Yellow Perch Larvae Research Articles

Altered Larval Yellow Perch Swimming Behavior Due to Methylmercury and PCB126 Detected Using Hidden Markov Chain Models.

Fish swimming behavior is a commonly measured response in aquatic ecotoxicology because behavior is considered a whole organism-level effect that integrates many sensory systems. Recent advancements in animal behavior models, such as hidden Markov chain models (HMM), suggest an improved analytical approach for toxicology. Using both new and traditional approaches, we examined the sublethal effects of PCB126 and methylmercury on yellow perch (YP) larvae (Perca flavescens) using three doses. Both approaches indicate larvae increase activity after exposure to either chemical. The middle methylmercury-dosed larvae showed multiple altered behavior patterns. First, larvae had a general increase in activity, typically performing more behavior states, more time swimming, and more swimming bouts per second. Second, when larvae were in a slow or medium swimming state, these larvae tended to switch between these states more often. Third, larvae swam slower during the swimming bouts. The upper PCB126-dosed larvae exhibited a higher proportion and a fast swimming state, but the total time spent swimming fast decreased. The middle PCB126-dosed larvae transitioned from fast to slow swimming states less often than the control larvae. These results indicate that developmental exposure to very low doses of these neurotoxicants alters YP larvae overall swimming behaviors, suggesting neurodevelopment alteration.

Utilization of Live‐Food Enrichment with Polyunsaturated Fatty Acids (PUFA) for the Intensive Culture of Yellow Perch Larvae

AbstractChallenges associated with first feeding have impeded the intensive culture of larval Yellow Perch Perca flavescens. Live‐food enrichment with polyunsaturated fatty acids (PUFAs) can increase the growth and survival of larval fish, but this method has not been tested with Yellow Perch. This study includes two experiments that were meant to evaluate (1) the relative proportion of docosahexaenoic acid (DHA; 22:6[n‐3]) and arachidonic acid (ARA; 20:4[n‐6]) in enrichment emulsions and (2) the provision of PUFA emulsions in ethyl ester (EE) or triacylglycerol (TG) form on Yellow Perch growth and survival. Fish were provided with live rotifers Brachionus plicatilis and brine shrimp Artemia nauplii for the first 10 d of exogenous feeding within a specialized recirculating system (phase I). Fish were then transferred to flow‐through tanks and were fed Artemia nauplii for 3 d before gradually transitioning to a formulated starter diet (5–7 d; phase II). Fish size, growth, survival, swim bladder inflation rates, and lipid/fatty acid concentrations were evaluated after each phase. Overall, rotifers assimilated ARA in higher concentrations (23.3% of total fatty acids) than Artemia (0.6–0.7% of total fatty acids). Rotifers also tended to assimilate PUFAs better in EE form than in TG form (71.3% versus 66.5% Σn‐3 + n‐6 fatty acids). In the first experiment, fish from the ARA‐ and DHA‐enriched diet groups had greater swim bladder inflation rates (phase I) and growth rates (phase II) than the unenriched control group. In phase I of the second experiment, the EE enrichment group had a significantly faster growth rate than the TG enrichment group (specific growth rate: mean ± SD = 40.5 ± 0.9% and 36.6 ± 1.8%, respectively). Fatty acid composition of zooplankton was heavily influenced by enrichments, and fatty acid composition of larvae/juveniles reflected that of their live prey. The results of this study suggest that PUFA enrichment of live feeds can accelerate Yellow Perch growth and reduce the time spent in the critical period of early development.

Hypoxic Threshold for Yellow Perch Embryonic Development

AbstractThe effects of hypoxia on the embryonic development and larval survival of Yellow Perch were examined at three different dissolved oxygen (DO) concentrations: hypoxia (H) 3–4 mg/L, moderate‐hypoxia (MH) 5 mg/L, and normoxia (N) 7–8 mg/L. Each DO concentration was tested in replicates of four within twelve 38‐L aquaria, at temperatures of 16.8 ± 0.4°C. To examine the effects of DO on the incubation of Yellow Perch embryos, samples of fertilized eggs (1.58 ± 0.1 g, 631 eggs/g) were placed in twelve 38‐L aquaria. The embryos were observed until hatching, or mortality. Significant differences were observed in embryonic survival and hatching among the three DO treatments. At 43 h after fertilization (haf, optic‐cup stage), embryonic development in H‐treatment groups was completely arrested, while the embryos of MH and N groups developed normally, possessing a distinct body trunk shape and optic caps at 43 haf. At 168 haf, all embryos were either developmentally arrested or dead in H treatment groups, while average percentage of live embryos in MH and N treatment groups was 12 ± 9.8% and 99 ± 0.4%, respectively. Heartbeat appeared at 72 haf in the N treatment groups, and about 96 haf in MH treatment groups. Heartbeat rate differed significantly (P < 0.05) between the N and MH groups (143 ± 10/min and 117 ± 17/min, respectively). Hatching rate in N groups (78.3 ± 8.6%) was significantly higher than that of MH groups (20.0 ± 8.7%), and there was no hatching observed in H groups. In the second experiment, 300 freshly hatched (72haf) larvae were stocked to each of the 12 aquaria to observe the effect of different oxygen concentrations (H, MH, and N) on survival for 5 d. We did not observe an effect on survival of the larvae. Overall, results indicate that hypoxic conditions below 3.5 mg/L (39% saturation at 16°C) have a profound negative effect on the development and survival of Yellow Perch embryos, while Yellow Perch larvae are capable of surviving this low‐DO environment.

The role of phototaxis in the initial swim bladder inflation of larval yellow perch (Perca flavescens)

The yellow perch (Perca flavescens) is a high priority species for aquaculture, with strong demand in the USA. Unfortunately, numerous developmental problems during larval rearing prevent its commercial viability. Failed swim bladder inflation (SBI) has been reported in the culture of numerous physoclistous fish species and is a prominent problem in the culture of yellow perch. Initial SBI occurs within a short period of ontogeny, and missing this opportunity results in permanent malformation of the organ. Lighting cues appear to play a role in triggering the response of rising to the surface to swallow the air required for initial SBI in several fishes including yellow perch. Larval yellow perch are photopositive, and this phototactic response seems to co-occur with the window of opportunity for SBI. Thus, we examined the role of phototactic behavior and low-intensity, moonlight-like illumination in initial SBI in yellow perch. Lights were positioned below and above the water surface in larval culture tanks to see if the presence of nighttime illumination impacted SBI success, and if the phototactic behavior of yellow perch helps them find the water surface when inflating at night. The results of this study reveal that even very low-intensity nighttime light reduces the proportion of yellow perch larvae to initially inflate regardless of the direction of the light source. Also, on treatment with no nighttime illumination, higher than expected SBI was observed, and the culture conditions that produced this success should be examined when focusing on improving SBI in the future. This research suggests that the photopositive response of yellow perch is not involved in SBI success, and lighting could play a role in hindering the process.

Developmental Methylmercury Exposure Affects Swimming Behavior and Foraging Efficiency of Yellow Perch (Perca flavescens) Larvae.

Methylmercury (MeHg) is a pervasive and ubiquitous environmental neurotoxicant within aquatic ecosystems, known to alter behavior in fish and other vertebrates. This study sought to assess the behavioral effects of developmental MeHg exposure on larval yellow perch (Perca flavescens)—a nonmodel fish species native to the Great Lakes. Embryos were exposed to MeHg (0, 30, 100, 300, and 1000 nM) for 20 h and then reared to 25 days post fertilization (dpf) for analyses of spontaneous swimming, visual motor response (VMR), and foraging efficiency. MeHg exposures rendered total mercury (THg) body burdens of 0.02, 0.21, 0.95, 3.14, and 14.93 μg/g (wet weight). Organisms exposed to 1000 nM exhibited high mortality; thus, they were excluded from downstream behavioral analyses. All MeHg exposures tested were associated with a reduction in spontaneous swimming at 17 and 25 dpf. Exposure to 30 and 100 nM MeHg caused altered locomotor output during the VMR assay at 21 dpf, whereas exposure to 100 nM MeHg was associated with decreased foraging efficiency at 25 dpf. For the sake of comparison, the second-lowest exposure tested here rendered a THg burden that represents the permissible level of consumable fish in the United States. Moreover, this dose is reported in roughly two-thirds of consumable fish species monitored in the United States, according to the Food and Drug Administration. Although the THg body burdens reported here were higher than expected in the environment, our study is the first to analyze the effects of MeHg exposure on fundamental survival behaviors of yellow perch larvae and advances in the exploration of the ecological relevance of behavioral end points.

The expression of hypoxia-inducible factor-1α gene is not affected by low-oxygen conditions in yellow perch (Perca flavescens) juveniles

Hypoxia can affect various fish populations, including yellow perch Perca flavescens, which is an economically and ecologically important species in Lake Erie, a freshwater system that often experiences hypoxia in the hypolimnetic part of the lake. Fish, similarly to mammals, possess molecular oxygen sensor-hypoxia-inducible factor-1 (HIF-1), a transcription factor that can affect expression of many downstream genes related to animal growth and locomotion, protein synthesis, as well as ATP and amino acid metabolism. HIF-1 is a heterodimer, which consists of two subunits: oxygen-sensitive and oxygen-insensitive subunits, α and β, respectively. In this study, we report first on the molecular cloning and sequencing of P. flavescens HIF-1α. The full-length complementary DNA (cDNA) was isolated and submitted to the GenBank with accession number KT783483. It consists of 3529 base pairs (bp) carrying a single open-reading frame that encompasses 2250bp of the coding region, 247bp of the 5' untranslated region (UTR), and 1032bp of the 3' UTR. The "de novo" prediction of the 3D structure of HIF-1α protein, which consists of 749 amino acids, is presented, too. We then utilized One-Step Taqman® real-time RT-PCR technology to monitor changes in HIF-1α messenger RNA (mRNA) copies in response to chronic hypoxic stress. An experiment was conducted using 14-day post-swim-up stage yellow perch larvae with uninflated swim bladders. This experiment included three treatment groups: hypoxia, mid-hypoxia, and normoxia, in four replicates (four tanks per treatment) with the following dissolved oxygen levels: 3, 4, and >7mg O2/L, respectively. At the end (2weeks) and in the middle (1week) of the experiment, fish from each tank were sampled for body measurements and molecular biology analysis. The results showed no differences in survival (∼90%) between treatment groups. Oxygen concentration was lowered to 3.02±0.15 (mean±SE) mg O2/L with no adverse effect on fish survival. The highest growth rate was observed in the normoxic group. A similar trend was observed with fish body length. The growth rate of fish declined with decreasing water-dissolved oxygen. The number of HIF-1α mRNA copies was not significantly different between hypoxic, mid-hypoxic, and normoxic conditions, and this was true for fish obtained in the middle and at the end of the experiment. Graphical abstract.

Forecasting the Impacts of Silver and Bighead Carp on the Lake Erie Food Web

AbstractNonindigenous bigheaded carps (Bighead CarpHypophthalmichthys nobilisand Silver CarpH. molitrix; hereafter, “Asian carps” [AC]) threaten to invade and disrupt food webs and fisheries in the Laurentian Great Lakes through their high consumption of plankton. To quantify the potential effects of AC on the food web in Lake Erie, we developed an Ecopath with Ecosim (EwE) food web model and simulated four AC diet composition scenarios (high, low, and no detritus and low detritus with WalleyeSander vitreusand Yellow PerchPerca flavescenslarvae) and two nutrient load scenarios (the 1999 baseline load and 2× the baseline [HP]). We quantified the uncertainty of the potential AC effects by coupling the EwE model with estimates of parameter uncertainty in AC production, consumption, and predator diets obtained using structured expert judgment. Our model projected mean ± SD AC equilibrium biomass ranging from 52 ± 34 to 104 ± 75 kg/ha under the different scenarios. Relative to baseline simulations without AC, AC invasion under all detrital diet scenarios decreased the biomass of most fish and zooplankton groups. The effects of AC in the HP scenario were similar to those in the detrital diet scenarios except that the biomasses of most Walleye and Yellow Perch groups were greater under HP because these fishes were buffered from competition with AC by increased productivity at lower trophic levels. Asian carp predation on Walleye and Yellow Perch larvae caused biomass declines among all Walleye and Yellow Perch groups. Large food web impacts of AC occurred in only 2% of the simulations, where AC biomass exceeded 200 kg/ha, resulting in biomass declines of zooplankton and planktivorous fish near the levels observed in the Illinois River. Our findings suggest that AC would affect Lake Erie's food web by competing with other planktivorous fishes and by providing additional prey for piscivores. Our methods provide a novel approach for including uncertainty into forecasts of invasive species' impacts on aquatic food webs.

Influence of the aquatic vegetation landscape on larval fish abundance

Abstract Aquatic vegetation (AV) is an important component of aquatic system, affecting habitat carrying capacity and fish productivity. By modulating habitat complexity, AV has the potential to influence the early ontogenetic stages of many fish species. However, understanding how variations in AV abundance influence fish distribution and abundance at the landscape scale of freshwater ecosystems is a considerable challenge due to the difficulty of collecting the high-resolution data needed for such analyses. We used yellow perch ( Perca flavescens ) as a biological model to test the hypothesis that larval fish abundance is positively related to a AV-rich landscape. Combining seven years of extensive larval sampling and satellite imagery, our results suggest that fish larvae tend to be associated with AV habitats after hatching. Based on zero-inflated binomial models, the probability of observing perch larvae increased from approximately 20% in low AV habitats to nearly 100% in dense AV habitats (pseudo- R 2 = 0.54). Our results also show that the probability of observing yellow perch larvae was lower during years of low water level and low AV biomass, likely limiting the availability of proper spawning or nursery habitats for fish. Furthermore, we demonstrate that larvae use both new AV as well as vegetative debris from the previous year that persisted through the winter. In agreement with a growing literature, our study gives additional support to the idea that AV plays a key role in freshwater fish recruitment.

Influence of habitat heterogeneity on the foraging ecology of first feeding yellow perch larvae, Perca flavescens, in western Lake Erie

The diet of first-feeding fish larvae can influence their future growth and survival. The foraging ecology of yellow perch (YP) larvae was studied in western Lake Erie, a region characterized by habitat heterogeneity associated with the Maumee River Plume (MRP) and a high prevalence of invasive species. To determine the influence of the MRP on YP diet, water physical characteristics, zooplankton prey community, and larval YP diet and foraging selectivity were compared between MRP and non-MRP waters, 2006–2008. Water temperature was higher, while water clarity was lower in the MRP when compared to non-MRP waters. The zooplankton prey community (groups constituting >1% of YP prey items) did not differ between MRP and non-MRP waters, being composed of small cladocerans, cyclopoid and calanoid copepods and non-native dreissenid mussel veligers. Ration increased with YP total length (TL), with no differences found between MRP and non-MRP waters. Diet composition also varied with larval YP length, with the smallest larvae preying more heavily on dreissenid veligers than larger fish, and no differences between MRP and non-MRP waters. Most sizes of larvae positively selected for cyclopoid copepods in MRP and non-MRP waters, while selection for other prey was neutral or negative. Our study reveals a similar zooplankton community and larval foraging ecology between MRP and non-MRP waters during spring season, despite habitat physical differences, and points to mechanisms unassociated with larval foraging (i.e., predation) as a reason for higher recruitment of YP residing inside versus outside of the MRP as larvae.

Modulation of Specific Apoptotic DNA Fragmentation after Short Term Exposure to Natural UVR in Fish Larvae

The goal of this study was to determine the short-term effects of the quality (UV-A/UV-B ratio) and quantity (irradiance) of natural ultraviolet radiation (UVR) on the apoptosis levels in Yellow perch (Perca flavescens) larvae. Apoptosis, or programmed cell death, is an essential event in many physiological processes as well as in pathological conditions. Western blots were used to measure the expression of several key proteins of the apoptotic cascade, such as p53, Bax, Bcl-2, and PARP-1, whereas specific apoptotic DNA fragmentation was measured by an ELISA assay. We predicted that higher UVR exposure would be related to higher levels of apoptosis. Our results showed that specific apoptotic DNA fragmentation was reduced by visible light + UV-A as well as by visible light + UV-A and UV-B treatments although it was not significantly affected by light quantity. However, the expression of p53, Bax/Bcl-2 ratio and PARP-1 were not significantly affected in larvae by the quantity or the quality of the light after two days of exposure. Altogether our results suggest that UVR may modulate the apoptotic process in Yellow perch larvae proposing an interesting role for this stressor on the early development of living organism under natural exposure condition.

Spatial distribution of pelagic fish larvae in the northern main basin of Lake Huron

Larval fish occurrence in inshore and offshore zones in the northern main basin of Lake Huron was assessed during 2007 as part of a larger ecological examination of Lake Huron foodwebs and habitats. Day and night collections using neuston and conical nets at inshore (1.5–15 m depths) and offshore (37 and 91 m depths) locations at De Tour and Hammond Bay to assess the abundance, phenology, and spatial distribution of pelagic ichthyoplankton during spring and early summer were made. In general, densities of larval fishes were higher at De Tour than Hammond Bay during daytime neuston net collections, with the exception of Longnose Sucker, which were only collected at Hammond Bay. Lake Whitefish, Burbot, and Rainbow Smelt dominated inshore catches in early spring with Cisco, Deepwater Sculpin, Emerald Shiner, Bloater, Slimy Sculpin, Ninespine Stickleback, and Yellow Perch larvae also collected. Nighttime nearshore and offshore sampling revealed that Rainbow Smelt and Burbot larvae were present in relatively high abundances compared to inshore densities. Concentrations of larvae of deepwater demersal fishes such as Lake Whitefish and Deepwater Sculpin suggest that inshore zones in northern Lake Huron are important nursery habitats emphasizing a critical production and recruitment linkage between inshore and deepwater zones.

Inferring Processes from Spatial Patterns: The Role of Directional and Non–Directional Forces in Shaping Fish Larvae Distribution in a Freshwater Lake System

Larval dispersal is a crucial factor for fish recruitment. For fishes with relatively small-bodied larvae, drift has the potential to play a more important role than active habitat selection in determining larval dispersal; therefore, we expect small-bodied fish larvae to be poorly associated with habitat characteristics. To test this hypothesis, we used as model yellow perch (Perca flavescens), whose larvae are among the smallest among freshwater temperate fishes. Thus, we analysed the habitat association of yellow perch larvae at multiple spatial scales in a large shallow fluvial lake by explicitly modelling directional (e.g. due to water currents) and non-directional (e.g. due to aggregation) spatial patterns. This allowed us to indirectly assess the relative roles of drift (directional process) and potential habitat choice on larval dispersal. Our results give weak support to the drift hypothesis, whereas yellow perch show a strong habitat association at unexpectedly small sizes, when compared to other systems. We found consistent non-directional patterns in larvae distributions at both broad and medium spatial scales but only few significant directional components. The environmental variables alone (e.g. vegetation) generally explained a significant and biologically relevant fraction of the variation in fish larvae distribution data. These results suggest that (i) drift plays a minor role in this shallow system, (ii) larvae display spatial patterns that only partially covary with environmental variables, and (iii) larvae are associated to specific habitats. By suggesting that habitat association potentially includes an active choice component for yellow perch larvae, our results shed new light on the ecology of freshwater fish larvae and should help in building more realistic recruitment models.

Effect of light intensity, prey density, and ontogeny on foraging success and prey selection of larval yellow perch (Perca flavescens)

AbstractLight intensity has been shown to influence the foraging success of larval fish. However, the effect of light intensity on larval foraging is likely variable and influenced by both the density and characteristics of planktonic prey. In this study we examined the influence of light intensity of 0.1, 2.0, and 60 μmol·s−1·m−2 Photosynthetically Active Radiation (PAR) on foraging of yellow perch (Perca flavescens) larvae at two prey densities. We fed them with a mixture of zooplankton taxa common to lakes inhabited by yellow perch. In addition to light intensity and prey density, the effect of larval yellow perch size was examined by using fish ranging from 9 to 15 mm. The results of our study indicated that yellow perch larvae are well adapted to feed at a wide range of light intensities, as there was no difference in foraging success at investigated light intensities. Increasing prey density from 25 to 150 (zooplankton·l−1) significantly improved the foraging success of larval yellow perch. However, the influence of prey density on foraging success was dependent on fish length. Improved foraging success at increased prey densities occurred only for individuals with a total length >10 mm. Overall, prey selection by fish larvae was influenced by light intensity, prey density, and fish length. However, the factors that influenced selection for specific prey types differed. Our study, combined with evidence from other field and laboratory work, highlight the need for a better understanding of the influence of prey density on foraging throughout ontogeny.

Diet and Feeding Success of Fast‐Growing Yellow Perch Larvae and Juveniles in Perturbed Boreal Lakes

AbstractThe principal objective of this study was to test the hypothesis that enhanced early growth of yellow perch Perca flavescens in lakes affected by forest harvesting was related to favorable feeding conditions after the perturbation. Yellow perch larvae and juveniles and their zooplankton prey were sampled three times in three unperturbed lakes and in three perturbed lakes where forest harvesting had occurred in the catchment 2 years earlier. Univariate and multivariate analyses of the diets of age‐0 yellow perch from both treatments showed that fish in perturbed lakes primarily preyed upon Daphnia spp. and Polyphemus pediculus, whereas fish in unperturbed lakes preyed upon more diverse food items. Perturbed lakes showed higher dissolved organic carbon concentrations, algal biomass, and Daphnia spp. abundance. The feeding success index (number of prey items in the stomach per millimeter of fish length) and recent growth rates of age‐0 yellow perch showed a significant type II functional relationship with the abundance of Daphnia spp. We hypothesized that the increase in Daphnia spp. abundance and a darkening of water color in perturbed lakes may have favored prey detection and growth for larval and juvenile yellow perch, thereby affecting population recruitment.

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

AbstractTo 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 Akaike's 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 zooplankton density. The fourth Ricker model that was deemed robust included spring–summer water temperature. The four best models provided a good fit to age‐0 yellow perch abundance estimates based on fall seining catches along the Illinois shoreline of Lake Michigan during 1989–2007. Our findings indicate that over the last two decades, yellow perch recruitment benefited during years associated with relatively warm water, low alewife abundance, and high zooplankton density.

The effects of UVR irradiance and spectral composition on yellow perch (Perca flavescens) larvae survival

The purpose of this study was to determine experimentally the effects of the quality (UV-A/UV-B ratio) and quantity (irradiance) of natural ultraviolet radiation (UVR) on the survival of yellow perch (Perca flavescens) larvae and on the oxidative stress in their cytoplasm, estimated by the activity of the superoxide dismutase (SOD). We also estimated the potential accumulation of photodamage in DNA by using UV dosimeters. Freshly-hatched yellow perch and UV dosimeters were incubated in controlled conditions under a factorial combination of selective and non-selective filters offering different levels of UVR protection and exposed to natural solar light. Larval survival was inversely related to the UVR intensity gradient, and responded similarly to the presence of both UV-A and UV-B or UV-A only. In contrast, the responses of SOD activity and UV dosimeter were stronger in the presence of both UV-A and UV-B than UV-A only, leading to a partial mismatch with the results on survival. Our results, obtained under natural solar light, suggest that incident UV-A radiation, despite its lower energy per unit photon than UV-B, could be a serious threat for yellow perch larvae. They also show that UV dosimeters and SOD activity predict only some components of UVR risk for yellow perch larvae. The partial mismatch between UV dosimeters results and larval survival cautions against the use of UV dosimeters alone as a proxy for UVR risk in the field.

Match–Mismatch Regulation for Bluegill and Yellow Perch Larvae and Their Prey in Sandhill Lakes

AbstractFood availability may regulate fish recruitment, both directly and indirectly. The availability of zooplankton, especially to newly hatched larvae, is thought to be crucial to their early growth and survival. We examined stomach contents of larval bluegill Lepomis macrochirus and yellow perch Perca flavescens in Pelican Lake and Cameron Lake, Nebraska, in 2004 and 2005. We also determined zooplankton availability and calculated prey selection using Chesson's α. In addition, we investigated potential match–mismatch regulation of recruitment from 2004 to 2008. Bluegill positively selected copepod nauplii and Bosmina spp., and yellow perch often selected copepods. Abundant zooplankton populations were available for consumption. Matches of both larval bluegill and yellow perch abundance to zooplankton abundance were detected in all years; exact matches were common. Mismatches in predator and prey production were not observed. Predation by age-0 yellow perch on age-0 bluegill was not observed, even though yellow perch hatched 2 mo prior to bluegill. Given that zooplankton were abundant and well-timed to larval fish relative abundance over the time span of this study, the match–mismatch hypothesis alone may not fully account for observed recruitment variability in these populations. Environmental conditions may also affect recruitment and warrant further investigation.

Examination of Sampling Bias for Larval Yellow Perch in Southern Lake Michigan

Evidence suggests larval yellow perch, Perca flavescens, utilize nearshore and offshore habitat during the 30–40 day period between hatch and transition from pelagic to demersal habitat. In a large, open system like Lake Michigan this represents a significant increase in available habitat and it is important to understand how this increase may impact our ability to sample larval yellow perch in an unbiased manner. We measured the vertical distribution of larval yellow perch in southern Lake Michigan as a function of size, age, and diel period. Larval yellow perch were collected from two zones (surface and epilimnion) from 1 to 32 km from shore in 2001 during the day; on four dates surface samples were also collected at night. Results indicate larval perch are more abundant at the surface at night han during the day. Larval yellow perch < 15 mm total length (TL) and younger than 18 days post hatch were found in both surface and epilimnion habitat during the day, but larvae > 15 mm TL were captured only in the epilimnion and farther than 5 km from shore, which suggests a different spatial distribution for larger, older larvae. Diel differences in larval abundance and size at the surface suggest more and larger larvae will be caught for a similar effort at night as compared to daytime sampling. Observed differences in larval distribution with size and age also suggest that sampling concentrated nearshore and/or at the surface has the potential to under-sample larger/older yellow perch larvae in Lake Michigan.

Short-term Water Mass Movements in Lake Michigan: Implications for Larval Fish Transport

Water mass movement within the Great Lakes may rapidly transport fish larvae from favorable nursery areas to less favorable habitats, thereby affecting recruitment success. During 2001 and 2002, we released satellite-tracked drifting buoys in eastern Lake Michigan to follow discrete water masses, and used ichthyoplankton nets to repeatedly sample larval fish within these water masses. Observed nearshore water currents were highly variable in both direction and velocity. Current velocities far exceeded potential larval fish swimming speeds, suggesting that currents can potentially rapidly advect fish larvae throughout the lake. Evidence suggests that while paired drifters released during 2002 were able to track relatively small alewife ( Alosa pseudoharengus) and yellow perch ( Perca flavescens) larvae within an alongshore coastal current, paired drifters released during 2001 failed to track larger alewife larvae when flow was more offshore and highly variable. These results are consistent with the decorrelation scales associated with alongshore and offshore transport.

Evidence across multiple scales for offshore transport of yellow perch (Perca flavescens) larvae in Lake Michigan

Most freshwater fishes have short pelagic early life stages. Lake Michigan presents an interesting scenario for yellow perch (Perca flavescens), a species with a long pelagic larval stage that may not be well adapted to lakes with an expansive pelagic environment and extensive offshore transport. We investigated the possibility that early life stages of yellow perch were transported well offshore from their nearshore spawning grounds and explored whether food resources were more or less favorable offshore. To determine the extent to which pelagic age-0 yellow perch moved offshore, we sampled at multiple scales ranging from local (&lt;2 km) to across the lake (&gt;120 km). Evidence of offshore movement by fish larvae occurred at each scale. Yellow perch larvae were quickly transported offshore from nearshore spawning sites and remained in the offshore pelagia to sizes of at least 30 mm. Zooplankton density was greater offshore than nearshore, suggesting that pelagic age-0 yellow perch find improved food resources offshore compared with their nearshore spawning sites. Currents operating at oceanographic scales likely influenced the offshore movement of pelagic age-0 yellow perch in Lake Michigan. These currents, coupled with prey availability for pelagic age-0 individuals, may influence the recruitment success of this species.