Habitat Selection of Predator and Prey: Atlantic Salmon and Rainbow Smelt Overlap, Based on Temperature and Dissolved Oxygen

Abstract

We investigated the predator-prey interactions of two pelagic species, landlocked Atlantic salmon Salmo salar and rainbow smelt Osmerus mordax, in a large-lake ecosystem. Our goal was to determine the overlap of habitats selected, based on profiles of temperature and dissolved oxygen (DO). We used hydroacoustics to ascertain the seasonal habitat selection of rainbow smelt and gill nets to sample Atlantic salmon in the Inland Sea of Lake Champlain, Vermont. We identified patterns of smelt habitat selection by overlaying the acoustically determined vertical distributions of smelt onto profiles of water temperature and DO. To verify species composition of acoustical targets, we performed midwater trawls using a stepped-oblique method and found that rainbow smelt constituted 99.5% of trawl catches. Trawl catches and acoustic fish density were correlated, indicating that acoustic targets represented trawled fish. Atlantic salmon habitat selection was estimated from temperature and DO profiles taken at gill nets that caught salmon. Data for Atlantic salmon and rainbow smelt demonstrated extensive spatial overlap in habitat selection during the three sampling seasons. Our results provide greater insight into the predator-prey interactions of these species as mediated by environmental factors. Because Atlantic salmon are stocked, this insight into the predator-prey interactions may assist managers in effectively regulating stocking numbers.