Wisconsin Fishery Project
Electrofishing catchability of juvenile muskellunge in northern and southern Wisconsin lakes
July 2015 - December 2016
- Wisconsin Department of Natural Resources
To assess the effectiveness of muskellunge stocking, biologists conduct electrofishing surveys in fall to estimate catch per effort (CPE) and relative contribution of stocked fish. Inherent assumptions of this sampling are that wild and stocked fish have equal probability of capture and that changes in CPE reflect changes in actual abundance. However, capture rates of age-0 muskellunge tend to be low for both wild and stocked fish, making it difficult to determine if electrofishing catch is a meaningful predictor of actual abundance. The goal of our study was to determine the effectiveness of electrofishing for capturing individual age-0 muskellunge by determining locations of stocked fish released into two lakes in northern Wisconsin. All stocked fish received a fin clip and at least 40 fish per lake were inserted with radio transmitters. All fish were released at a single boat ramp on each lake, which followed standard Wisconsin Department of Natural Resources (DNR) protocols. Stocked muskellunge with transmitters were tracked weekly for one month after release. Fish were also sampled weekly using standard Wisconsin DNR electrofishing methods that included a single boat following single line transect around the shoreline of each lake. Comparing known locations of radio-tagged fish to the area sampled by the electrofishing boat revealed that most of the sampling effort was expended outside the area where stocked fish were located. Our initial results suggest that the majority of hatchery fish remained in the vicinity of the release location, with fish moving a max distance of 0.4 – 0.7 km on average away from the release location within four weeks of being stocked. Based on these results, biologists will be able to improve sampling protocols to evaluate muskellunge stocking success by stratifying sampling effort so that more time is spent sampling where the fish are located.