Larval Bluegill Research Articles

Competition during early ontogeny: Effects of native and invasive planktivores on the growth, survival, and habitat use of bluegill

Abstract Early life stages of fishes are sensitive to ecological and environmental disturbances and experience very high mortality rates. During early ontogeny, the growth and survival of larval fish often depends on food availability. Because habitat and diet shifts are strongly tied to individual body size, factors that influence the growth rates of individuals (e.g. resource limitation, competition) also affect other aspects of ontogeny including the timing of habitat or diet shifts. In the context of biological invasions, non‐native species can potentially disrupt the interaction of larval fish with their food via competition for shared prey, reducing growth and survival during a vulnerable period of an organism's life history. We hypothesised that invasive planktivores negatively affect native species through the vulnerable larval life stage via competition for zooplankton resources. To test this hypothesis, we conducted a series of experiments to assess and contrast the effects of invasive (bighead carp, Hypophthalmichthys nobilis) and native (golden shiners, Notemigonus crysoleucas) planktivores on zooplankton densities, and their effects on the growth, survival, abundance, and habitat use of larval bluegill (Lepomis macrochirus). Overall, the effects of the invasive planktivore were consistently greater than the native planktivore in terms of reduced prey densities, reduced bluegill growth rates, and delays to the timing of ontogenetic habitat shifts. Growth rates of bluegill larvae were reduced by 58–87% in the presence of bighead carp and 37% in the presence of golden shiners (relative to controls), but such reductions did not consistently lead to reduced survival (in mesocosm experiment) or relative abundance (in pond experiment). However, we estimated that bighead carp and golden shiners delayed ontogenetic habitat shifts in bluegill by 9–24 and 1–3 days, respectively. Although we did not detect an effect of planktivores on the numbers of larval bluegill, our findings suggest that bighead carp may still affect bluegill ontogeny and freshwater food webs by disrupting the timing of ontogenetic habitat shifts. By affecting the coupling of habitats via organism movements during early ontogeny, bighead carp may indirectly disrupt predator–prey interactions of native taxa.

Use of main channel and two backwater habitats by larval fishes in the Detroit River

Recent investigations in the Detroit River have revealed renewed spawning activity by several important fishes, but little is known about their early life history requirements. We surveyed two main channel and two backwater areas in the lower Detroit River weekly from May to July 2007 to assess habitat use by larval fishes. Backwater areas included a soft-sediment embayment (FI) and a hard-sediment area (HIW). Main channel sites were located adjacent to each backwater area. Water temperature, velocity and clarity measurements and zooplankton samples were collected weekly. A macrophyte assessment was conducted in July. Growth and diet of larval yellow perch (Perca flavescens), bluegill (Lepomis macrochirus) and round goby (Neogobius melanostomus) were used to assess habitat quality. Macrophyte diversity and percent cover were higher and velocity lower at FI than HIW. Although larval fish diversity was highest in the main channel, yellow perch and bluegill larvae only grew beyond the yolk stage at FI, where they preferentially selected copepods, while Daphnia were selected in the main channel. Round goby ate harpacticoid copepods and Daphnia and grew at similar rates in HIW and the main channel. These data indicate that FI was a valuable nursery area for yellow perch and bluegill, whereas HIW was better suited to round goby. We only assessed two backwater areas, thus a complete census of wetland areas in the Detroit River is needed to identify valuable habitats. Restoration of shallow backwater areas is essential for rehabilitating fish populations and should be a priority in the Detroit River.

Growth and Survival of Largemouth Bass following Supplemental Feeding of Bluegills in Small Impoundments

AbstractWe investigated whether providing supplemental pellet feed to Bluegills Lepomis macrochirus in small impoundments increased their growth and reproductive rates after stocking and whether the supplemental feeding of Bluegills had positive indirect effects on Largemouth Bass Micropterus salmoides during the initial stocking year. In 2010, we stocked adult Bluegills and Largemouth Bass into nine 0.1‐ha ponds; three replicate ponds were each provided with no pelleted food (control), a low ration (1.52 kg·ha−1·d−1), or a high ration (2.68 kg·ha−1·d−1). Supplemental feeding yielded increases in the growth of newly stocked Bluegills, the gonadosomatic index of female Bluegills, and the density of larval Bluegills within 4 months of stocking. In contrast, the sizes of adult and age‐0 Largemouth Bass and the density and biomass of age‐0 Bluegills during fall were not affected by feeding within the time frame of our study. The results demonstrate that supplemental pellet feeding is useful when the management goal is to increase Bluegill size and reproductive output and that these effects develop soon after stocking. We conclude that supplemental feeding is a beneficial enhancement technique for application to Bluegills in recently stocked impoundments.Received May 13, 2012; accepted November 20, 2012

Match–Mismatch Regulation for Bluegill and Yellow Perch Larvae and Their Prey in Sandhill Lakes

AbstractFood availability may regulate fish recruitment, both directly and indirectly. The availability of zooplankton, especially to newly hatched larvae, is thought to be crucial to their early growth and survival. We examined stomach contents of larval bluegill Lepomis macrochirus and yellow perch Perca flavescens in Pelican Lake and Cameron Lake, Nebraska, in 2004 and 2005. We also determined zooplankton availability and calculated prey selection using Chesson's α. In addition, we investigated potential match–mismatch regulation of recruitment from 2004 to 2008. Bluegill positively selected copepod nauplii and Bosmina spp., and yellow perch often selected copepods. Abundant zooplankton populations were available for consumption. Matches of both larval bluegill and yellow perch abundance to zooplankton abundance were detected in all years; exact matches were common. Mismatches in predator and prey production were not observed. Predation by age-0 yellow perch on age-0 bluegill was not observed, even though yellow perch hatched 2 mo prior to bluegill. Given that zooplankton were abundant and well-timed to larval fish relative abundance over the time span of this study, the match–mismatch hypothesis alone may not fully account for observed recruitment variability in these populations. Environmental conditions may also affect recruitment and warrant further investigation.

Intra‐ and Intersystem Variation in Largemouth Bass Recruitment: Reproduction, Prey Availability, and the Timing of Year‐Class Establishment

AbstractIncorporating potentially important events during the first year of life across multiple environmental conditions is needed to generalize models of fish recruitment. Using previous conceptual models as a framework, we quantified sources of intra‐ and intersystem variation in recruitment of largemouth bass Micropterus salmoides. We measured age‐0 abundances, first‐year growth, and potentially important environmental variables across 12 populations and 5–7 year‐classes. Interpopulation differences in average recruitment to age 1 were set by variation in number of age‐0 fish surviving to the fall. Survival to fall was in turn positively related to density of juvenile bluegills Lepomis macrochirus. First‐year growth was positively related to turbidity and adult largemouth bass abundance. For individual lakes, variables explaining a significant amount of intrapopulation variation in recruitment strength were factors associated with either production of age‐0 fish from the parental care stage (peak density of age‐0 largemouth bass) or prey fish abundance (densities of larval and juvenile bluegills). Abundance of larval bluegills was higher in systems where largemouth bass recruitment to age 1 was not related to bluegill abundance than in lakes where recruitment strength was sensitive to annual fluctuations in prey fish abundance. The relationship between output from the parental care stage and recruitment strength suggests that largemouth bass management should focus on actions designed to influence nest success. Where recruitment is also limited by prey fish availability, management actions can also be directed towards community attributes that influence the growth and production of important prey species.

Ultraviolet radiation affects invasibility of lake ecosystems by warm‐water fish

Predicting where species invasions will occur remains a substantial challenge in ecology, but identifying factors that ultimately constrain the distribution of potential invaders could facilitate successful prediction. Whereas ultraviolet radiation (UVR) is recognized as an important factor controlling species distribution and community composition, the role of UVR in a habitat invasibility context has not been explored. Here we examine how underwater UVR can regulate warm-water fish invasion. In Lake Tahoe, California and Nevada, USA, established populations of exotic bluegill sunfish (Lepomis macrochirus) are currently limited to turbid, low-UVR embayments. An in situ incubation experiment that manipulated incident UVR exposure of larval bluegill, combined with an assessment of UVR exposure levels in nearshore habitats around Lake Tahoe, demonstrates that UVR can mediate habitat invasibility. Our findings suggest that the susceptibility to invasion by UVR sensitive species may increase in transparent aquatic systems threatened by declining water quality, and they highlight the importance of abiotic factors as regulators of invasion risk in ecosystems.

Patterns of Ultraviolet Radiation Exposure in Bluegill Nests over the Course of the Spawning Season

AbstractUltraviolet radiation (UVR; wave length, 280‐400 nm) can be an important source of mortality for fish, particularly during early life history stages. Because UVR exposure varies seasonally owing to solar angle, climatic conditions, and changes in the UV transparency of water, UVR‐induced mortality among temperate fishes may vary as a function of spawning time. We examined patterns of UVR exposure in nests of bluegill Lepomis macrochirus over the course of a spawning season in a highly transparent lake in northeastern Pennsylvania. At the beginning, middle, and end of the spawning season, we measured nest depth and estimated the cumulative UVR exposure of all bluegill nests along three 250‐m transects. Cumulative exposure was then used to predict the UVR‐induced mortality for bluegill larvae in each nest. The median UVR exposure in bluegill nests was highest at the start of the spawning season, and the predicted UVR‐induced larval mortality was at least 10% in 38% of the nests. As the season progressed, the median UVR exposure decreased, and only 4% of the nests were predicted to have larval mortality of at least 10% by the middle and end of the spawning season. This decrease in exposure was partly due to a seasonal decline in UVR transparency. In addition, mean nest depth increased over the course of the spawning season, as bluegills increasingly nested at depths of 4 m or more. Because UVR attenuates with depth, deeper nests received less UVR exposure than did nests closer to the surface. For many species, reproductive success is strongly dependent on spawning time. Our results suggest that in some systems a consequence of early spawning may be an increased risk of UVR‐induced mortality.

Quantifying Ultraviolet Radiation Mortality Risk In Bluegill Larvae: Effects Of Nest Location

Ultraviolet (UV) radiation (280-400 nm) is an increasing threat to aquatic organisms due to stratospheric ozone depletion and reductions in concentrations of dissolved organic carbon. Because fish are most vulnerable to UV during the egg and larval stages, parental spawning site selection can strongly influence mortality risk. We examined the role of nest location in determining UV-induced mortality risk for bluegill (Lepomis macrochirus) in Lake Giles, Pennsylvania, USA. In a series of five short-term incubation experiments, we found that survival of yolk sac larvae across the range of depths at which bluegill spawn was significantly lower in the presence of ambient-UV levels relative to larvae that were shielded from UV radiation. In addition, survival decreased as a function of cumulative UV exposure, as measured by the number of cyclobutane pyrimidine dimers per megabase DNA in DNA dosimeters. Although UV had the potential to significantly reduce larval survival, DNA dosimeters placed in bluegill nests concurrently with incubation experiments indicated that most nests were exposed to relatively low levels of UV. Only 19% of nests had predicted UV-induced mortality greater than 25%. Consequently, current levels of UV may be an important mortality source at the level of individual nests, but not at the population level. One reason for the weak predicted effect of UV on bluegill survival is that many nests were located at depths by which much of the incident UV had been attenuated. In addition, many of the shallower nests were protected by overhanging trees or other submerged structures. It is important to note that Lake Giles is highly transparent and therefore not representative of all lakes in which bluegill are found. Nevertheless, Lake Giles is a natural system and may be representative of north temperate lakes in the future.

Food web interactions between larval bluegill (Lepomis macrochirus) and exotic zebra mussels (Dreissena polymorpha)

Food web interactions between native larval bluegill (Lepomis macrochirus), exotic invasive zebra mussels (Dreissena polymorpha), and zooplankton were examined with a mesocosm experiment. Hatchling larval bluegill collected from nests were reared in the presence of size-structured populations of zebra mussels in 1500-L limnocorrals suspended in an artificial pond for 2 weeks. Chlorophyll a, other limnological variables, and zooplankton abundance and biomass (including copepod nauplii and rotifers) were monitored over time. During their first 2 weeks of life, larval fish reared in the presence of mussels grew 24% more slowly than fish reared alone. Differential growth rates can be explained by competition between mussels and bluegill for food in the form of microzooplankton. Also likely was an indirect competition via starvation of the zooplankton community as zebra mussels consumed phytoplankton. Either direct or indirect trophic competition between zebra mussels and obligate planktivores may result in ecological harm as zebra mussels spread throughout inland lakes of North America.

Zooplankton responses to predation by larval bluegill: an enclosure experiment

SUMMARY 1. Larval fish are gape‐limited predators that forage on prey of specific sizes, and thus may be expected to differentially affect members of a zooplankton community, possibly altering the size‐structure or species composition.2. I used an enclosure experiment to look at the effect of predation by larval bluegill on the dynamics of two zooplankton communities, one dominated by large‐bodied individuals and the other by small‐bodied individuals. Enclosures containing these zooplankton received a zero, low, medium, or high density of larval bluegill predators.3. Increasing larval density had a negative effect on zooplankton abundance and abundance declined similarly in the large‐bodied and small‐bodied communities.4. Zooplankton size‐structure, as estimated by the length of the average zooplankton, increased and then decreased during the experiment, decreasing faster at higher larval fish densities. When zooplankton size‐structure was estimated as the length of the average cladoceran, size‐structure declined in the large‐bodied but not in the small‐bodied community and the greatest decline in size‐structure was seen in the medium and high larval density treatments.5. Ordination of each community using multidimensional scaling (MDS) indicated that the trajectory of change in species composition differed between the presence and absence of larval fish. In both communities, the degree of response by individual taxa depended on the density of bluegill larvae. This effect on zooplankton abundance, size‐structure and community composition suggests that larval fish may make an important contribution to zooplankton dynamics in many lakes and ponds.

The Effects of Growth, Predation, and First-Winter Mortality on Recruitment of Bluegill Cohorts

Abstract Previous work with centrarchid fishes suggests that recruitment success is higher for fish hatched early in the spawning season. Similar recruitment patterns have been shown for bluegills Lepomis macrochirus, but only in piscivore-free waters and at the northern extent of their range. We investigated the role of predation and first-winter mortality in governing bluegill recruitment. Spawning date distributions for larval bluegills taken in ichthyoplankton tows were compared with distributions for juveniles in shoreline rotenone samples from the fall and the following spring. Daily otolith rings were used to determine ages and spawning dates for bluegills in Ridge Lake, Illinois, during 3 years. Spawning took place from mid-May to mid-August of each year and produced several peaks in larval abundance. Differences between the spawning date distributions of larval bluegills and juveniles surviving to fall suggested that fish spawned early in the season experienced higher mortality than those spawned...

Influence of gizzard shad on phytoplankton size and primary productivity in mesocosms and earthen ponds in the southeastern U.S.

Gizzard shad (Dorosoma cepedianum), a filter feeding omnivore, can consume phytoplankton, zooplankton and detritus and is a common prey fish in U.S. water bodies. Because of their feeding habits and abundance, shad have the potential to affect primary productivity (and hence water quality) directly through phytoplankton grazing and indirectly through zooplankton grazing and nutrient recycling. To test the ability of shad to influence primary productivity, we conducted a 16-day enclosure study (in 2.36-m3 mesocosms) and a 3-year whole-pond manipulation in 2–5 ha earthen ponds. In the mesocosm experiment, shad reduced zooplankton density and indirectly enhanced chlorophyll a concentration, primary productivity, and photosynthetic efficiency (assimilation number). While shad did not affect total phytoplankton density in the mesocosms, the density of large phytoplankton was directly reduced with shad. Results from the pond study were not consistent as predicted. There were few changes in the zooplankton and phytoplankton communities in ponds with versus ponds without gizzard shad. One apparent difference from systems in which previous work had been conducted was the presence of high densities of a potential competitor (i.e., larval bluegill) in our ponds. We suggest that the presence of these extremely high larval bluegill densities (20–350 larval bluegill m−3; 3–700 times higher density than that of larval gizzard shad) led to the lack of differences between ponds with versus ponds without gizzard shad. That is, the influence of gizzard shad on zooplankton or phytoplankton was less than the influence of abundant bluegill larvae. Differences in systems across regions must be incorporated into our understanding of factors affecting trophic interactions in aquatic systems if we are to be able to manage these systems for both water quality and fisheries.

Direct and Indirect Effects of Gizzard Shad on Bluegill Growth and Population Size Structure

Abstract Competition with gizzard shad Dorosoma cepedianum has been shown to influence survival of larval bluegills Lepomis macrochirus as well as growth and size structure of largemouth bass Micropterus salmoides, which prey on these planktivorous species. However, little is known about how the presence of gizzard shad influences bluegills beyond the larval stage. We examined bluegill–gizzard shad interactions across 10 reservoirs with and 10 without gizzard shad to determine direct and indirect effects of gizzard shad on bluegill population size structure. In the presence of gizzard shad, bluegills exhibited smaller adult (>3 years old) size structure. Benthic invertebrate densities were higher in non-gizzard shad reservoirs, which may have contributed to increased bluegill growth in these systems. In contrast, zooplankton densities were similar in reservoirs with and without gizzard shad. Turbidity was higher in reservoirs with gizzard shad, which may have reduced foraging success and growth of bluegil...

Interactions between adult and larval bluegill sunfish: positive and negative effects.

Adult fish may affect the growth and survival of conspecific larvae through a variety of pathways, including negative interactions via competition for shared limiting resources or via predation (i.e., cannibalism), and positive interactions due to the consumption of larval predators and via resource enhancement (i.e., presence of adults increases availability of larval prey). To examine the overall effect of adult bluegill sunfish (Lepomis macrochirus) on larval bluegill, we conducted a field experiment in which we manipulated adult densities and quantified larval growth and survival, prey abundance, invertebrate predator abundance, and cannibalism. The presence of adult bluegill had a negative effect on final larval mass. This response was consistent with competition for zooplankton prey. Adult bluegill reduced the abundance of large zooplankton (e.g., Chaoborus and Daphnia), which were the dominant prey of bluegill larvae in the absence of adults. Larvae in the no-adult treatment also had significantly more prey in their stomachs compared to larvae in the presence of adults. Larval survival was maximized at intermediate adult densities and the overall production of larvae peaked at intermediate adult densities. The higher larval survival at intermediate adult densities is attributed to a reduction in invertebrate predators in treatments with adult bluegill; invertebrate predators experienced an 80% reduction in the presence of adult fish. Decreased larval survival at the highest adult density was not due to resource limitation and may be due to cannibalism, which was not directly observed in our study, but has been observed in other studies.

Adult Fish Predation on Freshwater Limnetic Fish Larvae: A Mesocosm Experiment

Abstract We demonstrated that predation by adult bluegills Lepomis macrochirus and white crappies Pomoxis annularis may be a major source of mortality for freshwater larval fish. In 5.3-m3 mesocosms, we compared the survival of larval bluegill prey (19 larvae/m3; mean standard length (SL), 8.6 mm; range, 3–22 mm) in the presence of adult bluegills, adult white crappies, or adult gizzard shad Dorosoma cepedianum with the survival of predator-free controls. The duration of the experiments was 3.7 h for bluegills, 3.2 h for white crappies, 5.5 h for gizzard shad, and 4.3 h for the predator-free controls. Larval fish survival in both the bluegill and white crappie predator treatments was lower than that of the predator-free controls, whereas larval fish survival in the gizzard shad treatments did not differ from that of the controls. The instantaneous hourly mortality rate attributable to predation was 0.11 for bluegill (9.8 larvae consumed/predator each hour) and 0.05 for white crappie (4.8 larvae consumed/p...

Regulation of Growth and Mortality in Larval Bluegills: Implications for Juvenile Recruitment

Abstract Factors related to growth and survival of 10-d cohorts of larval bluegills Lepomis macrochirus were examined in two small impoundments via daily growth increments on otoliths. Successful spawning occurred from April through September, producing peak larval densities greater than 360 fish/m3. Larval bluegill density was negatively correlated with zooplankton density in both ponds, suggesting that larvae reduced zooplankton abundance via predation. Several variables were related to larval growth and mortality. Cohorts whose larval densities were low tended to have faster growth and higher survival than cohorts with high larval densities. The mechanism responsible for this density-dependent relation was not clear in all instances; however, some evidence suggested that control occurred via intraspecific competition for zooplankton. Relative survival of larval bluegills to the juvenile stage was negatively correlated with limnetic larval fish density; however, no relations were detected between larval...

Growth and Survival of Larval Bluegills in the Laboratory under Different Feeding Regimes

Abstract The objective of this study was to develop a procedure for rearing larval bluegills Lepomis macrochirus in tanks. In preliminary experiments, seven commercial diets were fed to larval bluegills from the onset of exogenous feeding to 28 d posthatch. Although all diets were eaten by the larvae, none were observed to pass through the fish's digestive tract, and survival was essentially zero. In the next set of experiments, bluegill larvae survived on commercial diets when they were fed nauplii of brine shrimp Artemia franciscana for an initial 7-d period before being switched to commercial feed. Using this protocol, we compared three feeds (BioKyowa Fry Feed Kyowa B-250, Argent Hatchery Encapsulon Grade II, and Zeigler Larval AP-100) over a 28-d period. There were no significant (α = 0.05) differences in growth (length and weight) among fish fed the three diets at the end of 28 d, but survival was significantly higher for fish fed BioKyowa. In another experiment, we fed BioKyowa to larval bluegills after feeding them brine shrimp nauplii for 3, 7, or 14 d. Larvae fed brine shrimp for 14 d had significantly higher growth and survival than larvae in the other two treatments. Our results indicate that the feeding protocol for tank-rearing larval bluegills should start with brine shrimp before a commercial diet is used.

Foraging Characteristics of Larval Bluegill Sunfish and Larval Longear Sunfish in the Kanawha River, West Virginia

ABSTRACT We determined spatial and temporal foraging characteristics of larval bluegill sunfish (Lepomis macrochirus) and longear sunfish (Lepomis megalotis)in the upper Kanawha River, West Virginia during the summer of 1989. Stomach contents were examined among habitat types (i.e., main channel, main-channel border, and shoreline habitats) and depth (surface, middle, and bottom). Diet of larval bluegill sunfish was dominated by Chironomidae, temporally and spatially. Chironomidae dominated larval longear sunfish diet in main channel and main-channel border collections from all three depths. However, along the shoreline, larval longear sunfish diet was dominated by Cladocera.

Predation by Hydra on larval fish: Field and laboratory experiments with bluegill (Lepomis macrochirus)

We found high population densities of Hydra canadensis (up to 30,000 m−2) on macrophytes in Lake Opinicon (Ontario, Canada) and tested whether they influenced the survival of larval bluegill, Lepomis macrochirus. Hydra were observed to capture and ingest bluegill larvae in laboratory trials. Individuals that ingested fish larvae turned black; those fed a variety of crustacean species remained brown. The ingestion rate of Hydra on larvae in 8‐liter laboratory microcosms was higher during the night (0.197 larvae predator−1 h−1) than during the day (0.111 larvae predator−1 h−1). Many larvae also died after escaping from the stinging tentacles of Hydra (on average 26% of larval mortality). Population densities of Hydra were highest on the macrophyte Myriophyllum spicatum. Bluegill colonies were surrounded by dense beds of M. spicatum in some areas, and larvae in the colonies had to swim through the plants (with the attached Hydra) in order to reach open water. We sampled Hydra in the vicinity of bluegill colonies on the morning after larval swim‐up. The number of black Hydra decreased with increasing distance from a colony; 72% black within colonies, 45% at 0.5 m outside colonies, and 31% at 2 m outside of colonies. We estimate that up to 20% of the larvae produced by a colony can be killed by Hydra within this 2‐m zone. Many more larvae likely die as a result of encounters with Hydra that are abundant throughout the lake.

Morphological and Growth Rate Differences between Bluegill Males of Alternative Reproductive Life Histories

We characterized the morphology of mature cuckolder and mature parental male bluegills Lepomis macrochirus from Lake Opinicon, Ontario. By rearing bluegill larvae to maturity in experimental ponds in Illinois we also examined whether morphological differences between males of the two reproductive life histories were conserved across widely varying environmental conditions. Cuckolder and parental males collected in Lake Opinicon differed in their size-adjusted body shape. They also differed in their pattern of mass allocation to testis versus somatic tissue. Cuckolder males allocated significantly more of their total body mass to testes compared to parental males. Body shape and testis:somatic ratio differences between male types reared in experimental ponds in Illinois were nearly identical to those observed in bluegills from Lake Opinicon. This divergence between male types remained consistent even when bluegills were reared over a 10-fold variation in growth rate. Average growth rate within ponds was strongly associated with the probability that a male would mature as a parental male within the first year. However, the proportion of males maturing as cuckolders was relatively constant among ponds and was not influenced by growth rate differences. These findings have important implications for management of bluegills and other Lepomis species where growth differences or reproductive divergence occur within single populations.