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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]

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]

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]

Invasive macrophytes drive substantial changes to freshwater fish habitats. Such changes can influence how fish select for habitats, but fish-habitat relationships in many invasive macrophytes are often poorly understood at micro-scales. Fish habitat use is influenced by dissolved oxygen (DO) and habitat complexity, but this response can be nonlinear and dependent upon fish density. This study tested whether microhabitat use of sunfish ( Lepomis spp.) in invasive macrophyte beds was density-dependent. Fish were sampled with underwater video point counts in six 0.405 ha experimental ponds with surface-matted hydrilla Hydrilla verticillata and stocked with varying densities of sunfishes. Regression models were used to evaluate the key drivers for fish habitat selection across DO, complexity and fish densities. Both fish occurrence and fish counts were positively influenced by DO and negatively influenced by habitat complexity, but the fish counts-DO relationship was dome-shaped and both fish occurrence and counts depended upon fish densities. For example, at high fish densities, fish used low and high DO and high macrophyte complexity; at low fish densities, fish avoided such areas. Fish counts peaked at intermediate DO and low macrophyte complexity. Density-dependent fish habitat selection appeared to mitigate detrimental effects of invasive macrophytes on fish habitats, indicating that fish can and do use 'inhospitable' habitats with potential positive population growth. Understanding density-dependent habitat selection is needed when evaluating the quality of habitats, as apparently inhospitable habitats can be utilized when fish density is high. [ABSTRACT FROM AUTHOR]

Why certain species of fish become invasive is poorly understood and a key obstacle to restoring many of the world's ecosystems. In this study we tested whether variation in biotic resistance exerted by native predators might explain the reproductive success of the common carp, a large and fecund invasive species that typically spawns in outlying and unstable shallow habitat. An initial three-year study of the relative abundance of young-of-year (YOY) carp in interconnected lakes in the Upper Mississippi River Basin discovered that YOY carp are only found in shallow waters that experience winter hypoxia (winterkill) and have low densities of the native egg-predators that otherwise dominate these locales. A follow-up experiment tested if native fish predation on carp eggs could explain this distribution. It found that while carp eggs survived in winterkill lakes, they only survived in non-winterkill lakes when protected by a mesh that excluded fish. Large numbers of carp eggs were found in the stomachs of native fish inhabiting lakes that did not winterkill. We conclude that common carp, and likely many other highly mobile and fecund invasive fish, have evolved life histories to avoid egg predators and can become invasive when they are absent. [ABSTRACT FROM AUTHOR]

Despite the central role that female mate choice plays in the production of biological diversity, controversy remains concerning its evolution and maintenance. This is particularly true in systems where females are choosy but do not receive obvious direct benefits such as nuptial gifts that increase a female's survival and fecundity. In the absence of such direct benefits, indirect benefits (i.e., the production of superior offspring) are often invoked to explain the evolution of mate choice. However, females may receive less obvious, or "cryptic," direct benefits, particularly in species with prolonged pre-mating interactions (e.g., precopulatory mate guarding). We assessed the 'cryptic' direct benefits of female choice for large male size in two species of freshwater amphipods that do not receive obvious direct benefits. Females paired with large males experienced decreased predation from fish. However, we found that the size of a female's mate did not affect her predation risk against predatory dragonflies or the harassment she received by single males while paired. Our results demonstrate that even when females receive no traditional direct benefits, female choice for large male size can still provide important direct benefits. Such 'cryptic' direct benefits may be common, especially in species with prolonged mating interactions, and are likely important for fully understanding the evolution of mate choice. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity in response to environmental cues can create distinct morphological types within populations. This variation in form, and potentially function, may be a factor in initiating population divergence and the formation of new species. Here we show the translation of sympatric, habitat-specific morphological divergence into performance differences in energy economy, maneuverability and steady-state locomotion. Littoral and pelagic bluegill sunfish ecomorphs show differences in performance that appear adaptive within their respective habitats: greater maneuverability in the heavily vegetated littoral; greater steady-state swimming speed and economy in the open-water pelagic. This represents a trade-off in unsteady versus steady swimming performance, likely because morphological features associated with maximizing maneuverability are incompatible with enhancing steady-swimming performance. This may constrain the direction of adaptive change, maintaining the divergence created by phenotypic plasticity. The combination of habitat specific sympatric adaptation and constraints imposed by performance trade-offs may be an important factor underlying the high rate of speciation in freshwater fishes from post-glacial lakes. [ABSTRACT FROM AUTHOR]

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]

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]

As disease incidence increases worldwide, there is increased interest in determining the factors controlling parasitism in natural populations. Recently, several studies have suggested a possible role of predation in reducing parasitism, but this idea has received little experimental attention. Here, I present the results of an experiment in which I manipulated predation rate in large field enclosures to test the effects of predation on parasitism using a bluegill predator– Daphnia host–yeast parasite system. Based on previous work showing high bluegill sunfish selectivity for infected over uninfected Daphnia, I anticipated that predators would reduce infection levels. Contrary to expectations, predation did not reduce infection prevalence. Instead, there were large epidemics in all treatments, followed by reductions of host density to very low levels. As Daphnia density decreased, phytoplankton abundance increased and water clarity decreased, suggesting a parasite-driven trophic cascade. Overall, these results suggest that selective predation does not always reduce infection prevalence, and that parasites have the potential to drastically reduce host densities even in the presence of selective predators. [ABSTRACT FROM AUTHOR]

Prey fish selection by Far Eastern catfish and largemouth bass were examined using bluegill, Japanese dace and crucian carp as food fish. In both aquaria (1.2 m × 0.45 m) and ponds (2.8 m × 1.2 m), bluegill was not preyed on by catfish and bass more than dace and crucian carp. In aquaria, there was no significant difference in the consumption of dace and crucian carp between catfish and bass, but in ponds, catfish preyed on dace and crucian carp more and less than bass, respectively. In the case that only bluegill and catfish were introduced in ponds, catfish consumed 4–15 g of bluegill per day. The introduction of catfish into ponds and lakes for the purpose of eradicating bluegill is considered appropriate for areas with few native fish species. [ABSTRACT FROM AUTHOR]

Bluegill sunfish (Lepomis macrochirus) are known to diversify into two forms specialized for foraging on either limnetic or littoral prey. Because juvenile bluegills seek vegetative cover in the presence of largemouth bass (Micropterus salmoides) predators, natural selection should favor the littoral body design at size ranges most vulnerable to predation. Yet within bluegill populations, both limnetic and littoral forms occur where vegetation and predators are present. While adaptive for foraging in different environments, does habitat-linked phenotypic variation also influence predator evasiveness for juvenile bluegills? We evaluate this question by quantifying susceptibility to predation for two groups of morphologically distinct bluegills; a limnetic form characteristic of bluegills inhabiting open water areas (limnetic bluegill) and a littoral form characteristic of bluegills inhabiting dense vegetation (littoral bluegill). In a series of predation trials, we found that bluegill behaviors differed in open water habitat but not in simulated vegetation. In open water habitat, limnetic bluegills formed more dense shoaling aggregations, maintained a larger distance from the predator, and required longer amounts of time to capture than littoral bluegill. When provided with simulated vegetation, largemouth bass spent longer amounts of time pursuing littoral bluegill and captured significantly fewer littoral bluegills than limnetic fish. Hence, morphological and behavioral variation in bluegills was linked to differential susceptibility to predation in open water and vegetated environments. Combined with previous studies, these findings show that morphological and behavioral adaptations enhance both foraging performance and predator evasiveness in different lake habitats. [ABSTRACT FROM AUTHOR]

Gills of bluegill sunfish, Lepomis macrochirus, exhibited varied degrees of structural damage following a 24-h exposure to sublethal concentrations (15 μg/l, 30 μg/l, 45 μg/l, 60 μg/l and 75 μg/l) of Diazinon [ O, O-diethyl- O-(2-isopropyl-6-methyl-4 pyrimidinyl ester or phosphorothioate]. Exposure to 15 μg/l and 30 μg/l resulted in exocytosis of some material to the cell surface and perforations of the microridges. At higher doses (above 45 μg/l), the extrusion was reduced and the cells were swollen. Compared to control values, the thickness of the microridge on the gill arch and on the gill filament generally increased with exposure to Diazinon. Also, the distance between microridges decreased with increased exposure concentrations. At 60 μg/l, gill arch microridges fused and some ridges of gill filaments disappeared. At 75 μg/l exposure, epithelial cells of the gill arch became obscured with severe cellular extrusions and the lamellar surfaces swelled. The mucus extrusion, lamellar swelling and reduced microridges may be related to a defence mechanism which reduces the water surface around the gill and increases the barrier distance for diffusion of toxicants from outside to the blood capillaries. Although this mechanism protects the fish from toxicants, it also reduces the oxygen supply which leads to suffocation of the fish. [ABSTRACT FROM AUTHOR]

Bluegill sunfish (Lepomis macrochirus) and fathead minnow (Pimephales promelas) responses to a nonionic linear alcohol ethoxylate (LAE) surfactant were examined in 10-day laboratory and 30-day outdoor stream mesocosm experiments. Larval fathead minnow survival was determined in a 10-day laboratory study with nominal concentrations of 0, 1.0, 3.0, 7.0, 13.0 and 25.0 mg LAE l−1. Bluegill sunfish survival and growth and fathead minnow survival, reproduction and behaviour were evaluated in replicated stream mesocosms with mean measured concentrations of 0, 0.73, 2.04, 4.35, 5.7 and 11.24 mg LAE l−1. The 10-day laboratory No Observed Effect Concentration (NOEC) for larval fathead minnow survival was 1.0 mg l−1. The 30-day stream NOEC for bluegill sunfish survival and growth was 5.7 mg l−1. In the stream mesocosms, NOECs for adult fathead minnow survival, reproduction and behaviour were 2.04 mg l−1, 0.73 mg l−1 and 0.73 mg l−1, respectively. Surviving fathead minnows that had ceased reproduction following exposure to LAE in the streams re-established normal reproduction during a post- treatment observation period in the laboratory. Laboratory studies in conjunction with the stream mesocosm study yielded complementary results which provided a detailed assessment of threshold responses of fish to LAE [ABSTRACT FROM AUTHOR]

The effects of tadpole body size, tadpole sibship, and fish body size on predation of gray treefrog tadpoles, Hyla chrysoscelis, were studied in laboratory and artificial pond experiments. Tadpole body size had a significantly positive effect on the survival of tadpoles in all experiments. The relationship between tadpole biomass eaten and biomass available suggested that fish were not satiated when consuming the largest tadpoles. Large tadpoles were probably better able to evade predators. A difference in survival among full sib families of tadpoles was only present in one family, suggesting that genetic differences in predator avoidance behavior or palatability were probably secondarily important to body size per se. Fish body size had a significantly negative effect on the survival of tadpoles. Larger fish consumed a larger number and proportion of tadpoles as well as greater biomass. These results indicate that environmental factors affecting the growth rate of tadpoles cand dramatically alter their vulnerability to gape-limited predators. [ABSTRACT FROM AUTHOR]

The article presents a study regarding the cloning the alpha 2-macroglobulin (α2-M), proteinase substance in the plasma of vertebrates and invertebrates, from bluegill or Lepomis macrochirus. It mentions that the researchers observe the transcription the organs such as liver, brain, heart, gonad, muscle, kidney and gill of the fish during the breeding season. They also examine the similarities and differences of gene sequence of bluegill to other species' gene sequences. Moreover, they state that the transcription of α2-M is present in the liver and brain of bluegill.

We evaluated how water residence time mediated the impact of zebra mussels Dreissena polymorpha and bluegill sunfish Lepomis macrochirus on experimental food webs established in 1100-l outdoor mesocosms. Water residence time was manipulated as a surrogate for seston resupply- a critical variable affecting growth and survival of suspension-feeding invertebrates. We used a 2x2x2 factorial experimental design with eight treatment combinations (3 replicates/treatment) including the presence or absence of Dreissena (2000 per m2), juvenilebluegill (40 per mesocosm), and short (1100 l per d) or long (220 l per d) water residence time. Measures of seston concentration (chlorophyll a, turbidity and suspended solids) were greater in the short- compared to long water-residence mesocosms, but intermediate in short water-residence mesocosms containing Dreissena. Abundance of rotifers(Keratella and Polyarthra) was reduced in Dreissena mesocosms and elevated in short residence time mesocosms. Cladocera abundance, in general, was unaffected by the presence of Dreissena; densities were higher in short-residence time mesocosms, and reduced in the presence ofLepomis. The growth of juvenile Lepomis were unaffected by Dreissenabecause of abundant benthic food. The final total mass of Dreissena was significantly greater in short- than long-residence mesocosms. Impacts of Dreissena on planktonic food webs may not only depend on thedensity of zebra mussels but also on the residence time of the surrounding water and the resupply of seston. [ABSTRACT FROM AUTHOR]