Foraging Behavior of Fishes

BACKGROUND: Small species of fish and juveniles of larger species occupy aquatic plant patches for food (Pardue 1973; Keast 1984) and protection from predators (Crowder and Cooper 1982; Savino and Stein 1989). Differences in density and morphology of plants influence foraging intensity and degree of predator avoidance (Dionne and Folt 1991; Lillie and Budd 1992; Wychera et al. 1993; Dibble, Killgore, and Dick 1996), which in turn influence fish growth and survival. Foraging efficiency decreases in dense plant beds (Savino and Stein 1982; Anderson 1984), but plant architecture (e.g., interstitial space formed by the arrangement of stems and leaves) can mediate negative effects (Lynch and Johnson 1989; Lillie and Budd 1992; Johnson 1993). High-density plant beds, however, offer greater protection from predators than mediumor low-density beds (Hayse and Wissing 1996). These tradeoffs, between reduced foraging value and increased protection from predators, make assessments of optimal or threshold densities of aquatic plants difficult.