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The types and sizes of prey fishes consumed by predatory fish often are limited by gape dimensions of the predator (Slaughter and Jacobson 2008). In general, the size of prey consumed is positively related to predator size when prey are available across a wide range of sizes (Werner and Hall 1974). Opportunistic predators with large gape dimensions, such as smallmouth bass (Micropterus dolomieu), may consume a wide range of prey types and sizes, thereby exerting top-down influences on prey population dynamics and potentially restructuring aquatic communities (e.g., Werner and Hall 1974, Jackson 2002). Although feeding ecology of smallmouth bass varies with location and prey availability, they typically undergo several ontogenetic diet shifts throughout their development. After yolk sac depletion and as smallmouth bass increase in size from larvae to juveniles (~50 mm total length; TL), targeted prey typically proceeds from microcrustaceans (e.g., copepods) to larger zooplankters (e.g., cladocerans) to macroinvertebrates (e.g., ephemeropterans; Brown et al. 2009). Opportunistic feeding behaviors become more apparent during the juvenile stage (TL > 50 mm) when smallmouth bass begin to consume readily available aquatic macroinvertebrates and prey fishes (Clady 1974, Easton and Orth 1992). Studies evaluating adult feeding ecology highlight the importance of crayfish (Gangl et al. 1997, Liao et al. 2002, Bacula 2009) but also reveal the piscivorous nature of smallmouth bass in some locations (e.g., Jackson 2002, Liao et al. 2002, Bacula 2009, Wuellner et al. 2010).
The Prairie Naturalist
South Dakota State University
Schake, Craig L.; Dembkowski, Daniel J.; and Wuellner, Melissa R., "Gape:Body Size Relationship for Smallmouth Bass" (2014). Natural Resource Management Faculty Publications. 112.