Selective Predation, Optimal Foraging, and the Predator-Prey Interaction Between Fish and Crayfish

摘要: Through laboratory experimentation, I quantified the behavioral interaction between an inshore fish predator, smallmouth bass (Micropterus dolomieui) and active, defensive prey organism, crayfish (Orconectes propinquus). Experiments, run in aquaria or large wading pools, involved placing different sizes life stages of with to document selective predation. To determine whether bass, preying selectively on maximized net energy intake, a predictive foraging model, which handling pursuit times are balanced against digestible organic ((Ht + Pt)/O), was developed tested. Fieldwork, designed yield electivity indices such that findings could be confirmed denied, simultaneously sampling predators from 3 lakes northern Wisconsin. In experiments, when offered choice sand, (25 cm, total length) chose smallest (4 mm, carapace first, then consumed animals ascending order size. When same choices pebble (16-32 mm), intermediate-sized (16-20 mm) were eaten first. On substrates, small size classes relatively less exposed than classes. Therefore, increased search (i.e., waiting) time obtain these appears decrease their value relative more available intermediate Both pre- dicted (Ht Pt)/O selection sequence substrate agreed quite closely field indices, suggesting optimal foragers. Within any class adults, ordered low high susceptibility predation by were: ovigerous Y Y, Form (FI, capable breeding) d s, II (FII, incapable 6, recent molts. Determined empirically via this validated predicted construct. As result differential predators, some (juveniles, molts) appeared modify microdistribution minimize risk predators. general, densities sand inversely related fishes; degree response individual correlated vulnerability. Fish not only but also cause shifts behavior. fish-crayfish interactions, greatest vulnerability due morpholog- ical physiological traits possessed most significant attributes for reducing risk. particular populations makes ecological sense; fish- interactions as predator-prey systems persist. Their persistence results subtle in- teraction predator prey, ultimately producing stable system "important" (ovigerous Fl d) exempt predatory mortality.