Adult Walleye Abundance and Subsequent Fry Production in the Tamarac River, MN

Author

Phillip Oswald

Date of Award

9-2018

Document Type

Thesis

Department

Biology

First Advisor

Andrew Hafs

Abstract

Walleye reproductive success is of critical interest for the Red Lakes as this system is maintained entirely by natural reproduction and supports robust commercial and recreational fisheries. The Tamarac River, a major tributary to the Red Lakes, hosts a substantial Walleye spawning migration annually. The river drains the largest peat bog in the lower 48 states and thus experiences low dissolved oxygen at times. It is largely unknown how the potential anoxic bog water affects Walleye reproductive success each year and subsequent year class strength. Fyke nets were set from 2014-2018 to assess the relative abundance of adult Walleye spawning in the river with mean peak CPUE ranging from 10 – 288 fish/net. Additionally, in 2017, a Jolly-Seber abundance estimator was used to assess the magnitude of the spawning migration. A total of 13 capture-recapture sampling events resulted in the capture of 9,648 spawning Walleye. Sampling occurred throughout the spawning migration with peak abundance estimated at 268,877 (76,952- 460,802 95% CI) Walleye, or about 6.5% of the Red Lakes’ Walleye population. It is estimated that 86,040, or 7.9% of the females present in the Red Lakes spawned in the Tamarac River in 2017. Larval drift nets were set later to assess the success of Walleye reproduction in the Tamarac River. Mean peak larval Walleye densities ranged from 0.03 – 0.86 fish/m3 throughout sampling years. Total fry output from the Tamarac River in 2017 was estimated at 277,462 (95% CI = 273,040-281,884) larval Walleye, or 0.3% of the wild fry estimate of the Red Lakes. Dissolved oxygen ranged from 2.95 – 10.8 mg/L and discharge ranged from -0.32 - 14.80 m3/s. Reproductive activity in the Tamarac River may vary annually due to these changing stream characteristics, however remains important to the health of the Red Lakes’ Walleye population.

Recommended Citation

Oswald, Phillip, "Adult Walleye Abundance and Subsequent Fry Production in the Tamarac River, MN" (2018). Biology Graduate Theses. 16.
https://pines.bemidjistate.edu/thesis-biol/16