparities between adult groups sampled in Lake Michigan and the Manistee River were notable for observed heterozygosity (0.662 vs 0.488) and allelic richness (11.7 vs 6.6). Significant levels of inter-population variance in microsatellite allele frequencies (F_ST 0.154 to 0.208) were detected between Lake Michigan and the Manistee River samples. Results indicate reproductive isolation between what plausibly may be riverine and lacustrine spawning life history types. Pedigree analyses for three cohorts sampled in the Manistee River revealed that a sizeable number of adults contributed reproductively to multiple cohorts, indicating spawning philopatry. While data were collected from restricted areas in lacustrine and river habitats, analyses revealing microgeographic genetic structuring, potentially attributed to life history polymorphisms, have significant implications for burbot management in the Great Lakes.     

Movement and growth indicators in resident and adfluvial coaster brook trout (Salvelinus fontinalis) in the Hurricane River,Lake Superior,Michigan, USA

Brook trout (Salvelinus fontinalis) are found throughout Lake Superior, Lake Nipigon, and their tributaries. Lacustrine and adfluvial life history variants were historically popular with anglers and were called coasters; coaster brook trout populations are now severely reduced and are of conservation concern. Coasters were known to grow larger and mature later than their stream resident counterparts. This study compared movement patterns, age, size, condition, and relative weight of wild coaster and resident brook trout from the Hurricane River, Pictured Rocks National Lakeshore, Michigan. Wild brook trout ≥ 100 mm from the Hurricane River downstream from Hurricane Falls were tagged with passive integrated transponder tags and monitored for stream-lake movement behavior from May 2003 to November 2007. During 2006 and 2007, brook trout were scale sampled and aged to construct a regression that was then used to calculate the age of all brook trout tagged from 2003 to 2007. Most brook trout movement took place in the fall with October the peak month of emigration with a secondary peak in late spring/early summer and some activity nearly year round. There were no differences found in age structure, size or condition between coasters and residents while in the stream. Our data suggest that a priori growth differences are not determining the expression of coaster outmigration and that stream-lake movements made by coasters, likely driven by habitat requirements, may be highly flexible and facultative.     

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.     

Cylindrospermopsis in Lake Erie: Testing its Association with Other Cyanobacterial Genera and Major Limnological Parameters

We report the first documented observation of the potentially toxic cyanobacterium Cylindrospermopsis in Lake Erie and Sandusky Bay in 2005 (0.043–1.326 mg L^-1 wet weight, 16–1,942 trichomes mL^-1) and quantify the physical and chemical parameters and the cyanobacterial community composition contemporaneous to its occurrence. We hypothesize that the high temperature, low light intensity, and high nutrient content of Sandusky Bay, a shallow, drowned river mouth along the southwestern shore of Lake Erie, provides an ideal habitat for Cylindrospermopsis. This is consistent with published laboratory and field studies that show these physical and chemical conditions facilitate Cylindrospermopsis growth. Using multivariate statistics, we found that Cylindrospermopsis biomass correlated with high temperatures and shallow depths, conditions often found in Sandusky Bay. Light climate and nutrient concentrations were not associated with Cylindrospermopsis biomass, most likely because the light climate did not systematically change during the season and because nutrients exceeded demand. We propose that Cylindrospermopsis will increase in importance in Lake Erie, as previous research on climate change in the Great Lakes region predicts future higher water temperatures and lower water levels.     

Distribution and abundance of freshwater polychaetes, Manayunkia speciosa (Polychaeta), in the Great Lakes with a 70-year case history for western Lake Erie

Manayunkia speciosa has been a taxonomic curiosity for 150 years with little interest until 1977 when it was identified as an intermediate host of a fish parasite (Ceratomyxa shasta) responsible for fish mortalities (e.g., chinook salmon). Manayunkia was first reported in the Great Lakes in 1929. Since its discovery, the taxon has been reported in 50% (20 of 40 studies) of benthos studies published between 1960 and 2007. When found, Manayunkia comprised < 1% of benthos in 70% of examined studies. In one extensive study, Manayunkia occurred in only 26% of 378 sampled events (1991–2009). The taxon was found at higher densities in one area of Lake Erie (mean = 3658/m²) and Georgian Bay (1790/m²) than in five other areas (mean = 60 to 553/m²) of the lakes. A 70-year history of Manayunkia in western Lake Erie indicates it was not found in 1930, was most abundant in 1961 (mean = 8039, maximum = 67,748/m²), and decreased in successive periods of 1982 (3529, 49,639/m²), 1993 (1876, 25,332/m²), and 2003 (79, 2583/m²). It occurred at 48% of stations in 1961, 58% in 1982, 52% in 1993, and 6% of stations in 2003. In all years, Manayunkia was distributed primarily near the mouth of the Detroit River. Causes for declines in distribution and abundance are unknown, but may be related to pollution-abatement programs that began in the 1970s, and invasion of dreissenid mussels in the late-1980s which contributed to de-eutrophication of western Lake Erie. At present, importance of the long-term decline of Manayunkia in Lake Erie is unknown.     

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.     

Evidence for Remote Effects of Dreissenid Mussels on the Amphipod Diporeia: Analysis of Lake Ontario Benthic Surveys, 1972–2003

The status of invasive dreissenid mussels (Dreissena polymorpha and D. bugensis) and native amphipods (Diporeia spp.) in Lake Ontario was assessed in 2003 and compared with historical data. D. polymorpha (zebra mussels) were rarely observed in 2003, having been displaced by D. bugensis (quagga mussels). D. bugensis expanded its depth range from 38 m depth in 1995 to 174 m in 2003 and this dreissenid reached densities averaging 8,000/m² at all sites < 90 m. During the same time period, Diporeia populations almost completely disappeared from 0–90 m depth, continuing a declining trend from 1994–1997 reported in previous studies. The average density of Diporeia in the 30–90 m depth interval decreased from 1,380/m² to 63/m² between 1997 and 2003. Prior to 2003, areas deeper than 90 m represented a refuge for Diporeia, but even these deep populations decreased, with densities declining from 2,181/m2 in 1999 to 545/m2 in 2003. Two common hypotheses for the decline of Diporeia in the Great Lakes are food limitation and a toxin/pathogen associated with dreissenid pseudofeces. The Diporeia decline in deep waters preceded the expansion of D. bugensis to these depths, and suggests that shallow dreissenid populations remotely influence profundal habitats. This pattern of decline is consistent with mechanisms that act from some distance including nearshore dreissenid grazing and downslope transport of pseudofeces.     

First occurrence of the mysid Hemimysis anomala in an inland lake in North America,Oneida Lake,NY

Hemimysis anomala (Crustacea, Mysidae) is a recent invader to North America that until now was reported only from the Laurentian Great Lakes and their immediate embayments, along with the St. Lawrence River. In August 2009, we identified Hemimysis in diets of white perch and yellow perch in Oneida Lake, NY. Night time vertical plankton net tows detected Hemimysis at four sites across the lake. Hemimysis in fish diets (5.5–8.6 mm) were larger than in net tows (2.2–7.0 mm) and reproduction is occurring as some females had brood sacs. This is the first documented introduction of Hemimysis to an inland lake in North America, outside the Great Lakes. Oneida Lake is located 53 river km upstream from Lake Ontario, the nearest known source of Hemimysis. No genetic differences were found between Hemimysis in Oneida Lake and Lake Ontario, indicating this is likely the source of introduction. Several large rapids, locks, and dams separate the two lakes, and as a result the most likely vector of introduction to Oneida Lake is pleasure boat or light commercial traffic via the canal system or overland transport. The presence of Hemimysis in Oneida Lake 3 years after it was first found in Lake Ontario suggests this species may spread rapidly throughout the basin. Despite an intensive monitoring program on Oneida Lake directed at fish, zooplankton, and limnology, Hemimysis was only detected in fish diets and night time zooplankton tows, indicating it may go undetected in lakes for some time using traditional daytime net tows.