Application of novel encounter and predation models to the natural behavior of slimy sculpin Cottus cognatus

Abstract

Sculpins play a critical mid-trophic role in lacustrine food webs, converting production by benthic and migrating pelagic invertebrates into biomass available to higher trophic levels. Although sculpin diets and habitat choices are relatively well described, much less is known about their in situ behavior which governs trophic interactions and, in part, prey behavior. We measured the natural behavior of slimy sculpin Cottus cognatus in Lake Champlain using video data originally collected to quantify Mysis diluviana abundance in benthic habitat. After characterizing slimy sculpin movement behaviors according to body size, we incorporated these data into encounter and predation rate models at the individual and population levels, the latter based on bottom trawl data from Lake Champlain. Saltatory movement varied with body length in terms of distance traveled, duration traveled, and duration at rest, but strike distances at prey did not vary across individual sculpins. Slimy sculpin predation rate increased with depth and was limited by pursuit time rather than prey availability, and their populations exerted predation rates on Mysis up to 5 predation events/m 2 /day. Assessment of benthic predation risks affords the opportunity to test hypotheses about the role of predation risk in Mysis diel vertical migration (DVM), and DVM more broadly. Furthermore, the methods we describe here can easily be employed for other benthic fishes such as the invasive round goby Neogobius melanostomus .