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The bluegill sunfish, Lepomis macrochirus, is a widespread exotic species in Japan that is considered to have originated from 15 fish introduced from Guttenberg, Iowa, in 1960. Here, the genetic and phenotypic traits of Japanese populations were examined, together with 11 native populations of the USA using 10 microsatellite markers and six meristic traits. Phylogenetic analysis reconfirmed a single origin of Japanese populations, among which populations established in the 1960s were genetically close to Guttenberg population, keeping high genetic diversity comparable to the ancestral population. In contrast, genetic diversity of later-established populations significantly declined with genetic divergence from the ancestral population. Among the 1960s established populations, that from Lake Biwa showed a significant isolation-by-distance pattern with surrounding populations in which genetic bottlenecks increased with geographical distance from Lake Biwa. Although phenotypic divergence among populations was recognized in both neutral and adaptive traits, P- F comparisons showed that it is independent of neutral genetic divergence. Divergent selection was suggested in some populations from reservoirs with unstable habitats, while stabilizing selection was dominant. Accordingly, many Japanese populations of L. macrochirus appear to have derived from Lake Biwa population, expanding their distribution with population bottlenecks. Despite low propagule pressure, the invasion success of L. macrochirus is probably because of its drastic population growth in Lake Biwa shortly after its introduction, together with artificial transplantations. It not only enabled the avoidance of a loss in genetic diversity but also formed a major gene pool that supported local adaptation with high phenotypic plasticity. [ABSTRACT FROM AUTHOR]

A biorobotic pectoral fin was developed and used to study how the flexural rigidities of fin rays within a highly deformable fish fin affect the fin's propulsive forces. The design of the biorobotic fin was based on a detailed analysis of the pectoral fin of the bluegill sunfish (Lepomis macrochirus). The biorobotic fin was made to execute the kinematics used by the biological fin during steady swimming, and to have structural properties that modeled those of the biological fin. This resulted in an engineered fin that had a similar interaction with the water as the biological fin and that created close approximations of the three-dimensional motions, flows, and forces produced by the sunfish during low speed, steady swimming. Experimental trials were conducted during which biorobotic fins of seven different stiffness configurations were flapped at frequencies from 0.5 to 2.0 Hz in flows with velocities that ranged from 0 to 270 mm s1. During these trials, thrust and lift forces were measured, kinematics were recorded in three dimensions, and digital particle image velocimetry was used to evaluate flow hydrodynamics. The results of the trials revealed that slight changes to the fin's mechanical properties or to the operating conditions can have significant impact on the direction, magnitude and time course of the propulsive forces. In general, the magnitude of the 2-D (thrust and lift) propulsive force scaled with fin ray stiffness, and increased as the fin's flapping speed increased or as the velocity of the flow decreased. [ABSTRACT FROM AUTHOR]

Attention to non-coplanar polychlorinated biphenyl (PCB) congeners in immunotoxicological research is increasing. However, the exact mechanism by which these congeners may induce immune dysfunction is still undefined. Because the serotonergic nervous system has been shown to be involved in the regulation of some immune responses, and also serves as a sensitive target for PCBs, the relationship (if any) between non-coplanar PCB exposure, immune responsiveness and the neurotransmitter serotonin (5-HT) was examined. Using bluegill sunfish ( Lepomis macrochirus) as a model, changes in brain 5-HT levels, 5-HT synthesis and metabolism, and innate and cell-mediated immune parameters were evaluated following a single intraperitoneal injection of PCB 153 (5.0 or 50 μg/g body weight). Results revealed that 3 d following administration, PCB exposure decreased brain 5-HT levels (in the absence of effects on some enzymes involved in 5-HT synthesis and metabolism), increased oxyradical production by kidney phagocytes, and reduced splenic T- and B-lymphocyte proliferation. In vivo treatment of PCB-exposed fish with 5-hydroxy-L-tryptophan (the immediate precursor to 5-HT) ameliorated the observed PCB-induced immunotoxicity; in vitro treatment of immune cells from PCB-exposed fish with 5-HT failed to reverse the effects. Taken together, results from this study could suggest a link between PCB-induced alterations of brain 5-HT levels and subsequent immune dysfunction. These studies highlight the importance of indirect mechanisms of immunotoxicity, and, specifically, suggest a role for the neuroimmune axis in non-coplanar PCB-induced immune alterations. [ABSTRACT FROM AUTHOR]

Abstract: Elevated concentrations of acidity and metals in acid mine drainage (AMD) may be effectively addressed by active and passive treatment technologies. However, typical evaluations consider only chemical water quality with little if any regard for biological metrics. Robust evaluations including both chemical and biological indicators of water quality improvement are needed. In this study, injection of alkaline fluidized bed ash (FBA) into a flooded underground coal mine was coupled with a five-cell passive treatment system to ameliorate an abandoned AMD discharge in eastern Oklahoma. The passive system included process units promoting both aerobic and anaerobic treatment mechanisms. Resulting water quality changes and biological responses were evaluated. Organisms of two distinct functional groups (the filter-feeding mollusk Corbicula fluminea and the wide-spectrum feeding fish Lepomis macrochirus) were exposed to mine waters in several treatment cells. The combination of treatment technologies was hypothesized to limit potential negative effects on these aquatic organisms. Tissues were harvested and analyzed for concentrations of several metals (Al, Fe, Mn, Mg, Ca, Ni, Cu and Zn) of interest. Organismal responses, such as hepatosomatic index, condition factor, and condition index, did not vary significantly among organisms exposed within different treatment cells when compared to non-AMD impaired waters. Metal tissue accumulation trends, compared to aqueous concentrations, were observed for Fe, Ni and Zn. Exposure experiments with these two organisms indicated that FBA introductions coupled with passive treatment decreased the potential adverse effects of AMD to biological systems. [Copyright &y& Elsevier]

A 4 year mark–recapture study examined the pattern of nesting site fidelity of parental-type male bluegill Lepomis macrochirus. The study results indicated that iteroparous male L. macrochirus choose new nest sites near their own previously used sites. The scale of site fidelity varied, but generally males choose to renest within shoreline areas rather than specific or exact nest locations (94% within-year, 86% among-years). Iteroparous males also displayed no preference to nest in proximity to neighbouring males from previous colonies to suggest social fidelity. Contrary to expectation, manipulating males' reproductive success had no significant effect on the pattern or scale of male reproductive site fidelity. [ABSTRACT FROM AUTHOR]

Metacommunity theory suggests that relationships between diversity and ecosystem stability can be determined by the rate of species dispersal among local communities. The predicted relationships, however, may depend upon the relative strength of local environmental processes and disturbance. Here we evaluate the role of dispersal frequency and local predation perturbations in affecting patterns of diversity and stability in pond plankton metacommunities. Pond metacommunities were composed of three mesocosm communities: one of the three communities maintained constant "press" predation from a selective predator, bluegill sunfish (Lepomis macrochirus); the second community maintained "press" conditions without predation; and the third community experienced recurrent "pulsed" predation from bluegill sunfish. The triads of pond communities were connected at either no, low (0.7%/d), or high (20%/d) planktonic dispersal. Richness and composition of zooplankton and stability of plankton biomass and ecosystem productivity were measured at local and regional spatial scales: Dispersal significantly affected diversity such that local and regional biotas at the low dispersal rate maintained the greatest number of species. The unimodal local dispersal-diversity relationship was predator-dependent, however, as selective press predation excluded species regardless of dispersal. Further, there was no effect of dispersal on beta diversity because predation generated local conditions that selected for distinct community assemblages. Spatial and temporal ecosystem stability responded to dispersal frequency but not predation. Low dispersal destabilized the spatial stability of producer biomass but stabilized temporal ecosystem productivity. The results indicate that selective predation can prevent species augmentation from mass effects but has no apparent influence on stability. Dispersal rates, in contrast, can have significant effects on both species diversity and ecosystem stability at multiple spatial scales in metacommunities. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAH) have been demonstrated to affect immune system modulation. The freshwater species of fish, Lepomis macrochirus (bluegill), was employed to investigate the effects of a 14-day dietary exposure to PAH including 2-aminoanthracene (2-AA), 2-methylnaphthalene (2-MN), and 9,10-dimethylanthracene (9,10-DMA) and a mixture of these 3 compounds at a total dose of 3.1 ± 0.01 mg on lymphocyte proliferation stimulated with 3 mitogens (concanavalin A [Con A], phorbol ester, and calcium ionophore). 2-Aminoanthracene was mitogenic itself and with added mitogens. 2-Methylnaphthalene induced some stimulatory and some inhibitory effects upon cell proliferation by Con A. 9,10-DMA and the mixture each suppressed cell proliferation. The mixture was highly suppressive to lymphocytes. Intracellular baseline calcium levels were reduced, possibly as a step prior to cell death. All PAH compounds tested were immunomodulatory to bluegill lymphocytes. Bluegill were demonstrated to have utility as a biomarker species for investigation of immunotoxicity. [ABSTRACT FROM PUBLISHER]

This article discusses a study which examined whether bluegill growth varies within Lake Biwa, Japan. The study used fish samples from 21 different sites within the lake and determined length-weight relationships for each site. It also calculated body weights of the samples. The study revealed several biotic factors that are responsible for the difference between the northern and southern basins in terms of the body weight, including the population density of bluegill and the number of submerged plants.

Genetic linkage maps were constructed for bluegill sunfish, Lepomis macrochirus, using AFLP in a F1 inter-population hybrid family based on a double-pseudo testcross strategy. Sixty-four primer combinations produced 4,010 loci, of which 222 maternal loci and 216 paternal loci segregated at a 1:1 Mendelian ratio, respectively. The female and male framework maps consisted of 176 and 177 markers ordered into 31 and 33 genetic linkage groups, spanning 1628.2 and 1525.3 cM, with an average marker spacing of 10.71 and 10.59 cM, respectively. Genome coverage was estimated to be 69.5 and 69.3% for the female and male framework maps, respectively. On the maternal genetic linkage map, the maximum length and marker number of the linkage groups were 122.9 cM and 14, respectively. For the paternal map, the maximum length and marker number of the linkage groups were 345.3 cM and 19, respectively, which were much greater than those on the maternal genetic linkage map. The other genetic linkage map parameters of the paternal genetic linkage map were similar to those in the maternal genetic linkage map. For both the female and male maps, the number of linkage groups was greater than the haploid chromosome number of bluegill (2 n = 48), indicating some linkage groups may distribute on the same chromosome. This genetic linkage mapping is the first step toward to the QTL mapping of traits important to cultured breeding in bluegill. [ABSTRACT FROM AUTHOR]

In the present study, the efficacy of Letrozole, a potent nonsteroidal aromatase inhibitor (AI), on gonadal sex differentiation and sex reversal was examined in bluegill sunfish ( Lepomis macrochirus). In Experiment 1, using AI diet treatments (50, 150, 250 and 500 mg kg−1) from 30 to 90 days posthatch (dph), AI interrupted ovarian cavity formation at a dose of 500 mg kg1 diet and one intersex fish was identified in this group. The proportions of males in all the treated groups were significantly higher than those in the control group. In Experiment 2, using AI immersion treatments (250, 500 and 1000 μg L−1) during 30–50 dph, the treated groups of 500 and 1000 μg L−1 produced significantly more males than the control and 250 μg L−1 groups. Histological examination revealed no differences in ovary or testis tissue between control and AI-treated fish. There were no significant differences detected in body weight and length among the AI treated and control groups ( P>0.05) for both experiments. The results from these two experiments suggest that inhibition of aromatase activity by AI could influence sex differentiation in bluegill sunfish. [ABSTRACT FROM AUTHOR]

Both social and demographic factors can affect size structure of bluegill (Lepomis macrochirus) populations, but these two factors have not been assessed in South Dakota impoundments. We compared length and age at maturity of bluegill in four southeastern South Dakota impoundments (two with historically low size structure and two with historically high size structure and related bluegill growth patterns to size structure and relative abundance. Despite large differences in size structure and maximum observed total lengths among lakes, all males from three of four populations were mature by age 3, with the only exception being Lake Mitchell (high size structure population; 89% mature). Mean total length at 100% maturity was lower in the two low size structure populations, and bluegill in the two low size structure populations matured at a smaller length than in the two high size structure populations; however, at least 50% of males in all four systems reached sexual maturity by 140 mm in all years. Negative relationships between mean catch-per-unit-effort and both proportional size distribution (r2 =0.47) and proportional size distribution of preferred length fish (r2=0.86) values for all populations indicated that density-dependence was likely in these systems. Indications of social influence on bluegill behavior were observed; however, density-dependence was likely more influential on size structure. [ABSTRACT FROM AUTHOR]

The channel catfish Ictalurus punctatus is a popular sport fish commonly maintained by annual stocking in small impoundments. We sought to determine whether channel catfish negatively affect two other sport fishes (bluegill Lepomis macrochirus and largemouth bass Micropterus salmoides) in Alabama's state public fishing lakes (ASPF lakes) through competition or predation. Using a variety of gears, we sampled channel catfish, largemouth bass, and bluegills in 12 ASPF lakes with variable channel catfish stocking and harvest rates. Four of these lakes were sampled more intensively to quantify the diets of these three species. Bioenergetics simulations were used to predict the annual consumption of channel catfish and largemouth bass populations of average density, size structure, and growth from these impoundments. Metrics of growth, condition, abundance, and population structure were not related between species. Latitude was negatively related to channel catfish growth. The diets of channel catfish and bluegills were moderately similar across all seasons in all lakes, while those of channel catfish and largemouth bass were highly dissimilar. Within species, diet similarity was high among lakes. Bioenergetics simulations suggest that the channel catfish populations in these lakes consume relatively little fish, particularly when compared with a typical largemouth bass population. We found little evidence of negative effects of channel catfish on the bluegill and largemouth bass populations in ASPF lakes, although largemouth bass growth and condition were poorest in the lake with the highest channel catfish stocking rate. However, current stocking and exploitation rates in most lakes appear to maintain channel catfish abundance below the level at which negative effects may occur. [ABSTRACT FROM AUTHOR]

Maintenance feeding (MF) followed by higher submaximum feeding was evaluated to reduce waste feed, fecal solids, and feed conversion ratios (FCRs) in aquaculture. Individually housed juvenile hybrid bluegills constituted a control and two treatments. Controls were fed daily at maximum consumption indicated by a lead control group. In feeding cycle 1 (FC1), treatments (T1 and T2) received 14 d of MF followed by higher submaximum feeding for 28 d at 75% (SM75) and 100% (SM100) of control ration. FC2 followed with 7 d of MF in T1 and T2, followed by 28 d of SM75 and SM100, respectively. Over the 77-d experiment, controls wasted 38.34% of feed provided; SM100 (10.64%) and SM75 (3.84%) wasted significantly less. Mean FCRs were controls (1.60), SM100 (0.98), SM75 (0.80); treatments were significantly below controls. Mean feces produced per feed consumed (%) were controls (5.54), SM100 (4.00), and SM75 (3.81). Treatments were significantly below controls by approximately 30%. Control and treatment SGRs did not differ; full catch-up growth occurred in treatments. Feeding hybrid bluegills on cycles of MF followed by higher submaximum feeding reduced waste feed and feces while improving FCRs. Maintenance/submaximum feeding may be applicable in aquaculture for reducing feed costs and improving effluent quality without reducing growth. [ABSTRACT FROM AUTHOR]

In aquatic environments, visual communication is expected in animals that inhabit clear, shallow waters. Here, we investigate variation in the colorful traits of bluegills, Lepomis macrochirus, to elucidate their possible function. Bluegills use alternative mating tactics whereby males develop into one of two irreversible phenotypes termed parental and cuckolder. Parentals build and defend nests and care for offspring whereas cuckolders obtain matings by sneaking copulations. We hypothesized that bluegill coloration might function as a sexual ornament in parental males and that ornamental coloration might serve as an honest indicator of male quality. We predicted that coloration should be more pronounced in parental males than in females and immature males and should be more pronounced during the breeding season. We also predicted that males in better condition should be more intensely colored than fish in poor condition. To test our predictions, we sampled 510 bluegills during the breeding and post-breeding seasons at nine lakes in southern Ontario, Canada, in 2007. We used reflectance spectrometry to quantify the coloration of five body regions, aged and sexed each fish, and calculated Fulton’s condition factor from morphological measurements. A separate experiment showed that color did not fade several minutes post capture, suggesting that coloration could be measured reliably and consistently. We found that color was influenced by maturity, sex, and season, in the predicted direction, for three body regions (breast, cheek, and opercular flap). We also found that color varied with the condition of males such that males in better condition were darker for the sexually dichromatic ventral and facial regions. Our findings therefore suggest that some colorful traits in bluegills may serve as condition-dependent sexual signals during the breeding season. Our research contributes to a growing appreciation of the importance of visual signaling in aquatic environments. [ABSTRACT FROM AUTHOR]

Female choice for male ornamental colouration has been demonstrated in a number of different taxa. Among fishes, most studies have been conducted in a laboratory setting and show that females prefer more colourful male ornaments. In this study, we observed female bluegills (Lepomis macrochirus) spawning in their natural environment and compared spawning behaviours to male traits and position within a colony. We observed spawning activities of 76 parental males in Lake Opinicon, Ontario. We captured each male and used reflectance spectrometry to objectively quantify the colour of six body regions and measured morphological characteristics. Our results show that female spawning behaviours did not significantly differ between central and peripheral males, although egg scores were higher in central nests. During spawning, females appeared to enter the nests of parental males haphazardly. However, our results suggest that male cheek colouration influenced the number of females spawning, the number of eggs they released, and the amount of time they spent in the nest. Moreover, male breast colouration significantly predicted reproductive success as quantified through egg scores. Together, our findings suggest that females may use male cheek and breast colouration, condition-dependent sexual ornaments, as key traits on which to base their mate choice decisions. [ABSTRACT FROM AUTHOR]

The project to exterminate nonindigenous fish was initiated in Lake Biwa in April 2002 because nonindigenous fish, especially large-mouth bass ( Micropterus salmoides) and bluegill ( Lepomis macrochirus), had adversely affected the diversity of indigenous fish. This project allowed fishers to catch nonindigenous fish whenever, wherever, and however they wished and to sell their entire daily landing to the Shiga Prefectural Government (SPG) on a fixed-price basis. That is, the SPG regarded nonindigenous fish as an "open-access resource." This project defined success as the extermination of nonindigenous fish. This study focused on how the fishers behaved after the project began and attempted to identify the factors influencing their behavior. I observed that the ranks of fishers increased because of the policies pertaining to nonindigenous fish. At one level, this result supports the model of "the tragedy of open-access resources." However, this study also found that the behavior of fishers did not always result in "tragedy." In Okishima, fishers' behavior is strongly influenced by merchants. More specifically, fishers must abide by their contracts with merchants, and these effectively prevent them from catching nonindigenous fish even when these appear to bring greater profits. This local mechanism served to limit excessive levels of fishing and impeded "the tragedy of open-access resources." Consequently, the results of this project did not meet the expectations of the SPG. [ABSTRACT FROM AUTHOR]

The article offers information on the heterogenous ecological effects of lakeshore zoning in Vilas County, Wisconsin. It cites an economic model used to estimate lot subdivisions and the number of new lots that will be created as a function of zoning. It says that zoning significantly affects residential density, coarse woody debris (CWD) counts and bluegill growth rates. In addition, zoning with higher minimum shoreline frontage has a larger ecological effects to lakes that are less developed.

This study examined mercury concentrations in whole fish from Camp Far West Reservoir, an 830-ha reservoir in northern California, USA, located downstream from lands mined for gold during and following the Gold Rush of 1848–1864. Total mercury (reported as dry weight concentrations) was highest in spotted bass (mean, 0.93 μg/g; range, 0.16–4.41 μg/g) and lower in bluegill (mean, 0.45 μg/g; range, 0.22–1.96 μg/g) and threadfin shad (0.44 μg/g; range, 0.21–1.34 μg/g). Spatial patterns for mercury in fish indicated high concentrations upstream in the Bear River arm and generally lower concentrations elsewhere, including downstream near the dam. These findings coincided with patterns exhibited by methylmercury in water and sediment, and suggested that mercury-laden inflows from the Bear River were largely responsible for contaminating the reservoir ecosystem. Maximum concentrations of mercury in all three fish species, but especially bass, were high enough to warrant concern about toxic effects in fish and consumers of fish. [ABSTRACT FROM AUTHOR]

A bio-robotic fin has been developed that models the pectoral fin of the bluegill sunfish as the fish turned to avoid an obstacle. This work involved biological studies of the sunfish fin, the development of kinematic models of the motions of the fin's rays, CFD based predictions of the 3D forces and flows created by the fin, and the implementation of simplified models of the fin's kinematics and mechanical properties in a physical model. The resulting robotic fin produced the forces and flows that drove the manoeuvre and had a sufficiently high number of degrees of freedom to create a variety of non-biologically derived motions. The results indicate that for robotic fins to produce a level of performance on par with biological fins, both the kinematics and the mechanical properties of the biological fin must be modelled well. [ABSTRACT FROM AUTHOR]

Collingsworth, PD and Kohler, CC. 2010. Abundance and habitat use of juvenile sunfish among different macrophyte stands. Lake Reserv. Manage. 26:35-42. Juvenile Lepomis sunfish (< 75 mm total length, TL) density, plant stem density and invertebrate density were compared in the 3 most common habitats in the littoral zone of Cedar Lake, a Midwestern North American reservoir: nonvegetated areas, stands of the exotic macrophyte Eurasian watermilfoil (Myriophyllum spicatum) and stands of American pondweed (Potomogeton nodosus). Eurasian watermilfoil stands consistently had significantly higher stem density and invertebrate density than American pondweed stands. Juvenile sunfish densities were significantly higher in vegetated habitats than nonvegetated areas, but no significant differences were observed between the 2 vegetated habitats. Juvenile sunfish densities were initially higher in American pondweed stands than Eurasian watermilfoil stands, but fish density in American pondweed stands declined dramatically as water levels fell in autumn. Juvenile sunfish size structure was related to habitat type, with the smallest fish associated with Eurasian watermilfoil (38.2 mm TL), intermediate fish associated with American pondweed (43.1 mm TL), and the largest fish associated with nonvegetated habitats (51.2 mm TL). We suggest resource agencies should focus vegetation management efforts on eradicating Eurasian watermilfoil stands to provide foraging access for largemouth bass to improve their growth rate and reduce stunting of sunfish. However, management agencies must recognize that a healthy plant community below the depth of water level fluctuation may be the only source of cover for juvenile centrarchids during late summer in reservoirs prone to fluctuating water levels. [ABSTRACT FROM PUBLISHER]

Initial relative mass ( WR, low v. high) and energetic trajectory in time (starved v. fed) were experimentally manipulated in bluegill Lepomis macrochirus. Fed fish starting at low WR grew more and gained more WR than fed fish starting at high WR. Similarly, starved fish starting at high WR lost more mass and WR than did starved fish starting at low WR. Temporal changes in other variables did not consistently match that of WR, but, by the end of the experiment, proximate composition showed a high correlation to WR. Regression slopes of WR on proximate composition increased with time in the laboratory. Differences between wild and laboratory fish appeared to result from relaxation of environmental stress. When excess resources are available such that L. macrochirus grow, condition indices will increase, but individual response will depend on initial values and thus past environmental experience. [ABSTRACT FROM AUTHOR]

The potential influence of social familiarity in shoal-choice decisions was investigated in two sympatric species of north temperate fishes, juvenile banded killifish Fundulus diaphanus and juvenile bluegill sunfish Lepomis macrochirus. Groups of socially familiar and unfamiliar conspecifics were formed in the laboratory using wild-caught fishes. Juvenile F. diaphanus demonstrated a strong preference for familiar conspecific shoalmates, whereas juvenile L. macrochirus exhibited no preference for either unfamiliar or familiar conspecific shoalmates. The differential influence of familiarity on shoalmate choice in juveniles of these two species could be due to their different ecologies, local population densities and life histories. [ABSTRACT FROM AUTHOR]

The amplified fragment-length polymorphism (AFLP) technique was used to identify sex-specific markers in bluegill sunfish. A total of 12 835 loci were produced by 256 primer combinations, of which nine (0·73‰) exhibited presumed sex-associated amplifications in the pooled samples; however, none of which revealed sex specificity upon individual evaluation. [ABSTRACT FROM AUTHOR]

Top predators can have different foraging modes that may alter their interactions and effects on food webs. Interactions between predators may be non-additive resulting from facilitation or interference, whereas their combined effects on a shared prey may result in emergent effects that are risk enhanced or risk reduced. To test the importance of multiple predators with different foraging modes, we examined the interaction between a cruising predator (largemouth bass, Micropterus salmoides) and an ambush predator (muskellunge, Esox masquinongy) foraging on a shared prey (bluegill sunfish, Lepomis macrochirus) with strong anti-predator defense behaviors. Additive and substitution designs were used to compare individual to combined predator treatments in experimental ponds. The multiple predator interaction facilitated growth of the cruising predator in the combined predator treatments, whereas predator species had substitutable effects on the growth of the ambush predator. The combined predator treatments created an emergent effect on the prey; however, the direction was dependent on the experimental design. The additive design found a risk-reducing effect, whereas the substitution design found a risk-enhancing effect for prey fish. Indirect effects from the predators weakly extended to lower trophic levels (i.e., zooplankton community). Our results highlight the need to consider differences in foraging mode of top predators, interactions between predators, and emergent effects on prey to understand food webs. [ABSTRACT FROM AUTHOR]

Intermittent locomotion, characterized by moves interspersed with pauses, is a common pattern of locomotion in animals, but its ecological and evolutionary significance relative to continuous locomotion remains poorly understood. Although many studies have examined individual differences in both intermittent locomotion and boldness separately, to our knowledge, no study to date has investigated the relationship between these 2 traits. Characterizing and understanding this relationship is important, as both locomotion and boldness are associated with several ecologically relevant behaviors such as foraging, mating, predator evasion, exploration, and dispersal. Here, we report on individual differences in boldness (risk-taking behavior) and intermittent locomotion in a novel laboratory environment in field-caught juvenile bluegill sunfish (Lepomis macrochirus). Our results show that juvenile bluegill sunfish exhibited individual-level variation in 2 modes of intermittent locomotion (undulatory and labriform swimming) and that this variation was correlated with differences in their boldness behavior. Generally, bolder individuals spent more time moving fast for longer durations and with shorter pauses than more timid individuals. Neither boldness nor locomotion was correlated with body size or body condition. This study provides the first empirical evidence for a link between an animal “personality” trait and intermittent locomotion. [ABSTRACT FROM PUBLISHER]

Water quality in the Reedy River basin of Greenville, South Carolina, has been impacted by diverse and highly urbanized land uses. It has been demonstrated that urban runoff and point sources, such as effluent from wastewater treatment facilities, introduce organic pollutants and potentially endocrine disrupting compounds (EDCs) into the watershed. The objective of this study was to investigate the potential toxicological effects of EDCs that may be present in the Reedy River watershed using a set of biomarkers measured in indigenous fish to characterize the exposure and biological effects of these contaminants. Bluegill ( Lepomis macrochirus) were collected during three different sampling seasons (spring, summer, and fall) from several sites along the length of the Reedy River and from an unimpacted site at Lake Robinson. Fish were analyzed for xenoestrogenic exposure (estrogenic effect of bile extracts) and effects (vitellogenin production in juvenile fish), which were compared to the hepatosomatic index as a general health parameter. Samples downstream of Greenville, especially downstream of the wastewater treatment facilities, were found to have significantly higher levels of estrogenic activity in bile extracts, which correlated well with elevated plasma vitellogenin concentrations relative to the specimens collected in reference sites. The results provide evidence that bluegill in the Reedy River were exposed to elevated concentrations of xenoestrogenic compounds and that these xenoestrogens were bioavailable, resulting in biological effects. [ABSTRACT FROM AUTHOR]

The effect of digestion by a predatory fish (largemouth bass Micropterus salmoides) on stable isotopic (δ13C and δ18O) and trace elemental (Sr:Ca and Ba:Ca) compositions of prey fish (bluegill Lepomis macrochirus) otoliths was investigated in a laboratory experiment. Trace element and stable-isotopic signatures of L. macrochirus otoliths were not significantly altered for up to 16 h after L. macrochirus were consumed by M. salmoides. Prey fish otoliths recovered from predator digesta can retain environmental stable isotopic and trace elemental signatures, suggesting that determination of environmental history for prey fishes by stable-isotope and trace-element analysis of otoliths recovered from stomachs of piscivorous fishes will be feasible. [ABSTRACT FROM AUTHOR]

This study investigated polychlorinated biphenyl (PCB) bioaccumulation patterns across age classes of bluegill (Lepomis macrochirus) and cisco (Coregonus artedi) collected from Sharbot Lake, Ontario. For bluegill, lipid normalized concentrations of PCB congeners of log Kow < 6.8 did not demonstrate any significant increases across individuals 2–5 years of age. In similarly aged cisco, however, significant age-related increases in lipid normalized PCB concentrations were observed for the majority of these congeners. For PCBs of log Kow > 6.8, these congeners demonstrated significant and similar age-related fugacity increases in both species. These patterns indicated that the bioaccumulation of less hydrophobic PCB congeners in bluegill suggest quicker growth kinetics and demonstrate the potential of this species to achieve steady state within their lifetime. In contrast, PCB bioaccumulation patterns in cisco demonstrated that biomagnification and non-steady state kinetics better reflect the capacity of this species to bioaccumulate PCBs. These results demonstrated that for pollutants of log Kow < 6.8, growth dilution and age-specific metabolic rates are critical for understanding their bioaccumulation by freshwater fish. However, for increasingly hydrophobic pollutants, their bioaccumulation reflects the biology and ecology of these species in their respective warm- and cold-water habitats. [ABSTRACT FROM AUTHOR]

We investigated the relationship between stomach capacity and total body length in bluegill (Lepomis macrochirus), spotted bass (Micropterus punctulatus), white crappie (Pomoxis annularis), black crappie (Pomoxis nigromaculatus), channel catfish (Ictalurus punctatus), and white bass (Morone chrysops). The rate of change in stomach capacity for a given change in fish length was greatest for spotted bass and channel catfish, which may indicate greater ontogenetic shifts in feeding strategies. Fish with larger stomach capacities should have more plastic diets because they are capable of consuming a wider range of prey sizes, particularly when they already have prey present in their stomach, compared to fish with smaller stomach capacities and similar feeding strategies. [ABSTRACT FROM AUTHOR]

It has been hypothesized that the production of diapausing eggs in Daphnia can be induced by fish kairomones. A population of Daphnia could survive severe predation using this predator avoidance strategy. However, in changing environments, diapausing eggs experience various temperature conditions, and hatchlings at emergence may be exposed to the same predation risks as their mothers. Therefore, staying in diapause or an immediate response upon hatching to available environmental information could be important for hatchling survival. For this study, we investigated the impact of water temperature (10, 15, 20, and 25°C) in the presence and absence of fish kairomones ( Lepomis macrochirus) on the hatching success of resting eggs ( D. galeata). Results show that no diapausing eggs hatched at the lowest temperature (10°C), and the highest hatch percentage occurred at 15°C. Although higher water temperatures reduced hatching success, diapausing eggs hatched more quickly. The number of hatchlings was significantly higher after exposure to fish kairomones, and this was more noticeable at higher temperatures (20 and 25°C). The present results suggest that the diapausing eggs were produced as a predator avoidance strategy in Daphnia; however, the presence of fish works as a positive signal to increase hatchlings when the diapausing stage is terminated. [ABSTRACT FROM AUTHOR]

Abstract: A rigorous solid phase extraction/liquid chromatography/tandem mass spectrometry method for the measurement of 10 perfluorinated compounds (PFCs) in fish fillets is described and applied to fillets of bluegill sunfish (Lepomis macrochirus) collected from selected areas of Minnesota and North Carolina. The 4 PFC analytes routinely detected in bluegill fillets were perfluorooctane sulfonate (PFOS), perfluorodecanoic acid (C10), perfluoroundecanoic acid (C11), and perflurododecanoic acid (C12). Measures of method accuracy and precision for these compounds showed that calculated concentrations of PFCs in spiked samples differed by less than 20% from their theoretical values and that the %RSD for repeated measurements was less than 20%. Minnesota samples were collected from areas of the Mississippi River near historical PFC sources, from the St. Croix River as a background site, and from Lake Calhoun, which has no documented PFC sources. PFOS was the most prevalent PFC found in the Minnesota samples, with median concentrations of 47.0–102ng/g at locations along the Mississippi River, 2.08ng/g in the St. Croix River, and 275ng/g in Lake Calhoun. North Carolina samples were collected from two rivers with no known historical PFC sources. PFOS was the predominant analyte in fish taken from the Haw and Deep Rivers, with median concentrations of 30.3 and 62.2ng/g, respectively. Concentrations of C10, C11, and C12 in NC samples were among the highest reported in the literature, with respective median values of 9.08, 23.9, and 6.60ng/g in fish from the Haw River and 2.90, 9.15, and 3.46ng/g in fish from the Deep River. These results suggest that PFC contamination in freshwater fish may not be limited to areas with known historical PFC inputs. [Copyright &y& Elsevier]

To capture prey with suction, fish must get sufficiently close to their prey to allow the suction flow to overwhelm the prey and draw it into the mouth. Both swimming towards the prey and suction flow create a hydrodynamic disturbance, which can elicit an escape response by the prey. Using particle image velocimetry, we measured flow speeds and derived fluid deformation rates at the location of the prey as bluegill sunfish fed. In front of the mouth, flows had a composite time-dependent nature. First, the bow wave pushed water away from the fish, but when the mouth opened and suction commenced, flow reversed and water deformation rates increased rapidly. Our inferences indicate that, at the prey, the approaching bluegill is detected primarily based on its suction-induced disturbance, rather than its bow wave-induced disturbance. A comparison of suction-induced disturbance with the signal produced by active suspension feeders indicated that fish are able to produce a more subtle disturbance than expected based on their flow speeds and mouth size alone. Jaw protrusion and the rapid opening of the mouth during the strike both help to minimize the signal available to the prey. We propose that the temporally quick strikes and high jaw protrusion that are seen in many zooplanktivorous teleosts represent adaptations that minimize the time available to prey for executing an escape response. [ABSTRACT FROM AUTHOR]

Energetic analysis of ecologically relevant behaviors can be useful because animals are energetically limited by available muscle mass. In this study we hypothesized that two major determinants of suction feeding performance, the magnitudes of buccal volumetric expansion and subambient buccal pressure, would be correlated with, and limited by, available muscle mass. At least four individuals of three centrarchid species were studied: largemouth bass (Micropterus salmoides), bluegill (Lepomis macrochirus) and green sunfish (Lepomis cyanellus). Buccal pressure was measured directly via cannulation of the buccal cavity with a catheter-tipped pressure transducer. Buccal expansion was estimated from lateral high-speed video (500 or 1000Hz) sequences and published data on internal kinematics of largemouth bass. These estimates were calibrated from silicone casts made of the buccal cavity post-mortem. Estimated work and power were found to be significantly correlated with muscle mass over all individuals. The slopes of these relationships, estimates of mass-specific muscle work and power, were found to be 11±2 J kg-1 and 300±75W kg-1, respectively. These estimates are consistent with observations made of in vivo and in vitro muscle use and with digital particle image velocimetry measurements of water flow in feeding centrarchids. A direct trade-off between mean pressure and change in volume was observed, when the latter was normalized to muscle mass. We conclude that available muscle mass may be a useful metric of suction feeding performance, and that the ratio of muscle mass to buccal volume may be a useful predictor of subambient buccal pressure magnitude. [ABSTRACT FROM AUTHOR]

Angling can adversely affect populations of bluegill Lepomis macrochirus, and many state agencies have begun to explore restrictive creel and length limits. The fate of released fish can be influenced by a variety of factors, and the success of regulations could be reduced if the mortality of released bluegills is high. We conducted experiments using bluegills caught by the general angling public in Ridge Lake, Illinois, to quantify bluegill hooking mortality and test for the effects of bait type (live versus artificial), season (spring versus summer), retention time in live wells (1, 3, or 5 h), and retention gears (live wells versus fish baskets). Across all seasons and baits, the mortality of caught-and-released bluegills was low; the initial and short-term mortality for fish immediately released was 4.4%. There were significant differences in hooking mortality with respect to bait type, retention gear, and retention time. Bluegills caught on live bait experienced higher mortality (6.6%) than those caught on artificial baits (0%), and wire fish baskets caused higher mortality (34.0%) than live wells (7.6%). The mortality of bluegills held in live wells was higher for the 3- and 5-h retention times than for the 1-h treatment. The probability of dying from catch and release decreased with increasing fish length. We applied our results to a bluegill population under a restrictive harvest regulation consisting of a 203-mm minimum size limit and a 10-fish daily bag limit. Under these restrictive regulations, fish lost from catch and release represented 27.4% of the total kill (harvest and hooking mortality). While catch-and-release angling can cause some mortality, it does not appear from our study that releasing fish will have a deleterious effect on bluegill populations. [ABSTRACT FROM AUTHOR]

The influence of ontological diet shifts on infracommunity nestedness was examined by comparing the infracommunity structure of Lepomis gulosus and Lepomis macrochirus at 2 localities in Par Pond, South Carolina, United States. Fill-constrained, occurrence-constrained, and abundance-constrained null models were used to evaluate the degree of nestedness. The presence-absence matrices from all 4 component communities had significantly fewer discrepancies than those produced by the fill-constrained model, and none had significantly fewer discrepancies than those produced by the occurrence-constrained model. Only the presence-absence matrix for the infracommunities of L. gulosus from the Cold Dam locality had significantly fewer discrepancies than those produced by the abundance-constrained null model. The nestedness of the 4 samples could not be distinguished from that expected under a hypothesis of passive sampling. A positive correlation between host size and total parasite abundance indicates the passive mechanism has a deterministic basis. Thus, even in the absence of habitat or diet shifts, nestedness can arise in infracommunities of freshwater fishes when older, larger fish have sampled more individuals from an uneven distribution of infective stages. [ABSTRACT FROM AUTHOR]

The effects of acute temperature change on the cost of bluegill Lepomis macrochirus swimming were quantified. At 14° C, maximum labriform swimming speed ( Ulab,max) was reduced relative to that at the acclimation temperature of 22° C, but total cost of transport ( TTC) remained unchanged. At 30° C, Ulab,max was the same as at 22° C, but TTC was 66% greater. [ABSTRACT FROM AUTHOR]

Abstract: Bluegill (Lepomis macrochirus) monosex culture holds considerable potential as a method to improve bluegill aquaculture production as males grow much faster than females. A detailed understanding of the time of gonadal development and differentiation is critical to control sex and optimize culture. In the present study, we systematically studied gonadal sex differentiation of the bluegill sunfish and its relation to fish size and age from hatching to 90days post hatching (dph) using a slow-growing batch (SGB) and a fast-growing batch (FGB) of fish. The results indicated that the gonadal differentiation in bluegill was more related to body size than to age. In presumptive ovaries, germinal and somatic differentiation began between 13.2 and 16.0mm (60dph in SGB and 30dph in FGB) in total length (TL). The outgrowths from the proximal and distal portions of the gonads and the fusion of the outgrowths to form the ovarian cavity occurred between 16.0 and 21.0mm TL (80dph in SGB and 50dph in FGB) with germ cells undergoing meiosis. The gonads in the females larger than 25.5mm TL always had peri-nucleolus oocytes. In presumptive testes, the efferent duct formed in the fish ranging from 25.4 to 28.0mm TL (90dph in SGB and 70dph in FGB) with the onset of meiosis and testes contained spermatocytes exhibiting active meiosis in males larger than 33.0mm TL. These findings indicate that bluegill is a differentiated gonochorist and sex differentiation occurs earlier in females than males. Based on our results, we suggest that the critical period of sex differentiation in bluegill occurs between 13.2 and 16.0mm TL and histological sex differentiation is distinguishable in most fish larger than 21.0mm TL. [Copyright &y& Elsevier]

Naïve kin groups and mixed-family groups of bluegill Lepomis macrochirus larvae were exposed to a novel predator cue. The larvae responded by increasing shoal cohesiveness in kin groups but not in mixed-family groups; moreover, larvae sired by males of the ‘cuckolder’ life history tended to have an enhanced ability to respond to direct cues of kinship v. larvae sired by males of the ‘parental’ life history, which instead appeared to respond to cues of life history rather than relatedness per se. The increased shoal cohesion among related individuals probably confers a survival benefit and indicates that the antipredatory shoaling response is innate in L. macrochirus. [ABSTRACT FROM AUTHOR]

This study describes the parasite communities of juvenile bluegill and examines the development of parasite communities in juvenile bluegill from 2 Michigan lakes. Parasitological examination of 510 juvenile bluegill from 2 Michigan lakes (Three Lakes II [TL] and Gull Lake [GL]) demonstrated that TL bluegill harbored 19 parasite species and GL bluegill harbored 16 parasite species. Parasite communities of juvenile bluegill from both lakes were dominated by larval parasites, particularly larval trematodes. A nonmetric multidimensional scaling analysis showed bluegill of similar lengths to have similar parasite communities. Relative influences of species richness on parasite infracommunities of juvenile bluegill suggest similar patterns of parasite community structure between TL and GL. Patterns in parasite colonization evident in both lakes suggest that the smallest juvenile bluegill are primarily vulnerable to colonization by parasites acquired through direct contact, particularly larval trematodes, while the majority of parasites acquired through ingestion are not acquired until juvenile bluegill are larger and less-gape limited. [ABSTRACT FROM AUTHOR]

The hydrodynamics of a highly deformable fish pectoral fin used by a bluegill sunfish (Lepomis macrochirus) during steady forward swimming are examined in detail. Low-dimensional models of the fin gait based on proper orthogonal decomposition (POD) are developed, and these are subjected to analysis using an incompressible Navier-Stokes flow solver. The approach adopted here is primarily motivated by the quest to develop insights into the fin function and associated hydrodynamics, which are specifically useful for the design of a biomimetic, pectoral fin propulsor. The POD analysis shows that the complex kinematics of the pectoral fin can be described by a few (<5) POD modes and that the first three POD modes are highly distinct. The significance of these modes for thrust production is examined by synthesizing a sequence of fin gaits from these modes and simulating the flow associated with these gaits. We also conduct a scale study of the pectoral fin in order to understand the effect of the two key non-dimensional parameters, Reynolds number and Strouhal number, on the propulsive performance. The implications of the POD analysis and performance scaling on the design of a robotic pectoral fin are discussed. [ABSTRACT FROM AUTHOR]

Concerns over the economic feasibility of commercial aquaculture production of bluegills Lepomis macrochirus have heightened the need for strategies to enhance growth. Recent studies have shown that individually reared bluegill males can grow twice as fast as females; such studies have generated increased interest in development of mostly male or all-male populations. In this study, we developed a practical procedure to establish mostly male bluegill groups through grading selection and we tested their growth against that of a normal population. A single cohort of bluegill juveniles was cultured in a pond for 1 year; when the fish reached a mean weight of 30.1 g, the cohort was graded and divided into two mostly male groups (top 25% and top 50% of fish by total length) and a mixed-sex control group. The percentage of males in each group was as follows: 50.0% in the mixed control group, 75.4% in the top 25% group, and 69.7% in the top 50% group. Weight gain per fish in the top 25% group was significantly greater (P < 0.05) than that in the mixed group throughout most of the experiment. There were no significant differences detected in survival among the three groups, although the top 25% group had survival of 96.0% compared with 90.6% and 90.5% for the top 50% group and the mixed control group, respectively. The top 25% group had the highest percentage (46.3%) of fish reaching 150 g at the end of the experiment, followed by the top 50% group (28.3%), and the mixed control group (12.7%). The coefficient of variation (CV) for weight decreased in all three groups over time; the mostly male groups maintained lower initial and final CV values than did the mixed control group. Results indicate that mostly male bluegill groups are able to grow faster than typical mixed-sex populations, and social interaction costs among communally reared males did not significantly decrease growth of mostly male populations in the aquaculture settings. [ABSTRACT FROM AUTHOR]

The article details a study which compared the contractile properties between feeding muscles and swimming muscle in bluegill and largemouth bass. The study examined the influence of body size on muscle contraction and the physiological basis of the scaling of muscle contraction kinetics. It hypothesized that maximum shortening velocity (Vmax) of feeding muscle would scale differently from the locomotor muscle. Study authors concluded that their findings suggest that scaling patterns of contractile properties are closely related to muscle function than size patterns.

We described spawning periodicity, hatching duration, and peak larval densities for bluegill (Lepomis macrochirus) in five lakes of the northern Great Plains in Nebraska and South Dakota, USA from 2004 to 2007. Hatching generally began in early June, and duration ranged from 28 to 77 days. Peak larval density was highly variable among lakes and years and was primarily unimodal, with peaks occurring from late June to late July. Peak larval density ranged from 2 to 1,760 larvae/ 100 m³. Multimodal peaks in abundance occurred in four instances. Although multiple peaks in larval abundance within years were noted at southern latitudes, there were also many instances of a single peak. Larval density and spawning duration were generally lower than other reported studies of bluegill from southern latitudes although geographic location alone did not consistently explain these patterns. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the longitudinal distribution of torrentfish (Cheimarrichthys fosteri) and bluegill bully (Gobiomorphus hubbsi). The study aims to establish any variation within and between longitudinal size distributions of both species. New Zealand Rivers were the locations of the study, one in Hutt River in Wellington, and another in Rakaia river in Canterbury. Quantile regression analysis has showed variation in migration rate within each specie.

As global temperature shifts due to anthropogenic impacts, seasonal temperatures in shallow aquatic ecosystems are expected to increase. Previous studies on freshwater fishes that experience significant temperature changes during the annual seasons found pronounced physiological restructuring not observed in animals inhabiting more thermally stable environments. Studies evaluating mitochondrial bioenergetics in fish are often performed on animals acclimated to constant temperatures in the laboratory. However, natural habitats are much more complex. Fishes may experience substantial daily and seasonal variation in temperature, energy requirements and resource availability, which are impossible to emulate on acclimation studies. Our study explores the effects of these more complex natural environments on whole-organism thermal tolerance and mitochondrial bioenergetics in bluegill sunfish (Lepomis macrochirus) , a native fish to the temperate zone of North America. Compensatory mechanisms and variations in physiological thresholds were observed in specimens acclimatized to the fall season compared to specimens acclimatized to spring and summer seasons. Somatic indices, such as relative weights and hepatosomatic indices, showed significant differences across seasons and critical thermal maxima significantly decreased in the cold acclimatized specimens. Liver mitochondria from L. macrochirus also showed significantly higher uncoupled proton conductance, cytochrome c oxidase (COX) activity, and reduced respiratory control ratios in individuals sampled in the colder season. These findings suggest that mechanisms regulating proton conductance and COX activity modulate mitochondrial function across seasons to sustain physiological fitness in ectotherms inhabiting shallow, inland aquatic habitats. • Bluegill sunfish mitochondria increase electron transfer capacity upon seasonal acclimatization to cold temperatures. • Increase in electron transfer capacity was found to be independent of the oxidase's abundance. • Evidence points to multiple regulatory mechanisms of cytochrome c oxidase as adaptive strategies to cope with cold water temperatures. [ABSTRACT FROM AUTHOR]

Apparent digestibility of dry matter and energy, and availability of amino acids from blood meal (BM), fish meal (FM), meat and bone meal (MBM), poultry by-product meal (PBM), soybean meal (SBM), corn, wheat and yellow grease (YG) were determined for bluegill Lepomis macrochirus (mean weight, 57 g), and likewise, but not for BM or wheat, for largemouth bass Micropterus salmoides (mean weight, 30 g). To avoid nutrient interaction from a reference diet, diets containing 98.5% (985 g kg−1) of test ingredients were used, except for semi-solid, YG which was mixed with corn to permit pelletization. Faeces were collected by a siphoning method. Apparent dry matter digestibility values ranged from 50% (corn) to 87% (BM) for bluegill and from 53% (MBM) to 76% (PBM) for largemouth bass. Apparent energy digestibility values ranged from 53% (corn) to 92% (BM) for bluegill and from 63% (MBM) to 93% (YG) for largemouth bass. Apparent digestibility of most amino acids exceeded 90% for evaluated protein sources, except for MBM which showed slightly lower values (80–90%) for both fishes. Isoleucine digestibility from BM was relatively low (82%) for bluegill. High digestibility values for SBM, PBM and BM, indicate good potential for replacing FM in diets for both fishes. [ABSTRACT FROM AUTHOR]

Growth and survival of bluegills Lepomis macrochirus and redbreast sunfish L. auritus (N = 5,664) were examined in 13 river sections located in the southern half of Georgia. Bluegills tended to grow faster than redbreast sunfish within rivers where the two species were collected together. Annual survival of redbreast sunfish (range = 18-52%; mean = 38%) was greater than that of bluegills (range = 21-34%; mean = 29%). For both species, growth of males was generally greater than females, though annual survival did not differ significantly between sexes for either species. Growth of redbreast sunfish and bluegills appeared to increase along a northwest to southeast gradient across the state of Georgia. Growth variation of these sunfishes was likely mediated by prey availability, habitat, and physicochemical variables within each river section. [ABSTRACT FROM AUTHOR]

DNA-protein cross-links (DPXs) in fish erythrocytes represent a potential biomarker for exposure to metal cations, such as hexavalent chromium (Cr[VI]) and divalent nickel (Ni[II]). Species-specific sensitivities to DPX formation were studied by coexposure of juvenile specimens of rainbow trout, hybrid bluegill, and channel catfish to waterborne metals, such as Cr(VI) and Ni(II). In a species comparison, 4 days of exposure to 2 ppm Cr(VI) induced highest DPXs in bluegill erythrocytes, followed by trout and catfish, at 186%, 97%, and 48% above controls, respectively. A similar pattern of species sensitivity was observed following co-exposure of the fish to 15 ppm Ni(II) for 4 days, with 237%, 124%, and 82% increased DPXs above control bluegill, trout, and catfish, respectively. Biological stability of Cr(VI)-induced DPXs was demonstrated in Cr(VI)-exposed bluegill, as DPX levels remained elevated for up to 20 days after discontinuation of exposure. Similar results were found following exposure of catfish to Ni(II), with detectable DPXs found 10 days after acute exposure. In both bluegill and catfish, a continued increase in DPX formation in erythrocytes was seen for 5–10 days after Cr(VI) was removed from tank water, suggesting that residual Cr(VI) may be involved in DPX formation following acute exposure of fish. [ABSTRACT FROM AUTHOR]

Evolutionary patterns of intrinsic caudal musculature in ray-finned fishes show that fine control of the dorsal lobe of the tall evolved first, followed by the ability to control the ventral lobe. This progression of increasing differentiation of musculature suggests specialization of caudal muscle roles. Fine control of fin elements is probably responsible for the range of fin conformations observed during different maneuvering behaviors. Here, we examine the kinematics of the caudal fin and the motor activity of the intrinsic caudal musculature during kick-and-glide, braking and backing maneuvers, and compare these data with our previous work on the function of the caudal fin during steady swimming. Kick-and-glide maneuvers consisted of large- amplitude, rapid lateral excursion of the tail fin, followed by forward movement of the fish with the caudal fin rays adducted to reduce surface area and with the tail held in line with the body. Just before the kick, the flexors dorsalis and ventralis, hypochordal longitudinalis, infracarinalis and supracarinalis showed strong activity. During braking, the dorsal and ventral lobes of the tail moved in opposite directions, forming an 'S'-shape, accompanied by strong activity in the interradialis muscles. During backing up, the ventral lobe initiated a dorsally directed wave along the distal edge of the caudal fin. The relative timing of the intrinsic caudal muscles varied between maneuvers, and their activation was independent of the activity of the red muscle of the axial myomeres in the caudal region. There was no coupling of muscle activity duration and electromyographic burst intensity in the intrinsic caudal muscles during maneuvers, as was observed in previous work on steady swimming. Principal-component analysis produced four components that cumulatively explained 73.6% of the variance and segregated kick-and-glide, braking and backing maneuvers from each other and from steady swimming. The activity patterns of the intrinsic caudal muscles during maneuvering suggest motor control independent from myotomal musculature, and specialization of individual muscles for specific kinematic roles. [ABSTRACT FROM AUTHOR]