Growth Of Yellow Perch Research Articles

Correlation of Parasites with Growth of Yellow Perch

The possible influence of parasites on the short-term and long-term growth and condition of yellow perch Perca flavescens was examined by investigating correlations between parasite abundance and specific growth variables. The following parasites were enumerated in age-1 yellow perch collected from Lake St. Pierre in June 2008: Apophallus brevis, Diplostomum spp., Ichthyocotylurus spp., Tylodelphys scheuringi, Phyllodistomum superbum, and Raphidascaris acus. Short-term growth was estimated using RNA/DNA ratios and long-term growth via the total length and condition as measured by the Fulton index. No correlation was found between parasite abundance and short-term growth, but a negative influence of combined infections of T. scheuringi and P. superbum on long-term growth was detected. In addition, the abundance of Ichthyocotylurus spp. was positively correlated with the condition of the yellow perch. Together these results suggest that limited or subtle pathogenic effects in juvenile fish are not discernable in recent growth but only in long-term growth indices. Furthermore, in future studies examination of parasite effects on fish growth should account for multiple infections.

The effect of dietary dipeptide lysine–glycine on growth, muscle proteins, and intestine PepT1 gene expression in juvenile yellow perch

The objective of the present study was to examine the effect of a wheat-gluten-based diet supplemented with the indispensable amino acid source in the form of free amino acid or dipeptide on growth, intestine oligopeptide transporter, PepT1, transcript levels using real-time RT-PCR, and muscle protein expression in yellow perch Perca flavescens juveniles. Yellow perch (initial size ~0.3 g) were randomly distributed into 12 glass aquaria, 60 fish per tank. Fish were fed 4 diets: wheat-gluten based diet supplemented with lysine–glycine dipeptide (LG), wheat-gluten based diet supplemented with free lysine (FL), diet not supplemented with lysine (NL; negative control) and a commercial diet (BO). Fish were fed at 90 % satiation level and the rate was re-adjusted to be equal across all treatments based on each day’s projected change in weight gain. It amounted to 3 % of the biomass per day for the first 14 days and 4–5 % until the end of the experiment. After 55 days of the experiment the mean weight of juvenile yellow perch fed the LG diet was larger compared to the NL diet fed group. There was no difference, however, between LG, FL, and BO groups (1.35 ± 0.11 g; 1.31 ± 0.03; 1.16 ± 0.10 g, respectively). Fish subjected to FL treatment showed an increase in the amount of PepT1 transcripts compared to the NL group value. The LG diet was associated with a significant increase in PepT1 mRNA transcript levels, compared with both FL and NL diets fed fish. We have also cloned and sequenced full-length cDNA representing yellow perch PepT1. The cDNA sequence (GeneBank: accession no. GQ906471), encompasses a total of 2,956 base pairs (bp) including a 5′-untranslated region of 94 bp, an open reading frame of 2,190 bp, and a 3′-untranslated region of 672 bp. The predicted 12 transmembrane domains and the 3D structure of the protein (729 amino acids) are presented. Proteomic fingerprinting showed that thirteen electrophoretically resolved protein/peptide bands from the muscle sarcoplasmic fraction were significantly different across treatments suggesting that muscle protein expression was influenced by dietary treatments.

The effect of dipeptide, Lys-Gly, supplemented diets on digestive tract histology in juvenile yellow perch (Perca flavescens)

The aim of the present study was to evaluate the effects of three formulated diets: wheat-gluten-protein-based diets supplemented with Lys-Gly dipeptide (LG) or free lysine and glycine (FL), a control diet without lysine supplementation (C) and commercial starter Bio Oregon (BO) for on the growth and digestive system morphology of yellow perch. After 48 days of experimental feeding, fish fed LG diet showed the highest body mass. Fish fed LG diet showed the highest number of gastrin/cholecystokinin positive cells and the lowest number of CD3-positive cells. The brush border of anterior intestine was the most PepT1 immunopositive in fish fed LG diet, the weakest in fish fed C diet. The largest hepatocytes were observed in fish fed BO, while the smallest in those fed FL diet, the difference being statistically significant. Relative hepatocyte cytoplasm volume occupied by lipids was higher in fish fed BO and FL compared to those fed C and LG. Number of proliferating cell nuclear antigen-positive hepatocyte nuclei did not significantly differ among experimental groups. These results indicate that wheat-gluten-protein-based diets supplemented with dipeptide Lys-Gly (LG) were appropriate for yellow perch.

Oligotrophication from wetland epuration alters the riverine trophic network and carrying capacity for fish

Submerged aquatic vegetation (SAV) constitutes a major component of fish habitat, providing support for epiphytes and invertebrates as well as shelter from predators. The effects of wetland epuration from a mesotrophic to a nearly oligotrophic state were examined over a 15 km long reach of the St. Lawrence River under the direct influence of major farmland tributaries. We hypothesized that the nutrient-enriched zone would support a higher biomass of SAV, epiphytes, macroinvertebrates and fish than the nitrogen-deficient epurated zone located downstream of the wetland. Predictions included that the enriched habitat would support a richer fish assemblage, with higher biomass and growth of juvenile yellow perch than found in the epurated zone. Results supported these hypotheses, demonstrating the chain of effects of nutrient reduction on the biomass of SAV (fourfold drop), invertebrate prey (ninefold), small (threefold) and large (1.5-fold) fish between the two zones. In addition to the reduction in SAV biomass, the replacement of filamentous chlorophytes by benthic mats of filamentous cyanobacteria in the epurated zone resulted in a less complex 3-D habitat structure and a low invertebrate availability for fish. Oligotrophication by wetland epuration exerted negative effects on fish habitat quality, food quantity and availability, with an impairment of juvenile perch growth and recruitment. A generalized model of the changes in habitat carrying capacity occurring with epuration (oligotrophication) or eutrophication is presented, with examples of other aquatic systems in which strong linkages between trophic status, SAV, invertebrates and fish productivity were also demonstrated.

Effects of Hypoxia on Consumption, Growth, and RNA:DNA Ratios of Young Yellow Perch

AbstractAs in various freshwater and coastal marine ecosystems worldwide, seasonal bottom water hypoxia is a recurring phenomenon in Lake Erie's central basin. While bottom hypoxia can strongly affect sessile benthic animals, its effects on mobile organisms such as fish are less understood. We evaluated the potential for bottom hypoxia to affect the growth rates of yellow perch Perca flavescens, a species of ecological and economic importance in the lake. To this end, we (1) conducted laboratory experiments to quantify the effects of reduced dissolved oxygen on consumption, somatic growth, and RNA : DNA ratios (an index of short‐term growth) of young yellow perch and (2) explored the effects of bottom hypoxia on young yellow perch growth in Lake Erie's central basin by collecting individuals in hypoxicand normoxic regions of the lake and quantifying their RNA : DNA ratios. Yellow perch consumption and growth in our experiments declined under hypoxic conditions (≤2 mg O2/L). While yellow perch RNA : DNA ratios responded strongly to experimental temperature, nucleic acid ratios were not significantly affected by dissolved oxygen or feeding ration. We did, however, observe a positive correlation between yellow perch growth and RNA : DNA ratios at low temperatures (11°C). The nucleic acid ratios of yellow perch collected in Lake Erie varied spatiotemporally, but their patterns were not consistent with hypoxia. In short, while yellow perch consumption and growth rates respond directly and negatively to low oxygen conditions, these responses are not necessarily reflected in RNA : DNA ratios. Moreover, in central Lake Erie, where yellow perch can behaviorally avoid hypoxic areas, the RNA : DNA ratios of yellow perch do not respond strongly to bottom hypoxia. Thus, this study suggests that there is no strong negative effect of bottom hypoxia on the growth of young yellow perch in Lake Erie.

Diet overlap of non‐native alewife with native yellow perch and spottail shiner in nearshore waters of southwestern Lake Michigan, 2000–2007

Abstract – Lake Michigan has experienced many ecological changes as a result of introductions of non‐native species. Arguably the most significant was that of alewife (Alosa pseudoharengus), yet studies on diet overlap with native species are lacking. We analysed diet trends of alewife, spottail shiner (Notropis hudsonius) and yellow perch (Perca flavescens) collected in summer and fall 2000–2007 near Waukegan, IL, in 3–10 m depths. Mean percentage composition by dry weight for 23 prey taxa was used in multivariate analysis to test whether diet differed across species and size classes. We also tested whether zooplankton and benthic invertebrate community composition changed over time. Fish diets were similar over all years but differed seasonally. In summer, diets of large alewife were similar to both small alewife and small yellow perch, with Bosminidae, chironomid larvae and copepods as primary common prey. During fall, alewife and yellow perch size classes exhibited strong intraspecific diet overlap, while there was low diet overlap between species. Primary distinctions between species’ diets in fall were higher consumption of amphipods by yellow perch and dreissenids by spottail shiners compared to alewife, which consumed higher proportions of zooplankton. Overall, high yellow perch diet overlap with alewife during summer and with their larger conspecifics during fall could lead to negative implications for yellow perch growth before the critical overwintering period. Detailed insights into diet overlap and prey availability are critical first steps in understanding competitive interactions between native and non‐native fish that dominate the nearshore community in southwestern Lake Michigan.

Growth and Survival of Age‐0 Yellow Perch across Habitats in Southwestern Lake Michigan: Early Life History in a Large Freshwater Environment

AbstractProcesses regulating the survival of early life stages are difficult to decipher for fishes, especially those occupying multiple spatially segregated habitats in large complex systems. Although the processes occurring during the juvenile period are often thought to regulate recruitment of freshwater fishes, those occurring during prolonged pelagic larval phases may be more important to fishes inhabiting large dynamic systems, as is the case with marine larvae. To assess the importance of biotic and abiotic factors on growth and survival of a freshwater fish with a prolonged larval phase, we collected age‐0 yellow perch Perca flavescens in Lake Michigan across multiple habitats and used otoliths to estimate daily ages, hatching distributions, and growth and mortality rates. Larval yellow perch hatched near shore over a 4‐ to 6‐week period but were quickly transported offshore, where they experienced prolonged pelagic durations. Water temperature and wind events influenced growth rates, whereas water temperature, wind events, prey availability, hatching date, and growth rate affected survival across habitats. Mechanisms regulating growth and survival of yellow perch during prolonged pelagic durations (stage duration, prey, and wind events) are consistent with recruitment mechanisms typically ascribed to marine systems, suggesting that abiotic mechanisms interact with biological factors to govern recruitment of fishes in large freshwater ecosystems.

Evaluation of 1-stage and 2-stage selection in yellow perch I: Genetic and phenotypic parameters for body weight of F1 fish reared in ponds using microsatellite parentage assignment1

Two selection methods, 1-stage selection (OSS) and 2-stage selection (TSS), for improving efficiency and profitability of selective breeding of yellow perch were evaluated, through examining the genetic and phenotypic parameters for BW of F(1) fish using microsatellite parentage assignment in this study. Approximately 94% of the sampled yellow perch progeny were assigned to single parental pairs using 8 microsatellite markers, which confirmed the applicability of the communal rearing technique in yellow perch breeding. Within OSS, the genetic correlation between 1-yr-BW and 2-yr-BW was high (0.98), indicating that the growth of yellow perch recorded at yr 1 could predict their growth for yr 2. Also mean family BW and family EBV for BW between yr 1 and 2 were found to be significantly correlated, suggesting yr 1 fast-growing yellow perch families continued to be the fast growing families in yr 2. Two-year random fish undergoing TSS were significantly heavier (P < 0.01) than those undergoing OSS. In addition, top males and females with TSS were heavier (P < 0.01) than those with OSS. Based on these results we concluded that the TSS was more desirable and effective for yellow perch breeding compared with OSS in terms of improving selection efficiency and reducing costs.

Diet partitioning, habitat preferences and behavioral interactions between juvenile yellow perch and round goby in nearshore areas of Lake Erie

Ecological interactions between native and non-indigeneous species depend on interspecies dietary and habitat overlap and species-specific behavior. In the Great Lakes, the exotic round goby ( Apollonia melanostoma) is very abundant in littoral areas used by the native yellow perch ( Perca flavencens). We examined yellow perch-round goby interactions using multiple approaches. Field surveys analyzing dietary overlap among three size classes of yellow perch and round goby detected significant overlap only between juvenile perch (< 95 mm TL) and gobies (< 60 mm TL). Laboratory experiments using juvenile stages tested for habitat preference differences (open sand, macrophytes and dreissenids) in solitary, intraspecific (2 perch) and interspecific (1 perch, 1 goby) treatments. In macrophyte and dreissenid habitats, we tested for treatment differences in fish behavior (intraspecific vs. interspecific) and yellow perch growth (solitary, intraspecific and interspecific). Round goby consistently preferred complex habitats. Yellow perch showed diurnal preference of complex habitats, but increased nocturnal use of sand in the solitary and interspecific treatments. Activity was greater in dreissenid than macrophyte habitat, but prey attacks showed the opposite trend. Activity and prey attacks were greater in the intraspecific than interspecific treatments. The trend was due to lower prey attacks executed by round goby. In macrophytes, individual yellow perch growth was lower in the intraspecific than in the solitary and interspecific treatments. In dreissenids, intraspecific and interspecific competitors equally decreased yellow perch growth. Our results suggest differences in diet, habitat preference and behavior between juvenile round goby and yellow perch may allow their coexistence in nearshore areas.

Defining environmental risk assessment criteria for genetically modified fishes to be placed on the EU market

Defining environmental risk assessment criteria for genetically modified fishes to be placed on the EU market

Response of yellow perch in Les Cheneaux Islands, Lake Huron to declining numbers of double-crested cormorants stemming from control activities

The yellow perch ( Perca flavescens) fishery of the Les Cheneaux Islands region of Lake Huron experienced an unprecedented collapse in 2000. Immediately prior to the collapse was the proliferation of double-crested cormorants ( Phalacrocorax auritus) in the area. Subsequent investigations established that double-crested cormorant predation was chief among the forces shaping the local yellow perch population and contributing to the collapse of the fishery. A double-crested cormorant control program was implemented in 2004 with the objective of benefiting the yellow perch population and fishery. This study used creel survey and gillnet fish community assessment data to evaluate the response of the yellow perch population and fishery. In all, seven key yellow perch metrics were analyzed using regression analysis with double-crested cormorant abundance as the independent variable. As double-crested cormorant abundance declined, yellow perch abundance increased, total mortality rate decreased, the angler catch rate and harvest in the recreational fishery improved, yellow perch growth rate declined and mean age increased. Increased yellow perch recruitment was documented since 2003 but it was the longevity of these year classes, (improved survival) as much or more than their magnitude of the year class, that allowed for the progress towards recovery. Questions facing managers are the sustainable level of double-crested cormorants in the region and the long term prognosis for the yellow perch fishery to fully recover to pre-double-crested cormorant levels.

Predicting the optimal dietary essential amino acid profile for growth of juvenile yellow perch with whole body amino acid concentrations

Rapid methods of estimating dietary essential amino acid (EAA) requirements might facilitate increases in aquaculture production, particularly for new or emerging industries. We conducted a 12-week feeding study to test the hypothesis that whole body EAA concentrations and the quantified methionine requirement could be used to predict the remaining dietary EAA requirements for juvenile all-female yellow perch. Six purified diets were developed and fed to triplicate groups of fish for 12 weeks. The diets contained the EAA profile of fishmeal (FM), the profile as predicted by whole body analysis, the quantified methionine requirement and resulting A/E ratios (PRED), PRED + 20% of all EAA (PRED20), PRED + 40% of all EAA (PRED40), PRED + 20% threonine, isoleucine and tryptophan (PRED320), and PRED + 40% threonine, isoleucine and typtophan (PRED340). Mean weight gain and feed consumption were significantly higher in fish fed PRED20 (35.7 ± 3.2 and 55.0 ± 5.3 g, respectively) than in fish fed FSM (25.1 ± 0.4 g wt gain, 41.0 ± 1.9 g cons), PRED (23.4 ± 2.3 g wt gain, 40.1 ± 4.2 g cons) and PRED340 (22.9 ± 3.3 g wt gain, 35.0 ± 3.8 g cons). There was no significant difference in feed efficiency among treatments. We recommend an EAA profile similar to PRED20 for feeding all-female juvenile yellow perch.

Seasonal and Sex-specific mRNA Levels of Key Endocrine Genes in Adult Yellow Perch (Perca flavescens) from Lake Erie

To better understand the endocrine mechanisms that underlie sexually dimorphic growth (females grow faster) in yellow perch (Perca flavescens), real-time quantitative polymerase chain reaction (qPCR) was used to measure pituitary, liver, and ovary mRNA levels of genes related to growth and reproduction-sex in this species. Adult perch were collected from Lake Erie and body mass, age, gonadosomatic index (I (G)), hepatosomatic index (I (H)), and gene expression for growth hormone (GH), prolactin, somatolactin, insulin-like growth factor Ib (IGF-Ib), estrogen receptor alpha (esr1), estrogen receptor betaa (esr2a), and aromatase (cyp19a1a) were measured. Females had higher body mass, I (H), and liver esr1 mRNA level than males, while males had higher liver IGF-Ib, liver esr2a, and liver cyp19a1a mRNA levels. In both sexes, season had a significant effect on GH and liver IGF-Ib mRNAs with higher levels occurring in spring, which also corresponded with higher liver cyp19a1a mRNA levels. For females, I (G), liver esr1, and ovary cyp19a1a mRNA levels were higher in autumn than the spring, and ovary cyp19a1a mRNA levels showed a significant negative correlation with pituitary GH and liver IGF-Ib mRNA levels. The most significant (p </= 0.001) relationships across the parameters measured were positive correlations between liver IGF-Ib and esr2a mRNA levels and liver IGF-Ib and cyp19a1a mRNA levels. This study shows significant effects of season and sex on adult yellow perch endocrine physiology.

Physiological correlates of growth and condition in the yellow perch ( Perca flavescens)

This study on yellow perch ( Perca flavescens) examines a series of enzymatic markers and the relative weights of pyloric caeca and visceral lipids, their response to changes in feeding regime and their potential use to infer recent changes in growth rate and fish condition. Fish were exposed to four different feeding regimes for 12 weeks resulting in specific growth rates ranging from 0.3% to 3.5% (%/day). Growth and condition responded rapidly to changes in ration and the weight of pyloric caeca and visceral lipids reflected increased feed intake. Growth rate was correlated with muscle citrate synthase and caecal nucleoside-diphosphate kinase activities, whereas condition was correlated with muscle citrate synthase and lactate dehydrogenase activities and with caecal glucose-6-phosphate dehydrogenase activity. Results showed that enzyme activities and biometric parameters responded rapidly to increased feed intake, but the response was slower when food intake decreased. Plateaus were attained for both condition and visceral lipid index, but the relative weight of pyloric caeca continued to increase throughout the experimental period. Results from this study could, in principle, be used to infer recent growth and energy status in wild yellow perch and thus provide an indicator of food availability in their environment.

Proteomic analysis of proteins associated with body mass and length in yellow perch, Perca flavescens

The goal of commercial yellow perch aquaculture is to increase muscle mass which leads to increased profitability. The accumulation and degradation of muscle-specific gene products underlies the variability in body mass (BM) and length observed in pond-cultured yellow perch. Our objective was to apply a combination of statistical and proteomic technologies to identify intact and/or proteolytic fragments of muscle specific gene products involved in muscle growth in yellow perch. Seventy yellow perch randomly selected at 10, 12, 16, 20, and 26 wk of age were euthanized; BM and length were measured and a muscle sample taken. Muscle proteins were resolved using 5-20% gradient SDS-PAGE, stained with SYPRO Ruby and analyzed using TotalLab software. Data were analyzed using stepwise multiple regression with the dependent variables, BM and length and proportional OD of each band in a sample as a potential regressor. Eight bands associated with BM (R(2) = 0.84) and nine bands with length (R(2) = 0.85) were detected. Protein sequencing by nano-LC/MS/MS identified 20 proteins/peptides associated with BM and length. These results contribute the identification of gene products and/or proteolytic fragments associated with muscle growth in yellow perch.

Direct and Indirect (Foodweb Mediated) Effects of Metal Exposure on the Growth of Yellow Perch (Perca flavescens): Implications for Ecological Risk Assessment

ABSTRACT Yellow perch (YP) are metal tolerant fish that form large populations in many metal-impacted regions across Canada. While they are able to survive and reproduce successfully in environments with water and sediment metal concentrations that are toxic to many invertebrates, perch experience a suite of direct and indirect impacts. YP were studied in a series of Canadian Precambrian Shield lakes near Sudbury, Ontario, along a gradient of metal exposure downwind from metal smelters. In lakes at the high end of our exposure gradient, concentrations of metals (Cu, Ni, and Cd) in YP liver and kidney were well above levels seen in fish from reference lakes. Direct effects linked to metal-exposure were observed, ranging from effects at the cellular level, to effects in organs and tissues, individuals, and populations. In addition to direct or physiological effects, we also documented indirect, foodweb-mediated effects of metals on YP in the most contaminated lakes resulting from the elimination of metal-sensitive large benthic invertebrates and their replacement by small metal-tolerant taxa. The most common indication of such indirect effects on YP is severely stunted growth coupled with a high degree of zooplankton dependence throughout their life. Such indirect effects have important implications for ecological risk assessment (ERA) because they indicate that higher trophic levels may be functionally altered even though the functional groups that they depend on are present and abundant. Although the functional groups important to yellow perch can be abundant in metal-impacted lakes, their benthic communities are impoverished and this is strongly reflected in their size structure upon which energy transfer to higher trophic levels depends. Thus indirect (foodweb-mediated) effects can be important in situations where invertebrate size structure is impacted in such a way as to reduce the efficiency of energy transfer to higher trophic levels, and therefore measures should be taken to protect and/or restore large sensitive benthic species.

A comparison of individual-based and matrix projection models for simulating yellow perch population dynamics in Oneida Lake, New York, USA

Both individual-based models (IBMs) and matrix projection models are commonly used to simulate fish population dynamics. We questioned whether matrix models could be used to predict population responses of the prey in a highly coupled predator–prey system. The matrix approach was evaluated for predicting yellow perch population responses to changes in survival, and comparing the responses to those from a detailed IBM. The IBM explicitly modeled effects of walleye predation and competition with yellow perch, whereas the matrix models used averaged values, and in some cases density-dependent relationships, for survival, growth, and reproduction of yellow perch that implicitly included walleye effects. We used the output from a 200-year simulation of the IBM as data for estimating the elements of three alternative versions of a matrix projection model. We constructed an age-structured matrix model and two stage-within-age matrix models for yellow perch. The stage-within-age versions both represented the young-of-the-year (YOY) stages, but differed in the timestep used for updating their density-dependent relationships (annual or daily). The predictions of the matrix models were first compared with the IBM under baseline conditions to confirm that parameter estimation of the matrix models was reasonable. We then simulated reduced and increased egg or adult survival in each model, and compared the relative responses among the four models. Predicted yellow perch spawner abundance under baseline conditions was similar among the IBM and two matrix models that used annual density-dependence, but underestimated by the stage-within-age matrix model that used daily density-dependence. Averaged annual abundances, YOY and yearling survival rates, and sizes at age were generally similar between the IBM and matrix models under baseline conditions. Density-dependent YOY survival was critical for accurately predicting yellow perch responses to changed egg and adult survival rates. Predicted responses to changed survival rates from the stage-within-age matrix model with daily density-dependence differed most from the IBM, and consistently predicted changes in juvenile stage survival opposite to those predicted by the other models. The matrix models that used annual density-dependence predicted similar abundance responses as the IBM to changed egg and adult survival rates. If sufficient data are available, we recommend a population and multispecies modeling approach. If data are available only for the species of interest, then we favor the stage-within-age matrix model with annual density-dependence because the stage structure for YOY allows for flexibility and because it performed better than other matrix models when compared to the IBM.

Density‐Dependent Growth of Yellow Perch in Southern Lake Michigan, 1984–2004

AbstractThe relationship between the growth rates and abundance of yellow perch Perca flavescens was evaluated in the Indiana waters of Lake Michigan from 1984 to 2004. Relative abundance values were taken from trawl catch per unit effort, while growth rates were determined by back‐calculation. Abundance was approximately one order of magnitude higher during the mid‐1980s than in 1990–2004. Growth rates were negatively related to relative abundance and were sexually dimorphic (females grew faster than males). Regression analysis indicated that approximately one‐half of the observed variation in growth was related to abundance; this was most apparent with smaller and younger fish. Lee's phenomenon was shown to be present during periods of high exploitation and not present during periods of low exploitation. Both intraspecific competition and physiological changes associated with age at maturity are plausible explanations for these relationships.

Live Fast and Die Young: Metal Effects on Condition and Physiology of Wild Yellow Perch from along Two Metal Contamination Gradients

ABSTRACT This review summarizes some of the main findings of our work with the Metals in the Environment Research Network examining seasonal and regional effects on metal accumulation, growth, condition, and physiology in wild yellow perch (Perca flavescens) from 10 lakes comprising two metal contamination gradients in the industrial regions of Sudbury, Ontario and Rouyn-Noranda, Québec, Canada. The specific objectives of this review are: (1) to propose threshold tissue metal concentrations to discriminate between fish from contaminated and reference sites; (2) to identify factors that can influence metal accumulation and fish condition; and (3) to define an experimental approach for measuring metal effects in wild yellow perch. Using tissue thresholds appeared useful not only for discriminating fish from clean or contaminated environments, but also provided a simple approach to examine metabolic consequences of tissue metal accumulation. Overall, fish from Sudbury grew faster, expressed higher aerobic capacities, and died younger, but also appeared better at limiting accumulation of some metals than Rouyn-Noranda fish. The condition of the latter fish was clearly more affected by metals than Sudbury fish. Finally, our dataset allows us to propose that yellow perch are highly suitable for ecological risk assessment studies of metal effects in wild fish, but that fish size, season, and region must be considered in sampling design and that several reference sites must be studied for meaningful conclusions to be reached.

Short-term growth (RNA/DNA ratio) of yellow perch (Perca flavescens) in relation to environmental influences and spatio-temporal variation in a shallow fluvial lake

Shallow fluvial lakes are heterogeneous ecosystems in which marked spatio-temporal variation renders difficult the analysis of key ecological processes, such as growth. In this study, we used generalized additive modelling of the RNA/DNA ratio, an index of short-term growth, to investigate the influence of environmental variables and spatio-temporal variation on growth of yellow perch (Perca flavescens) in Lake St. Pierre, Quebec, Canada. Temperature and water level had seemingly stronger effects on short-term growth than seasonal change or spatial variation between and along the lakeshores. Consistent with previous studies, the maximum RNA/DNA ratio was found at 20.5 °C, suggesting that our approach provides a useful tool for estimating thermal optima for growth in the field. The RNA/DNA ratio showed a positive relationship with water level, as predicted by the flood pulse concept, a finding with implications for ecosystem productivity in fluvial lakes. The RNA/DNA ratio was more variable along the north than the south shore, possibly reflecting exposure to more differentiated water masses. The negative influence of both high temperatures and low water levels on growth points to potential impacts of climatic change on fish production in shallow fluvial lakes.