AUTHORS: Robert Allison, University of Nebraska at Kearney
ABSTRACT: Lake McConaughy is the largest reservoir in Nebraska, and Walleye are a focus of management. The Walleye population has been supplemented and maintained by the Nebraska Game and Parks Commission (NGPC) through annual stockings since 1989. Historically, NGPC stocked age-0 Walleye fingerling at a rate of 124 fish/ha (1989-2021) but shifted to stocking a combination of fry (2,471 fish/ha) and fingerlings (75 fish/ha) from 2022-2024 to determine which product may lead to better recruitment. The objective of this study is to compare the stock contributions of fry, fingerling, and naturally produced age-0 Walleye from 2022-2024 to the contributions from 2015-2018 and compare the size of each product at the time of capture. Fish were marked via immersion in oxytetracycline (OTC) in the hatcheries and during transport prior to stocking. Age-0 Walleye were collected in early to mid-fall using nighttime boat electrofishing. All captured Walleye were enumerated, measured for total length, and sacrificed for otolith extraction. Preliminary results show that stock contributions of hatchery fish are similar, on average, between 2015-2018 and 2022-2024, though some variability from year to year exists. Additionally, the age-0 Walleye were larger at the time of capture when only fingerlings were stocked than when a combination of fry and fingerlings were stocked, due either to differing environmental conditions (e.g., reservoir elevations) or density-dependent factors. Information gathered from this study will help NGPC make informed decisions on what product and densities to stock in the future.
