Emerald Shiner Notropis Atherinoides Research Articles

Nearshore Fish Species Richness and Species–Habitat Associations in the St. Clair–Detroit River System

Shallow water riparian zones of large rivers provide important habitat for fishes, but anthropogenic influences have reduced the availability and quality of these habitats. In the St. Clair–Detroit River System, a Laurentian Great Lakes connecting channel, losses of riparian habitat contributed to impairment of fish populations and their habitats. We conducted a seine survey annually from 2013 to 2019 at ten sites in the St. Clair and Detroit rivers to assess riparian fish communities, and to identify habitat attributes associated with fish species richness and catches of common species. We captured a total of 38,451 fish representing 60 species, with emerald shiner Notropis atherinoides composing the largest portion of the catch. We used an information-theoretic approach to assess the associations between species richness and catches of 33 species with habitat variables (substrate, shoreline vegetation types, and aquatic macrophyte richness). Sand, cobble, and algal substrates and shoreline vegetation were important predictors of species richness based on a multimodel inference approach. However, habitat associations of individual species varied. This work identified manageable habitat variables associated with species richness, while identifying potential tradeoffs for individual species. Further, this work provides baselines for development and evaluation of fish community and shoreline habitat restoration goals.

Hydroacoustic survey standardization: Inter-vessel differences in fish densities and potential effects of vessel avoidance

Hydroacoustics is used broadly to assess fish populations in marine and freshwater systems. Large-scale surveys often employ multiple vessels to complete a survey. Vessels can be a source of variation in multi-vessel surveys, and accounting for this variation is critical to precise and accurate assessments, whether as indices or measures of absolute abundance. We examined areal and volumetric density estimates, area backscattering coefficient (ABC), and mean target strength (TS) produced by three vessels in Lake Erie along three cross-lake transects in July 2014. Our study showed positive correlation in areal ABC, mean TS, and density among vessels; however, there was an almost 30 % higher density obtained with the largest vessel, on average. As a result, vessel choice could contribute to variation and/or bias in forage fish surveys deploying multi-vessels conducted on Lake Erie. Additionally, in some situations, differential depth patterns of fish contributed to vessel related differences in survey results suggesting a difference in vessel avoidance behaviors among targeted forage species, primarily emerald shiner Notropis atherinoides and rainbow smelt Osmerus mordax. This work demonstrates the potential magnitude of differences among vessels and highlights the need to identify and account for or otherwise control for these effects when monitoring or managing fisheries through standardized hydroacoustic assessments surveys.

Factors Related to Age-0 Native Fish Catch per Unit Effort in the South Dakota Missouri River Reservoirs

AbstractThe Missouri River in South Dakota was dammed in the 1950s and 1960s, altering the biotic and abiotic factors that potentially affect native species in the mainstem reservoirs. Little research has been conducted regarding what factors regulate age-0 catch per unit effort (CPUE) of native fish species since the damming occurred. Thus, we examined age-0 CPUE for 13 native fish species in the four Missouri River mainstem reservoirs. We analyzed data from 1995 to 2015 in Lake Oahe, 2002 to 2016 in Lake Sharpe, 1998 to 2008 in Lake Francis Case, and 2000 to 2013 in Lewis and Clark Lake. Not all species were sampled in all reservoirs. We evaluated potential environmental (inflow, gauge height, peak flow, precipitation, air temperature) and biological (CPUE of other native species, nonnative species, and predators) factors that have documented impacts on age-0 native fish. Significant relationships existed between age-0 native fish CPUE and both biotic and abiotic factors in all four reservoirs, but were species- and reservoir-dependent. Age-0 CPUE was either stable or increasing in all species examined in all reservoirs except age-0 Emerald Shiner Notropis atherinoides in Lewis and Clark Lake. Age-0 Emerald Shiner CPUE in Lewis and Clark Lake was most supported by biological models (e.g., total age-0 nonnative and adult White Bass Morone chrysops CPUE), and a positive relationship existed between age-0 Emerald Shiner and both factors. We believe our findings provide valuable insight into successful management of native fish populations.

Enhanced inference of ecological networks by parameterizing ensembles of population dynamics models constrained with prior knowledge

BackgroundAccurate network models of species interaction could be used to predict population dynamics and be applied to manage real world ecosystems. Most relevant models are nonlinear, however, and data available from real world ecosystems are too noisy and sparsely sampled for common inference approaches. Here we improved the inference of generalized Lotka–Volterra (gLV) ecological networks by using a new optimization algorithm to constrain parameter signs with prior knowledge and a perturbation-based ensemble method.ResultsWe applied the new inference to long-term species abundance data from the freshwater fish community in the Illinois River, United States. We constructed an ensemble of 668 gLV models that explained 79% of the data on average. The models indicated (at a 70% level of confidence) a strong positive interaction from emerald shiner (Notropis atherinoides) to channel catfish (Ictalurus punctatus), which we could validate using data from a nearby observation site, and predicted that the relative abundances of most fish species will continue to fluctuate temporally and concordantly in the near future. The network shows that the invasive silver carp (Hypophthalmichthys molitrix) has much stronger impacts on native predators than on prey, supporting the notion that the invader perturbs the native food chain by replacing the diets of predators.ConclusionsEnsemble approaches constrained by prior knowledge can improve inference and produce networks from noisy and sparsely sampled time series data to fill knowledge gaps on real world ecosystems. Such network models could aid efforts to conserve ecosystems such as the Illinois River, which is threatened by the invasion of the silver carp.

Visual performance impaired by elevated sedimentary and algal turbidity in walleye Sander vitreus and emerald shiner Notropis atherinoides.

The objectives of this study were to determine the effects of different forms of elevated turbidity on the visual acuity of two native Lake Erie fishes and to assess the response of fishes from different trophic levels to elevated turbidity. Additionally, the role of visual morphology (e.g., eye and optic lobe size) on visual acuity was evaluated across visual environments. Reaction distance, a behavioural proxy for measures of visual acuity, was measured for a top predator, walleye Sander vitreus and a forage fish, emerald shiner Notropis atherinoides. In both S. vitreus (n = 27) and N. atherinoides (n = 40) reaction distance across all types of turbidity (sedimentary, algal, sedimentary + algal; 20 NTU) was approximately 50% lower relative to the clear treatment. Reaction distance was further reduced in algal compared with sedimentary turbidity for wild-caught S. vitreus. Eye and brain morphology also influenced reaction distance across turbidity treatments, such that larger relative eye and brain metrics were positively correlated with reaction distance. This study provides evidence for disrupted visual acuity as a potential mechanism underlying fish responses, such as decreased foraging efficiency, to increased turbidity and further indicates that algal turbidity will probably be more detrimental to visual processes than sedimentary turbidity. With the increasing occurrence and severity of harmful algal blooms due to cultural eutrophication globally, this could have significant implications for predator-prey relationships in aquatic systems.

Prey fish communities of the Laurentian Great Lakes: A cross-basin overview of status and trends based on bottom trawl surveys, 1978-2016

Annual bottom trawl surveys were initiated in the 1970s in Laurentian Great Lakes Superior, Huron, Michigan and Ontario and in 1990 in Erie to provide annual assessments of the status and trends of prey fish communities. Native Cisco Coregonus artedi and Bloater C. hoyi dominated the prey fish community of Lake Superior. Prey fish communities in lakes Huron and Michigan were dominated by nonnative Rainbow Smelt Osmerus mordax and Alewife Alosa pseudoharengus for much of 1978-2016, but Bloater was an important species during the 1980-1990s and more recently has become the dominant prey species in these lakes. Alewife dominated the prey fish community of Lake Ontario during all 1978-2016. While nonnatives dominated the prey fish community in Lake Erie, native Emerald Shiner Notropis atherinoides was an important species and occasionally the dominant prey fish after the establishment of Round Goby Neogobius melanostomus in the late 1990s. During the 1980s-1990s Bythotrephes cederstroemi, Dreissena polymorpha, and Dreissena bugensis caused profound changes in Laurentian Great Lakes ecosystems and likely contributed to declines in fish community biomass in lakes Michigan and Huron. The impacts of these invaders were more muted in lakes Erie and Ontario. Lake Superior stands out as the Laurentian Great Lakes success story: Lake Trout Salvelinus namaycush was restored, and native prey fishes dominate and support a viable fishery. Although the abundance of Bloater has increased recently in lakes Huron and Michigan, recovery of native prey fishes remains uncertain. The absence of native species among the principal prey fish in Lake Ontario indicates a lack of progress in native fish recovery. Recovery of native prey fishes remains unclear in Lake Erie. The ever-changing state of the Laurentian Great Lakes caused by the impacts of invasive species and ongoing climate and ecosystem change will continue to challenge restoration of native fish communities in the 21st Century.

Retail Baitfish in Michigan Harbor Serious Fish Viral Pathogens.

Indigenous small cyprinid fish species play an important role in Great Lakes ecosystems and also comprise the backbone of a multimillion‐dollar baitfish industry. Due to their widespread use in sport fisheries of the Laurentian Great Lakes, there are increasing concerns that baitfish may introduce or disseminate fish pathogens. In this study, we evaluated whether baitfish purchased from 78 randomly selected retail bait dealers in Michigan harbored fish viruses. Between September 2015 and June 2016, 5,400 baitfish divided into 90 lots of 60 fish were purchased. Fish were tested for the presence of viral hemorrhagic septicemia virus (VHSV), spring viremia of carp virus (SVCV), golden shiner reovirus (GSRV), fathead minnow nidovirus (FHMNV), fathead minnow picornavirus (FHMPV), and white sucker bunyavirus (WSBV). Using the epithelioma papulosum cyprini cell line and molecular confirmation, we demonstrated the presence of viruses in 18 of the 90 fish lots (20.0%) analyzed. The most prevalent virus was FHMNV, being detected in 6 of 30 lots of Fathead Minnow Pimephales promelas and 3 of 42 lots of Emerald Shiners Notropis atherinoides. We also confirmed GSRV in two fish species: the Golden Shiner Notemigonus crysoleucas (5 of 11 lots) and Fathead Minnow (3 of 30 lots). Two VHSV (genotype IVb) isolates were recovered from a single lot of Emerald Shiners. No SVCV, FHMPV, or WSBV was detected in any of the fish examined. Some of the infected fish exhibited clinical signs and histopathological alterations. This study demonstrates that live baitfish are a potential vector for the spread of viral pathogens and underscores the importance of fish health certifications for the Great Lakes baitfish industry.

The Postrelease Survival of Walleyes Following Ice‐Angling on Lake Nipissing, Ontario

AbstractNatural resource agencies have developed catch‐and‐release regulations for Walleyes Sander vitreus of prohibited size and number to reduce mortality in many recreational fisheries. The efficacy of such regulations is contingent upon the released fish surviving, but survival data on Walleyes captured by ice‐angling are lacking. We estimated the survival of Lake Nipissing (Ontario, Canada) Walleyes that were captured by both active and passive ice‐angling methods using a variety of hook types and lures baited with Emerald Shiners Notropis atherinoides. We also assessed the role of de‐hooking methods on the survival of deeply hooked Walleyes. After the angling event, Walleyes (n = 260) were held for 24 h in a submerged holding pen to estimate postrelease survival. Average mortality after the 24‐h holding period was 6.9%. Fewer Walleyes captured by active angling were deeply hooked (9.3%) than passively caught fish (50.4%), and deeply hooked Walleyes were observed to have more frequent postrelease mortality (14.8%) than shallow‐hooked Walleyes (3.0%). There was no significant difference in mortality rates of Walleyes caught by passive angling (9.8%) or active angling (2.8%); mortality rates of fish caught on circle hooks (6.1%), J‐hooks (8.2%), and treble hooks (5.6%) also did not differ. Neither air temperature nor the presence of barotrauma had a significant effect on mortality of captured Walleyes. Survival did not significantly differ between deeply hooked fish that had the line cut (11.1%) and those that had the hook removed (22.6%). Results from this study suggest a relatively high incidence of Walleye survival after catch‐and‐release angling through the ice.

Prey selectivity of common predators on Silver carp (Hypophthalmichthys molitrix): controlled laboratory experiments support field observations

Silver Carp Hypophthalmicthys molitrix (Valenciennes, 1844) are an invasive species in the Mississippi River Basin and their current role in this novel ecosystem is not fully understood. Juvenile Silver Carp can and do occur in great numbers after a successful spawn. These massive schools of small Silver Carp seem to be an obvious prey source for the common predators of the Mississippi River system. The level to which native piscivores are consuming this novel prey item is unclear. Therefore, the goal of this research was to assess the diets of native piscivores collected in Pool 26 and the Open River reach of the Mississippi River. Using diet contents and catch rates of small fishes, selection or avoidance could be determined for predator prey interactions. Then a controlled laboratory experiment was conducted to determine if common predators [White Bass Morone chrysops and Largemouth Bass Micropterus salmoides (Lacepede, 1802)] would select for or against this novel prey in the presence of two native prey fish [Gizzard Shad Dorosoma cepedianum (Lesueur, 1818) and Emerald Shiner Notropis atherinoides]. Understanding how predator-prey interactions occur in a controlled laboratory experiment may provide insight to trends observed in the field. The majority of native piscivores appeared to be avoiding Silver Carp in both reaches and selecting native prey fishes. The order in which prey fish were consumed by both predators showed significant avoidance of Silver Carp. It appears that the trends observed in the field were supported by our controlled laboratory experiment. The effectiveness of different native piscivores to consume Silver Carp may have impacts on future management decisions.

New host record and molecular characterization of Dicauda atherinoidi Hoffman & Walker (Bivalvulida: Myxobolidae): a parasite of the emerald shiner Notropis atherinoides Rafinesque, 1818 and mimic shiner Notropis vollucellus Cope, 1865

Updated morphological and histopathological descriptions for Dicauda atherinoidi (Bivalvulida:Myxobolidae) and an expanded host range are supplemented with the first molecular data and phylogenetic analyses of the genus. Plasmodia were located on the head, ventrum/body and fins of infected emerald shiner Notropis atherinoides Rafinesque, 1818 and mimic shiner Notropis vollucellus Cope, 1865, a new host species. Myxospores were spherical, ranging 9.3-11.4μm (10.5±0.4) in length, 9.0-11.0μm (9.7±0.4) in width and 6.6-7.0μm (6.8±0.2) thick in sutural view, and possessed 2-3 caudal processes (5.3-68.3μm, 31.1±13.6) connected to the spore body at the sutural groove, all of which are consistent with the genus Dicauda. In the absence of available Dicauda sequence data, the 18S rDNA sequences from Michigan isolates were most similar to Myxobolus spp. Phylogenetic analyses clustered these isolates with myxobolid species from cyprinid fish, suggesting these parasites may represent an underpopulated group of cyprinid-infecting myxozoans. Histopathology revealed thin-walled plasmodial pseudocysts in the dermis and associated connective tissue, where granulomatous inflammation and focal scale atrophy were also present. Further sampling/sequencing of myxobolids from Notropis spp. should expand these underrepresented myxozoans and offer further insight into Myxobolidae host family tropisms.

Polychlorinated Biphenyl Bioaccumulation Patterns Among Lake Erie Lower Trophic Level Consumers Reflect Species Ecologies.

Polychlorinated biphenyl (PCB) concentrations were quantified in lower trophic level consumers of the Lake Erie western basin food web to assess the capacity of PCBs to discriminate among trophically similar species inhabiting different compartments of the same ecosystem. Zooplankton were characterized by higher proportions of less chlorinated and hydrophobic homologs relative to zebra mussel (Dreissena polymorpha), mayfly (Hexagenia limbata) and emerald shiner (Notropis atherinoides) samples. PCB biota-sediment accumulation factors (BSAF) differed significantly among species with zebra mussels and emerald shiners having the highest BSAFs. Principal components analysis of sample PCB profiles reflected the contrasting pelagic and benthic habitats occupied by filter-feeding zooplankton and zebra mussel samples. Benthic mayfly PCB profiles were characterized by increasingly hydrophobic (logK OW ≥ 6.9) congeners with more variable emerald shiner profiles reflecting the greater mobility and extent of spatial habitat integration achieved by this secondary consumer. These results contribute to growing evidence for the use of PCBs as ecological tracers in aquatic ecosystems.

Range expansion and molecular confirmation of the Asian fish tapeworm in the lower Great Lakes and St. Lawrence River with notes on infections in baitfish

Abstract The Asian fish tapeworm, Schyzocotyle (formerly Bothriocephalus ) acheilognathi , was surveyed in fishes from the lower Great Lakes, surrounding waters, and St. Lawrence River between 2009 and 2015. Sequences of the internal transcribed spacer region (ITS1, 5.8S, ITS-2) and the barcode gene cytochrome oxidase 1 (CO1) are provided, confirming identification. Emerald shiners ( Notropis atherinoides ) collected in 2009–10 from the St. Clair River, the Detroit River, Lake Erie, the Niagara River, and Lake Ontario were infected at most localities with prevalence ranging from 1.9 to 20.0%. Infection intensity was negatively correlated with condition in these emerald shiners. Museum specimens of emerald shiners collected in 2007 from Lake Erie and vicinity also were infected at a prevalence of 5.0%. The parasite was observed for the first time in the St. Lawrence River at Beauharnois, QC, in a bluntnose minnow ( Pimephales notatus ) in June 2012. Subsequent infections in the St. Lawrence River were observed in two bluntnose minnows from Beauharnois in September 2012 and in emerald shiners from Beauharnois (prevalence = 12.0%) in June 2013, at Iles de la Paix, QC (prevalence = 6.7%) and Iles de Boucherville, QC (prevalence = 2.8%) in September 2013, and Ilet Vert, QC (prevalence = 1.8%) east of Montreal in September 2015. Samples of six other fish species from the Great Lakes, eight from surrounding small lakes and rivers, and eight species from the St. Lawrence River were uninfected. Of six species collected from six bait retailers along the north shore of Lake Erie and Lake Ontario, emerald shiners were infected at prevalences of 4.0 and 20.0% at two facilities out of six, indicating that infected baitfish have occurred in the wild at some harvest sites with sufficient prevalence to be transferred throughout the commercial supply chain. Results demonstrate that the Asian fish tapeworm has spread rapidly across the lower Great Lakes since its first observation in the Detroit River in 2002 and appears to be spreading eastward from its recent initial capture location in the St. Lawrence River.

Effects of historic flooding on fishes and aquatic habitats in a Missouri River delta

Understanding the effects of disturbances on aquatic biota is important for management of the world's rivers. Riverine deltas are among the most biologically productive ecosystems, yet the ecological effects of floods in deltas are poorly understood. Therefore, the goal of this study was to examine impacts of an historic flood in the Missouri River basin in 2011 on fishes and aquatic habitats in the Lewis and Clark Delta, located in South Dakota and Nebraska, USA. Fish community structural indices declined in the six years preceding the flood, with species richness and diversity (Fisher's α) decreasing from 25 to 22 and 4.56 to 3.48, respectively. However, the fish community exhibited short-term resistance to the flood as both metrics were similar to pre-flood levels after the disturbance in 2012. Evenness (J′) declined from 0.88 to 0.73 before the flood but increased to 0.84 after the disturbance. The majority of species exhibited greater relative abundance after the flood regardless of age class (i.e., juvenile, adult), morphology (i.e., small-bodied, large-bodied), introduction history (i.e., introduced, native), or recreational importance (i.e., sport fish, non-recreational). However, the flood reduced relative abundance of juvenile freshwater drum (Aplodinotus grunniens) and white crappie (Pomoxis annularis) and did not affect the three small-bodied species that were studied, including emerald shiner (Notropis atherinoides), red shiner (Cyprinella lutrensis), and spotfin shiner (Cyprinella spiloptera). The flood decreased side channel and backwater frequency and width/area but increased sandbar abundance. Physical alterations evidently had minimal effects on structural indices of the fish community. However, an overall increase in relative abundance across species suggests that interspersed fluvial and slackwater habitats in the delta provided refuge from floodwaters during the disturbance. Maintaining habitat connectivity in deltas during and after floods is particularly important for fisheries conservation. Illustrating the ecological effects and implications of a major flood, this study contributes to the nascent field of delta ecology.

Mesohabitat associations in the Mississippi River Basin: a long-term study on the catch rates and physical habitat associations of juvenile silver carp and two native planktivores

Fish community structure is a complex and integrated part of an aquatic ecosystem; a balanced system is often rich in species diversity and abundance. Invasive species can alter this balance, and the expansion of invasive silver carp may have similar deleterious effects. Recently, catches of silver carp in the Midwestern United States have increased and there is evidence of successful spawning and recruitment. However, early life history attributes of silver carp have not been fully evaluated within the Mississippi River Basin. A thorough understanding of early-life history is imperative to facilitate control efforts for silver carp populations. Furthermore, age-0 silver carp survival and subsequent recruitment may be regulated by habitat availability during this critical life stage. Thus, the objective of this study was to evaluate age-0 silver carp mesohabitat (i.e., depth, velocity, and substrate) use in three reaches of the Mississippi River Basin and potential habitat overlap with two native planktivorous fish species, gizzard shad Dorosoma cepedianum and emerald shiner Notropis atherinoides. Using data collected from the three lower most reaches of the Long Term Resource Monitoring Program (Pool 26 at Alton, Illinois, USA; Open River at Cape Girardeau, Missouri, USA of the Mississippi River; and the LaGrange reach at Havana, Illinois, USA of the Illinois River), we investigated age-0 silver carp, age-0 gizzard shad and age-0 emerald shiner habitat associations from 2007 to 2012. Overall, 79,358 age-0 silver carp, 89,990 gizzard shad and 41,119 emerald shiner were captured with mini fyke nets during this long-term study. Generally, all three species were collected most frequently in shallow (< 1.5 meters), low velocity (<0.6 meters/second) habitat with greater variability in substrate use ranging from silt to rock. Given the scarcity of these habitat types in the channelized Mississippi River Basin, our results suggest that invasive silver carp exhibit habitat overlap with gizzard shad and emerald shiner. This overlap may result in reduced growth and body condition of these fishes. To this end, this extensive data set has provided new information about silver carp early life history mesohabitat use and overlap occurring between two age-0 native planktivores in the Mississippi River Basin and potential consequences of this association.

Pathogenesis of spring viremia of carp virus in emerald shiner Notropis atherinoides Rafinesque, fathead minnow Pimephales promelas Rafinesque and white sucker Catostomus commersonii (Lacepede).

Spring viremia of carp (SVC) is a reportable disease to the World Organization of Animal Health (OIE) as it is known to cause significant international economic impact. In Canada, the first and only isolation of SVC virus (SVCV) was in 2006, from common carp Cyprinus carpio L., at Hamilton Harbour, Lake Ontario. The susceptibility of fathead minnow Pimephales promelas Rafinesque, emerald shiner Notropis atherinoides Rafinesque and white sucker Catostomus commersonii (Lacepede) to intraperitoneal injection of the Canadian isolate (HHOcarp06) was evaluated using experimental infection, virus isolation, quantitative reverse transcription polymerase chain reaction (qRT-PCR), histopathology and immunohistochemistry (IHC). Emerald shiner and fathead minnow were most susceptible with 43 and 53% cumulative mortality, respectively, compared with koi at 33%. Quantitative RT-PCR demonstrated that koi had high viral loads throughout the experiment. At 34days post-infection, SVCV was detected from sampled emerald shiner and white sucker in very low titre and was not detected from fathead minnow. Koi, fathead minnow and emerald shiner had gross lesions typical of SVC disease. The histopathological picture was mostly dominated by necrotic changes in kidney, spleen, liver, pancreas and intestine. IHC further confirmed SVCV infection, and staining was largely correlated with histological lesions.

Angler‐Caught Piscivore Diets Reflect Fish Community Changes in Lake Huron

AbstractExamination of angler‐caught piscivore stomachs revealed that Lake Trout Salvelinus namaycush, Chinook Salmon Oncorhynchus tshawytscha, and Walleyes Sander vitreus altered their diets in response to unprecedented declines in Lake Huron's main‐basin prey fish community. Diets varied by predator species, season, and location but were nearly always dominated numerically by some combination of Alewife Alosa pseudoharengus, Rainbow Smelt Osmerus mordax, Emerald Shiner Notropis atherinoides, Round Goby Neogobius melanostomus, or terrestrial insects. Rainbow Trout Oncorhynchus mykiss (steelhead), Coho Salmon Oncorhynchus kisutch, and Atlantic Salmon Salmo salar had varied diets that reflected higher contributions of insects. Compared with an earlier (1983–1986) examination of angler‐caught predator fishes from Lake Huron, the contemporary results showed an increase in consumption of nontraditional prey (including conspecifics), use of smaller prey, and an increase in insects in the diet, suggesting that piscivores were faced with chronic prey limitation during this study. The management of all piscivores in Lake Huron will likely require consideration of the pervasive effects of changes in food webs, especially if prey fish remain at low levels.Received December 19, 2013; accepted June 30, 2014

Experimental Transmission of VHSV Genotype IVb by Predation

Preliminary surveillance of wild baitfish during the 2006 viral hemorrhagic septicemia virus genotype IVb (VHSV IVb) outbreaks indicated Emerald Shiners Notropis atherinoides and Bluntnose Minnow Pimephales notatus were infected with high levels of VHSV without showing clinical signs of disease. The movement and use of baitfish was recognized as the most probable vector for the introduction of VHSV to inland waters, such as Conesus Lake and Skaneateles Lake in New York, Budd Lake in Michigan, and Little Lake Butte des Morts and Lake Winnebago in Wisconsin. While numerous government agencies implemented restrictions to stop the movement of potentially infected baitfish into new waters and prevent the spread of VHSV IVb, until now, studies to investigate whether these initial introductions were by an oral route of infection have not occurred. Our studies identified infected Fathead Minnow Pimephales promelas as suitable vectors for transmitting VHSV IVb when fed to Tiger Muskellunge ( ♂ Northern Pike Esox lucius × ♀ Muskellunge Esox masquinongy) during laboratory trials. Six of 16 Tiger Muskellunge were infected with VHSV IVb after consumption of infected Fathead Minnows when assayed with quantitative reverse transcriptase polymerase chain reaction and viral isolation in cell culture. Weekly sampling of water and feces from these Tiger Muskellunge individually reared showed intermittent shedding of VHSV IVb. Those exposed to similarly VHSV IVb-inoculated fathead minnows by cohabitation only became infected in 1 case out of 16. A similar trial of 12 Tiger Muskellunge fed Round Goby Neogobius melanostomus that survived a VHSV IVb immersion challenge did not result in infection. Overall, our findings imply that consumption of infected wild baitfish may be a risk factor for introduction of VHSV.

Analysis of Prey Selection by Double‐Crested Cormorants: A 15‐Year Diet Study in Oneida Lake, New York

AbstractPiscivorous birds, in particular cormorants Phalacrocorax spp., have been reported to cause declines in some fish populations in both Europe and North America, but not in others. This difference may be due to prey selection by cormorants that is further dependent on the composition of the fish assemblage present. We present 15 years of diet data collected from Oneida Lake, New York, where we have previously documented negative effects of double‐crested cormorants Phalacrocorax auritus on two fish populations valued by anglers: Walleye Sander vitreus and Yellow Perch Perca flavescens. The Oneida Lake fish community changed through the study period and this change was reflected in cormorant diet samples. Diet samples were variable based on season and year with Emerald Shiner Notropis atherinoides, Gizzard Shad Dorosoma cepedianum, Lepomis spp., Logperch Percina caprodes, Walleye, and Yellow Perch having the highest overall relative importance. In years when age‐0 Gizzard Shad were abundant they dominated double‐crested cormorant diets in the fall after the shad reached a length of 45 mm. Consumption of Emerald Shiner and Gizzard Shad was positively related to each species’ abundance, but no significant correlation between availability and consumption was found for Walleye, White Perch Morone americana, or Yellow Perch. Double‐crested cormorants may be displaying prey‐switching behavior and selecting for smaller, soft‐rayed, prey species. We conclude that variation in fish recruitment influences double‐crested cormorant food selection habits and highlight the importance of continued monitoring with changing fish communities to reliably assess potential impacts of cormorants on a fish community over time.

Experimental Infection of Koi Carp with Viral Hemorrhagic Septicemia Virus Type IVb

Viral hemorrhagic septicemia virus (VHSV) type IVb has a wide host range that includes at least three cyprinid species: Fathead Minnow Pimephales promelas, Emerald Shiner Notropis atherinoides, and Bluntnose Minnow P. notatus. To date, VHSV IVb has only been found in wild fish. However, the possibility of infection in culture facilities remains. Koi Carp Cyprinus carpio are a major ornamental aquaculture species in the United States; however, their potential to become infected with VHSV IVb has not yet been examined. In this study, we exposed Koi to 3 × 10(6) PFU VHSV Great Lakes isolate MI03 by intraperitoneal injection. While we observed low mortality (0-5%), VHSV was isolated in cell culture from the majority of fish up to 28 d postexposure (DPE) and was detected by a quantitative reverse transcription polymerase chain reaction (qRT-PCR) assay up to 90 DPE, when the trial was terminated. The results of this study strongly suggest that Koi are at risk for VHSV infection, although their susceptibility by intraperitoneal injection appears to be low. This study also provides more evidence of the sensitivity of qRT-PCR for detection of VHSV IVb.

Temporal and spatial patterns in pelagic trawl fish catches in Lake Winnipeg

To better understand patterns of temporal and spatial variation of fish assemblages in offshore waters of Lake Winnipeg (Manitoba, Canada), midwater trawl tows were conducted near lakewide monitoring stations from 2002 to 2008. Trawl samples collected during spring, summer, and fall from the south basin, channel, and north basin were used to study effects of season and geographic region within the lake on species biomass estimates. Within each region, effect of trawl depth was explored. Greatest biomass in trawl catches was from the south basin. Of the most commonly caught species, across all seasons, greater biomass of emerald shiner (Notropis atherinoides) and cisco (Coregonus artedi) were found in the south basin and the channel, compared to the north basin. Biomass of the non-native rainbow smelt (Osmerus mordax), by contrast, was greater in the north basin compared to the south basin or the channel. Yellow perch (Perca flavescens) and introduced white bass (Morone chrysops) biomass varied temporally and spatially, with greatest biomass captured in the summer in the south basin. Estimated biomass of walleye (Sander vitreus) was greatest in the south basin, followed by the channel, and the north basin. Patterns in species distribution in Lake Winnipeg probably are influenced by a combination of factors, including species interactions and differing temperature and light conditions in the lake. As no lakewide pelagic trawl studies have been reported for this lake, these data form a baseline against which effects of changes, such as lake trophic state or establishment of non-native species, can be assessed.