Parental care and the ontogeny of predator-avoidance in two species of centrarchid fish

Stamps (1978) suggested that the type and extent of parental care can influence the behavioural ontogeny of the offspring. Largemouth bass (Micropterus salmoides) males guard the fry for up to a month after they leave the nest while rock bass (Ambloplites rupestris) males guard the fry only until they leave the nest. In laboratory experiments, naive largemouth fry displayed reduced predator-avoidance responses to large and small predators during their first 3 weeks of free-swimming. Rock bass fry, on the other hand, avoided predators throughout the study period. From 6 weeks (largemouth) and 5 weeks (rock bass) of age the fry showed a significantly greater response to the large predator than the small predator. The responses of laboratory-reared largemouth bass fry to the small predator changed from avoidance to association as the fry grew. The size of the fry relative to predator size was found to be important.     

Effects of sulphuric acid exposure on the behaviour of largemouth bass,Micropterus salmoides

Synopsis Young-of-the-year largemouth bass,Micropterus salmoides, were exposed to four concentrations of sulphuric acid (pH levels 7.2, 6.1, 4.8, and 3.7) for 30 days, and the frequencies of feeding acts and activity bouts, and time budgets were recorded. Juveniles at pH 6.1 and at pH 4.8 performed the two feeding acts, bites and orientations, more often, and spent more time feeding than bass at pH 7.2. Bass at pH 3.7, however, reduced feeding, and spent a significantly larger portion of their time hovering in the water column. Frequencies of comfort and agonistic acts increased with a decline in pH. Alterations of behavioural repertoires of young-of-the-year largemouth bass were useful indicators of sulphuric acid exposure.     

Examining the effects of chronic,lake-wide elevated temperatures on behavioural expression in largemouth bass,Micropterus salmoides

Many behaviours have differential fitness consequences across thermal and ecological contexts, indicating that both ecological shifts and warming temperatures induced by climatic change may alter how organisms behave. However, empirical evidence of temperature-driven behavioural selection in natural systems is lacking. We compared behaviours and behavioural syndromes related to activity, exploration, boldness and aggression in populations of largemouth bass (Micropterus salmoides) from ambient lakes to the those from artificially warmed, power plant cooling lakes to investigate changes in behaviours associated with warmer environments. Activity, exploration, boldness and aggression of juvenile largemouth bass were assessed in laboratory conditions using a novel environment assay and a risky situation assay. We found that activity and exploratory behaviours were higher and decreased through first year ontogeny in populations from heated lakes, whereas these behaviours were lower and showed no relationship through ontogeny in populations from ambient lakes. We attribute these differences to the changes in food source availability in heated lakes associated with temperature-driven ecological effects. Bold and aggressive behaviours tended to differ between populations, as did correlations between behaviours, but did not differ between ambient and heated lakes. The findings of this work identify that large ecological changes associated with warming environments, such as food availability, may drive changes in some aspects of behavioural expression in largemouth bass but that other aspects of behavioural expression may be driven by lake-specific factors not related to warming.     

Predator naïve minnows respond to their conspecific alarm substance but not the odour from a non-native predator

When exposed to predator cues, ostariophysan fishes exhibit short-term anti-predator behavioural responses in order to minimise predation risk. Non-native predator cues are, however, likely to elicit poor behavioural responses in native prey fishes. This study investigated whether chubbyhead barb Enteromius anoplus, a native freshwater minnow in South Africa, had the innate ability to recognise and respond to largemouth bass Micropterus salmoides, a non-native piscivore. This was experimentally evaluated by investigating behavioural responses to both the non-native predator's odour and damage-released conspecific alarm substance (CAS). Chubbyhead barbs did not exhibit any behavioural response to largemouth bass odour both before and after exposure to CAS. This suggests that the chubbyhead barbs likely lacked the innate ability to recognise the non-native largemouth bass predator kairomones. By comparison, exposure to CAS was associated with significant behavioural responses, with chubbyhead barbs shifting from free-swimming to hovering, and frequent use of refugia. This suggests that despite ineffective response to non-native largemouth bass odour, chubbyhead barbs responded to general predator attack. Overall, this study suggests the potential for non-native largemouth bass to induce negative consumptive effects on chubbyhead barbs due to their inability to identify non-native predator's odour. In addition, nonconsumptive effects are likely due to altered activities in response to predator attack.     

Predation by rock bass on other stream fishes: experimental effects of depth and cover

Synopsis Effects of water depth and cover availability on predation rates by adult rock bass, Ambloplites rupestris, on juvenile central stoneroller, Campostoma anomalum, pumpkinseed, Lepomis gibbosa, and fantail darter, Etheostoma flabellare, were measured in a laboratory stream. A predation rate experiment and a prey activity experiment were conducted. In the first experiment, each prey type shared experimental chambers with predatory rock bass under all combinations of two depths (shallow and deep) and two cover levels (absent and present). Predation rates after 72 h were greater in deep (35–38 cm) than in shallow (7–10 cm) water for fantail darter and two sizes of central stoneroller, but not for pumpkinseed. Presence of cover (opaque plastic tubes) on the stream bottom had no direct effect on predation rates, which were higher for pumpkinseed and small stoneroller (35–64 mm total length) than for fantail darter and large stoneroller (70–89 mm total length). In the second experiment, diel patterns of small stoneroller activity were monitored under all combinations of two water depths and three levels of predation risk. Small stonerollers were more active during the day and in the absence of rock bass, but were not affected directly by water depth. My results suggest that effects of habitat features (e.g., depth, cover) on predator-prey interactions vary according to the natural history and behavior of particular prey and predators. Future research should integrate habitat-specific responses of prey to predation risk into models that predict the distribution of prey among available habitats.The unit is jointly supported by the U.S. Fish and Wildlife Service, the Virginia Department of Game and Inland Fisheries, the Wildlife Management Institute, and Virginia Polutechnic Institute and State University.     

Performance as a fish predator of largemouth bass [<Emphasis Type="Italic">Micropterus salmoides</Emphasis> (Lacepède)] invading Japanese freshwaters: a review

This review focuses on how predator performance of the invasive largemouth bass [Micropterus salmoides (Lacepède)] has been, or will be, formed in Japanese freshwaters. Predation impacts of largemouth bass on fish communities appear pervasive in both Japanese as well as North American freshwaters. Factors affecting performance as a piscivorous predator are (1) light intensity and water clarity, (2) oxygen depletion, (3) prey size and gape size, (4) behavioral refuge of prey, (5) weed beds as refuge for prey fish, (6) interaction with bluegill. Size and behavioral refuges requirements are so rigorous that they may have evolved only in some North American prey fish species like bluegill; therefore, most Japanese native fish species are unlikely to be equipped with such refuges. However, refuge habitats like aquatic weed beds could develop in Japanese freshwaters, allowing prey fish species to survive under predation pressure. The density, architecture, and species composition of aquatic plants may affect their suitability as refuges. Studies in Japanese waters have suggested that the presence of rich aquatic vegetation or invasive bluegill in bass-introduced waters have suppressed the predation impact of largemouth bass on fish communities. In addition to these environmental factors, original genotypic and phenotypic traits of the introduced largemouth bass, and hybridization between different lineages of largemouth bass or with Florida bass [Micropterus floridanus (Lesueur)] may be involved in further adaptation of invasive largemouth bass to Japanese freshwaters.     

The environmental basis of diet variation in pumpkinseed sunfish, Lepomis gibbosus, and largemouth bass, Micropterus salmoides, along an Iberian river basin

The diet composition of largemouth bass, Micropterus salmoides, and pumpkinseed sunfish, Lepomis gibbosus, and its relation to environmental factors was studied in intermittent watercourses of the lower Guadiana basin (southern Iberia) during the particularly dry summer of 1994. Overall, both species took food items similar to those found in their North American and acclimatised ranges, with pumpkinseed consuming invertebrates (chiefly Chironomidae) and bass preying on invertebrates (chiefly Micronecta meridionalis) and fish (chiefly L. gibbosus and Gambusia holbrooki). Both bass and pumpkinseed were opportunistic feeders, feeding on the most frequent and abundant prey. However, Diptera larvae were apparently preferred by pumpkinseed and avoided by bass, while the contrary occurred with respect to Heteroptera. The two main fish prey of bass were eaten on the basis of random encounter. The relative abundance of macro-prey (i.e. fish and Atyephira desmarestii) were the principal environmental variables constraining bass dietary variation along the basin. On the contrary, pumpkinseed diet variation was mainly related to pumpkinseed size and the presence of piscivorous bass nearby, although habitat size and cyprinid abundance were also influential. This revised version was published online in July 2006 with corrections to the Cover Date.     

Susceptibility of Transgenic and Wildtype Zebra Danios, Danio rerio, to Predation

The effects to ecosystems by genetically modified organisms are still unknown, yet a transgenic version (the red glofish or red fluorescent protein (RFP) transgenic zebra danio) of the zebra danio, Danio rerio, a common aquarium fish, has become the first transgenic pet sold in the USA. It has been hypothesized that RFP zebra danios will not persist in nature because they will be preferentially preyed upon due to their red coloration; however, the bright coloration of wildtype zebra danios may indicate they are aposematic since they are not preyed upon immediately by predators in their native range. These hypotheses were addressed via nine predation experiments with largemouth bass, Micropterus salmoides, as predator and combinations of mosquitofish, Gambusia affinis, wildtype zebra danios, and RFP zebra danios as prey. Neither wildtype nor RFP transgenic zebra danios are aposematic since both varieties were readily consumed by largemouth bass in laboratory trials. Both varieties were preyed upon in approximately equal proportion (1.4 to 1.0) so the bright, apparently conspicuous coloration of the transgenic zebra danios did not increase their susceptibility to predation. In these laboratory trials, largemouth bass did not preferentially prey upon a native fish, the mosquitofish, relative to wildtype zebra danios (1.2 to 1.0). Based on the results of these experiments, wildtype zebra danios and RFP transgenic zebra danios are likely to be preyed upon in a similar fashion as native forage fish.     

An analysis of the mechanisms governing species replacements in crayfish

Summary We investigated mechanisms governing replacement of the native crayfish Orconectes sanborni by an invading cryafish, Orconectes rusticus. The two species had similar life histories, habitat preferences, and feeding patterns in allopatric and sympatric stream areas. Orconectes rusticus young-of-year (YOY) grew faster than O. sanborni YOY in the field. Adult O. rusticus were larger and, hence, dominant over adult O. sanborni; YOY were non-aggressive. In laboratory experiments, adult crayfish (about 28 mm carapace length or larger) were not susceptable to predation by largemouth bass (Micropterus salmoides, 30 cm total length) and did not alter shelter use when fish were present. Orconectes rusticus YOY were less susceptible to predation than O. sanborni YOY. Orconectes rusticus YOY reduced their vulnerability to largemouth bass by occupying shelters more often than YOY O. sanborni. In mixed-species mateselection experiments, male O. rusticus and male O. sanborni preferentially mated with O. rusticus females. Inappropriate mate selection in sympatry may have caused the 90% reduction in recruitment for both species in 1982. Orconectes rusticus probably maintains greater population growth than O. sanborni, because (1) more gravid O. rusticus females occurred in sympatry, (2) O. rusticus produced more young than O. sanborni, and (3) O. rusticus young grew faster. Reproductive interference, acting synergistically with differences in aggressive dominance and young-of-year susceptibility to predation, appears to serve as the major mechanisms regulating replacement of O. sanborni by O. rusticus in Ohio streams.     

Nutritional condition and physiology of paternal care in two congeneric species of black bass (<Emphasis Type="Italic">Micropterus</Emphasis> spp.) relative to stage of offspring development

Parental care requires a complex integration of physiology and behaviour, yet little is known about the physiological and energetic consequences or correlates of these behaviours. Using two species of male black bass (smallmouth bass, Micropterus dolomieu; largemouth bass, M. salmoides) as a model, the focus of this study was to determine the biochemical and hematological indicators of change in nutritional status and potential for chronic stress. This was accomplished by randomly sampling individuals at four stages across parental care. Additionally, a subset of individuals was repeatedly sampled at three brood development stages to track changes in biochemical factors within the individual. Though there were changes in physiological factors across parental care in randomly sampled fish of both species (declines in plasma glucose in largemouth bass; decreases in hematocrit and plasma chloride in smallmouth bass), repeated sampling of individuals was determined to be a more appropriate sampling technique due to natural variability in biochemical factors among individual fish. Repeated sampling of smallmouth bass did not adversely influence physiological metrics or brood abandonment. However, there were higher incidences of nest abandonment in repeatedly sampled largemouth bass. Amongst the repeatedly sampled smallmouth bass, nutritional indicators such as plasma triglyceride levels decreased indicating individual fasting across the majority of parental care. Increases in plasma calcium and magnesium towards the end of care indicated that feeding most likely resumed when the brood was close to independence after ~3 weeks of care. Lastly, several indicators of chronic stress, such as plasma glucose and chloride levels, increased throughout the parental care period. These sublethal stressors are indicative of decreasing body condition associated with prolonged activity and fasting which may have marked impacts on the ability of an individual to continue parental care for the current brood and impact subsequent individual fitness. Further research into the mechanistic relationships between behaviour, physiology, and energetics during the parental care period will provide a better understanding of the decisions by individuals facing multiple trade-offs that ultimately lead to differences in individual fitness.     

Role of diet and experience in the development of feeding behaviour in largemouth bass, Micropterus salmoides

Two groups of largemouth bass, Micropterus salmoides , were reared in the laboratory. One group was reared on an artificial, passive diet (frozen brine shrimp) whereas the second was reared on a natural, active diet (cultured zooplankton). Observations on the development of feeding behaviour indicated that the motor patterns and duration (number of weeks in the behavioural repertoire) of the feeding acts did not differ between fry reared on the two diets. While feeding on their respective diets, natural-diet fry performed significantly more orientations and bites, the two major early feeding acts, than did the artificial-diet fry. When tested with live fish prey, fish reared on the natural diet performed fewer orientations and strikes and captured more prey per fry than did the artificial-diet fry. Natural-diet fry had a significantly better net efficiency (captures minus strikes minus orientations) than did artificial-diet fry. Diet, experience, and length (T.L.) of fry affected their predator efficiency significantly. We argue that providing hatchery-reared bass fry with an opportunity to prey on live forage fish once or twice before their release would enhance their survival and eventual recruitment into natural populations.     

The effects of enhancing cage complexity on the behaviour and welfare of laboratory rats

This experiment was carried out to investigate the long-term effects of enhancing cage complexity on behavioural measures of welfare in laboratory rats. We housed 72 rats in groups of four in either ‘enriched’ or ‘unenriched’ cages for six weeks. Scan and focal animal sampling were conducted in both the light and dark phase of the second, fourth and sixth weeks. Results revealed that rats in the ‘enriched’ cages showed longer durations of sleep behaviour, and low levels of agonistic behaviour compared to rats in the ‘unenriched’ cages. Results importantly demonstrated that the behavioural changes observed in the enriched environment were due to the presence of the enrichments themselves in the cages (indirect effects) and not due merely to rats interacting with the enrichment items in their environment. Thus, enhancing the complexity of conventional laboratory cages can promote behaviour such as longer bouts of sleep that is likely to be indicative of good welfare, and diminish levels of behaviour such as aggression that is likely to lead to poor welfare.     

Development of agonistic behaviour and vocalization in croaking gouramis

The development of agonistic behaviour and vocalization in the croaking gourami Trichopsis vittata was studied from hatching to sexual maturity (4 months of age). Initial interactions started when fry were 11 days old and consisted of approach and flight in a feeding context. More complex threat patterns appeared during dyadic encounters as fish grew older. Lateral display (spreading of median fins in a lateral position) first occurred during the third week, circling shortly afterwards and pectoral fin beating when fish were 7 weeks old. Rapid pectoral fin beating was first accompanied by sound emission at 8 weeks. Initially, croaking sounds were built up mainly of a series of single pulses, each one produced by one pectoral fin. Later, single pulses gave way to double pulses. Furthermore, pulse period and number of pulses increased, while the dominant frequency of croaks decreased significantly with age. After vocalization was established, frontal display, mouth biting and retreat behaviour occurred at the age of 10 weeks. Initially, young exhibited vertical bars which gave way to dots and horizontal bars at 8 weeks when fish started to vocalize. The order of appearance of behavioural patterns during ontogeny corresponds to the order of appearance in fights between adults. This is the first study demonstrating that the ontogenetic development of social signalling comprises characteristic changes in behaviour, vocalization and coloration in a teleost fish.     

Antipredator Behavior of American Bullfrogs (Lithobates catesbeianus) in a Novel Environment

Invasive species capable of recognizing potential predators may have increased establishment rates in novel environments. Individuals may retain historical predator recognition and invoke innate responses in the presence of taxonomically or ecologically similar predators, generalize antipredator responses, or learn to avoid risky species in novel environments. Invasive amphibians in aquatic environments often use chemical cues to assess predation risk and learn to avoid novel predators via direct experience and/or associated chemical cues. Ontogeny may also influence recognition; experience with predators may need to occur at certain developmental stages for individuals to respond correctly. We tested predator recognition in invasive American bullfrog ( Lithobates catesbeianus) tadpoles that varied in experience with fish predators at the population and individual scale. We found that bullfrog tadpoles responded to a historical predator, largemouth bass ( Micropterus salmoides), only if the population was locally sympatric with largemouth bass. Individuals from a population that did not co‐occur with largemouth bass did not increase refuge use in response to either largemouth bass chemical cues alone or chemical cues with diet cues (largemouth bass fed bullfrog tadpoles). To test whether this behavioral response was generalized across fish predators, we exposed tadpoles to rainbow trout ( Oncorhynchus mykiss) and found that tadpoles could not recognize this novel predator regardless of co‐occurrence with other fish species. These results suggest that environment may be more important for predator recognition than evolutionary history for this invasive species, and individuals do not retain predator recognition or generalize across fish predators.     

Behavioural and physiological stress responses to handling in wild guanacos

Both ethology and physiology can provide insights about stress conditions in wild animals during handling. Lama guanicoe (guanaco) is the major large herbivore inhabiting arid zones in Argentina. Since 2005, the Payún Matrú Cooperative, a business established and run by native people, has captured and handled guanacos for shearing at Payunia Reserve, Mendoza Province, Argentina, to market the species’ fibre for clothing and other products. The aim of our study was to evaluate the behavioural and physiological stress responses to handling of wild guanacos during these shearing activities. We evaluated stress conditions in guanacos by monitoring the frequency of agonistic behaviour in the holding corrals, following capture, the rate of vocalisation and agonistic behaviour during handling, and by estimating cortisol levels in handled animals. Crowding increased agonistic behaviour; this appeared to be related to dominance conflicts between males in the corrals. Time of corralling increased rate of agonistic behaviour and vocalisations during handling. The rate of behavioural stress responses was negatively related to cortisol levels in males; which may be due to animal fatigue or because behavioural stress responses may help mitigate physiological stress responses. Incorporating our results into animal welfare practices could help reduce stress conditions in wild guanacos. Our results suggest that both behavioural and physiological responses are important measures of stress in handled animals, and that behavioural stress responses cannot be used as a simple surrogate for glucocorticoid levels.     

Morphological correlates of swimming activity in wild largemouth bass (Micropterus salmoides) in their natural environment

Individual variation in morphology has been linked to organismal performance in numerous taxa. Recently, the relationship between functional morphology and swimming performance in teleost fishes has been studied in laboratory experiments. In this study, we evaluate the relationship between morphology and swimming activity of wild largemouth bass (Micropterus salmoides) during the reproductive period, providing the first data derived on free-swimming fish not exposed to forced swim trials in the laboratory. Sixteen male largemouth bass were angled from their nests, telemetered, and subsequently monitored by a whole-lake acoustic hydrophone array with sub-meter accuracy. Additionally, eleven morphological measurements were taken from digital images of each fish. A principal components analysis of the morphological measurements described 79.8% of the variance. PC1 was characterized by measures of overall body stoutness, PC2 was characterized by measures of the length and depth of the caudal region, and PC3 characterized individuals with relatively large anterior portions of the body and relatively small caudal areas. Of these variables, only PC3 showed significant relationships to swimming activity throughout the parental care period. PC3 was negatively correlated with multiple measures of swimming activity across the parental care period. Furthermore, swimming performance of individual male bass was noted to be repeatable across the parental care period indicating that this phenomenon extends beyond the laboratory.     

The influence of littoral zone coarse woody habitat on home range size, spatial distribution, and feeding ecology of largemouth bass (Micropterus?salmoides)

Coarse woody habitat (CWH) may be a critical feature of lakes that influences fish distributions, movement patterns, and feeding habits. We used radio telemetry to examine the role of CWH in determining the movements of largemouth bass (Micropterus salmoides Lacepede) in the context of two whole-lake experiments that provided a gradient of four lake basins varying in natural and manipulated CWH. We also conducted diet studies on largemouth bass in these lakes to test for correlates among consumption rate and prey selectivity with bass behavior. Our results indicated that largemouth bass in basins with lower CWH abundances had larger home ranges, spent more time in deep water, were more selective predators, and showed lower consumption rates. Largemouth bass in basins with higher CWH abundances showed the opposite patterns. Low CWH abundances were correlated with a shift in largemouth bass foraging behavior from sit-and-wait to actively searching. This increased activity, coupled with the potential decline of prey fish species in the absence of CWH, may decrease largemouth bass growth potential regardless of the prey type consumed. Our results suggest that lakeshore residential development and associated removals of CWH from lakes may influence fish behavior, while CWH augmentation may reverse some of those changes. Handling editor: Steven Declerck     

Differential effects of largemouth and smallmouth bass on habitat use by stoneroller minnows in stream pools

Previous investigations of within-reach distribution patterns of the stoneroller minnow, Campostoma anomalum Rafinesque, suggest that this species behavioural response to piscivorous bass differs among streams with different bass species. This study compares the responses of Camposloma to two common piscivorous fishes, largemouth bass, Micropterus salmoides Lacepede, and smallmouth bass, M. dolomieui Lacepede. Field experiments in Brier Creek, Oklahoma, U.S.A. showed that Campostoma responded to the presence of adult largemouth bass by shifting to shallow water habitats (commonly < 20 cm), but responded weakly or not at all to adult smallmouth bass. The magnitude of the response of Campostoma was positively related to activity level of the predators. Differences in behaviour between these two predator species may contribute to the differences in spatial distribution patterns of Micropterus and Campostoma observed in earlier investigations, but differences in stream channel morphology and temperature regimes among streams may also be important.     

Grazer identity changes the spatial distribution of cascading trophic effects in stream pools

Non-lethal effects of predators on prey behavior can mediate trophic cascades, but the extent of effects depends on habitat characteristics and risk sensitivity of prey. Furthermore, predation risk for stream organisms varies along the depth gradient and strongly influences their behavior. Grazing minnows (Campostoma anomalum) and crayfish (Orconectes virilis) are both prey for largemouth bass (Micropterus salmoides) in streams, but differ in their predator-avoidance behavior. This study contrasts the effects and mechanisms of non-lethal trophic cascades on the spatial distribution of filamentous green algae among stream pools and along a depth gradient within pools. Presence/absence of a largemouth bass was crossed with four combinations of the two grazer species (0 grazers, 30 minnows, 30 crayfish, and 15 each) in outdoor, experimental streams. Grazer densities were maintained by restocking. I used geostatistics to quantify spatial patterns of predator and grazer habitat use, height of filamentous algae in the water column, and spatial covariation of water depth with algal height, and depth with grazer habitat use. In streams with only minnows, bass were sedentary, and hid within tall algae in a single "bass pool". In pools with grazed algae, bass actively pursued prey within and among pools and used deeper water. This set up a hierarchy of risk to grazers along the depth gradient from bass in deep water to potential risk from terrestrial predators in shallow water. Thus, minnows were more sensitive than crayfish to predation risk from bass, but less sensitive than crayfish to risk from terrestrial predators. Minnows mediated cascades at the scale of whole pools by avoiding "bass pools", but only if crayfish were absent. Crayfish avoided potential interactions both with terrestrial predators and bass by grazing and burrowing in deeper water at night (when bass were inactive), and by hiding in burrows during daytime. Crayfish without burrows avoided bass and crayfish defending burrows by using shallow edges of pools as corridors, but did not graze there. Thus, crayfish-mediated cascades were limited to pool edges. Effects of grazer identity may extend to other consumers via modification of risk for biota that use filamentous algae as either foraging or refuge habitat.     

Gape Limitation, Prey Size Refuges and the Top–down Impacts of Piscivorous Largemouth Bass in Shallow Pond Ecosystems

Top–down control of phytoplankton biomass through piscivorous fish manipulation has been explored in numerous ecological and biomanipulation experiments. Piscivores are gape-limited predators and it is hypothesized that the distribution of gape sizes relative to distribution of body depths of prey fish may restrict piscivore effects cascading to plankton. We examined the top–down effects of piscivorous largemouth bass on nutrients, turbidity, phytoplankton, zooplankton and fish in ponds containing fish assemblages with species representing a range of body sizes and feeding habits (western mosquitofish, bluegill, channel catfish, gizzard shad and common carp). The experimental design consisted of three replicated treatments: fishless ponds (NF), fish community without largemouth bass (FC), and fish community with largemouth bass (FCB). Turbidity, chlorophyll a, cyclopoid copepodid and copepod nauplii densities were significantly greater in FC and FCB ponds than in NF ponds. However, these response variables were not significantly different in FC and FCB ponds. The biomass and density of shallow-bodied western mosquitofish were reduced and bluegill body depths shifted toward larger size classes in the presence of largemouth bass, but the biomass and density of all other fish species and of the total fish community were unaffected by the presence of largemouth bass. Our results show that top–down impacts of largemouth bass in ecosystems containing small- and deep-bodied fish species may be most intense at the top of the food web and alter the size distribution and species composition of the fish community. However, these top–down effects may not cascade to the level of the plankton when large-bodied benthivorous fish species are abundant.