Lake trout and their egg predators' ability to locate spawning substrate using olfaction

Abstract

Lake trout spawning sites, and the substrate on these sites, are structurally unique in many ways. These sites are generally at the end of the fetch of a lake, close to shore (1 m) and composed of small to medium sized rubble and cobble. Lake trout and their egg predators use the same site(s) annually. It was hypothesized that both lake trout and their egg predators utilize olfaction to locate the same sites annually. To test this hypothesis trap nets were baited with visually concealed lake trout spawning substrate or nonspawning substrate that was structurally similar to spawning substrate. Trap nets baited with lake trout spawning substrate captured significantly more lake trout and common white sucker (an egg predator) than trap nets that contained structurally similar nonspawning substrate. Spawning substrate-containing traps also caught more spawn-ready lake trout. In a second experiment, significantly more egg predators were captured in unbaited minnow traps on lake trout spawning sites than structurally-similar nonspawning sites. To test whether smaller egg predators, such as sculpin or crayfish, were attracted to visually concealed spawning substrate, two standard minnows traps were placed on 8-10 sites on three lakes. One trap was baited with lake trout spawning substrate and the other with structurally similar non-spawning substrate. Traps with spawning substrate captured significantly more egg predators as well other opportunists than those with non-spawning substrate. These results demonstrate that both lake trout and their egg predators are able to locate visually concealed spawning substrate.