Roy A. Stein

Predator-Prey Interaction between Largemouth Bass and Bluegills as Influenced by Simulated, Submersed Vegetation

Abstract Data from the literature suggest that predatory success declines as habitat complexity increases. To explain this phenomenon, we studied the predator-prey interaction between largemouth bass Micropterus salmoides and bluegills Lepomis macrochirus in four laboratory pools (2.4–3.0 m diameter, 0.7 m deep), each with a different density (0, 50, 250, 1,000 stems/m2) of artificial plant stems. Behavior was quantified for both predator and prey during largemouth bass feeding bouts lasting 60 minutes. Predation success (number of captures) by largemouth bass was similar at 0 and 50 stems/m2, then declined to near zero at 250 and 1,000 stems/m2. As stem density increased, predator activity declined due to a decrease in behaviors associated with visual contact with prey. Reduced predation success by largemouth bass in habitats of increased complexity apparently is related to increases in visual barriers provided by plant stems as well as to adaptive changes in bluegill behavior.

Behavior of fish predators and their prey: habitat choice between open water and dense vegetation

SynopsisBehavior of largemouth bass, Micropterus salmoides, and northern pike, Esox lucius, foraging on fathead minnows, Pimephales promelas, or bluegills, Lepomis macrochirus, was quantified in pools with 50% cover (half the pool had artificial stems at a density of 1000 stems m−2). Both predators spent most of their time in the vegetation. Largemouth bass searched for bluegills and ambushed minnows, whereas the relatively immobile northern pike ambushed all prey. Minnows were closer to predators and were captured more frequently than bluegills. Even when minnows dispersed, they moved continually and eventually wandered within striking distance of a predator. Bluegills dispersed in the cover with predators. Bass captured the few bluegills that strayed into the open and pike captured those that approached too closely in the cover. The ability of predators to capture prey while residing in habitats containing patches of dense cover may explain their residence in areas often considered to be poor ones for foraging.

Selective Predation by Three Esocids: The Role of Prey Behavior and Morphology

Abstract We documented differential vulnerability of fathead minnows Pimephales promelas, gizzard shad Dorosoma cepedianum, and bluegills Lepomis macrochirus to predation by muskellunge Esox masquinongy, northern pike E. lucius, and tiger muskellunge E. masquinongy × E. lucius in a 700-L tank. Individual esocids (150–225 mm in total length) were combined with singlespecies groups (N = 15) of optimal-sized prey (25–30% of predator length for bluegills, 37–43% for fathead minnows, and 30–36% for gizzard shad). Capture ability did not differ among esocids; however, mean captures per strike were higher for fathead minnow (0.67) and gizzard shad (0.78) than for bluegill (0A4). Morphology and antipredatory behavior, unique to each prey species, contributed to this differential vulnerability. In the field, we introduced equal numbers and similar sizes of these esocids into two systems, one with centrarchid prey and one with both centrarchid and gizzard shad prey. As predicted from laboratory work, esocids ate fe...

Round Goby Predation on Smallmouth Bass Offspring in Nests during Simulated Catch-and-Release Angling

Abstract Round goby Neogobius melanostomus first appeared in Lake Erie in 1993 and now occur in extremely high densities in some areas. As known nest predators, round goby currently pose a threat to nest-guarding smallmouth bass Micropterus dolomieu. We conducted manipulative experiments to evaluate the combined effects of round goby predation and catch-and-release angling during 1999–2001 in the Bass Islands, Lake Erie. We quantified how many smallmouth bass offspring were consumed by round goby when nest-guarding smallmouth bass males were present, removed, and recovering from angling-related stress. In 10 h of video observations, we only saw one instance of round goby consuming smallmouth bass offspring while the nest was guarded. Upon removal of nest-guarding smallmouth bass, round goby quickly entered unguarded nests (4.3 round goby/min for nests with unhatched embryos and 1.8 round goby/min for nests with hatched embryos). During experimental catch-and-release angling, round goby consumed an average...

RIVER DISCHARGE DRIVES SURVIVAL OF LARVAL WALLEYE

This work was funded by Federal Aid in Sport Fish Restoration Program project F-69-P, administered jointly by the U.S. Fish and Wildlife Service and the Ohio Division of Wildlife.

Detection of Predators and Habitat Choice by Small Bluegills: Effects of Turbidity and Alternative Prey

Abstract Studies of sunfish Lepomis spp. have demonstrated that predation regulates size-specific habitat use and competitive interactions both within and among species. However, all of these studies were conducted in clear-water systems with dense littoral vegetation, resulting in well-defined littoral and open-water habitats. In contrast, little is known about predator–prey interactions among fishes that inhabit turbid lakes and reservoirs. In these systems, turbidity reduces detection (reaction) distance for both predator and prey, and can eliminate submerged vegetation that serves as a refuge. In laboratory experiments, we quantified reaction distance of juvenile bluegills Lepomis macrochirus to a predator, largemouth bass Micropterus salmoides, and determined shifts by bluegills between nearshore and offshore habitats across a turbidity gradient. Bluegill reaction distance declined as a negative power function of turbidity from less than 2 m in clear water to 23 cm at 10 nephelometric turbidity units...

Food Consumption by Larval Gizzard Shad: Zooplankton Effects and Implications for Reservoir Communities

Abstract Because peak abundance of larval gizzard shad Dorosoma cepedianum occurs simultaneously with the midsummer decline of macrozooplankton in Ohio reservoirs, we hypothesized that zooplanktivory by larval gizzard shad caused this decline. To test this hypothesis, we compared larval food consumption with zooplankton productivity in two reservoirs. Larval gizzard shad began to influence zooplankton production in a reservoir with high zooplankton productivity (exceeding 125 mg·m−3·d−1) only after peak zooplankton biomass occurred, even at high larval densities (38 shad·m−3). However, consumption by early juvenile (25−30-mm) gizzard shad severely reduced zooplankton in this reservoir. Conversely, relatively low densities of larval gizzard shad (3–7 shad·m−3) had variable effects on zooplankton in a reservoir with low zooplankton productivity (at most 4 mg·m−3·d−1). Depending on larval gizzard shad density and zooplankton production, larval gizzard shad alone or in conjunction with early juveniles may con...

An analysis of the mechanisms governing species replacements in crayfish

SummaryWe 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.

Indirect Effects of Predation in a Freshwater, Benthic Food Chain

During part of this study C. Bronmark was supported by an Ohio State University post-doctoral fellowship, funded through the Graduate School, The Ohio State University. Support from the National Science Foundation (to R. A. Stein, BSR 850772) and from the Swedish Natural Science Research Board and the Swedish Institute (to C. Bronmark) is appreciated.

Using Time and Energetic Measures of Cost in Estimating Prey Value for Fish Predators

In the predator-prey interaction between redear sunfish (Lepomis mlcrolophus) and benthic, freshwater snails (Phj~sa, Helisoma, and Oxytrema), we document selective predation among genera and sizes of prey and use optimal foraging theory in an attempt to explain diet selection. In experiments, sunfish strongly selected against Oxytrema and weakly discriminated between Physa and Helisoma, with Phj~sa most often chosen; size selection within any genus did not occur. Among genera, selection results were consistent with differences in shell strength and a time cost/benefit (C/B) construct operationally defined as handling time divided by prey dry mass. Within any genus, neither shell strength (smallest snails had weakest shells) nor time C/B (largest snails had minimal C/B) provided predictions consistent with results from selective-predation experiments. To explain this discrepancy, we measured metabolic costs of handling and energy content of prey. Dividing net energy of prey (E, generated by subtracting the energetic cost of handling from prey energy content) by handling time (T) yielded values of E/T that were similar for Physa and Hellsoma. Within either genus, E/T was always highest for largest snails. Thus, this construct also provided predictions inconsistent with our experimental results. Only an energetic CIB ratio, in which the energetic costs of handling were divided by the energetic value of the prey, was consistent with selection of Phj~sa over Helisoma and no size selectivity within either genus. Whether predators add prey to their diet based on this construct is unknown at present. The lack of concurrence between theoretical predictions of how prey should be ranked by predators (i.e., according to energy gained per unit time expended) and our experimental results suggests these constructs should be re-evaluated. Unless we know the discriminatory ability of our predators (in terms of how fine a difference in prey types they can assess) and the currency used in making decisions, CIB or EIT constructs provide little insight into diet selection by predators.