OPTIMAL FORAGING AND HABITAT SHIFT IN PERCH (PERCA FLUVIATILIS) IN A RESOURCE GRADIENT

摘要: To better understand how and why foraging shifts between habitats among prey occur, to evaluate the ability of an optimal model predict diet breadth quantitatively, we studied food habitat use perch (Perca fluviatilis) in experimentally induced resource gradient. The purpose study was also see whether prey-type-dependent search rates were important for observed utiliza- tions. level one (pelagic) two (pelagic benthic) selectively reduced a field experiment by varying densities roach (Rutilus rutilus), inter- specific competitor (Percafluviatilis) that feeds preferentially on pelagic resources. We tested simple could (1) (2) when should shift from feeding benthic habitat. carried out pond divided into 10 enclosures. Perch density held constant enclosures, whereas planktivorous varied smallest size class used corresponded with what predicted basic model. However, mean larger than For prey, poorly predicted, reflecting problem extrapolating laboratory-estimated encounter handling times more complex field. During first half experiment, but not during second half, there positive correlation growth rate net return based Conversely, no significant relationship performance energy intake present while half. There time lag feeding. In addition, never complete since continued feed some after having shifted mainly prey. Different different may have given rise lags as well partial use. Habitat-dependent thus form complementary explanation learning sampling behavior, Flexible predator reinforce importance considering whole behavioral repertoire only predator's choice once has been encountered.