Sergiusz J. Czesny

The effect of egg fatty acid concentrations on embryo viability in wild and domesticated walleye (Stizostedion vitreum)

Abstract Eggs from three distinct populations of walleye Stizostedion vitreum , one domesticated (London State Fish Hatchery) and two wild (Lake Erie and Salt Fork Reservoir), were compared in terms of total lipid content and fatty acid profiles (phospholipids and neutral lipids). The concentrations of total lipids in eggs from domesticated broodstock were significantly lower (8.6 ± 1.0 % of wet weight) than those of both wild populations (13.3 ± 0.9 % and 10.9 ± 0.6 % of wet weight for Lake Erie and Salt Fork Reservoir, respectively). The profiles of fatty acids in egg lipids differed significantly among the three investigated populations. Domesticated females fed a formulated diet produced eggs containing significantly higher levels of linoleic acid (18:2n-6), characteristic of plant lipids. However, arachidonic acid (20:4n-6), was at significantly higher levels in eggs of wild walleye stocks. Although eicosapentaenoic acid (20:5n-3) was detected at significantly higher levels in eggs from Lake Erie walleye, docosahexaenoic acid (22:6n-3), the most abundant in polar lipids, was found at similar levels in eggs of all three populations. Survival of walleye embryos was correlated with the concentrations of polyunsaturated long chain fatty acids. Our data suggest that deficiency in n-3 fatty acids might be associated with impaired development of walleye, and thus poor larval and juvenile viability.

Growth, survival, and quality of juvenile walleye Stizostedion vitreum as influenced by n−3 HUFA enriched Artemia nauplii

Abstract We quantified how addition of n −3 highly unsaturated fatty acids (HUFA) to brine shrimp ( Artemia sp.) nauplii influenced growth, survival, osmotic challenge and fatty acid composition of juvenile walleye. Four groups of 6-day-old walleye were fed enriched Artemia . Lipids were altered to provide four treatments: (1) 100% cod liver oil (CLO), (2) 60% CLO/40% n −3 HUFA concentrate, (3) 40% CLO/60% n −3 HUFA concentrate, and (4) 100% n −3 HUFA concentrate. Different enrichments influenced neutral lipids of Artemia , but not their phospholipids. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) concentrations in Artemia neutral lipids in treatment 4 were doubled compared to treatment 1. Fatty acid composition of walleye body lipids, in both neutral and phospholipid fractions, reflected the changes in EPA and DHA concentrations found in enriched Artemia . After 3 weeks, walleye fed Artemia enriched with a combination of CLO and n −3 HUFA concentrate grew faster than those fed 100% n −3 HUFA enriched Artemia . Walleye fed Artemia nauplii enriched with 100% CLO survived better than all other treatments (25.0±4.5 vs. 11.4–13.1%). Walleye recovery after osmotic challenge was ordered treatment 1 through treatment 4; as n −3 HUFA in Artemia increased, so did susceptibility to this challenge. Furthermore, both survival and vitality of walleye were negatively correlated with the EPA/(arachidonic acid) AA ratio in their whole body phospholipids. The present work extends our knowledge on the effect on n −3 HUFA at higher levels in walleye juveniles diets (12.5% EPA, 5% DHA), and alterations in whole body fatty acids balance. We conclude that high EPA/DHA diet can be responsible for a decreased survival and higher susceptibility to stress in freshwater fish.

Nearshore energy subsidies support Lake Michigan fishes and invertebrates following major changes in food web structure

Aquatic food webs that incorporate multiple energy channels (e.g., nearshore benthic and pelagic) with varying productivity and turnover rates convey stability to biological communities by providing independent energy sources. Within the Lake Michigan food web, invasive dreissenid mussels have caused rapid changes to food web structure and potentially altered the channels through which consumers acquire energy. We used stable C and N isotopes to determine how Lake Michigan food web structure has changed in the past decade, coincident with the expansion of dreissenid mussels, decreased pelagic phytoplankton production, and increased nearshore benthic algal production. Fish and invertebrate samples collected from sites around Lake Michigan were analyzed to determine taxa-specific 13C:12C (delta13C) and 15N:14N (delta15N) ratios. Sampling took place during two distinct periods, 2002-2003 and 2010-2012, that spanned the period of dreissenid expansion, and included nearshore, pelagic and profundal fish and invertebrate taxa. The magnitude and direction of the delta13C shift indicated significantly greater reliance upon nearshore benthic energy sources among nearly all fish taxa as well as profundal invertebrates following dreissenid expansion. Although the mechanisms underlying this delta13C shift likely varied among species, possible causes include the transport of benthic algal production to offshore waters and increased feeding on nearshore prey items by pelagic and profundal species. delta15N shifts were more variable and of smaller magnitude across taxa, although declines in delta15N among some pelagic fishes suggest a shift to alternative prey resources. Lake Michigan fishes and invertebrates appear to have responded to dreissenid-induced changes in nutrient and energy pathways by switching from pelagic to alternative nearshore energy subsidies. Although large shifts in energy allocation (i.e., pelagic to nearshore benthic) resulting from invasive species appear to affect total production at upper trophic levels, changes in trophic structure and utilization of novel energy pathways may help to stabilize food webs following species invasions.

Effect of feeding cottonseed meal-containing diets to broodstock rainbow trout and their impact on the growth of their progenies

Rainbow trout Oncorhynchus mykiss broodstocks were fed five experimental diets in which fish meal protein was gradually replaced with cottonseed meal (CS) protein (0%, 25%, 50%, 75%, and 100%; diets 1–5, respectively) during a 22-month period. The effect of increasing dietary levels of CS on reproductive performance was gender specific. Sperm fertilizing ability significantly decreased when CS exceeded 50% protein replacement (72.6±2.0%, 73.6±2.0%, 69.0±3.3%, 43.3±5.1%, and 36.8±4.7%, for diets 1–5, respectively). In contrast, in females, the viability of embryos was only significantly affected at 25% and 50% replacement levels (56.7±15.6%, 20.5±24.9%, 11.4±18.6%, 48.8±25.9%, and 39.6±31.1%, for diets 1–5, respectively). Progenies from multiple parents per dietary treatment were combined and reared on a commercial diet over a 2- or 3-month period fed at a rate of 4% of their body weight. The paternal origin (fresh sperm, experiment 1) had a highly significant effect on growth performance of progenies, and progenies from males fed with 25%, 50%, and 75% CS grew significantly (P<0.05) faster than progenies from males fed with 0% and 100% CS. Growth performance of progenies produced using cryopreserved sperm (experiment 2) was not affected regardless of the CS levels fed to male rainbow trout. Progenies from females (experiment 3) fed a diet containing 50% CS grew significantly (P<0.05) slower than the other groups. Sex ratio was examined histologically after completion of feeding experiments with progenies. Regardless of maternal or paternal origin, males dominated among the progenies. Thus, we postulated that other substances such as flavonoids, present in the CS and possibly transferred to yolk sac reserves, might affect the sex ratio in favor of males.

Old Tales in Recent Context: Current Perspective on Yellow Perch Recruitment in Lake Michigan

Abstract To evaluate factors affecting recruitment of yellow perch Perca flavescens in southwestern Lake Michigan, a Ricker stock–recruitment model was fitted to age-0 abundance estimated from a fall bottom trawl survey (1989–2007) and spawning stock biomass estimates. Models were built for all possible combinations of four external variables: spring–summer water temperature, June nearshore zooplankton density, spring abundance of alewives Alosa pseudoharengus, and an index of wind-induced transport of yellow perch larvae. Four relatively parsimonious models were deemed robust, and three external variables were represented (spring–summer water temperature, spring alewife abundance, and June zooplankton density). The Ricker stock–recruitment model with the lowest value of Akaikes information criterion (i.e., the best-supported model) included spring–summer water temperature and spring alewife abundance. The basic Ricker stock–recruitment model ranked second, followed by the Ricker model that included June...

Ecological Consequences of Swim Bladder Noninflation for Larval Yellow Perch

Abstract Swim bladder inflation is a fundamental developmental step during the larval stage of many fishes. Although the physiological mechanisms of swim bladder inflation are well documented, the ecological costs of noninflation are poorly understood. If high proportions of newly hatched fish larvae fail to inflate their swim bladders and swim bladder noninflation negatively affects individual survival probability, the population-level effects could be dramatic. To determine whether fish larvae without inflated swim bladders perform differently than their conspecifics with inflated swim bladders, we compared growth rate, feeding selectivity and efficiency, susceptibility to predation, oxygen consumption, and starvation mortality of two size-classes of larval yellow perch Perca flavescens with and without inflated swim bladders in a series of experiments. In the laboratory, growth rates of yellow perch with uninflated swim bladders were less than those for fish with inflated swim bladders, and fish with i...

The effect of fasting, prolonged swimming, and predator presence on energy utilization and stress in juvenile walleye (Stizostedion vitreum).

We evaluated how two diets with different lipid levels (4% vs. 10%) influenced nutrient expenditure in juvenile walleye Stizostedion vitreum subjected to starvation, prolonged swimming, and predator presence. We also determined how exercise and predator presence influenced stress indicators such as blood plasma cortisol and glucose. Groups of six fish were placed in triplicate rectangular wire cages per treatment and submerged randomly in three artificial stream compartments at a water temperature of 14 degrees C. Three treatments were established: (A) no water current and no predator, (B) water current (1.5 body lengths s(-1)) and no predator, (C) water current and predator. Six 1-year-old muskellunge (Esox masquinongy, 28.4+/-2.3 cm) were used as predators. They were allowed to swim freely outside walleye cages and were fed with walleye. To simulate poststocking period of fasting, walleyes were exposed to experimental treatments for 6 weeks and were deprived of food. Regardless of the prior diet, fish weight significantly declined in all treatments but no differences were found among them. Lipids declined in both dietary groups of fish; in turn, body moisture increased. Protein levels were only affected in fish fed with high-lipid diet prior to the experiment and subjected to current and predator presence. Plasma glucose gradually declined in fish fed with high-lipid diet prior to the study; whereas in the fish fed with low-lipid diet before the experiment, it remained low regardless of the treatment severity. Plasma cortisol concentrations never exceeded 30 ng ml(-1) indicating no signs of acute stress during the experiment. We concluded that fish fed with diet containing higher lipid levels prior to stocking would possess better potential of withstanding adverse conditions and better survival once released to the wild.

Dietary Ascorbyl Monophosphate Depresses Lipid Peroxidation in Rainbow Trout Spermatozoa

Abstract This study was designed to analyze lipid peroxidation in spermatozoa of rainbow trout Oncorhynchus mykiss by an optimized thiobarbituric acid (TBA) method, and to evaluate the effect of graded levels of dietary antioxidant (ascorbic acid in the form of ascorbyl monophosphate, AP) on TBA values of spermatozoa. Sperm from rainbow trout fed diets supplemented with AP at 0, 110, or 870 mg/kg were sampled during the reproductive season. The group given the unsupplemented diet had the lowest ascorbic acid concentration in seminal plasma during most of the spermiation season compared with groups fed diets with AP While the ascorbic acid concentration in seminal plasma decreased toward the end of the reproductive season, spermatozoa malondialdehyde production, indicative of increasing peroxidation, tended to increase. At the end of the season, significant differences (P < 0.05) were found in peroxidation levels in spermatozoa from fish fed different levels of ascorbic acid. The most abundant polyunsatura...

Linking Egg Thiamine and Fatty Acid Concentrations of Lake Michigan Lake Trout with Early Life Stage Mortality

The natural reproduction of lake trout Salvelinus namaycush in Lake Michigan is thought to be compromised by nutritional deficiency associated with inadequate levels of thiamine (vitamin B1) in their eggs. However, mortality driven by thiamine deficiency (commonly referred to as early mortality syndrome [EMS]) is not the only significant cause of low lake trout survival at early life stages. In this study, we sought to better understand the combined effects of variable levels of thiamine and fatty acids in lake trout eggs on prehatch, posthatch, and swim-up-stage mortality. We sampled the eggs of 29 lake trout females from southwestern Lake Michigan. The concentrations of free thiamine and its vitamers (e.g., thiamine monophosphate [TMP] and thiamine pyrophosphate [TPP]) as well as fatty acid profiles were determined in sampled eggs. Fertilized eggs and embryos were monitored through the advanced swim-up stage (1,000 degree-days). Three distinct periods of mortality were identified: prehatch (0-400 degree-days), immediately posthatch (401-600 degree-days), and swim-up (601-1,000 degree-days). Stepwise multiple regression analysis revealed (1) that cis-7-hexadecenoic acid in both neutral lipids (NL) and phospholipids (PL) correlated with prehatch mortality, (2) that docosapentaenoic acid in PL and docosahexaenoic acid in NL correlated with posthatch mortality, and (3) that total lipids, TPP, and palmitoleic acid in NL, linoleic acid, and palmitic acid in PL correlated with the frequency of EMS. These results indicate the complexity of early life stage mortality in lake trout and suggest that inadequate levels of key fatty acids in eggs, along with variable thiamine content, contribute to the low survival of lake trout progeny in Lake Michigan.

Use of Erythrocyte Measurements to Identify Triploid Saugeyes

Abstract The use of erythrocyte size measurements as a possible alternative to flow cytometry for identifying triploid saugeyes (female walleye Stizostedion vitreum × male sauger S. canadense) was evaluated. Blood smear preparations were made from 32 heat-shocked saugeyes (1.0-42.7 g; 52-185 mm total length), which consisted of 12 diploids and 20 triploids, as determined by flow cytometry after blood cells were stained with propidium iodide. The length, width, surface area, and volume of the cell and nucleus of 100 erythrocytes were determined for each fish. The cell and nuclear dimensions were measured at 1,000× magnification with a calibrated ocular micrometer. Discriminant analysis was used to distinguish diploids and triploids based on their score profiles. Results showed that triploid saugeyes had significantly larger erythrocyte cell and nucleus measurements than their diploid counterparts (N = 32; P < 0.0001). Erythrocyte measurements correctly distinguished 93.8% of fish samples as diploids or tri...