Lake Whitefish Research Articles

The effects of chronic cadmium exposure on repeat swimming performance and anaerobic metabolism in brown trout (Salmo trutta) and lake whitefish (Coregonus clupeaformis)

This study investigates the effect of chronic Cd exposure on the ability to perform repeat swim challenges in brown trout (Salmo trutta) and lake whitefish (Coregonus clupeaformis). Fish were exposed to waterborne Cd (18nM) in moderately hard water (120mgL−1 CaCO3) for 30 days. This level of exposure has been shown to cause sublethal physiological disruption and acclimation responses but no impairment of sustained swimming capacity (Ucrit) in single swim challenges. Swim trials were done over the course of the exposure and each one consisted of an initial swim to 85% of the Ucrit of control fish, a 30min recovery period and finally a second swim challenge to determine Ucrit. Plasma and tissue samples were collected before and after each of the swim periods. As expected from previous studies, Cd exposure resulted in significant accumulation of Cd in gills, liver and kidney but not in white muscle. Exposure also induced a loss of plasma Ca followed by subsequent recovery (in lake whitefish but not brown trout) with few mortalities (100% survival for lake whitefish and 93% for brown trout). Both control and exposed fish swam to 85% of the single swim Ucrit and no differences in performance were seen. The Ucrit of unexposed controls in the second swim challenges were not different from the single swim Ucrit. However, second swim performance was significantly reduced in Cd exposed fish, particularly after a week of exposure where 31% and 38% reductions were observed for brown trout and lake whitefish respectively. Swimming to 85% Ucrit resulted in metabolic expenditure with little recovery after 30min. Few differences were observed between control and Cd exposed fish with the exception of a reduction in resting white muscle ATP stores of Cd exposed fish after 1 week of exposure. The results show that chronic sublethal Cd exposure results in an impairment of swimming ability in repeat swim challenges but this impairment is generally not related to metabolic processes in white muscle.

Thermal stress and the heat shock response in embryonic and young of the year juvenile lake whitefish

We investigated the effects of thermal stress on embryonic (fin flutter, vitelline circulation stage) and young of the year (YOY) juvenile lake whitefish by characterizing the kinetics of the heat shock response (HSR). Lake whitefish were subjected to one of three different heat shock (HS) temperatures (3, 6, or 9°C above control) for six different lengths of time (0.25, 0.50, 1, 2, 3, or 4h) followed by a 2h recovery period at the control temperature of 2°C or 14°C for embryos and YOY juveniles, respectively. The duration of the HSR was examined by allowing the fish to recover for 1, 2, 4, 8, 12, 16, 24, 36, or 48h following a 2h HS. In embryos, at the fin flutter stage, only hsp70 mRNA levels were upregulated in response to the various HS treatments. By comparison, all three typically inducible hsps, hsp90α, hsp70 and hsp47, were upregulated in the YOY juveniles. In both instances the HSR was long lasting, but much more so in embryos where hsp70 mRNA levels continued to increase for 48h after a 2h HS and remained significantly higher than untreated controls. Collectively our data indicate that both embryo and YOY juvenile lake whitefish have a robust HSR which permits them to survive a 4h, 9°C HS. Moreover, both life history stages are capable of triggering a HSR following a moderate 3°C HS which is likely an important protective mechanism against environmental stressors during embryogenesis and early life history stages of lake whitefish.

Genetic structure and within-generation genome scan analysis of fisheries-induced evolution in a Lake Whitefish (Coregonus clupeaformis) population

Size-selective harvest may lead to over-exploitation of commercial fisheries, but the population genetic and evolutionary consequences of such practices remain poorly understood. We investigated the role of within-generation selection in a historically over-exploited Lake Whitefish (Coregonus clupeaformis) population associated with fisheries-induced evolution in Lesser Slave Lake, Alberta, Canada. DNA from archived scales of Lake Whitefish collected between 1986 and 1999 were genotyped at 20 microsatellites and 51 gene-coding SNPs associated with growth and reproduction. We found that the Lake Whitefish in Lesser Slave Lake consisted of a single genetic stock, with microsatellites revealing more temporal than spatial variation in allele frequencies. A comparative genome scan among replicate cohorts from commercially harvested versus random survey samples identified one candidate SNP under divergent selection. This SNP localized within a gene encoding nucleoside diphosphate kinase A, a protein associated with differential growth. Collectively, the results highlight the utility of within-generation genome scans towards investigating the evolutionary consequences of harvest in the wild.

Creating World-Class Gathering Places for People and Wildlife along the Detroit Riverfront, Michigan, USA

Metropolitan Detroit, Michigan, USA is the automobile capital of the world, part of the industrial heartland and Rust Belt, and a major urban area. For over two centuries, the Detroit River was perceived as a working river that supported commerce and industry. Like many other large North American cities, the Motor City made the Detroit River its back door, with businesses facing inland and away from the river. Compounding the problem, Detroit became indifferent to the water pollution that was perceived as a necessary by-product of industrial progress. By the 1960s, the Detroit River was one of the most polluted rivers in North America. Today, the cleanup and recovery of the Detroit River represent one of the most remarkable ecological recovery stories in North America with the return of bald eagles, peregrine falcons, osprey, lake sturgeon, lake whitefish, mayflies, and more. Out of this recovery has come two transformational projects—the Detroit River International Wildlife Refuge and the Detroit RiverWalk—that are helping change the perception of the region from that of a Rust Belt city to one of a leader of urban sustainability that reconnects people to nature, improves quality of life, promotes sustainable redevelopment, and enhances community pride. Key lessons learned include: recruit a well-respected champion; ensure broad support from key stakeholder groups; establish core delivery team, focused on outcomes; build trust; adopt a strategic approach to community engagement, creating a connected community; evoke a sense of place; and measure and celebrate successes to sustain momentum.

PCB concentrations of lake whitefish (Coregonus clupeaformis) vary by sex

We determined whole-fish polychlorinated biphenyl (PCB) concentrations in 26 female lake whitefish (Coregonus clupeaformis) and 34 male lake whitefish from northern Lake Huron. In 5 of the 26 female lake whitefish, we also determined PCB concentrations in the somatic tissue and ovaries. In addition, bioenergetics modeling was used to determine the contribution of the growth dilution effect to the observed difference in PCB concentrations between the sexes. Whole-fish PCB concentrations for females and males averaged 60 ng/g and 80 ng/g, respectively; thus males were 34% higher in PCB concentration compared with females. Based on the PCB determinations in the somatic tissue and ovaries, we predicted that PCB concentration of females would increase by 2.5%, on average, immediately after spawning due to release of eggs. Thus, the change in PCB concentration due to release of eggs did not explain, to any degree, the higher PCB concentrations observed in males compared with females. Bioenergetics modeling results indicated that the growth dilution effect could account for males being only 0.7% higher in PCB concentration compared with females. Thus, the growth dilution effect contributed very little to the observed difference in PCB concentrations between the sexes. We conclude that males were higher than females in PCB concentration most likely due to a higher rate of energy expenditure, stemming from greater activity and a greater resting metabolic rate. A higher rate of energy expenditure leads to a higher rate of food consumption, which, in turn, leads to a higher PCB accumulation rate.

The Microbiota of Freshwater Fish and Freshwater Niches Contain Omega-3 Fatty Acid-Producing Shewanella Species.

Approximately 30 years ago, it was discovered that free-living bacteria isolated from cold ocean depths could produce polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA) (20:5n-3) or docosahexaenoic acid (DHA) (22:6n-3), two PUFA essential for human health. Numerous laboratories have also discovered that EPA- and/or DHA-producing bacteria, many of them members of the Shewanella genus, could be isolated from the intestinal tracts of omega-3 fatty acid-rich marine fish. If bacteria contribute omega-3 fatty acids to the host fish in general or if they assist some bacterial species in adaptation to cold, then cold freshwater fish or habitats should also harbor these producers. Thus, we undertook a study to see if these niches also contained omega-3 fatty acid producers. We were successful in isolating and characterizing unique EPA-producing strains of Shewanella from three strictly freshwater native fish species, i.e., lake whitefish (Coregonus clupeaformis), lean lake trout (Salvelinus namaycush), and walleye (Sander vitreus), and from two other freshwater nonnative fish, i.e., coho salmon (Oncorhynchus kisutch) and seeforellen brown trout (Salmo trutta). We were also able to isolate four unique free-living strains of EPA-producing Shewanella from freshwater habitats. Phylogenetic and phenotypic analyses suggest that one producer is clearly a member of the Shewanella morhuae species and another is sister to members of the marine PUFA-producing Shewanella baltica species. However, the remaining isolates have more ambiguous relationships, sharing a common ancestor with non-PUFA-producing Shewanella putrefaciens isolates rather than marine S. baltica isolates despite having a phenotype more consistent with S. baltica strains.

Changes in depth occupied by Great Lakes lake whitefish populations and the influence of survey design

Understanding fish habitat use is important in determining conditions that ultimately affect fish energetics, growth and reproduction. Great Lakes lake whitefish (Coregonus clupeaformis) have demonstrated dramatic changes in growth and life history traits since the appearance of dreissenid mussels in the Great Lakes, but the role of habitat occupancy in driving these changes is poorly understood. To better understand temporal changes in lake whitefish depth of capture (Dw), we compiled a database of fishery-independent surveys representing multiple populations across all five Laurentian Great Lakes. By demonstrating the importance of survey design in estimating Dw, we describe a novel method for detecting survey-based bias in Dw and removing potentially biased data. Using unbiased Dw estimates, we show clear differences in the pattern and timing of changes in lake whitefish Dw between our reference sites (Lake Superior) and those that have experienced significant benthic food web changes (lakes Michigan, Huron, Erie and Ontario). Lake whitefish Dw in Lake Superior tended to gradually shift to shallower waters, but changed rapidly in other locations coincident with dreissenid establishment and declines in Diporeia densities. Almost all lake whitefish populations that were exposed to dreissenids demonstrated deeper Dw following benthic food web change, though a subset of these populations subsequently shifted to more shallow depths. In some cases in lakes Huron and Ontario, shifts towards more shallow Dw are occurring well after documented Diporeia collapse, suggesting the role of other drivers such as habitat availability or reliance on alternative prey sources.

From genes to populations: how fisheries-induced evolution alters stock productivity.

By removing individuals with certain heritable characteristics such as large body size, harvesting may induce rapid evolutionary change in fish life history. There is controversy, however, as to the prevalence of fisheries-induced evolution (FIE) and to what extent it should be considered as part of sustainable resource management. Recent research has shown that FIE can be difficult to detect and its economic effects might not always be significant. Here, we show how population growth rate (r), a critical factor affecting sustainability and recovery, is affected by FIE through the analysis of a simulation model that demonstrates the link between individual-level genetic processes and stock dynamics. We examine how different levels of evolvability, fishing intensity, and density-dependence interact to influence r in three commercially harvested species: Atlantic cod (Gadus morhua), lake whitefish (Coregonus clupeaformis), and yellow perch (Perca flavescens). We demonstrate that at low harvest levels, evolution has minimal effect on r for all three species. However, at the harvest rates experienced by many fish stocks, evolution increases r and reduces the risk of collapse for cod and whitefish. During the initial stages of a harvest moratorium, a switch occurs, and r becomes reduced as a consequence of evolution. These results explain how evolution increases stock resilience, but also impedes recovery after periods of intense harvesting.

Modeling spatiotemporal variabilities of length-at-age growth characteristics for slow-growing subarctic populations of Lake Whitefish, using hierarchical Bayesian statistics

Though Lake Whitefish are ecologically, culturally and economically important to aboriginal communities in the Northwest Territories, Canada, growth characteristics of the fish populations have not received extensive interpretations, resulting in a lack of quantitative information to support fisheries management efforts in subarctic great lake systems. The overall objective of this study is to investigate spatiotemporal variations of growth characteristics of Lake Whitefish populations in Great Slave Lake (GSL) from 1972–2009. Using hierarchical Bayesian statistics, we structured four candidate growth models: generalized (GGM), logistic (LGM), Gompertz (PGM), and von Bertalanffy (VBM), with four parameterization scenarios combining all possible options of varying or constant L∞ and K. In terms of deviance information criterion (DIC) and multimodel inference (MMI), the plausibility of the candidate models was evaluated to select the best combinations of growth models and the parameter scenarios. The GGM with varying L∞ and K best delineated the fish growth characteristics in almost all areas of GSL, while the fish growth model parameterized with constant L∞ and varying K performed best in the shallow western basin. The VGM where L∞ and K were varied partially described fish growth in the shallow waters. Applying the MMI-based growth analysis, we found that smaller and slower-growing fish were mainly distributed in deep waters, while larger and faster-growing fish inhabited shallow waters. These spatiotemporal variations of fish growth characteristics have been attributed to the presence of coupled impacts derived from both climate-driven and anthropogenic events.

Cross-basin analysis of long-term trends in the growth of lake whitefish in the Laurentian Great Lakes

Abstract We conducted a basin-wide analysis of trends in the growth rate of lake whitefish ( Coregonus clupeaformis ), a commercially harvested species in the Laurentian Great Lakes. Juvenile growth (measured as the growth between ages 1 and 2 years) was back-calculated from agency archived scale collections going back as far as the 1950s. We examined trends for 11 locations within the Great Lakes, and investigated the role of multiple explanatory factors (dreissenid mussel establishment; lake whitefish relative abundance; growing degree days) in contributing to the variation observed. Juvenile growth rates declined in all but one location where dreissenid mussels have had widespread establishment. Growth of juvenile lake whitefish from Lake Ontario showed the largest decline following dreissenid establishment, decreasing by 32%. In several locations, lake whitefish growth rates declined or had breakpoints prior to dreissenid establishment and have stabilized or increased in recent years, thus indicating the contribution of other factors. One location in Lake Superior (Apostle Islands) also showed a marked decline and subsequent increase in growth, whereas the other two Lake Superior locations showed no obvious trends. Changes in relative abundance of lake whitefish and growing degree days contributed to growth patterns among locations, but the effect was inconsistent and in most cases weaker than that from the timing of dreissenid establishment. Although our study cannot identify a specific mechanism involved, the suite of changes at the base of the food web that coincided with the timeline of dreissenid establishment appear to have had a broad-scale impact on lake whitefish.

Recruitment of sympatric vendace (Coregonus albula) and whitefish (C. lavaretus) is affected by different environmental factors

AbstractVendace and whitefish in Lake Osensjøen (boreal south‐east Norway) were studied by means of gillnet test fishing (1976–2013) and hydro acoustic acquisition (1986–2011). Vendace increased in number between 1998 and 2009 while growth and size at maturity decreased. The relative density of whitefish decreased in the pelagic habitat, whereas growth and size remained the same. Both species exhibited varying year‐class strength. Whereas strong year‐classes of both species became less frequent after 1980 than before this, this seemed to change after 2000, especially for vendace. Generalised additive models suggested a strong positive relationship between July/August mean air temperature and year‐class strength of both vendace and whitefish. Whitefish recruitment was also negatively affected by the new regulation regime implemented since 1981, and positively correlated with water level after hatching and by late ice off. The reason for the diverging impacts of environmental factors on the two species may be that vendace spawn in deeper waters that whitefish do. The results indicate that increasing summer temperatures benefit recruitment of both species, whereas low water level and early ice off will harm whitefish recruitment. Both trends are caused by climate warming. It may be speculated that increased density of the specialised plankton feeding vendace may affect the algal community through increased predation on herbivorous zooplankton and potentially affect the trophic state of the lake.

Adaptation and acclimation of aerobic exercise physiology in Lake Whitefish ecotypes (Coregonus clupeaformis).

The physiological mechanisms underlying local adaptation in natural populations of animals, and whether the same mechanisms contribute to adaptation and acclimation, are largely unknown. Therefore, we tested for evolutionary divergence in aerobic exercise physiology in laboratory bred, size-matched crosses of ancestral, benthic, normal Lake Whitefish (Coregonus clupeaformis) and derived, limnetic, more actively swimming "dwarf" ecotypes. We acclimated fish to constant swimming (emulating limnetic foraging) and control conditions (emulating normal activity levels) to simultaneously study phenotypic plasticity. We found extensive divergence between ecotypes: dwarf fish generally had constitutively higher values of traits related to oxygen transport (ventricle size) and use by skeletal muscle (percent oxidative muscle, mitochondrial content), and also evolved differential plasticity of mitochondrial function (Complex I activity and flux through Complexes I-IV and IV). The effects of swim training were less pronounced than differences among ecotypes and the traits which had a significant training effect (ventricle protein content, ventricle malate dehydrogenase activity, and muscle Complex V activity) did not differ among ecotypes. Only one trait, ventricle mass, varied in a similar manner with acclimation and adaptation and followed a pattern consistent with genetic accommodation. Overall, the physiological and biochemical mechanisms underlying acclimation and adaptation to swimming activity in Lake Whitefish differ.

Embryonic development of lake whitefish Coregonus clupeaformis: a staging series, analysis of growth and effects of fixation.

A reference staging series of 18 morphological stages of laboratory reared lake whitefish Coregonus clupeaformis is provided. The developmental processes of blastulation, gastrulation, neurulation as well as development of the eye, circulatory system, chromatophores and mouth are included and accompanied by detailed descriptions and live imaging. Quantitative measurements of embryo size and mass were taken at each developmental stage. Eggs were 3·19 ± 0·16 mm (mean ± s.d.) in diameter at fertilization and embryos reached a total length (LT ) of 14·25 ± 0·41 mm at hatch. Separated yolk and embryo dry mass were 0·25 ± 0·08 mg and 1·39 ± 0·17 mg, respectively, at hatch. The effects of two common preservatives (formalin and ethanol) were examined throughout development and post hatch. Embryo LT significantly decreased following fixation at all points in development. A correction factor to estimate live LT from corresponding fixed LT was determined as live LT = (fixed LT )(1·025) . Eye diameter and yolk area measurements significantly increased in fixed compared with live embryos up to 85-90% development for both measurements. The described developmental stages can be generalized to teleost species, and is particularly relevant for the study of coregonid development due to additionally shared developmental characteristics. The results of this study and staging series are therefore applicable across various research streams encompassing numerous species that require accurate staging of embryos and descriptions of morphological development.

RAD-QTL Mapping Reveals Both Genome-Level Parallelism and Different Genetic Architecture Underlying the Evolution of Body Shape in Lake Whitefish (Coregonus clupeaformis) Species Pairs.

Parallel changes in body shape may evolve in response to similar environmental conditions, but whether such parallel phenotypic changes share a common genetic basis is still debated. The goal of this study was to assess whether parallel phenotypic changes could be explained by genetic parallelism, multiple genetic routes, or both. We first provide evidence for parallelism in fish shape by using geometric morphometrics among 300 fish representing five species pairs of Lake Whitefish. Using a genetic map comprising 3438 restriction site−associated DNA sequencing single-nucleotide polymorphisms, we then identified quantitative trait loci underlying body shape traits in a backcross family reared in the laboratory. A total of 138 body shape quantitative trait loci were identified in this cross, thus revealing a highly polygenic architecture of body shape in Lake Whitefish. Third, we tested for evidence of genetic parallelism among independent wild populations using both a single-locus method (outlier analysis) and a polygenic approach (analysis of covariation among markers). The single-locus approach provided limited evidence for genetic parallelism. However, the polygenic analysis revealed genetic parallelism for three of the five lakes, which differed from the two other lakes. These results provide evidence for both genetic parallelism and multiple genetic routes underlying parallel phenotypic evolution in fish shape among populations occupying similar ecological niches.

The 2013–2014 Fenske Fellowship: Learning the Ins and Outs of Lake Whitefish Management in the Upper Great Lakes

FisheriesVolume 40, Issue 7 p. 300-301 Student Angle The 2013–2014 Fenske Fellowship: Learning the Ins and Outs of Lake Whitefish Management in the Upper Great Lakes Marissa L. Hammond, Marissa L. Hammond hammo146@msu.edu Department of Fisheries and Wildlife, Michigan State University, Manly Miles Building, 1405 South Harrison Rd., East Lansing, MI, 48823Search for more papers by this author Marissa L. Hammond, Marissa L. Hammond hammo146@msu.edu Department of Fisheries and Wildlife, Michigan State University, Manly Miles Building, 1405 South Harrison Rd., East Lansing, MI, 48823Search for more papers by this author First published: 01 July 2015 https://doi.org/10.1080/03632415.2015.1049694Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume40, Issue7July 2015Pages 300-301 RelatedInformation

Measuring the effects of food availability on Lake Superior Diporeia consumption rates using radiolabeled algae

Abstract Within the Lake Superior benthic macroinvertebrate community, Diporeia spp. are the most abundant organisms and account for the largest proportion of biomass. As detritivores that feed on organic material in surficial sediments, Diporeia play a major role in transferring energy and nutrients to higher trophic level consumers and are favored prey for Lake Whitefish and other benthivorous fish species. The objective of this study is to quantify and model the response of the Diporeia consumption rate to changes in food availability. Diporeia were introduced to microcosms containing various concentrations of 14 C-labeled green algae ( Selenastrum capricornutum ) and incubated for 24 hours. Consumption was calculated as the radioisotope content of each animal divided by the specific activity of the labeled algae. A hyperbolic (Michaelis–Menten) function was fit to the data, yielding a maximum consumption rate of 1.76 ± 0.4 SE mg C/g DW/d. The predicted consumption rate corresponding to average Lake Superior algal carbon fluxes was 0.08 ± 0.15 mg C/g DW/d. For the observed range of carbon fluxes to benthic habitats in the Great Lakes, the relationship between consumption and food supply is well described by a linear function, with consumption rates ranging from 0.08–0.38 mg C/g DW/d. The parameter estimates presented here may act as inputs for a bioenergetics model used to predict Diporeia growth and production in Lake Superior.

Climate change projections for lake whitefish ( Coregonus clupeaformis ) recruitment in the 1836 Treaty Waters of the Upper Great Lakes

Abstract Lake whitefish ( Coregonus clupeaformis ) is an ecologically, culturally, and economically important species in the Laurentian Great Lakes. Lake whitefish have been a staple food source for thousands of years and, since 1980, have supported the most economically valuable (annual catch value ≈ US$16.6 million) and productive (annual harvest ≈ 7 million kg) commercial fishery in the upper Great Lakes (Lakes Huron, Michigan, and Superior). Climate changes, specifically changes in temperature, wind, and ice cover, are expected to impact the ecology, production dynamics, and value of this fishery because the success of recruitment to the fishery has been linked with these climatic variables. We used linear regression to determine the relationship between fall and spring air temperature indices, fall wind speed, winter ice cover, and lake whitefish recruitment in 13 management units located in the 1836 Treaty Waters of the Upper Great Lakes ceded by the Ottawa and Chippewa nations, a culturally and commercially important region for the lake whitefish fishery. In eight of the 13 management units evaluated, models including one or more climate variables (temperature, wind, ice cover) explained significantly more variation in recruitment than models with only the stock–recruitment relationship, using corrected Akaike's Information Criterion comparisons (ΔAICc > 3). Isolating the climate–recruitment relationship and projecting recruitment with the Coupled Hydrosphere-Atmosphere Research Model (CHARM) indicated the potential for increased lake whitefish recruitment in the majority of the 1836 Treaty Waters management units. These results can inform adaptive management strategies by providing anticipated implications of climate on lake whitefish recruitment.

Trends in growth and recruitment of Lake Huron lake whitefish during a period of ecosystem change, 1985 to 2012

Abstract We use fishery-independent survey data to describe trends in growth and recruitment for lake whitefish ( Coregonus clupeaformis ) in the southern main basin of Lake Huron. We also used a model selection approach to evaluate the potential contribution of key variables (population biomass, temperature, dreissenid mussel establishment in 1993, and the regime shift in 2003) to trends in growth and recruitment. Overall, mean growth of juvenile whitefish (i.e. back-calculated growth occurring between ages 1 and 2 years) has been reduced to approximately half of what it was before dreissenids invaded. The number of recruits per kg spawner biomass averaged 36.1 before dreissenids were established, 2.48 between dreissenid establishment and the regime shift, and 4.61 thereafter. Accounting for the timing of dreissenid establishment and the regime shift greatly improved the ability of both density-dependent growth and stock-recruitment relationships to explain the variation in growth and relative recruitment over time, providing evidence that both of these relationships have been altered by recent ecosystem changes. Current rates of growth and recruitment are much lower than before dreissenids became established, likely reducing the productivity of these populations, and in turn affecting sustainable harvest levels.

Potential effects of climate change on the growth of fishes from different thermal guilds in Lakes Michigan and Huron

Abstract We used a bioenergetics modeling approach to investigate potential effects of climate change on the growth of two economically important native fishes: yellow perch ( Perca flavescens ), a cool-water fish, and lake whitefish ( Coregonus clupeaformis ), a cold-water fish, in deep and oligotrophic Lakes Michigan and Huron. For assessing potential changes in fish growth, we contrasted simulated fish growth in the projected future climate regime during the period 2043–2070 under different prey availability scenarios with the simulated growth during the baseline (historical reference) period 1964–1993. Results showed that effects of climate change on the growth of these two fishes are jointly controlled by behavioral thermoregulation and prey availability. With the ability of behavioral thermoregulation, temperatures experienced by yellow perch in the projected future climate regime increased more than those experienced by lake whitefish. Thus simulated future growth decreased more for yellow perch than for lake whitefish under scenarios where prey availability remains constant into the future. Under high prey availability scenarios, simulated future growth of these two fishes both increased but yellow perch could not maintain the baseline efficiency of converting prey consumption into body weight. We contended that thermal guild should not be the only factor used to predict effects of climate change on the growth of a fish, and that ecosystem responses to climate change should be also taken into account.

Impacts of degraded DNA on restriction enzyme associated DNA sequencing (RADSeq).

Degraded DNA from suboptimal field sampling is common in molecular ecology. However, its impact on techniques that use restriction site associated next-generation DNA sequencing (RADSeq, GBS) is unknown. We experimentally examined the effects of in situDNA degradation on data generation for a modified double-digest RADSeq approach (3RAD). We generated libraries using genomic DNA serially extracted from the muscle tissue of 8 individual lake whitefish (Coregonus clupeaformis) following 0-, 12-, 48- and 96-h incubation at room temperature posteuthanasia. This treatment of the tissue resulted in input DNA that ranged in quality from nearly intact to highly sheared. All samples were sequenced as a multiplexed pool on an Illumina MiSeq. Libraries created from low to moderately degraded DNA (12-48 h) performed well. In contrast, the number of RADtags per individual, number of variable sites, and percentage of identical RADtags retained were all dramatically reduced when libraries were made using highly degraded DNA (96-h group). This reduction in performance was largely due to a significant and unexpected loss of raw reads as a result of poor quality scores. Our findings remained consistent after changes in restriction enzymes, modified fold coverage values (2- to 16-fold), and additional read-length trimming. We conclude that starting DNA quality is an important consideration for RADSeq; however, the approach remains robust until genomic DNA is extensively degraded.