Effects of depth and crayfish size on predation risk and foraging profitability of a lotic crayfish

Abstract

AbstractWe conducted field surveys and experiments to determine whether observed distributions of crayfish among habitats were influenced by differential resource availability, foraging profitability, and predation rates and whether these factors differed with crayfish size and habitat depth. We sampled available food resources (detritus and invertebrates) and shelter as rock substrate in deep (>50 cm) and shallow (<30 cm) habitats. We used an enclosure–exclosure experiment to examine the effects of water depth and crayfish size on crayfish biomass and survival, and to determine whether these factors affected silt accrual, algal abundance (chlorophyll a [chl a]), and detritus and invertebrate biomass (g ash-free dry mass) differently from enclosures without crayfish. We conducted tethering experiments to assess predation on small (13–17 mm carapace length [CL]) and large (23–30 mm CL) Orconectes marchandi and to determine whether predation rates differed with water depth. Invertebrate biomass was signific...