White Perch Research Articles

Effects of recent ecosystem changes on the recruitment of young-of-the-year fish in western Lake Erie

We compared the variability in forage fish recruitment over the last 27 years against major ecological changes that occurred in Lake Erie over the same time period. During a period of high adult walleye abundance and declining phosphorus loading (1976-1982), we observed a decline in the abundance of later hatching forage fish species (e.g., July) and those species that did not shift their diets from zooplankton to benthos during the summer of their life. During years of high young-of-the-year (YOY) white perch abundance (1983-1990), forage fishes whose hatching dates and (or) diet overlapped with YOY white perch declined in abundance. When the zebra mussel (Dreissena polymorpha) became abundant (1991-1995), most forage fishes showed no change in abundances. Given a YOY's ability to switch to benthos during summer, the date on which this occurred was determined by a combination of zooplankton abundance and fish size. Hence, the dates individual taxa of fish hatch relative to seasonal cycles of zooplankton abundance and the size at which they can undergo an ontogenetic diet shift to benthos and (or) fish could be influencing fish growth and recruitment and need to be incorporated into YOY recruitment models.

Molecular and pharmacological properties of GABA-rho subunits from white perch retina.

Five gamma-aminobutyric acid (GABA)-rho subunits were cloned from a white perch retinal cDNA library and expressed in Xenopus oocytes. The deduced amino acid sequences indicated that all are highly homologous to the GABA-rho subunits cloned from mammalian retinas; two clones (perch-rho 1A and perch-rho 1B) were in the rho 1 family, two (perch-rho 2A and perch-rho 2B) were in the rho 2 family, and one clone has been tentatively identified as a perch-rho 3 subunit. When expressed in Xenopus oocytes, all but one of the subunits (rho 3) formed functional homooligomeric receptors. However, the receptors expressed by each of the GABA-rho subunits displayed unique response properties that distinguished one from the other. For example, receptors formed by perch-rho 1B subunits were more sensitive to GABA than the receptors formed by other GABA-rho subunits, the dose-response curves for the various receptors revealed different Hill coefficients, and there were differences in the kinetics of the GABA-induced currents. In addition, the GABA-mediated current-voltage curve for rho 2 receptors was approximately linear, whereas the responses from rho 1 receptors showed outward rectification. A further division in the properties of the GABA-rho subunits was revealed in their responses to imidazole-4-acetic acid (I4AA); the drug behaved as an antagonist on A-type rho receptors and a partial agonist on the B-type rho receptors. These results suggest that there is a large diversity of GABAC receptors in the vertebrate retina, probably formed by homooligomeric and heterooligomeric combinations of GABA rho subunits, that exhibit different functional properties.

Projected Changes to the Trophodynamics of PCBs in the Western Lake Erie Ecosystem Attributed to the Presence of Zebra Mussels (Dreissena polymorpha)

A food web bioaccumulation model was used to hindcast PCB congener concentrations in aquatic biota from western Lake Erie in the years prior to the zebra mussel invasion, and these results were compared to post-mussel predicted concentrations that had been verified previously against measured data to estimate the effects of mussels on the trophodynamics of PCB congeners in western Lake Erie. Two hindcasting scenarios were compared to a third, previously verified, scenario to determine the changes in PCB congener concentrations in biota in response to (i) modifications to food web structure, before and after the introduction of mussels, and (ii) modifications to food web structure combined with a decline in particulate organic carbon (POC) concentrations resulting from removal of seston from the water column by mussel filtering activities. The reduction in the concentration of POC, attributed to the prodigious filter-feeding of large zebra mussel populations, was predicted to have caused increases in the freely dissolved concentrations of PCB congeners ranging from 2.9% to 9.3%. These increases in dissolved chemical were predicted by the model to cause small increases (range 0−7.3%) in the PCB congener burdens of many biota including zooplankton, prey fish species, and walleye. Other organisms, such as Gammarus, small white suckers, and freshwater drum, were predicted to have larger increases in their PCB body burdens (9.1−22.2%) as a result of the increase in freely dissolved chemical and a shift in diet. For crayfish, yellow perch, black crappie, white perch, large white suckers, gizzard shad, and largemouth bass, the increased exposure to chemical via water was offset by decreased chemical exposure via the diet, which resulted from shifts in diet toward less contaminated items brought about by the presense of zebra mussels. The results of this study are relevant to Lake Erie resource managers that are concerned about the potential of zebra mussels to alter PCB congener dynamics in the western basin.

Seasonal and Size-Related Food Habits of Largemouth Bass in Two Connecticut Lakes

Stomach contents of 425 largemouth bass were identified and quantified using the Relative Importance (RI) index over three seasons (spring, summer, and fall) from Lake Lillinonah and Pickerel Lake, Connecticut. In Lake Lillinonah during spring, aquatic insects had the highest RI, followed by crayfish and fish (primarily white perch). During summer and fall, the RI of aquatic insects decreased, the RI of crayfish remained consistent, and the RI of fish approximately doubled. Fish (primarily bluegill) was the most important diet item of largemouth bass from Pickerel Lake during all seasons. Aquatic insects were the second most important diet item during spring and summer. In Lake Lillinonah and Pickerel Lake, the RI of aquatic insects decreased and the RI of fish increased with increasing fish length; aquatic insects were most important in largemouth bass less than 300 mm. In contrast to Lake Lillinonah where the RI of crayfish and fish were of equal importance in largemouth bass ≥ 380 mm, largemouth bass ≥ 380 mm in Pickerel Lake fed almost exclusively on fish. Our results suggest that food habits of largemouth depend on the type of lake system and the dominant prey types. In Connecticut lakes that lack suitable littoral areas and associated panfish species, largemouth bass may rely on pelagic fishes and crayfish as food sources.

Diets of White Bass in the Ohio Waters of Lake Erie during June–October 1988

Although white bass Morone chrysops support a valuable commercial fishery in Lake Erie, little is documented about their diets, growth, abundance, or other population characteristics. This study sought to describe the growth and feeding habits of 1-year-old and older white bass in the Ohio waters of Lake Erie. Between 13 June and 31 October 1988, I sampled 246 white bass ranging from 158 to 332 mm in total length. White bass were primarily piscivorous, feeding on shiners (Notropis spp.), white perch M. americana yellow perch Perca flavescens and chironomids in June but shifting to primarily gizzard shad Dorosoma cepedianum during July–October (56–97%). Prey sizes of white bass reflected the change from a large number, but low biomass, of invertebrates in June and July (mean size, 3.15 and 6.45 mm, respectively) to mostly age-0 prey fish in August through October (mean prey size, 50.97–85.27 mm). During this time, growth of white bass was nearly linear. Walleye Stizostedion vitreum is the dominant piscivore in Lake Erie. Due to the importance of gizzard shad in the walleye diet, this species has been suggested as the cornerstone of walleye production in Lake Erie. The high use of gizzard shad by white bass throughout most of the growing season lends further support to the belief that gizzard shad were the cornerstone of piscivore production in western Lake Erie during the late 1980s.

Walleye Prey Selection in Lake McConaughy, Nebraska: A Comparison between Stomach Content Analysis and Feeding Experiments

We investigated walleye (Stizostedion vitreum) prey selection by comparing results from feeding experiments and stomach content analysis. Walleye captured from Lake McConaughy, Nebraska in June through September, 1995, were presented treatments of three prey species-yellow perch (Perca flavescens), white sucker (Catostomus commersoni) and either alewife (Alosa pseudoharengus) or gizzard shad (Dorsoma cepedianum). In the feeding experiments, walleye selected white sucker and yellow perch over alewife and gizzard shad. However, alewife were the most abundant prey species in walleye stomachs and not significantly different from their proportion in the natural prey fish assemblage. Differences in prey selection between experiments and field studies suggest that walleye altered their foraging behavior to take advantage of vulnerable or more accessible prey.

Acute Toxicity of 5% Non‐Synergized Emulsifiable Rotenone to White River Crayfish Procambarus acutus acutus and White Perch Morone americana

AbstractAnnual drawdown of crayfish culture ponds to plant forage crops also serves to eradicate most predaceous finfish. Without annual drawdown predaceous fish populations may reach numbers that can significantly reduce the crayfish crop. Frequent drawdown may not be feasible or desirable in some management schemes. Evidence in the literature suggests that differential toxicity of rotenone would allow removal of fish without harming crayfish in the same pond. In the current study, laboratory and in situ acute toxicity bioassays (96 h) were conducted with 5% non‐synergized emulsifiable rotenone to define the maximum non‐lethal concentration (LC100) for white river crayfish Procambarus acutus acutus and the minimum lethal concentration (LC100) for white perch Morone americana. Six concentration levels of rotenone formulation were tested in each of six toxicity trials with crayfish using dechlorinated tap water at 21–25 C. LC0 (compensated for control mortality) was determined to be 3.0 mg/L. Significant crayfish mortality began at 4.0 mg/L. Acute toxicity to white perch was anticipated to be within recommended concentration levels on product label for similar fish, and was corroborated by laboratory bioassay (LC100 of 0.15 mg/L). Both species were then tested together in laboratory aquaria utilizing pond water at room temperature. Concentration levels of 0.05–2.5 mg/L killed all white perch with no crayfish mortality. In the final phase of the study a 1.0 mg/L concentration of rotenone was applied to a pond containing both species held in cages. All white perch were dead within 24 h; no crayfish mortality was observed for the 96‐h duration of the trial. It may therefore be possible to use this rotenone formulation to control white perch and other finfish in active crayfish culture ponds.

Consumption, Selectivity, and Use of Zooplankton by Larval Striped Bass and White Perch in a Seasonally Pulsed Estuary

Abstract Many estuaries exhibit seasonal pulses of phytoplankton and zooplankton production. Larval fishes that co-occur with these “blooms” should be at a growth and survival advantage compared with larvae that occur before or after the bloom, although this has been difficult to observe in many systems. We tested this potential advantage for larval (< 10 mm notochord length) striped bass Morone saxatilis and white perch M. americana in the Hudson River by examining consumption and feeding selectivities with respect to zooplankton blooms. The cladoceran Bosmina longirostris and large copepodite and adult copepods together composed 97.4%, and 90.9% of larval striped bass and white perch diets, respectively. Peak consumption rates of Bosmina coincided with the bloom. whereas copepod consumption rates continued to increase throughout the sampling period. Selectivity for copepods was inversely related to selectivity for Bosmina and was high, except at those sites and times when Bosmina densities exceeded 14 a...

Estimating piscine prey size from partial remains: testing for shifts in foraging mode by juvenile bluefish

Knowledge of prey sizes consumed by a predator aids in the estimation of predation impact. Young-of-the-year bluefish, Pomatomus saltatrix, attack their prey tail-first and often bite their prey in half; this poses a unique problem in determining prey sizes from stomach content analysis. We developed a series of linear regressions to estimate original prey lengths from measurements of eye diameter and caudal peduncle depth for striped bass, Morone saxatilis, bay anchovy, Anchoa mitchilli, American shad, Alosa sapidissima, blueback herring, Alosa aestivalis, Atlantic silverside, Menidia menidia, and white perch, Morone americana. We then used these regressions to estimate original prey sizes from pieces of prey found in stomachs of bluefish collected in the Hudson River estuary from 1990–1993. Lengths of prey that were swallowed whole were compared to estimated lengths of prey that were consumed in pieces. Lengths of prey that were consumed in pieces were larger than prey that were consumed whole. We determined the prey length/predator length ratio at which bluefish began shifting from swallowing their prey whole to partial consumption. Shifting occurred at a ratio of approximately 0.35 irrespective of prey species, suggesting that prey length plays an important role in predator foraging decisions and may contribute to gape limitations. Shifts in foraging mode effectively reduce gape limitation and allow bluefish to consume larger prey sizes which may increase their effect on prey populations.

Mercury Concentrations in Maine Sport Fishes

Abstract To assess mercury contamination of fish in Maine, fish were collected from 120 randomly selected lakes. The collection goal for each lake was five fish of the single most common sport fish species within the size range commonly harvested by anglers. Skinless, boneless fillets of fish from each lake were composited, homogenized, and analyzed for total mercury. The two most abundant species, brook trout Salvelinus fontinalis and smallmouth bass Micropterus dolomieu, were also analyzed individually. The composite fish analyses indicate high concentrations of mercury, particularly in large and long-lived nonsalmonid species. Chain pickerel Esox niger, smallmouth bass, largemouth bass Micropterus salmoides, and white perch Morone americana had the highest average mercury concentrations, and brook trout and yellow perch Perca flavescens had the lowest. The mean species composite mercury concentration was positively correlated with a factor incorporating the average size and age of the fish. Lakes conta...

Habitat requirements of northern pike (Essox lucius)

Over the past half century, habitat changes have significantly affected production of northern pike ( Esox lucius), especially in the Great Lakes Basin. Loss of wetlands, reduction of shoreline cover and structure, cultural eutrophication, and siltation have negatively affected water transparency, abundance of macrophyte habitat, and even body condition. We review recent habitat restoration programs conducted in the Great Lakes Basin to reverse this trend. However, assessment has usually been inadequate to evaluate their success. Spawning and nursery requirements (first year of life) are examined, using a system for classifying and ranking major physical characteristics and requirements. Depth of nursery habitat is directly correlated with fish size and age. Spawning habitat is usually less critical or limiting but more easily manipulated and restored than nursery or juvenile-adult habitats. Year-class strength over 22 yr in eastern Lake Ontario was correlated positively with midsummer temperature and negatively with late summer-early fall water elevation; also, the largest year-class appeared immediately after catastrophic winterkill of a predator, white perch ( Morone americana). Both implicate nursery rather than spawning associations. Adult abundance is related to the extent of macrophyte cover, which is optimal from 35 to 80% but inversely related to body size.

Fish Species in Chicago Harbors of Lake Michigan, 1988 to 1990, as Determined by Electrofishing and Creel Surveys

ABSTRACT We surveyed the fish species in five Chicago harbors of Lake Michigan from the spring of 1988 until the end of June of 1990 to establish a baseline of information regarding this fishery. The study took place prior to the invasion of the zebra mussel and exotic fish species such as the round goby and the ruffe, which have subsequently altered the habitat. Twenty-six fish species were captured by electrofishing. These species included five species which were not known to occur in Illinois waters of Lake Michigan; they were: white perch, quillback carpsucker, longear sunfish, black crappie, and the freshwater drum. Seventeen species were caught by sport fishermen. One of these species, the channel catfish, was never previously caught by fishermen or other sampling techniques in the Illinois waters of Lake Michigan. The abundant species were alewife, carp, gizzard shad, golden shiner, and yellow perch. Other species included largemouth bass, smallmouth bass, rock bass, bluegill, pumpkinseed, green sunfish, black bullhead, and white sucker. Chinook salmon, coho salmon, brown trout, rainbow trout, and a single lake trout were caught during the fall months. Yellow perch was the primary sport fish caught, and rainbow smelt was caught by gillnets in spring.

Characterization of a vitellogenin receptor in white perch (Morone americana).

Receptors for white perch vitellogenin (wVTG) were characterized using wVTG, labeled in vivo with [3H]leucine or in vitro with 125I, and semipurified ovarian membranes. Specific binding of wVTG to the membranes was temperature-dependent, proportional to the amount of membrane, and saturable. Scatchard analyses revealed a single class of binding sites of low maximum binding capacity (MBC; approximately 35 pmol VTG/mg membrane protein) and high affinity (Kd approximately 400 nM), consistent with wVTG levels (540-2700 nM) circulating in maturing females. Ligand blotting revealed a receptor protein of M(r) approximately 157000 and a smaller protein, possibly its degradation product. Striped bass vitellogenin, chicken egg yolk very low density lipoprotein, and suramin displaced wVTG from its receptor, but BSA did not. No change in Kd was noted over the course of vitellogenesis in maturing perch, and MBC increased only slightly very late in the gametogenic cycle. The wVTG bound specifically to membranes prepared from liver, muscle, and mesenteric fat, but not to erythrocyte membranes. The Kd for ovary (394 nM) and liver (345 nM) were similar, but the Kd for muscle (1440 nM) was much higher.

Growth, survival and size-selective predation mortality of larval and juvenile inland silversides, Menidia beryllina (Pisces; Atherinidae)

A series of laboratory and field experiments were conducted to determine the relative importance of food limitation and predation as sources of mortality for Menidia beryllina (Cope) larvae and juveniles. Seven-day experiments using in situ mesocosms to exclude predators demonstrated significant growth (mean instantaneous growth rate of 0.122–0.135 day −1) and survival (mean 88–89%) for M. beryllina larvae in a Rhode Island, USA, estuary. These results suggest that food was not limiting for growth or survival and, therefore, that predation is likely the primary source of mortality for young-of-the-year (YOY) M. beryllina. Predation experiments were conducted in laboratory aquaria and in in situ mesocosms to assess the size-selectivity of potential predators. Laboratory-reared striped bass, Morone saxatilis Walbaum and field-collected white perch, Morone americana Gmelin, crevalle jack, Caranx hippos Linnaeus and bluefish, Pomatomus saltatrix Linnaeus, were presented with a choice of two or three size classes of laboratory-reared M. beryllina and allowed to feed for 3–24 h. For field-collected predators the experimental prey size range was similar to the size present in the field. Striped bass, white perch and crevalle jack selectively preyed on the smallest size classes. Bluefish, however, selectively preyed on the largest size class. These results suggest that size-specific survival of YOY M. beryllina may vary spatially and temporally depending on the particular suite of predators encountered by individual populations or cohorts. However, in the estuary studied predation mortality appears to be directed towards the larger members of the M. beryllina cohort.

Polychlorinated Biphenyl Contamination in Selected Estuarine and Coastal Marine Finfish and Shellfish of New Jersey

Analysis of polychlorinated biphenyls (PCBs) in selected finfish and shellfish from the estuarine and coastal marine waters of New Jersey reveals variable levels of contamination in different regions of the state. Monitoring surveys conducted by the New Jersey Department of Environmental Protection during the last two decades indicate that biota from the northeast region are the most severely contaminated with PCBs. Early monitoring in the 1970s showed that as much as 75% of the finfish and 50% of the shellfish analyzed for Aroclor 1254—the most persistent and toxic mixture of PCBs—contained detectable levels of PCB in their edible flesh. The American eel (Anguilla rostrata), bluefish (Pomatomus saltatrix), striped bass (Morone saxatilis), white catfish (Ictalurus catus), white perch (M. americana), and blue crab (Callinectes sapidus) exhibited high PCB levels in 1981–1982, generally approaching or exceeding the United States Food and Drug Administration action level of 2 ppm fresh weight for these organisms. PCB contamination in finfish and shellfish collected during survey periods of 1986–1987 and 1988–1991 was consistent with the previous years' data showing the northeast region of the state to be the most severely contaminated. Despite decreases in contaminant levels in some species (e.g., striped bass) and regions, results of the most recent survey confirm widespread occurrences of PCBs above background levels in the edible portions of various species from many areas of New Jersey.

Blood Plasma Levels of Sex Steroid Hormones and Vitellogenin in Striped Bass ( Morone saxatilis ) Exposed to 3,3',4,4'-Tetrachlorobiphenyl (TCB)

Exposure to polychlorinated biphenyls (PCB) can impair reproductive processes in fish. Laboratory studies have demonstrated adverse effects in several different fish species. Evidence also exits for an association between exposure to PCBs and related compounds and impaired reproduction in wild fish. Although the mechanism of reproductive toxicity of PCBs is unclear, it appears that PCBs act of several different levels of the hypothalamus-pituitary-gonadal axis (HPG). Because of their structural similarity to 2,3,7,8-tetrachlorodibenzo-p-dioxin (dioxin), planar PCB congengers (e.g. 3,3`,4,4`-tetrachlorobiphenyl (TCB)) are among the most toxic PCBs. Both TCB and dioxon are reproductive toxicants in fish. TCB exposure (via intraperitoneal injections) impaired maturation in adult female white perch (Monroe americana) and reduced egg deposition in killifish (Fundulus heteroclitus). Larval or fry survival was also reduced following either maternal exposure to TCB for white perch or injections of TCB into fertilized eggs of rainbow trout. This study investigate the effects of exposure to TCB on reproductive processes in female striped bass. 12 refs., 2 tabs.

Notes: Temperature Constraints on Overwinter Survival of Age-0 White Perch

Abstract We evaluated the relative importance of energy depletion and osmoregulatory stress as possible mechanisms regulating overwinter mortality of age-0 white perch Morone americana. Fish used less energy, took up more water, and had much higher mortality at 2.5°C than at 4.0°C. Mortality, energy use, and water uptake were all related to body size. Relationships of empirically derived endurance time (ET, days to 50% mortality) to body mass were allometric with weight exponents of 0.29 at 2.5°C and 0.77 at 4.0°C. Theoretically derived weight exponents were 0.82 for ET models based on starvation and 0.18 for models based on osmotic mechanisms. The theoretical and empirical models suggest that overwinter mortality of white perch is caused primarily by starvation at 4.0°C and by osmoregulatory dysfunction as well as starvation at 2.5°C.

Gynogen Production in Hybrid Striped Bass

Abstract.— Meiotic gynogens were produced using hybrid striped bass (♀ white bass, Morone chrysops, ×♂ striped bass, M. saxatilis) eggs and white perch M. americana UV‐irradiated sperm. Diploidy of the fertilized eggs was restored by application of hydrostatic pressure, which induced retention of the second polar body. Use of white perch sperm provided an unmistakable marker for detection of a paternal genetic contribution. Two assays were developed using the polymerase chain reaction (PCR) to amplify specific regions of the Morone genome. Primers for gene amplification were developed based on the DNA sequence of the striped bass growth hormone gene (SB‐GH) or an anonymous striped bass locus (SBI‐10). Control experiments using DNA from the three Morone species demonstrated that gene amplification yielded species‐specific patterns of DNA fragments for both of these loci. Therefore, any progeny with a paternal contribution of a set of white perch chromosomes could be identified. Using these assays, we demonstrated that greater than 75% of the progeny obtained from successful experiments were true gynogens. These striped bass hybrid gynogens will provide the basis for future efforts to calculate gene‐centromere distances and to identify markers linked to specific traits of interest to aquaculture.

Trophic Analysis of Ruffe ( Gymnocephalus cernuus) and White Perch ( Morone americana) in a Lake Superior Coastal Food Web, Using Stable Isotope Techniques

We examined the trophic roles of two nonindigenous species, ruffe ( Gymnocephalus cernuus) and white perch ( Morone americana), in the food web of a western Lake Superior coastal wetland, using stable isotope techniques. The δ 15N signature of ruffe was similar to published values for YOY yellow perch ( Perca flavescens), and intermediate to those of white sucker ( Catostomus commersoni), a ben-thivore, and alewife ( Alosa pseudoharengus), a planktivore. Ruffe of all sizes sampled had an approximately 4%c enrichment in 15N over published values for benthos, and a 3%c 15N enrichment over values for plankton. A 3–4%c difference is consistent with commonly reported shifts in 5 I5N signature between food and prey. These results suggest that ruffe in this food web feed on both benthos and plankton. White perch undergo ontogenetic shifts in nitrogen isotope signatures similar to those reported earlier for yellow perch, and appear to become piscivorous by the time they are 25 cm long. Our data suggest that interactions between ruffe and yellow perch could represent a competitive bottleneck. If yellow perch are able to grow large enough to become piscivorous, they should be able to escape competition with ruffe. In contrast, white perch appear to have the potential to compete with yellow perch throughout their lives.

Involvement of gonadal steroids in final oocyte maturation of white perch (Morone americana) and white bass (M. chrysops): in vivo and in vitro studies

Plasma estradiol-17β (E2), testosterone (T), 17α,20β-dihydroxy-4-pregnen-3-one (DHP) and 17α,20β,21-tri-hydroxy-4-pregnen-3-one (20β-S) levels were measured by radioimmunoassay (RIA) in white perch (Morone americana) and white bass (M. chrysops) that were induced to undergo final oocyte maturation (FOM) with human chorionic gonadotropin (hCG). Plasma DHP levels increased in females of both species in association with oocyte germinal vesicle migration (GVM) and germinal vesicle breakdown (GVBD) and decreased thereafter. Plasma 20β-S levels also increased with oocyte GVM in white bass, but were several-fold lower than DHP levels. Circulating E2 and T levels were greatest during GVM and GVBD in both species and decreased to low levels during oocyte hydration and ovulation. Follicles from white perch and white bass which received a priming injection of hCG in vivo, produced both DHP and 20β-S in vitro after exposure to hCG and their oocytes underwent GVBD. Ovarian incubates from unprimed fish of either species produced only E2 and T and their oocytes did not complete GVBD. Oocytes from unprimed bass, but not perch, matured when follicles were exposed to hCG in vitro. Both trilostane and cycloheximide blocked in vitro production of DHP and 20β-S and oocyte GVBD by white perch follices. DHP and 20β-S were equipotent inducers of FOM in the GVBD bioassay. None of several other structurally-related steroids tested were effective within a physiological range of concentrations. These results indicate a role for DHP and 20β-S in the control of FOM in white perch and white bass.