Midwest Fish & Wildlife Conference 2018

AUTHORS. Heather Marjamaa, Bemidji State University; Dr. Andrew Hafs, Bemidji State University; Tony Kennedy, Minnesota Department of Natural Resources

ABSTRACT. Walleye (Sander vitreus) is the most sought-after sportfish in Minnesota. Minnesota is the third most popular inland fishing destination in the country and contributes a significant amount of revenue to the state. Cass Lake is one of the ten largest lakes in Minnesota and the largest in a chain of lakes that is a popular destination for Walleye anglers. The Minnesota Department of Natural Resources (MNDNR) collects Walleye eggs each spring from a tributary to Lake Andrusia, which lies immediately upstream of Cass Lake and is connected by the Mississippi River. As a matter of policy, 10% of the eggs collected are returned to the donor lake as fry which, in Lake Andrusia, results in elevated fry densities (range: 1,000 to 17,000 fry/littoral acre, mean: ~7,000) that may create negative density-dependent effects. However, if these fry distribute themselves throughout the chain, fry densities would be much lower (500 to 1,000 fry/littoral acre). In 2016 and 2017, approximately three million Walleye fry were marked with an oxytetracycline (OTC) solution and stocked into Lake Andrusia (~7,000 fry/littoral acre) to allow differentiation of stocked and wild fish. Walleye fingerlings were collected in the fall from each lake within the chain. Fish were measured for total length and weight and otoliths were then examined for the presence of an OTC mark. The three main objectives of this project are to: 1) document the dispersal of age-0 and age-1 Walleye throughout the chain, 2) determine the percentage of stocked age-0 and age-1 Walleye for each lake within the chain, and 3) examine length-at-capture of marked and unmarked fish. These results will help determine the effect stocking of Walleye fry in Lake Andrusia has on the Cass Lake chain and ensure stocking efforts are as efficient and effective as possible.