Sport Fish Behavioral Responses to a Littoral Coarse Woody Habitat Addition in a North-temperate Lake

Quinn Smith

PhD Student, University of Wisconsin - Madison

Abstract

The availability of appropriate habitat throughout an ecosystem is important for the long-term sustainability of natural resources. Coarse woody habitat (CWH) additions to littoral zones of north-temperate glacial lakes in the Midwestern United States have become popular as a way to mitigate the effects of increased lakeshore residential development and associated removal of natural CWH. Relatively few of these CWH additions have been treated as deliberate experiments regarding responses of fish and aquatic ecosystems. Whole-lake CWH removal studies have shown detrimental effects towards fishes that use the habitat for foraging, refuge, and spawning. Experimental whole-lake CWH additions have shown increased availability and diversity of prey available to fishes as well as pronounced behavioral changes, however many of these studies have only focused on singular behavioral responses in singular species. To address the question of multiple fish behavioral responses in a complex fish community to CWH addition, a long-term study was initiated in Sanford Lake, Vilas County, Wisconsin, where 160 trees were added to the littoral zone of the lake in 2018. We tested for behavioral responses in muskellunge (Esox masquinongy), smallmouth bass (Micropterus dolomieu), and walleye (Sander vitreus) to this CWH addition. To examine behavioral responses to CWH addition, we used radio telemetry data to examine home range changes, and passive integrated transponder (PIT) data along with radio telemetry data to examine movement rates between habitats in muskellunge, smallmouth bass, and walleye during pre-manipulation (2017) and post-manipulation (2018 and 2019). Across species, home ranges increased, movement rates between habitats increased, and fish were less likely to remain in littoral zones following large-scale, whole-lake CWH addition. Our results suggest that complex, species-specific behavioral responses to CWH addition can be expected, and should be taken into consideration before implementing littoral habitat enhancements in diverse fish communities.