Comparison of Bluegill Consumption Rates by Largemouth Bass and Sunshine Bass in Structured and Nonstructured Artificial Environments

—We compared consumption rates of bluegills Lepomis macrochirus by largemouth bass Micropterus salmoides and sunshine bass (female white bass Morone chrysops 3 male striped bass M. saxatilis) in structured (about 50% coverage with artificial vegetation) and nonstructured 2,000-L fiberglass tanks. In the presence of structure, instantaneous bluegill mortality from consumption by largemouth bass was significantly higher than that caused by sunshine bass but was similar when structure was absent. Instantaneous bluegill mortality from consumption by wild largemouth bass was significantly higher than by pellet-trained largemouth bass in both structured and nonstructured environments. When pellet-trained sunshine bass served as the predator, bluegill instantaneous mortality rate was similar within structured and nonstructured environments. Our findings indicate that sunshine bass are not as adept as largemouth bass at consuming bluegills in the presence of structure but that, unlike largemouth bass, their consumption rates on bluegills are not affected by prior predatory experience. Small freshwater impoundments in North America are often stocked with a combination of largemouth bass Micropterus salmoides, sunfish Lepomis spp., and channel catfish Ictalurus punctatus (Flickinger et al. 1999). Bluegills L. macrochirus thrive in these waters because the normally abundant stands of macrophytes provide excellent habitat for invertebrate prey (Savino et al. 1992) and also provide bluegills with some protection against predation (Savino and Stein 1982; Gotceitas 1990). Largemouth bass can move effectively through vegetated areas, and their ability to use an ambush foraging strategy makes them an efficient predator in such environments (Savino and Stein 1989). However, as plant density increases, the ability of piscivores to capture prey such as bluegills generally decreases (Savino and Stein 1982; Gotceitas and Colgan 1989). Other species of sport fish have been suggested to supplement the largemouth bass–bluegill combination. Of particular interest are hybrid striped * Corresponding author: [email protected] Received October 28, 2003; accepted May 26, 2004 bass (i.e., cross of white bass Morone chrysops and striped bass M. saxatilis). Hybrid striped bass are pelagic piscivores that forage on small prey living in open waters. They prefer to feed on soft-rayed fishes (e.g., clupeids) even when they are not the most abundant prey item (Crandall 1979), but will occasionally feed on small spiny-rayed fishes (Gilliland and Clady 1984; Neal et al. 1999). However, when stocked in small impoundments containing only centrarchid prey, the typical search and capture method employed by hybrid striped bass in open waters may not be sufficient, particularly in vegetated areas. Accordingly, we compared consumption of bluegills by largemouth bass and sunshine bass (female white bass 3 male striped bass) in structured and nonstructured environments. Because foraging success may be influenced by previous experience, we also compared predation on bluegills by wild and pellet-trained largemouth bass and hybrid striped bass.