Contribution and Performance of Stocked Walleyes in the Recovery of the Red Lakes, Minnesota, Fishery

Abstract

Oxytetracycline (OTC) marking and genetic assignment techniques were used to evaluate the contribution and performance of Walleye Sander vitreus fry stocked to accelerate the recovery of a recruitment-overfished population in the Red Lakes, Minnesota. Three stockings of OTC-marked fry from an egg source on the Pike River were conducted at densities of 274 to 358 fry/ha to expedite the recovery of the spawning stock in which the adult female biomass had fallen below 0.5 kg/ha for 10 consecutive years. Two additional stockings of OTC-marked fry from an egg source on a Red Lakes tributary were then conducted at 33 and 87 fry/ha to help quantify natural reproduction as the spawning stock recovered. Subsequent inspection of fish from seine and gill-net samples indicated that Pike River fish composed 50% to 94 % of the stocked year-classes and that the stocked year-classes were three of the strongest in the past 25 years. The Pike River fish survived, grew, and matured at rates similar to the native fish, contributing to an increase in adult female biomass ranging from 2.5 to 8.0 kg/ha. Natural reproduction also increased from a range of 8–120 fry/ha to a range of 199–908 fry/ha, with 49% to 53% Pike River ancestry. For the first 2 years after maturation of the first stocked year-class, however, Pike River ancestry was 13–31 percentage points below what was expected from the relative abundance of Pike River adults in the population. The proportion of Pike River adults present on the tributary spawning runs was also initially below expectations. Both spawning participation and success of Pike River adults increased in successive years, and the stocked fry were judged to have accelerated the recovery of the population to a sustainable and fishable status without the need for additional stocking.

Received October 20, 2015; accepted March 9, 2016 Published online July 7, 2016

Acknowledgments

We thank all the individuals who provided information and assistance during this project. Gary Barnard, Bruce Pittman, Ron Brooks, and Dave Lucchesi provided technical guidance on OTC marking, and the staffs from the MNDNR and the Red Lake Band of Chippewa Indians provided the catch data and assisted with marking and stocking Walleye fry. Steve Shroyer, Bill Evarts, Kevin Page, David Mattson, and Seth Luchau assisted in inspecting otoliths. Don Pereira, Steve Shroyer, and David Staples provided assistance in experimental design and data analysis, Pat Brown provided historical perspectives on the Red Lakes commercial fishery, and Andrew Williquett created the map of the study area. Paul Venturelli provided helpful comments to an earlier draft of this manuscript. This project was funded in part by the Federal Aid in Sport Fish Restoration Program (Project F-26-R).