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Wastewater algal cultivation (WAC) in outdoor raceway ponds is a promising means of removing nutrient pollutants from water while producing biomass feedstock for products like fertilizer or biofuel. However, algal cultivation in open ponds is often plagued by underproduction due to zooplankton contamination. The use of biological controls, i.e., natural predators to control zooplankton, was evaluated as a potential low-cost solution in this study. Eighteen pilot-scale raceway ponds were inoculated with algae and naturally-occurring zooplankton dominated by Moina, and bluegill sunfish (Lepomis macrochirus) were tested as biological control agents to suppress the zooplankton. Cages installed in the ponds protected fish from paddlewheels and controlled the area fish could access. The cage either surrounded the paddlewheel – in which case fish could access the remaining area – or the cage was opposite the paddlewheel, in which case fish could only access the smaller area inside the cage. Fishless controls were also implemented in both cage treatments. After 19 days, ponds with cages surrounding the paddlewheel had 93% more zooplankton regardless of fish presence, but fish had reduced zooplankton by 89% on average across cage treatments. Cage placement did not affect algal biomass, but ponds with fish had 45% higher algal dry weight and 84% higher algal biovolume. However, no differences in available nutrient levels were recorded among treatments. We concluded hardy zooplanktivorous fish represent a promising means of boosting algal production in WAC, although further research is needed to determine whether the change in algal biomass could eventually translate to improved nutrient removal. [ABSTRACT FROM AUTHOR]

Objective: Artificial light at night (ALAN) is one of the most pervasive and rapidly expanding sources of anthropogenic pollution. Aquatic ecosystems may be especially vulnerable to the effects of ALAN due to their disproportionate exposure to anthropogenic pressures. However, research on mechanisms of response to ALAN by aquatic species remains sparse. Our research investigated the extent to which ALAN influences the nocturnal feeding efficiency of Bluegill Lepomis macrochirus. Methods: Using an array of outdoor mesocosm tanks, we assigned juvenile Bluegill to five nighttime lighting treatments (control dark, 1 lx, 4 lx, 12 lx, and intermittent 12 lx). We conducted weekly nighttime feeding trials for 6 weeks to assess four prey capture variables, including capture efficiency (the effectiveness of prey strikes), capture rate (the number of prey items captured), strike rate (the frequency of prey strikes), and latency (time elapsed before the first prey strike). Result: The steady lighting treatments, which were selected based on nighttime urban light intensities we previously measured in the field, had no apparent effect on any of the prey capture variables. However, flashing high‐intensity lights (intended to mimic the effect of passing car headlights on a busy highway) had a significant negative effect on capture rate and strike rate, thereby inhibiting the ability of fish to strike at and capture prey. Conclusion: Our results demonstrate the potential for light pollution (especially flashing or intermittent lights) to interfere with the foraging behavior of this ecologically and economically important sportfish. Impact statementLight pollution, especially flashing lights, may interfere with the foraging behavior of an ecologically and economically important sport fish. [ABSTRACT FROM AUTHOR]

North American sunfishes (Family Centrarchidae) are among the most popular sportfish throughout the United States and Canada. Despite the popularity of sunfishes, their ecological importance, and their extensive stocking and aquacultural history, few molecular studies have examined the evolutionary relationships and species boundaries among members of this group, many of which are known to hybridize. Here, we describe a chromosome-scale genome assembly representing Bluegill (Lepomis macrochirus), one of the most widespread centrarchid species. By combining long-read, Oxford Nanopore sequencing data with short-insert, whole-genome and HiC sequence reads, we produced an assembly (Lm_LA_1.1) having a total length of 889 Mb including 1,841 scaffolds and having a scaffold N50 of 36 Mb, L50 of 12, N90 of 29 Mb, and L90 of 22. We detected 99% (eukaryota_odb10) and 98% (actinopterygii_odb10) universal single-copy orthologs (BUSCOs), and ab initio gene prediction performed using this new assembly identified a set of 17,233 genes that were supported by external (OrthoDB v10) data. This new assembly provides an important addition to the growing set of assemblies already available for spinyrayed fishes (Acanthomorpha), and it will serve as a resource for future studies that focus on the complex evolutionary history of centrarchids. [ABSTRACT FROM AUTHOR]

Research on Bluegills, Lepomis macrochirus R., is abundant but typically focuses on water bodies with similar environmental conditions. We assessed Bluegill density, relative abundance (catch per unit effort [CPUE] by electrofishing), growth, and size structure in 60 lakes with wide-ranging surface areas (2–12,412 ha), trophic states (oligotrophic–hypereutrophic), and macrophyte abundances (0.3–100 percent of lake volume inhabited [PVI]) across Florida, USA. Bluegill density and CPUE increased with lake productivity and decreased with macrophyte abundance. Bluegill growth increased with lake productivity and CPUE of stock-length Florida Bass, Micropterus floridanus L., a Bluegill predator. Bluegill size structure increased with lake productivity and decreased with Bluegill density. Results indicate that Bluegill fisheries with abundant individuals of quality size (≥150 mm) require productive (>25 μg/L chlorophyll-a concentration) lakes with moderate to high macrophyte coverage (PVI 50–100), abundant stock-length Florida Bass (>40 fish/h of electrofishing), and Bluegill densities <300 fish/ha. This study provides an approach to predict Bluegill population demographics based on abiotic and biotic factors, establish fisheries management expectations, and develop regional and lake-specific management tools. [ABSTRACT FROM AUTHOR]

Research on Bluegills, Lepomis macrochirus R., is abundant but typically focuses on water bodies with similar environmental conditions. We assessed Bluegill density, relative abundance (catch per unit effort [CPUE] by electrofishing), growth, and size structure in 60 lakes with wide-ranging surface areas (2–12,412 ha), trophic states (oligotrophic–hypereutrophic), and macrophyte abundances (0.3–100 percent of lake volume inhabited [PVI]) across Florida, USA. Bluegill density and CPUE increased with lake productivity and decreased with macrophyte abundance. Bluegill growth increased with lake productivity and CPUE of stock-length Florida Bass, Micropterus floridanus L., a Bluegill predator. Bluegill size structure increased with lake productivity and decreased with Bluegill density. Results indicate that Bluegill fisheries with abundant individuals of quality size (≥150 mm) require productive (>25 μg/L chlorophyll-a concentration) lakes with moderate to high macrophyte coverage (PVI 50–100), abundant stock-length Florida Bass (>40 fish/h of electrofishing), and Bluegill densities

Population demographics are used by biologists and managers to determine the quality of a fishery and set regulations to achieve desired management goals. Regulating a large river system fishery that spans a substantial geographical region is often complicated by spatially variable environmental factors that affect fish population dynamics (e.g. habitat, water quality); these dynamics are rarely examined within an entire system. In this study we compared spatial differences in population age and length at capture, growth, fecundity and body condition of bluegill Lepomis macrochirus among two different river reaches (e.g. basin width, gradient, velocity) of the Illinois River (Illinois, USA) and a disconnected floodplain lake, the Emiquon Preserve. Variations in selected population demographics were evaluated in relation to well-documented habitat characteristics (e.g. water quality, aquatic vegetation, backwater availability). Differences in bluegill demographic traits between the disconnected floodplain lake and river reaches were distinct, and variations between river reaches were sex specific. The floodplain lake generally had older bluegill that expressed a higher maximum length at age and a lower growth rate and fecundity than bluegill in river reaches. River bluegill differed between river reaches in male growth, and fecundity in both sexes. Body condition was not significantly different among bluegill populations. Early research on floodplain lakes indicates that this habitat supports greater fish growth and higher reproductive fitness than mainstem habitat. We conclude that increasing the availability of quality backwater habitat, even within a highly modified large river system like the Illinois River, could substantially increase the quality and stability of bluegill populations.

Thermal stratification can significantly impact the distribution of species in aquatic systems. Organisms often travel between these thermoclines in order to locate prey and find optimal thermal condition. Since most aquatic animals are ectotherms, changes in ambient temperature can have immediate impacts on performance. We aimed to understand how prey capture kinematics change when bluegill sunfish (Lepomis macrochirus) are exposed to brief acute temperature changes that represent foraging bouts below the thermocline. To do this, we exposed bluegills to either 21°C (above thermocline) or 17°C (below thermocline) and fed them a cloud of defrosted brine shrimp. After digitizing high‐speed videography, we found that performance increased at the below thermocline temperature contrary to our prediction. During these feeding bouts, we noticed high variability in prey capture behaviors as the fish encountered the first prey item and subsequent prey items. In these successive feeding events, they demonstrated a remarkable amount of modulation in close succession. We conclude that acute exposure to the thermocline temperature tested here does not negatively impact prey capture. Furthermore, feeding in rapid succession could be a way to maximize prey captured while reducing energy for searching and capture. [ABSTRACT FROM AUTHOR]

A murine monoclonal antibody (mAb, IgG2a) was produced for the detection of smallmouth bass (Micropterus dolomieu) immunoglobulin (IgM). The antibody is specific for IgM heavy chain and was shown to also recognize the Ig heavy chain of largemouth bass (Micropterus salmoides) and bluegill (Lepomis macrochirus) using Western Blot analysis of plasma from 9 teleost taxa. When applied to the analysis of smallmouth bass total plasma IgM using ELISA, the mAb was found to be effective when used in an inhibition kinetic assay. • Mouse IgG 2a Monoclonal antibody produced against smallmouth bass IgM. • Antibody reacts with IgM from smallmouth and largemouth bass as well as bluegill. • Application of antibody in Western Blot and ELISA demonstrated. [ABSTRACT FROM AUTHOR]

Population demographics are used by biologists and managers to determine the quality of a fishery and set regulations to achieve desired management goals. Regulating a large river system fishery that spans a substantial geographical region is often complicated by spatially variable environmental factors that affect fish population dynamics (e.g. habitat, water quality); these dynamics are rarely examined within an entire system. In this study we compared spatial differences in population age and length at capture, growth, fecundity and body condition of bluegill Lepomis macrochirus among two different river reaches (e.g. basin width, gradient, velocity) of the Illinois River (Illinois, USA) and a disconnected floodplain lake, the Emiquon Preserve. Variations in selected population demographics were evaluated in relation to well-documented habitat characteristics (e.g. water quality, aquatic vegetation, backwater availability). Differences in bluegill demographic traits between the disconnected floodplain lake and river reaches were distinct, and variations between river reaches were sex specific. The floodplain lake generally had older bluegill that expressed a higher maximum length at age and a lower growth rate and fecundity than bluegill in river reaches. River bluegill differed between river reaches in male growth, and fecundity in both sexes. Body condition was not significantly different among bluegill populations. Early research on floodplain lakes indicates that this habitat supports greater fish growth and higher reproductive fitness than mainstem habitat. We conclude that increasing the availability of quality backwater habitat, even within a highly modified large river system like the Illinois River, could substantially increase the quality and stability of bluegill populations. [ABSTRACT FROM AUTHOR]

During aquatic suction feeding, the predator opens its mouth and rapidly expands its buccal cavity, generating a flow field external to the mouth. The rapid expansion of the buccal cavity produces high fluid velocities and accelerations that extend only a short distance from the mouth ( about half of one mouth diameter), and only persist for several milliseconds. Therefore, the predator must precisely time its strike to locate the prey within the narrow region of high flow, during the brief period when flow is at its peak. With flow being the agent for transferring force to the prey, the predator may enhance these forces by producing higher water velocities and faster acceleration at the mouth, but also through increasing the strike's accuracy, i.e. locating the prey closer to the mouth at the instant of peak flow speed. The objectives of this study were to directly measure forces exerted by bluegill Lepomis macrochirus on their prey and to determine how bluegill modify force output. Bluegill were offered ghost shrimp tethered to a load cell that recorded force at 5000 Hz, and feeding sequences were synchronously recorded using 500 Hz video. Peak forces exerted on attached 20 mm shrimp ranged from 0.005 N to 0.506 N. In accordance with the short duration of the strikes ( average time to peak gape of similar to 13 ms), the forces recorded were brief (similar to 12 ms from initiation to peak force), and force magnitude declined rapidly after peak force. Statistical analysis indicated that rate of buccal expansion, and prey size, but not strike initiation distance, significantly affected peak force. These observed variables were used with results from flow visualization studies to estimate the flow at the prey's location, which allowed the calculation of drag, pressure gradient force and acceleration reaction force. The relationship between these calculated forces and the measured forces was strong, indicating that the model can be used to estimate forces from strike kinematics. This model was then used to study the effects of strike initiation distance on peak force and on the rate of increasing force. Comparisons of model output to empirical results indicated that bluegill time their strike so as to exert an average of similar to 70% of the peak possible force on the prey, and that the observed strike initiation distance corresponded to the distance that maximized modeled force on an attached prey. Our results highlight the ability of bluegill to produce high forces on their prey, and indicate that precision and visual acuity play important roles in prey acquisition, beyond their recognized role in prey detection.

A mortality event involving an estimated 1,000 adult bluegills (Lepomis macrochirus) was observed in an ice‐covered backwater lake of the upper Mississippi River near Alma, Wisconsin, in December of 2017. Macroscopic signs of disease included abdominal distension due to fluid accumulation within the internal organs as well as external and internal haemorrhaging. Histological evaluation revealed chronic peritonitis with peritoneal adhesions in all fish examined. Kidney, spleen and ascites fluid samples were collected from diseased bluegills and examined for the presence of pathogens. Bluegill picornavirus (BGPV) was isolated using tissue cell culture methods utilizing a recently developed, uncharacterized bluegill fry cell line (BF‐4), and the presence of this virus was confirmed through molecular identification. The current geographic range, known susceptible hosts as well as historical epizootics associated with BPGV is discussed. The ability of BGPV to cause significant mortality in wild fish further emphasizes the importance of monitoring both wild and hatchery populations for this pathogen. [ABSTRACT FROM AUTHOR]

Bluegill sunfish (Lepomis macrochirus) have two male morphotypes, α- and β-males, each differing in appearance and mating strategy. Alpha-males use nest-building tactics, whereas β-males use sneaker or satellite tactics. Lepomis macrochirus are important members of the aquatic community, and are often involved in parasitic life cycles. Among the most common parasites infecting L. macrochirus are strigeids, which include white grub (Posthodiplostomum minimum), black grub (Uvulifer ambloplitis), and yellow grub (Clinostomum marginatum). Previous studies found a higher abundance of strigeid parasites in α-males, even though β-males spend increased time in the littoral zone. One hypothesis is that α-males recruit the parasites during the spawn because of their nest-guarding behavior, which potentially increases their interactions with snail intermediate hosts. To test this hypothesis, L. macrochirus were collected between February and July in consecutive years from 2015 to 2017 from 13 lakes and ponds in northwestern Virginia. The fish were necropsied and all of the endo- and ectoparasites infecting the fish were identified and enumerated. The results supported the hypothesis and showed that α-males had greater infections postspawn, whereas β-males and females had no increase in infection from pre- to postspawn. Additionally, α-males recruited strigeid parasites at a greater rate than β-males, which negatively affected their body condition. The body condition of both α-males and females were negatively affected by P. minimum and U. ambloplitis, but β-males were not affected by either parasite. This shows that the differences in mating strategies between male morphotypes may result in greater strigeid infection in α-males compared with β-males. This may affect the fitness and reproductive output of α-males and be a contributing factor to the maintenance of β-males in the ecologically stable system, despite decreased reproductive success. [ABSTRACT FROM AUTHOR]

Successful predator evasion is essential to the fitness of many animals. Variation in escape behaviour may be adaptive as it reduces predictability, enhancing escape success. High escape velocities and accelerations also increase escape success, but biomechanical factors likely constrain the behavioural range over which performance can be maximized. There may therefore be a trade-off between variation and performance during escape responses. We have used bluegill sunfish (Lepomis macrochirus) escape responses to examine this potential trade-off, determining the full repertoire of escape behaviour for individual bluegill sunfish and linking this to performance as indicated by escape velocity and acceleration. Fish escapes involve an initial C-bend of the body axis, followed by variable steering movements. These generate thrust and establish the escape direction. Directional changes during the initial C-bend were less variable than the final escape angle, and the most frequent directions were associated with high escape velocity. Significant inter-individual differences in escape angles magnified the overall variation, maintaining unpredictability from a predator perspective. Steering in the latter stages of the escape to establish the final escape trajectory also affected performance, with turns away from the stimulus associated with reduced velocity. This suggests that modulation of escape behaviour by steering may also have an associated performance cost. This has important implications for understanding the scope and control of intra- and inter-individual variation in escape behaviour and the associated costs and benefits.

In many populations, males compete for mates and contribute to genetic diversity, but are assumed to have little impact on population growth rates and density, because one father is all that is necessary to fertilize a large number of eggs and sire a potential cohort. A factor affecting male reproductive output is exposure to contaminants that either disrupt endocrine function or mimic hormones. Polychlorinated biphenyls (PCBs) persist in aquatic ecosystems and may interfere with the reproductive contribution of male fish to populations. We quantified 28 PCB congeners in adult male bluegills across eight Illinois lakes. In spring 2011 and 2012, mature male bluegills from lakes with conspecifics with PCB whole‐body residues ranging from undetectable to high (2,000 ng/g dry mass total PCBs) were placed in experimental ponds with mature females containing no detectable PCB body residues and allowed to reproduce in spring under natural conditions. The presence of PCBs in fish had no effect on the presence of intersex or other gonadal deformities in adult males nor was gonad size, lipid concentration, and survival affected. Males with high PCBs were heavier than those from lakes with low PCB concentrations. The relative density of juvenile bluegills produced in ponds by fall, a fitness endpoint in this species, was negatively related to contaminant concentration in fathers. Contaminant exposure and other factors that affect male reproduction may not only suppress the relative contribution of males to genetic diversity, but also the overall density of cohorts within populations.

Present study was performed to survey infection status of digenetic trematode metacercariae in 2 alien fish species, Micropterus salmoides (largemouth bass) and Lepomis macrochirus (bluegill), in 2 rivers draining Chungcheongbuk- do, Republic of Korea. A total of 107 largemouth bass and 244 bluegills were caught in Daecheong-ho (ho=lake) and Musim-cheon (a branch of Geum-gang), in Chungcheongbuk-do April-July 2015. Additionally, 68 native fish of 5 species, i.e., Zacco platypus, Hemibarbus longirostris, Carassius auratus, Pseudogobio esocinus and Puntungia herzi, were caught from the same water bodies. All of the fish collected were examined by artificial digestion method. The metacercariae of Centrocestus armatus, Clinostomum complanatum, Metagonimus sp. and Diplostomum spp. were detected from 4 out of 5 native fish species in Daecheong-ho. However, any metacercariae were not found from 87 M. salmoides and 177 L. macrochirus in Daecheong-ho. In Musim-cheon, metacercariae of Exorchis oviformis and Metacercaria hasegawai were detected from 78% Z. platypus and 34% L. macrochirus, but any metacercariae not found in M. salmoides. We report here that the 2 alien fish species were less infected with the metacercariae than the native ones. Surveys on the metacercariae in the alien fish species in geographically various rivers should be undertaken for better understanding on the role of alien fish species in the trematode infections in Republic of Korea. [ABSTRACT FROM AUTHOR]

A prerequisite to studying the physiological status of wild animals is the ability to obtain blood samples that reflect the condition prior to capture or handling. Based on research in avian taxa, it is recommended that such samples be obtained within 3 min of capture; however, this guideline has not been validated in wild teleosts. The present study addresses the time course of physiological changes in a number of blood metrics across six species of freshwater fish. Fishes were caught using a standardized angling protocol and held in a water-filled trough prior to the collection of a blood sample, via caudal phlebotomy, between 0.5 and 11 min after capture. Changes in whole-blood glucose and lactate concentrations, hematocrit, and plasma cortisol concentrations were assessed. Change-point analyses indicated that blood lactate concentrations and hematocrit did not deviate from baseline values until ∼2-5 min of handling for all species, whereas blood glucose concentrations generally did not deviate significantly from baseline over the 11 min test period. In all species, plasma cortisol concentrations began to increase above baseline between ∼4 and 8 min after capture. Thus, to ensure that blood samples are representative of baseline conditions across multiple metrics, we recommend that sampling be limited to less than 2 min in teleost fishes. [ABSTRACT FROM AUTHOR]

Abstract: Polymorphic populations are often considered as intermediate stages of speciation. Bluegill sunfish (Lepomis macrochirus) from Lake Waban, Wellesley, MA have diverged into two ecomorphs based on their diet, occupied habitat and morphology. Littoral bluegills are generalist feeders that consume a variety of aquatic invertebrates. Pelagic bluegills feed primarily on Daphnia. We aimed to understand if suction pressure generation, prey capture behaviors and pharyngeal jaw morphology differed between the littoral and pelagic ecomorphs feeding on three prey types. Littoral and pelagic bluegills showed similar feeding kinematics and peak pressure, however, significant differences were observed among prey types within an ecomorph. Feeding events on brine shrimp were slower and accompanied by less negative pressure for both ecomorphs. Littoral bluegills varied their use of ram among prey types, however, pelagic bluegills (zooplankton specialists) did not. Similar to previous studies, when presented with different prey items both dietary generalists and specialists varied equally in most aspects of their feeding behaviors. However, pelagic bluegills (dietary specialists) did not vary in their approach behaviors. Despite the lack of differences in trophic morphology among the individuals sampled here, the prey approach behaviors of dietary specialists appears to be fixed in pelagic bluegills. This result deemphasizes the importance of suction during feeding and places more importance on prey approach behaviors. [ABSTRACT FROM AUTHOR]

Sea lamprey (Petromyzon marinus) control in the Laurentian Great Lakes of North America often relies on the application of 3-trifluoromethyl-4-nitrophenol (TFM) and niclosamide mixtures to kill larval sea lamprey. Selectivity of TFM against lampreys appears to be due to differential detoxification ability in these jawless fishes compared to bony fishes, particularly teleosts. However, the proximate mechanisms of tolerance to the TFM and niclosamide mixture and the mechanisms of niclosamide toxicity on its own are poorly understood, especially among non-target fishes. Here, we used RNA sequencing to identify specific mRNA transcripts and functional processes that responded to niclosamide or a TFM:niclosamide mixture in bluegill (Lepomis macrochirus). Bluegill were exposed to niclosamide or TFM:niclosamide mixture, along with a time-matched control group, and gill and liver tissues were sampled at 6, 12, and 24 h. We summarized the whole-transcriptome patterns through gene ontology (GO) term enrichment and through differential expression of detoxification genes. The niclosamide treatment resulted in an upregulation of several transcripts associated with detoxification (cyp , ugt , sult , gst), which may help explain the relatively high detoxification capacity in bluegill. Conversely, the TFM:niclosamide mixture resulted in an enrichment of processes related to arrested cell cycle and growth, and cell death alongside a diverse detoxification gene response. Detoxification of both lampricides likely involves the use of phase I and II biotransformation genes. Our findings strongly suggest that the unusually high tolerance of bluegill to lampricides is due to these animals having an inherently high capacity and flexible detoxification response to such compounds. [Display omitted] • · Sea lamprey control uses TFM (3-trifluoromethyl-4-nitrophenol) & niclosamide as lampricides. • Bluegill were exposed to a TFM:niclosamide mixture or niclosamide for up to 24h; Gill & liver were sampled. • Tissues underwent RNA-seq with transcriptome analyses for differential expression & gene ontogeny (GO) term enrichment. • Niclosamide had minimal impact; Mixture had high detoxification response & enrichment of GO terms with cell death/growth. • Bluegill have a high inherent capacity to detoxify lampricides leading to high lampricide tolerances. [ABSTRACT FROM AUTHOR]

Mobility is essential to the fitness of many animals, and the costs of locomotion can dominate daily energy budgets. Locomotor costs are determined by the physiological demands of sustaining mechanical performance, yet performance is poorly understood for most animals in the field, particularly aquatic organisms. We have used 3-D underwater videography to quantify the swimming trajectories and propulsive modes of bluegills sunfish ( Lepomis macrochirus, Rafinesque) in the field with high spatial (1-3 mm per pixel) and temporal (60 Hz frame rate) resolution. Although field swimming trajectories were variable and nonlinear in comparison to quasi steady-state swimming in recirculating flumes, they were much less unsteady than the volitional swimming behaviors that underlie existing predictive models of field swimming cost. Performance analyses suggested that speed and path curvature data could be used to derive reasonable estimates of locomotor cost that fit within measured capacities for sustainable activity. The distinct differences between field swimming behavior and performance measures obtained under steady-state laboratory conditions suggest that field observations are essential for informing approaches to quantifying locomotor performance in the laboratory. [ABSTRACT FROM AUTHOR]

The bluegill sunfish ( Lepomis macrochirus) is a notorious exotic fish, which causes serious damages to freshwater ecosystems in the world. Therefore, it is a matter of urgency to control this species for the conservation of ecosystem. New microsatellite loci were developed for L. macrochirus using high throughput 454 GS-FLX+ pyrosequencing. We selected 24 primer pairs that were tested on 47 individuals from Lake Biwa, which encompasses the oldest and largest population of L. macrochirus in Japan. Allele per locus varied 2-17. Expected and observed heterozygosities ranged from 0.185 to 0.888 and 0.120 to 0.872, respectively. Applied to L. macrochirus in Lake Biwa, these markers could detect genetic differentiation among populations, which showed a pattern of isolation by distance. These markers are expected to be useful in the estimation of population structure and ecology of L. macrochirus. [ABSTRACT FROM AUTHOR]

A wide range of chemical signals have been demonstrated to affect the swimming behaviour of Daphnia, including molecules associated with predation threat. In this contribution, we investigate how the concomitant presence of kairomones from the predaceous fish Lepomis macrochirus and alarm pheromones from crushed conspecifics affect the small-scale swimming behaviour of Daphnia pulicaria. In particular, we studied both the light/dark and summer/winter variations in the swimming motion of the cladoceran in the presence and absence of these infochemicals, and related them to the limnology of the environment. At summertime temperature, in the presence of light and infochemicals D. pulicaria confined its motion to the first few centimetres of the observation vessel, expressing positive phototaxis. In all other conditions, instead, no significant difference in the time spent in the upper and lower parts of the chamber was recorded. The upward displacement of D. pulicaria recorded in our experiments deviates from the most traditionally accepted downward migration used to move into darker layers to avoid visual predation. Our results highlight additional behavioural mechanisms that might be efficiently exploited by D. pulicaria to contrast predation by L. macrochirus. [ABSTRACT FROM AUTHOR]

The drag coefficient bluegill sunfish Lepomis macrochirus was estimated from coasting deceleration as (mean ± SD) 0.0154 ± 0.0070 at a Reynolds number of 41,000 ± 14,000. This was within the coasting range in other species and lower than values obtained from dead drag measurements in this species and others. Low momentum losses during coasting may allow its use during intermittent propulsion to modulate power output or maximize energy economy. [ABSTRACT FROM AUTHOR]

Morphological responses to flowing water have been documented in many fishes, but rarely reported in species with gibbose body types, despite their use of riffles in rivers and streams. In this study, we compared morphological responses to water flow in three gibbose centrarchids: bluegill ( Lepomis macrochirus Rafinesque, 1819), pumpkinseed ( Lepomis gibbosus (L., 1758)), and rock bass ( Ambloplites rupestris (Rafinesque, 1817)). Flow-through plexiglass units, set to either a sustained flow or static conditions, were used to rear juveniles from each species for an 80-day period. All three species developed more streamlined body forms, longer and thinner caudal peduncles, and longer pectoral fins when reared in sustained current. Pumpkinseed exhibited the highest level of phenotypic plasticity in response to water flow, followed closely by bluegill; rock bass was the least plastic species. Rock bass developed longer predorsal and prepectoral lengths, which differ from the morphological changes observed in bluegill and pumpkinseed. The findings not only suggest that some gibbose fishes are capable of exhibiting strong phenotypic responses to water flow, but that many morphological changes are species specific, even within the same taxonomic family. Lastly, all three species developed shorter dorsal fin base lengths when reared under flowing condition, which differs from some previously documented work on fusiform fishes. The results of this study provide a better understanding of how morphology in three closely related species varies in response to environmental conditions. [ABSTRACT FROM AUTHOR]

In teleosts, the area of peak ganglion cell density in the retina (area centralis, AC) is thought to reflect the primary visual axis for feeding. The bluegill Lepomis macrochirus are known to undergo ontogenetic shifts in diet preference, but because their diet is affected by population density, interspecific competition, and seasonal changes in prey availability, they are considered generalist predators. We investigated whether the diet shifts of the bluegill were associated with a change in the location of the AC (total length of fish specimens, range 44-243 mm). The AC was located temporally in the retina of smaller fish (40-100 mm), and the area of increased density included the ventral and central regions of the retina. Conversely, the AC was located in the dorso-temporal region of the retina in larger (100-200 mm) fish. Lastly, in the largest bluegill (> 200 mm), the AC was located in the temporal region of the retina. In all cases, the orientation of the visual axis was consistent with the known diet preferences of the different size classes. [ABSTRACT FROM AUTHOR]

To generate mortality estimates for fish that are captured and released in recreational and commercial fisheries, it is common to temporarily hold fish in captivity. Typically, captured fish are placed in some form of pen, cage or tank with control individuals, yet little is known about how the type of holding environment influences fish condition or mortality. Here we captured freshwater fish (bluegill; Lepomis macrochirus ) via angling and fyke net and retained them in one of four holding environments; a round flow-through tank on shore [TANK], a knotless nylon pen with natural substrate in the lake [PEN], a knotless nylon floating cage with a rigid structure [RCAGE], and a knotless nylon floating cage that lacked rigid structure [CAGE]. Mortality was low (1%) across both capture techniques and holding environments during the 14-day retention period. All mortalities were associated with capture by fyke net. A chronic stress indicator, blood glucose, was determined for a subset of fish on day 5. Although there were significant differences in blood glucose between angled RCAGE and angled PEN (Tukey, P = 0.047) and angled RCAGE and fyke PEN (Tukey, P = 0.015), the observed levels were generally quite low (range: 1.0–3.9 mmol L −1 ) and the differences were likely associated with differences in feeding; fish in the PEN group with access to substrate (and presumably the most food) had slightly higher glucose levels. At the conclusion of the study Fulton's condition factor was similar among all groups (ANOVA, P > 0.05, all terms). However, fish held in the TANK treatment had the highest levels of external protozoan parasite infection by Ichthyopthirius (Tukey, P < 0.05). This study illustrates that in situ holding environments (rather than tanks) may help reduce mortality, stress, and disease during studies that estimate post-release mortality. We encourage additional research to explore how the holding environment can influence inferences made about post-release mortality and sublethal impacts of fishing. [ABSTRACT FROM AUTHOR]

Many bluegill (Lepomis macrochirus) populations are characterized by a stunted adult size structure and consist primarily of individuals that mature at a relatively young age and small size. Little is known about maternal effects in bluegill populations and whether they may explain the occurrence of stunted growth. We spawned bluegill from both stunted and non-stunted populations in experimental tanks and collected eggs and larvae from each clutch. We determined whether differences in egg and oil globule diameter and larval growth existed between eggs collected from females from each population. Egg and oil globule diameter were not related to female length and did not differ between stunted and non-stunted populations. Larvae length after 21 d was positively related to egg diameter but was not related to either female length or oil globule diameter. Consequently, egg diameter had a greater influence on larval growth than female source population or size. No differences were observed between source populations indicating that some aspects of early life history are more heavily influenced by egg properties than adult life history differences between parental source populations. [ABSTRACT FROM AUTHOR]