Yellow Perch Research Articles

Informing the Exposure Landscape: The Fate of Microplastics in a Large Pelagic In-Lake Mesocosm Experiment.

Understanding microplastic exposure and effects is critical to understanding risk. Here, we used large, in-lake closed-bottom mesocosms to investigate exposure and effects on pelagic freshwater ecosystems. This article provides details about the experimental design and results on the transport of microplastics and exposure to pelagic organisms. Our experiment included three polymers of microplastics (PE, PS, and PET) ranging in density and size. Nominal concentrations ranged from 0 to 29,240 microplastics per liter on a log scale. Mesocosms enclosed natural microbial, phytoplankton, and zooplankton communities and yellow perch (Perca flavescens). We quantified and characterized microplastics in the water column and in components of the food web (biofilm on the walls, zooplankton, and fish). The microplastics in the water stratified vertically according to size and density. After 10 weeks, about 1% of the microplastics added were in the water column, 0.4% attached to biofilm on the walls, 0.01% within zooplankton, and 0.0001% in fish. Visual observations suggest the remaining >98% were in a surface slick and on the bottom. Our study suggests organisms that feed at the surface and in the benthos are likely most at risk, and demonstrates the value of measuring exposure and transport to inform experimental designs and achieve target concentrations in different matrices within toxicity tests.

Transcriptome profile of sex-related gene expression and effects of cyp19a1 siRNA-silencing on sex differentiation and determination in yellow perch

In this study, we first sequenced the whole genome of the yellow perch (YP, Perca favencens) and screened transcripts of brain, liver, and gonadal tissues from fish of different sexes. By comparing known female sex-related genes in fish such as cyp19a1 and dmrt1 with YP genome, we obtained full-length sequences through genomic homology analysis. Then an experiment was conducted to evaluate the effects of cyp19a1-siRNA interference on gonadal development and sex differentiation and determination in YP. Transcriptome analysis revealed that the gonadal tissue of female YP exhibited predominantly and differentially up-regulated expression of genes than males, and cyp19a1 was predominantly expressed in the gonads while cyp19a2 showed predominant expression in the brain. KEGG pathway enrichment analysis illustrated the metabolic pathways of the top 25 enriched genes and confirmed CYP19 (P450) pathway in YP. For the cyp19a1-siRNA interference experiment, four intermittent in vivo injections of siRNA were administered to interfere with cyp19a1 gene expression in an all-female group of YP. The results collected at 180 dph revealed that the siRNA interference resulted in an incomplete masculinization and hermaphroditism of all-female monosex YP, displaying the presence of male spermatocytes along with female oocytes. In contrast, tissues from the blank control and negative control groups only contained oocytes. The appearance of the gonads in the experimental group appeared more irregular, lacking the smooth surface and typical histoarchitecture observed in the blank control and negative control groups. In addition, the cyp19a1-siRNA treatment group had significantly (P < 0.05) lower body weight than the control groups, indicating that the interference with cyp19a1 might have affected the expression of estrogen, leading to a trend similar to the growth of males; similarly, the gonad weight and GSIs of the cyp19a1 group were significantly (P < 0.05) lower than those in the control groups, suggesting that the cyp19a1-siRNA interference might have led to a trend of male type of gonadal development. Meanwhile, the treatment group had significantly (P < 0.05) higher HSI and VSI levels compared to control groups, indicating that stimulation of external siRNA might have resulted in more vigorous liver metabolism processes. Furthermore, the expression level of the dmrt1 in the treatment group was significantly (P < 0.05) upregulated compared to the control groups, suggesting the correlation roles between these two genes in the regulation of sex development. The findings provide valuable insights for future research into the underlying mechanisms involved and hold significant promise for sex control in aquaculture.

Ecological impact of a generalist invader in the aquatic food web is mediated by environmental context

Abstract Freshwater ecosystems are threatened by the introduction of invasive species. Generalist invaders often compete with native species for shared resources, resulting in possible native species niche displacement. However, environmental heterogeneity may modulate the level of individual specialisation in invasive species, altering the outcome of interspecific competition between invasive and native species. The objectives of our study were to (1) evaluate the environmental context of dietary specialisation and trophic position of an invasive species according to the Environmental Matching Hypothesis (EMH), and (2) consider how the environmental context of invasive species dietary resource use may influence the dietary niche of native species competing for similar resources. Resource use, trophic position and dietary niche were determined using gut content and stable isotope analyses for the invasive round goby (Negobius melanostomus) and the native yellow perch (Perca flavescens), along environmental gradients in an invaded fluvial ecosystem. Our results were in support of EMH for the invader diet and resource specialisation, but not trophic position. Under environmental conditions of high water‐conductivity, round gobies were generalists feeding mostly on pelagic prey. Under more challenging environmental conditions of low water‐conductivity, the invader specialised on preferred high‐quality benthic prey. The ecological impact of the round goby was greatest at low water‐conductivity sites where the invader was a benthic specialist; there was a greater relative dietary niche overlap between the invader and the native species. Our study uniquely illustrates how invasive species’ resource specialisation can be modulated by spatial environmental heterogeneity within ecosystems, and how this can subsequently alter the ecological impact of the invader on native species in aquatic food webs.

A multi-metric approach to characterize variability in Yellow Perch (Perca flavescens) use of Lake Ontario and two barrier-protected coastal wetlands

AbstractYellow Perch (Perca flavescens) inhabit both nearshore and coastal wetland habitats of the Laurentian Great Lakes throughout their lifetime and are known to exhibit different movement life histories. However, uncertainty persists in the spatial extent of this variation and in the duration of habitat use. To explore these uncertainties, we used a multi-metric approach that included water and otolith microchemistry and tissue stable isotope ratios (δ13C, δ15N). The ratio of manganese to calcium in otoliths was used to identify transitional movements between nearshore Lake Ontario and wetland habitats while carbon and nitrogen tissue isotope ratios revealed variable duration of wetland inhabitance. Our research suggests that the multi-metric approach was useful for addressing questions that could not be answered by one method alone. Our results demonstrate individual differences in duration of coastal wetland habitat residence among Yellow Perch, which may influence their susceptibility to recreational harvest. As Yellow Perch are an important species of consideration for management agencies such as the Great Lakes Fishery Commission, exposing such diversity is important when considering the potential for differential contributions of individuals with variable movement life histories to overall population stability and resilience over time.

Heterologous Exchanges of Glycoprotein and Non-Virion Protein in Novirhabdoviruses: Assessment of Virulence in Yellow Perch (Perca flavescens) and Rainbow Trout (Oncorhynchus mykiss).

Infectious hematopoietic necrosis virus (IHNV) and viral hemorrhagic septicemia virus (VHSV) are rhabdoviruses in two different species belonging to the Novirhabdovirus genus. IHNV has a narrow host range restricted to trout and salmon species, and viruses in the M genogroup of IHNV have high virulence in rainbow trout (Oncorhynchus mykiss). In contrast, the VHSV genotype IVb that invaded the Great Lakes in the United States has a broad host range, with high virulence in yellow perch (Perca flavescens), but not in rainbow trout. By using reverse-genetic systems of IHNV-M and VHSV-IVb strains, we generated six IHNV:VHSV chimeric viruses in which the glycoprotein (G), non-virion-protein (NV), or both G and NV genes of IHNV-M were replaced with the analogous genes from VHSV-IVb, and vice versa. These chimeric viruses were used to challenge groups of rainbow trout and yellow perch. The parental recombinants rIHNV-M and rVHSV-IVb were highly virulent in rainbow trout and yellow perch, respectively. Parental rIHNV-M was avirulent in yellow perch, and chimeric rIHNV carrying G, NV, or G and NV genes from VHSV-IVb remained low in virulence in yellow perch. Similarly, the parental rVHSV-IVb exhibited low virulence in rainbow trout, and chimeric rVHSV with substituted G, NV, or G and NV genes from IHNV-M remained avirulent in rainbow trout. Thus, the G and NV genes of either virus were not sufficient to confer high host-specific virulence when exchanged into a heterologous species genome. Some exchanges of G and/or NV genes caused a loss of host-specific virulence, providing insights into possible roles in viral virulence or fitness, and interactions between viral proteins.

Transcriptome analyses in juvenile yellow perch (Perca flavescens) exposed in vivo to clothianidin and chlorantraniliprole: Possible sampling bias.

The St. Lawrence River is an important North American waterway that is subject to anthropogenic pressures including intensive urbanization, and agricultural development. Pesticides are widely used for agricultural activities in fields surrounding the yellow perch (Perca flavescens) habitat in Lake St. Pierre (Quebec, Canada), a fluvial lake of the river where the perch population has collapsed. Clothianidin and chlorantraniliprole were two of the most detected insecticides in surface waters near perch spawning areas. The objectives of the present study were to evaluate the transcriptional and biochemical effects of these two pesticides on juvenile yellow perch exposed for 28d to environmental doses of each compound alone and in a mixture under laboratory/aquaria conditions. Hepatic mRNA-sequencing revealed an effect of chlorantraniliprole alone (37 genes) and combined with clothianidin (251 genes), but no effects of clothianidin alone were observed in perch. Dysregulated genes were mostly related to circadian rhythms and to Ca2+ signaling, the latter effect has been previously associated with chlorantraniliprole mode of action in insects. Moreover, chronic exposure to clothianidin increased the activity of acetylcholinesterase in the brain of exposed fish, suggesting a potential non-target effect of this insecticide. Further analyses of three clock genes by qRT-PCR suggested that part of the observed effects of chlorantraniliprole on the circadian gene regulation of juvenile perch could be the result of time-of-day of sacrifice. These results provide insight into biological effects of insecticides in juvenile perch and highlight the importance of considering the circadian rhythm in experimental design and results analyses.

Stable isotope analysis provides novel insights for measuring lake ecosystem recovery following acidification

Unstable and simplified freshwater food webs impair the resilience of Canadian fisheries facing environmental stressors. This study utilizes stable isotope analyses to assess trophic recovery to explore food web resiliency in lakes historically impacted by metal mining in Sudbury, Ontario. Carbon (δ 13C) and nitrogen (δ 15N) stable isotope ratios were quantified in yellow perch (Perca flavescens), smallmouth bass (Micropterus dolomieu), and baseline organisms to develop quantitative population metrics and describe dietary niche partitioning. The most severely damaged lake with a barren watershed had the lowest trophic positioning, smallest body size and niche area, and greatest niche overlap among fish species. Semi-barren and forested watershed lakes were more similar to reference lakes in isotopic metrics; however elevated niche overlap and reduced trophic positioning suggests recovery in these lakes is ongoing. We found that including stable isotope analyses in lake recovery studies provided critical insights not captured by traditional biomonitoring approaches.

Exploitation and survival of Yellow Perch introduced into community ponds

Increased urbanization paired with stagnant or decreasing fishing license sales has bolstered the importance of community fishing programs. Community fisheries require fish introductions, have highly variable chemical and physical characteristics, and are situated in urban settings with non-traditional fishers that can prefer unique species. Community ponds also often receive high angling pressure and exploitation that can hinder the establishment of sustainable populations. We evaluated angler exploitation and its effects as well as biotic (i.e., stocking density, predator relative abundance) and abiotic (i.e., water temperature, pond size, pond depth) factors affecting survival of stocked adult Yellow Perch Perca flavescens in community ponds. We tagged 580 adult Yellow Perch (≥150 mm) and stocked them into four community ponds at 74 or 148 fish/ha in September 2018. We collected two years of fishery dependent (angler tag reporting) and independent recapture data to estimate angler exploitation and survival of Yellow Perch using a joint live-recapture and dead-recovery model. We estimated anglers harvested 44% (95% CI ± 6%) of stocked Yellow Perch across the four ponds in two years, with the majority (81%) coming from one pond. Additionally, anglers harvested 66% of captured Yellow Perch and harvest probability increased with fish size. Seasonal exploitation ranged from 0% to 37% and was more prevalent in cold water seasons. Yellow Perch survival was negatively related to harvest (β = −0.14; 95% CI = −0.17 to −0.10) and a quadratic effect of water temperature (temperature: β = 0.28; 95% CI = 0.02–0.53; temperature2: β = 0.01; 95% CI = −0.01–0.01). Yellow Perch survival was not related to stocking density or pond characteristics. After two years, cumulative survival in three ponds ranged from 0.83 to 0.87 whereas survival in one pond with high exploitation was 0.22. Our results suggest Yellow Perch can be successfully introduced in community fisheries, but populations may not be sustainable when harvest is high. Thus, management strategies to mitigate excessive harvest or multiple put-and-take stockings may be necessary to maintain Yellow Perch populations in community fishing programs.

Establishment of reed canarygrass (Phalaris arundinacea) in the context of floodplain restoration: impact of companion plant and sowing rate

Habitat loss and degradation is a leading cause of the current biodiversity crisis. In the lake Saint-Pierre floodplain, agricultural intensification has led to the loss of substantial spawning and rearing areas for the yellow perch ( Perca flavescens Mitchill). Restoring perennial vegetation cover is key to ensure the persistence of the population, but the floodplain conditions limit our ability to do so. In this study, we tested the impact of companion plants ( Avena sativa L., Lolium multiflorum L.) and sowing rate on the establishment success of reed canarygrass ( Phalaris arundinacea L.; RCG) in year 2. RCG tolerates a wide range of environmental conditions and can provide the plant cover essential to the reproduction of yellow perch. We hypothesized that companion plants would reduce weed pressure and in turn improve RCG establishment, and that increasing the sowing rate would improve the establishment success. Contrary to our expectations, using companion plants generally reduced the cover and biomass of RCG. It also led to increased weed prevalence in most treatments. In addition, sowing at high rates did not impact RCG cover and biomass. Sowing RCG alone appears to be the most effective option to establish perennial vegetation supporting the recovery of the yellow perch population.

Revisiting the influence of top-down and bottom-up pressures on Wa hia hé:ta (yellow perch Perca flavescens Mitchill, 1814) population dynamics in Kaniatarowanenneh (the Upper St. Lawrence River): Implications for collaborative research

Kaniatarowanenneh (St. Lawrence River) is the outflow of one of the world’s largest freshwater ecosystems and its ecological health has implications for resource management. The population dynamics of an ecologically and economically important fish, the Wa hia hé:ta, Mohawk for yellow perch (Perca flavescens Mitchill, 1814), are considered by including data that extends to the past century to redress temporal gaps in comparative literature. We found both a significant top-down effect from piscivorous fish as well as a significant bottom-up effect related to total phosphorus on yellow perch relative abundance in the Lake Ontario-Upper St. Lawrence system. Regarding the bottom-up effect, the current state of yellow perch reflects the population size prior to cultural eutrophication (pre-1940s/50s) likely responding to the re-oligotrophication of the system. These findings emphasize the importance of considering historical records in fish population dynamics research to incorporate shifting population baselines into fisheries management. The study also demonstrates the need for collaborative approaches that bring critical new insights and multivocality.

The antiviral role of largemouth bass STING against iridovirus infection

Stimulator of interferon gene (STING) plays a crucial role in the innate immune response against viral and bacterial pathogens. However, its function in largemouth bass iridovirus (LMBV) infection remains uncertain. Here, a STING homolog (MsSTING) from largemouth bass (Micropterus salmoides) was cloned and characterized. MsSTING encoded a 407-amino-acid polypeptide, which shared 84.08% and 41.45% identity with golden perch (Perca flavescens) and human (Homo sapiens) homologs, respectively. MsSTING contained four transmembrane domains and a conserved C-terminal domain. The mRNA level of MsSTING was significantly increased in response to LMBV infection in vitro. Subcellular localization observation indicated that MsSTING encoded a cytoplasmic protein, which co-localized predominantly with endoplasmic reticulum (ER) and partially with mitochondria. Moreover, its accurate localization was dependent on the N-terminal transmembrane motif (TM) domains. MsSTING was able to activate interferon (IFN) response, evidenced by the activation of IFN1, IFN3 and ISRE promoters by its overexpression in vitro. Mutant analysis showed that both the N-terminal and C-terminal domain of MsSTING were essential for its activation on IFN response. In addition, overexpression of MsSTING inhibited the transcription and protein levels of viral core genes, indicating that MsSTING exerted antiviral action against LMBV. Consistently, the inhibitory effects were significantly attenuated when the N-terminal or C-terminal domains of MsSTING was deleted. Furthermore, MsSTING overexpression upregulated the transcriptions of interferon-related genes and pro-inflammatory factors, including TANK-binding kinase 1(TBK1), interferon regulatory factor 3 (IRF3), interferon regulatory factor 7 (IRF7), interferon stimulated exonuclease gene 20 (ISG20), interferon-induced transmembrane protein 1(IFITM1), interferon γ (IFN-γ), tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β), and interleukin 6 (IL-6). Together, MsSTING exerted antiviral action upon LMBV infection through positive regulation the innate immune response.

Variability in the drivers of microplastic consumption by fish across four lake ecosystems

Microplastic (&amp;lt;5 mm) pollution has been documented globally throughout freshwater and marine ecosystems. Exposure to and ingestion of microplastics presents a threat to the health of aquatic and marine organisms and humans through the consumption of fish and crustaceans. Understanding the factors which influence microplastic ingestion by fish is a key step in predicting the potential health risks. Drivers of microplastic consumption have been studied in lab settings, but there has been limited ability to confirm in field studies. Here we examine the roles and contributions of feeding guild, pelagic microplastic concentrations, and fish length to microplastic consumption by three species of fish across four lake ecosystems in Minnesota, United States. Fish samples were collected in the summers of 2019 and 2020 and processed to determine variability in microplastic ingestion. Identifying particles between 0.18 and 5 mm, plastic ingestion ranged from 0.6 microplastics fish−1 in Elk Lake (low surface water microplastics) bluegill to 1.09 microplastics fish-1 in White Iron Lake (moderate surface water microplastics) cisco. Results indicate that microplastic consumption by filter feeding cisco is driven by surface water microplastic concentrations, while microplastic consumption by visual feeding bluegill and yellow perch is not. Additionally, the high variability of ingestion between lake ecosystems coupled with the complex behavior of some fish species presents difficulties in identifying primary drivers of microplastic consumption that would be broadly applicable across ecosystems and species.

Quantifying the effect of water quality on eDNA degradation using microcosm and bioassay experiments

AbstractEnvironmental DNA (eDNA) is often used to determine the presence and absence of species in a specific environment, be it air, water, or soil. Numerous environmental conditions are known to directly alter the rate at which eDNA degrades, including pH, temperature, and UV‐B light exposure. Beyond these, many limnological parameters have not been thoroughly examined for their ability to modify the degradation rate of eDNA. Here we used 20 mL microcosms with water collected from 12 lakes from the Kawartha Highlands near Peterborough Ontario, Canada, to study the decay rates of dissolved Yellow perch (Perca flavescens) eDNA. We measured and related rates of eDNA loss to multiple water quality parameters: total dissolved phosphorus, total dissolved nitrogen, size‐fractionated carbon, and chlorophyll‐a levels. Bioassays were also conducted to examine the bacterial role in eDNA degradation using three treatments under natural system conditions: non‐filtered, filtered (0.22 μm), and non‐filtered with added phosphorus (50 μg/L). Each microcosm exhibited a unique rate of degradation with eDNA half‐life (C0.5) ranging from 2.5 to 12.9 h. Chlorophyll‐a levels exhibited a positive linear relationship to the rate of degradation, while all other parameters showed no effect. The bioassays showed a general trend of the filtered treatments exhibiting the lowest rate of degradation, followed by the phosphorus treatments with the non‐filtered treatment containing bacteria exhibiting the highest rate of degradation. Overall, water with an increased level of chlorophyll‐a, in conjunction with elevated bacteria (i.e. non‐filtered bioassay) will exhibit a faster overall rate of eDNA degradation. These results show the necessity to individualize eDNA survey plans to the water body of interest and to account for environmental conditions relating to the microbial processing of eDNA.

Efficacy of a novel reproductive tag to index spawn timing

Insight into fish annual reproductive dynamics (including spawn timing) can elucidate key determinants of recruitment. However, few methods, if any, are available to directly index individual spawn timing, hindering study of such processes. To this end, we developed two reproductive tags (RTs; internal and external) and evaluated their performance assessing spawn timing of female yellow perch ( Perca flavescens). Internal RTs performed well, especially in comparison to external RTs, displaying consistent long-term tag retention and clear tag release synchronized with egg mass release during spawning. These results demonstrate the utility of internal RTs to investigate previously unexplored mechanisms of reproductive timing.

Conflicting perspectives on ecosystem conservation in a cultivated floodplain: The role of science and the challenge of pluralism in decision‐making in Lac Saint‐Pierre (Quebec, Canada)

AbstractBy generating and explaining facts, science holds an important role in environmental policy decision‐making. However, scientific knowledge is often framed as objective and neutral in policy debates, which can be challenged by stakeholders who have a different view of the issue. To counter this situation, we propose a novel scientific approach to analyze problems that are highly contested and seem difficult to resolve, that is, wicked problems. Our study combined post‐normal science and environmental justice perspectives to shed light on a wicked problem—the largely unsuccessful efforts to rehabilitate yellow perch stocks in Lac Saint‐Pierre (LSP), Quebec, Canada. The combination of these two perspectives allows us to investigate the causes of the decrease of yellow perch stocks and the social and institutional barriers to rehabilitation—which can only be overcome if the injustice perceived by different stakeholders is overcome. Our study presents an approach that addresses uncertainties, integrates various knowledge forms, reassesses decision‐making procedures, and highlights inequalities within a specified territory. The research also underlines the importance of the qualitative dimension in the development of knowledge and the need to address equity in the development of environmental policies.

Thermal tolerance and habitat preferences mediate how freshwater fish body sizes respond to warming

Recent studies have linked ecosystem warming to decreased mean body size in aquatic ectotherms but have often relied on experimental approaches. This study explores how climate change modifies adult body sizes in natural communities for five culturally, commercially, and recreationally important freshwater fish species that vary in thermal preferences (lake trout ( Salvelinus namaycush), lake whitefish ( Coregonus clupeaformis), walleye ( Sander vitreus), yellow perch ( Perca flavescens), and smallmouth bass ( Micropterus dolomieu)). Using data for &gt;170 000 sampling records from &gt;600 lakes spanning the entire province of Ontario, Canada, we employ a spatial analysis technique based on Integrated Nested Laplace Approximation to detect body size changes due to warming lake conditions. With warming conditions, cold-adapted species (lake whitefish) decreased in adult body size, while cool- and warm-adapted species (walleye and smallmouth bass) increased in adult body size. Our study, like others recently conducted in marine and freshwater systems, demonstrates that the responses of fish body sizes to warming are not a unidirectional shift and may be linked to the habitat and thermal preferences of individual fish species.

Bidirectional energy subsidies for fish in river mouths of a large lake as revealed by stable isotopes and fatty acids

AbstractFreshwater river mouths may facilitate cross‐habitat resource use and bidirectional subsidization through (a) active cross‐habitat movement by consumers like fish and (b) water and material movement both downstream, from tributary to nearshore lake, and in the opposite direction due to backflow processes. Despite potential importance of freshwater river mouths, relative contributions of lentic and tributary energy sources to fishes along these ecotones remain understudied, in part because measuring cross‐habitat subsidization is not straightforward. We assessed cross‐habitat subsidization of three fish consumers round goby (Neogobius malanostomus), yellow perch (Perca flavescens), and alewife (Alosa psuedoharengus) in three river mouths of Lake Michigan, USA. Specifically, we (a) measured stable isotope ratios (δ13C, δ15N, δ2H, δ18O) in ambient water, bivalve shells, potential invertebrate prey, and fish soft tissue, and we assessed fish nutritional status based on essential fatty acid composition, and (b) estimated Bayesian ellipses and mixing models including either two (δ13C‐δ15N) or three (δ13C‐δ15N‐δ2H) isotope ratios. Results revealed evidence of bidirectional habitat subsidies for all fishes, but energy subsidies varied by species and across river mouths; likely related to differences in species‐specific behavior and hydrologic differences among river mouths. Relative to nearshore oligotrophic Lake Michigan, fish in productive tributary environments contained relatively low essential fatty acid content, suggesting a possible trade‐off between prey quantity and quality across habitats. This study advances our understanding of resource connectivity in lake ecosystems and the combined use of multiple stable isotopes (including mixing models) and fatty acids to document cross‐habitat subsidies along freshwater ecotones.

Naphthenic acid fraction compounds, produced by the extraction of bitumen from oil sands, alter survival and behaviour of juvenile yellow perch (Perca flavescens)

We evaluated whether naphthenic acid fraction compounds (NAFCs) extracted from oil sand tailings adversely affect fish survival and behaviour. Following a before–after-control-impact design, we housed wild-caught juvenile yellow perch ( Perca flavescens) in outdoor mesocosms to assess survival and behaviour under baseline conditions, then exposed fish to one of three treatments: negative control, 2 mg/L NAFC, or 15 mg/L NAFC. We performed behavioural assays (no-stimulus activity, food stimulus, and predator stimulus using a model bird) and assessed a comprehensive suite of endpoints (equilibrium losses, activity, shoaling, burst swimming, freezing, and space use). We found that exposure to 15 mg/L NAFCs substantially reduced fish survival and impaired fish equilibrium in all three behavioural tests. Furthermore, exposure to NAFCs impaired anti-predator behaviour: while the activity of control fish increased by two-fold in response to a predator stimulus, fish exposed to 2 or 15 mg/L NAFC did not change their activity levels after stimulation. No significant changes were observed in other behavioural endpoints. Overall, our findings suggest that a week-long exposure to NAFCs at concentrations commonly found in tailings ponds, constructed wetlands, and other mining-impacted waters may affect multiple facets of fish behaviour that could ultimately lead to reduced fitness in fish populations.

Controlling Proteocephalus ambloplites (Cestoda) Infections and Changing Fish Parasitic Fauna Following Post-Rotenone Rehabilitation of Lakes, With Light Microscopy

Efforts to establish desirable fish populations by rotenone treatment of lakes dominated by winter-kill resistant species, e.g., bullhead, and restocking have been attempted by the Wisconsin Department of Natural Resources, as well as by other agencies throughout the United States since the mid-1930s. Such efforts were performed in Little Elkhart Lake, eastern Wisconsin which was treated with rotenone (1.5 ppm) in 1981, to kill its rough fish and restock with desirable fish populations. Pre- and posttreatment samples of fish were examined for parasites in September 1981 and 1988, respectively. This is a revision and update of work originally published in 1993 with the addition of light microscope images of recovered parasites for the first time. Relatively heavy infections in largemouth bass, Micropterus salmoides, (Lacépède) and sunfish in 1981 with Proteocephalus ambloplites (Leidy, 1887) (Cestoda) disappeared after the rotenone treatment. Infections with Neoechinorhynchus cylindratus Van Cleave, 1913 decreased but drastically increased with Leptorhynchoides thecatus (Linton, 1891) Kostylew, 1924 with changes in their fish and invertebrate host populations following rotenone use. Metacercariae of Posthodiplostomum minimum (MacCallum, 1921) (Trematoda) in sunfish and Hysterothylacium brachyurum Ward and Magath, 1917 (Nematoda) in largemouth bass were also present before and after the chemical treatment, respectively. The observed loss of P. ambloplites after 1981 points to a possible method for its control. The unusual presence of the leech Myzobdella lugubris in the anterior intestine of a yellow perch, Perca flavescens (Mitchill) was documented.

Response of yellow perch to water level fluctuations in oligotrophic, north‐temperate inland lakes

AbstractInformation on yellow perch Perca flavescens population dynamics and responses to various abiotic and biotic factors in oligotrophic, north‐temperate inland lakes is limited. Water level fluctuations are known to influence available habitat and biological communities within the littoral zones of lakes, yet research is lacking for yellow perch in Wisconsin. The goal of our study was to characterize yellow perch population‐level responses to natural water level fluctuations in four northern Wisconsin lakes using a 39‐year time series. On average, increasing water level periods correlated with lower mean fyke net and gill net relative abundances (catch‐per‐unit‐effort), though generally not statistically significant. Yellow perch mean relative weight varied among lakes and was significantly greater during increasing water level periods for all lakes except one. The lack of statistically significant findings potentially suggests a buffering mechanism of north‐temperate oligotrophic lakes due to their small surface area to volume ratios, relative lack of nutrients, and(or) littoral structural habitat compared to other systems (e.g., shallow eutrophic lakes). Our results suggest that natural water level fluctuations may not be an environmental concern for yellow perch populations in some north‐temperate oligotrophic inland lakes.