Choice in the bluegill (Lepomis macrochirus)

To study matching in a species distantly related to mammals and birds, seven bluegill were trained to break a photobeam using a nose-poke response for access to pelleted food in their home aquaria during one-h sessions. Reinforcer ratios available from the two response alternatives varied among the following: 16:1, 8:1, 4:1, 1:1, 1:4, 1:8, and 1:16. The overall reinforcement rate was held at 0.8/min. All experiments were conducted in a closed economy, i.e., the fish's daily food ration was available only during experimental sessions. Matching functions are reported for each fish using all combinations of scheduled and obtained reinforcer ratios as the independent variables and response and time ratios as the dependent variables. All matching functions had slopes less than 1.0 and r² values above 0.70. Overall response rates were unrelated to the reinforcer ratios but, as with other species studied, changeover rates were highest for the 1:1 condition and lowest for the 16:1 conditions. These results are consistent with data obtained from more traditionally studied taxa (e.g., birds, mammals, and primates), and similar previous studies with fish, suggesting that matching has been conserved since fish, birds, and mammals evolved from a common ancestor over 400 million years ago.     

Mycobacteriosis in yellow perch (Perca flavescens) from two lakes in Alberta

Granulomatous skin lesions were identified in a population of yellow perch (Perca flavescens) from Sandy Lake (Alberta, Canada) in 1985. Severe granulomatous peritonitis and hepatitis was identified subsequently in a separate population of yellow perch from Wolf Lake (Alberta, Canada). Mycobacterium chelonae was isolated from affected fish in both epizootics. The source and route of infection were not determined in either case. The nature of the inflammatory reaction in both cases suggested a depressed immunity.     

Reproductive physiology of yellow perch (Perca flavescens): environmental and endocrinological cues

An understanding of the mechanisms involved in the regulation of reproductive processes in yellow perch is fundamental for intensive culture of this commercially important, freshwater, perciform fish. This paper describes the annual reproductive cycle of female and male perch. It presents the current state of knowledge on the regulation of ovarian steroidogenesis, final maturation of oocytes and ovulation in this species. Moreover, data concerning biochemistry of spermatozoa and seminal plasma as well as testicular steroidogenesis are summarized. In addition to endocrinological factors, the involvement of environmental (photoperiod and temperature) cues in the regulation of yellow perch reproduction is reviewed. Finally, practical aspects of controlling perch reproduction are outlined.     

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

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

Evidence of hypoxic foraging forays by yellow perch (Perca flavescens) and potential consequences for prey consumption

1. Previous studies in a variety of ecosystems have shown that ecologically and economically important benthic and bentho‐pelagic fishes avoid hypoxic (<2 mg O₂ L^?1) habitats by moving vertically or horizontally to more oxygenated areas. While avoidance of hypoxic conditions generally leads to a complete shift away from preferred benthic prey, some individual fish continue to consume benthic prey items in spite of bottom hypoxia, suggesting complex habitat utilisation and foraging patterns. For example, Lake Erie yellow perch (Perca flavescens) continue to consume benthic prey, despite being displaced vertically and horizontally by hypolimnetic hypoxia. 2. We hypothesised that hypolimnetic hypoxia can negatively affect yellow perch by altering their distribution and inducing energetically expensive foraging behaviour. To test this hypothesis, we used drifting hydroacoustics and trawl sampling to quantify water column distribution, sub‐daily vertical movement and foraging behaviour of yellow perch within hypoxic and normoxic habitats of Lake Erie’s central basin during August‐September 2007. We also investigated the effects of rapid changes in ambient oxygen conditions on yellow perch consumption potential by exposing yellow perch to various static and fluctuating oxygen conditions in a controlled laboratory experiment. 3. Our results indicate that, while yellow perch in general avoid hypoxic conditions, some individuals undertake foraging forays into hypoxic habitats where they experience greater fluctuations in abiotic conditions (pressure, temperature and oxygen concentration) than at normoxic sites. However, laboratory results suggest short‐term exposure to low oxygen conditions did not negatively impact consumption potential of yellow perch. 4. Detailed understanding of sub‐daily individual behaviours may be crucial for determining interactive individual‐ and ecosystem‐level effects of stressors such as hypoxia.     

Diet overlaps and feeding relationships between the year classes in the yellow perch (Perca flavescens)

Synopsis A comparative study of the diets of five year classes of perch in Lake Opinicon showed Year class 0 to be mainly Cladocera feeders, the Year class 11 to take a diversified range of insect larvae, whereas from Year class V onwards Anisoptera nymphs, decapods, and fish dominated the diet. Sizes of the dominant food items changed strikingly with growth, prey weights of 0.1, 0.5–1.0, and 100–250 mg predominating in these three age groupings. There were marked month to month changes in types and proportions of different prey consumed.Overall and month to month feeding overlaps between consecutive year classes were considerable, most values ranging from 0.68–1.0 by the Levins formula. However, diet overlap dropped sharply with increasing age gap.Month to month dietary changes and year class differences were interpreted relative to benthic invertebrate abundance cycles. Months of increased diet overlap were characteristically those when favored prey types peaked, thereby simultaneously attracting several year classes to them. Hence increased diet. overlap is not necessarily an indicator of increased intraspecific competition.Habitat differences between the year classes of perch in Lake Opinicon were partial and concerned mainly the smaller, and larger, fish relative to those in the middle size range.     

Mitochondrial genome sequence of the bluegill sunfish (Lepomis macrochirus)

The bluegill sunfish (Lepomis macrochirus) belongs to Lepomis genera of the family Centrarchidae, which is an economically important freshwater species in China. This study presents the complete mitochondrial genome of L. macrochirus, which is the first complete sequence from sunfish species. L. macrochirus mitochondrial DNA is 16,489 bp long, with the genome organization and gene order being identical to that of the typical vertebrate.     

Growth- and feeding-related isotopic dilution and enrichment patterns in young-of-the-year yellow perch (Perca flavescens)

1. Isotopic signatures (δ¹⁵N and δ¹³C) from young‐of‐the‐year (YOY) yellow perch (Perca flavescens) were collected over the initial 4 month summer growing period from three separate and distinctive sites in northern Alberta, Canada. Data were analysed to test the hypotheses that there are within‐ and among‐population differences in the patterns of isotopic δ¹⁵N and δ¹³C change over the growing season, and that observed isotopic dilution and/or enrichment patterns were influenced by site‐specific physical and chemical factors. 2. Increases in δ¹⁵N relative to spawned egg masses were observed in immediate posthatch (emergent) YOY and attributed to enrichment associated with the assimilation of yolk during embryonic development. 3. Posthatch dilution of YOY δ¹⁵N signatures associated with ontogenetic dietary shifts from yolk to exogenous feeding and zooplanktivory to benthivory occurred at all sites and was associated at most sites with a concomitant increase in δ¹³C. 4. The rate and pattern of δ¹⁵N dilution and δ¹³C enrichment observed for the study populations varied between and within sites and depended on maternal trophic status and timing of ontogenetic dietary shifts, as determined by prey availability and site‐specific biogeochemical factors. 5. Comparisons of isotopic dilution patterns among species, using results from this study and literature‐derived values, indicated that dilution rates and patterns are species dependent and may vary in relation to key life‐history events. 6. Seasonal and spatial isotopic variability among populations and between species complicates field sampling. In particular, the connectivity to site‐specific conditions found here suggests that for locally resident juvenile fishes, spatial, as well as temporal variability must be included in isotopic sampling programmes designed to characterise littoral zone foodweb relationships.     

The landscape genetics of yellow perch (Perca flavescens) in a large fluvial ecosystem

Landscape genetics is being increasingly applied to elucidate the role of environmental features on the population structure of terrestrial organisms. However, the potential of this framework has been little explored in aquatic ecosystems such as large rivers. Here, we used a landscape genetics approach in order to (i) document the population structure of the yellow perch ( Perca flavescens ) by means of genetic variation at microsatellite markers, (ii) assess to what extent the structure was explained by landscape heterogeneity, and (iii) interpret the relevance of interactions between genetics and landscape for management and conservation. Analysis of the genetic variation among 1715 individuals from 16 localities and distributed over 310 km in the freshwater section of the Saint Lawrence River (Québec, Canada) revealed a relatively modest level of genetic structuring ( F _ST = 0.039). Application of the Monmonier's algorithm combining geographical and genetic information identified three zones of restricted gene flow defining four distinct populations. Physical barriers played a more important role on gene flow and genetic structure than waterway geographical distance. We found correlations between genetic differentiation and presence of distinct water masses in the sector of Lake Saint-Louis ( r =  0.7177, P  = 0.0340) and with fragmentation of spawning habitats in the sector of Lake Saint-Pierre ( r =  0.8578, P  = 0.0095). Our results support the treatment of four distinct biological units, which is in contrast with the current basis for yellow perch management. Finally, this study showed that landscape genetics is a powerful means to identify environmental barriers to gene flow causing genetic discontinuities in apparently highly connected aquatic landscapes.     

Sex control and ploidy manipulations in yellow perch (Perca flavescens) and walleye (Stizostedion vitreum)

In both yellow perch ( Perca flavescens ) and walleye ( Stizostedion vitreum ), females grow significantly faster and reach a larger ultimate size than males. In addition, reproductive development in both of these species can have a significant negative impact on somatic growth and fillet yield. Accordingly, methods for producing monosex female populations and for inducing sterility, have important potential applications for both commercial fish culture and fisheries management. Of the several available methods for producing monosex female populations in fishes (such as yellow perch and walleye) in which females are homogametic, the preferred method (described herein) may be to treat juveniles with androgens to induce phenotypic sex inversion of genetic females, and to subsequently use sperm from these females to fertilize normal eggs. Initial efforts at inducing sterility focused on the direct use of either heat or hydrostatic pressure shocks to produce triploid yellow perch and walleye. The gonadal development of triploid yellow perch and walleye of both sexes is retarded compared to that of diploids, and triploid yellow perch can have higher fillet yields than diploids. The direct use of heat and pressure shocks to induce triploidy in yellow perch, however, has negative effects on growth that are independent of ploidy status. One way to circumvent this problem is to produce triploids by crossing fertile tetraploids with diploids. To date, methods of producing viable tetraploids (beyond the larval stage) have been developed for yellow perch but not for walleye.     

Manganese-54 accumulation by Chlorella spp., Daphnia magna and yellow perch (Perca flavescens)

Concentration factor and biological half-life of ⁵⁴Mn were determined in three species representing an ecologically and economically important food chain. Green algae (Chlorella spp.), Daphnia magna and yellow perch (Perca flavescens) were exposed to ⁵⁴Mn in water and assayed for ⁵⁴Mn uptake. Steady state concentration factors computed from the laboratory data for algae, Daphnia and perch were 4230, 17 000 and 11, respectively. Respective biological half-lives were 1.6, 1.2 and 8.3 days.     

Genetic paternity analysis and breeding success in bluegill sunfish (Lepomis macrochirus)

Fish have some of the most complex mating systems known in the animal kingdom. With the advent of powerful genetic markers and an emerging mathematical framework to calculate parentage, it is now possible to analyze genetic relatedness and gene flow in these systems. An important example is the bluegill sunfish (Lepomis macrochirus) which consists of parental males that provide sole care for the young, cuckolder males that parasitize the parentals, and females that actively choose among males within dense breeding colonies. In this article genetic markers for bluegill are characterized and their utility in parentage studies is demonstrated by calculating the genetic relatedness of parental males to their broods for an entire natural breeding colony. A novel Monte Carlo simulation is developed to calculate the confidence in the relatedness estimates and these data are used to provide an estimate of the mean breeding success of parental and cuckolder males. Finally, the applications of genetic analyses to understanding mating systems, parental care, and life-history evolution in bluegill are discussed.     

Laboratory constraints on feeding behaviours in polymorphic bluegill sunfish (Lepomis macrochirus)

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Calcium-induced quiescence of sperm motility in the bluegill (Lepomis macrochirus)

Before dilution in hypoosmotic media sperm of freshwater fish are maintained quiescent by a range of factors including osmolality, K+ and pH, and the onset of motility is generally associated with an increase in cytoplasmic Ca2+. In contrast, Ca2+ in conjunction with osmolality was found to inhibit motility of intact bluegill sperm. Consistent with seminal plasma composition, 0.16 mmol/L Ca2+ and greater, in conjunction with an osmotic concentration of 290 mOsm/kg, inhibited the onset of bluegill sperm motility; sperm diluted in saline at 290 mOsm/kg without Ca2+ became motile. Cations Mn2+ and Sr2+, in conjunction with osmolality, had an inhibitory effect on initiation of sperm motility similar to that of Ca2+. Sperm motility was inhibited by Ca2+ channel blockers nimodipine and nifedipine, the mitochondrial Ca2+ uniporter inhibitor ruthenium red and the calmodulin inhibitors W-7 and trifluoperazine dihydrochloride. These results provide evidence that elevated cytoplasmic Ca2+ inhibits sperm motility and yet low levels permit or promote motility. This study demonstrates a unique inhibitory action of Ca2+ on the motility of intact fish sperm at physiologically relevant levels.     

Sperm investment and alternative mating tactics in bluegill sunfish (Lepomis macrochirus)

Although alternative mating tactics are found in males of manyspecies, little is known about tactic-specific adaptations tosperm competition and the mechanism by which fertilization successis obtained. We now report on the sperm investment patternsof males that use alternative mating tactics in bluegill sunfish(Lepomis macrochirus). Bluegill males are characterized by threealternative mating tactics: parentals, sneakers, and satellites.Parentals delay maturation and adopt a courting and guardingtactic, whereas sneakers and satellites mature precociouslyand, respectively, use sneaking and female mimicry to stealfertilizations from parentals. We found differences among thetactics in testes weight, sperm longevity, and ejaculate spermdensity and competitiveness. Parentals had the largest testes,but the smallest relative to their body weight. Satellites hadintermediate-sized testes, and sneakers had the smallest testes,but the largest relative to their body weight. Within each tactic,there was a positive relationship between testes weight andbody weight, but the exact relationship differed among the tacticsand could not be attributed solely to allometry. Parentals hadlonger-lived sperm compared with that of both sneakers and satellites.Ejaculate sperm density was greatest in sneakers, satelliteswere intermediate, and parentals had the lowest. Competitionexperiments involving equal volumes of ejaculate showed thatfertilization success increased linearly with sperm number,consistent with a rafflelike process. However, independent ofsperm number, parental sperm were superior at fertilizing eggs.We interpret these sperm investment patterns in relation todifferences in sperm competition risk, number of mating opportunities,and alternative investment options.     

The historical ecology of yellow perch (Perca flavescens[Mitchill]) and their parasites

Aim To determine the origins of the host–parasite association between among yellow perch (Perca flavescens[Mitchill]) and the parasites Crepidostomum cooperi Hopkins, Proteocephalus pearsei La Rue and Urocleidus adspectus Beverly Burton. Of secondary interest are the parasites Bunodera luciopercae (Muller) and Proteocephalus percae (Muller) predictably associated with the Eurasian perch. Location The areas considered are the Holarctic, since the upper‐Cretaceous, and contemporary North America. Methods Published and new information from host and parasite phylogenies, palaeontology, palaeogeography and plate tectonics and host biology is incorporated to assess the origins of yellow perch and several of its parasites. This information is used to determine the origins for these host–parasite associations. Results Cladistic analysis suggests a Laurasian origin for Percidae and Perca, and that Perca is sister to the other genera in the family. Parasite phylogenies support a North American origin for the three species associated with yellow perch and a Laurasian origin for B. luciopercae. Proteocephalus pearsei and P. percae are not sister taxa. The fossil record for Perca dates to the Miocene in Europe and the Pleistocene in North America. North America and Europe were connected across the North Atlantic since at least the upper Cretaceous with separation complete by the Miocene. Europe was separated from Asia by the Obik Sea from the late Cretaceous until the Oligocene. Western cordillera orogeny and its accompanying high rates of water flow and Pleistocene glaciation represent barriers to Perca dispersal. Main conclusions The origin of Perca in North America dates at least to the late Oligocene when North America and Europe were connected across the North Atlantic and Europe and Asia were separate landmasses, and does not result from Pleistocene dispersal across Beringia from Asia. The present disjunction of Perca species in North America and Europe is due to the vicariant separation of North America and Europe. Based on the available information, yellow perch and its parasites have a North America origin. The association between yellow perch and the parasites in all cases is a consequence of host switching from other sympatric host species in North America and is not explained by co‐speciation. Even the association between the host‐specific Urocleidus adspectus and yellow perch originated with a host switch and is not due to co‐speciation. The basis for this host switching is geographical and ecological sympatry, especially shared feeding habits, with other North American fish hosts.     

Pharmacology of the retractor lentis muscle of the bluegill (Lepomis macrochirus)

We studied accommodative nerve-muscle transmission in a teleost fish, the bluegill (Lepomis macrochirus). The muscle contracted with electrical stimulation to move the spherical lens along the pupil plane in the eye ball so that the distance between the lens and retina changes. The dose-dependent effect on the lens muscle of acethylcholine and its related substances (nicotine, muscarine, curare and atropine), glutamate, gamma-aminobutyric acid, serotonin, glycine, dopamine and noradrenaline was observed with a binocular microscope. Its video image was processed by a computer to measure the shortening of the muscle. Among the transmitter candidates applied only acethylcholine caused a contraction and elicited the lens movement. Muscarine caused strong contraction of the muscle even in a low concentration (1 nM) while nicotine did not. The contraction was antagonized by atropine but not curare. Previous studies based on intraperitoneally injected reagents suggested a cholinergic innervation on the lens muscle. Our pharmacologic results verified by direct anatomical measurements on the isolated lens-muscle-nerve preparation unambiguously establish the dose-dependent muscarinic-cholinergic innervation to the lens muscle by parasympathetic postganglionic fibers.Abbreviations Ach Acetylcholine - GABA gamma-aminobutyric acid - TTX tetrodotoxin - RML Resting muscle length     

Epitheliocystis,a new infectious disease of the bluegill (Lepomis macrochirus)

A new infectious, benign and chronic disease, histopathologically distinct from the viral disease lymphocystis, has been found in the bluegill. The symptoms are much enlarged cells in skin and gill epithelium, filled with basophilic granules. By electron microscopy these granules were shown to be organisms with the morphological characteristics ofBedsonia (Miyagawanella). During an attempt to isolate the agent in the bluegill fibroblast cell line BF-2, a cytopathic effect somewhat resembling the lesionsin vivo was found in the first passage. In later passages the agent was lost, but a true virus eliciting a distinctive fusiform cytopathic effect was recovered from these passages. The virus was found to be cytopathogenic also for the rainbow trout cell line RTG-2, but no recognizable disease could be evoked in young bluegills by inoculation of infected cell culture material. While the larger sized, non-viral organism is almost certainly the etiological agent of epitheliocystis, the role of the virus is, therefore, conjectural. Electron microscopy of thin sections has shown the virus to resemble influenza virus in morphology.