Sport fish movement responses to a littoral zone coarse woody habitat addition

Objective: Fish movements and distributions throughout an ecosystem are important for understanding ecological interactions, conservation, and management. Coarse woody habitat (CWH) additions are a popular habitat enhancement tool that can influence movements and distributions of fishes; however, behavioral responses in relation to CWH additions are understudied. The objectives of our study were to test for changes in habitat use and behavioral responses of Muskellunge Esox masquinongy, Smallmouth Bass Micropterus dolomieu, and Walleye Sander vitreus to CWH additions in a small inland northern lake over 3 years and to evaluate two common forms of fish tracking to estimate daily movement of these fishes. Methods: We used passive integrated transponder tag data collected continuously at 10 littoral sites and radiotelemetry data collected biweekly during the summer–fall months prior (2017) and following (2018–2019) CWH addition to examine movement behaviors and estimate daily probability of movement for the three species among lake habitats using multistate models. Result: Walleye were the most likely to remain near CWH, followed by Smallmouth Bass and Muskellunge. All species were more likely to move away from the modified and unmodified littoral zones and were more likely to remain in the offshore zone. Increased movement of fish may be in response to CWH creating a refuge for forage fish and subsequent increases in prey search times. Conclusion: Our results suggest that CWH additions may alter established species-specific annual movements, distributions, and habitat use to differing degrees in ecosystems, as our results differ from other CWH studies. Methodologically, radio-tagging was most effective for offshore tracking but most labor intensive. Novel passive integrated transponder arrays (less labor intensive once installed) worked well to monitor movement between habitat types in shallow littoral areas. Long-term monitoring of behavioral changes will be essential to assessing the stability changes caused by these habitat alterations.