Effects of Rainbow Trout on Brook Trout Population Size in Tributaries to Lake Superior in Cook County, Minnesota

Authors

Craig Tangren

Document Type

Article

Abstract

This study looked at the effects of Rainbow Trout stocking on the size of Brook Trout populations above migratory barriers. Linear mixed effects models were used to determine if there was a relationship between Brook Trout and Rainbow Trout catch rates. Age 1 or older Brook Trout populations were influenced by relative abundance of age 1 or older Rainbow Trout, according to the best supported model based on AIC scores. Population responses varied by stream, ranging along a gradient from high catch rates with a positive relationship to a negative relationship with low relative abundances. Streams with a positive relationship are likely more productive, with more prey and smaller territories, which allows for greater relative abundance. Streams with a weak relationship may have Brook Trout populations limited by the capacity for natural reproduction, a factor which would not influence Rainbow Trout. A clear negative relationship in some streams is likely due to density-dependent effects. This study did not perform an analysis comparing Brook Trout population sizes before and after the presence of Rainbow Trout. It is possible, but undetermined, that Brook Trout populations in this study would be larger if not for the introduction of Rainbow Trout. Management of Brook Trout and Rainbow Trout populations should be considered on a stream-by-stream basis due to the wide variation in population responses, and particular attention should be paid to the potential effects of Rainbow Trout introduction on streams with low abundances of Brook Trout.

Publication Date

2019

Comments

Faculty sponsor: Dr. Andrew Hafs, Department of Biology, Aquatic Biology Program

Recommended Citation

Tangren, Craig, "Effects of Rainbow Trout on Brook Trout Population Size in Tributaries to Lake Superior in Cook County, Minnesota" (2019). Journal of Earth and Life Science. 23.
https://pines.bemidjistate.edu/j-earth-life-sci/23