Spatial and Temporal Variability in Post-Larval Yellow Perch Density

Author

Steve Hauschildt

Date of Award

2-9-2019

Document Type

Thesis

Department

Biology

First Advisor

Andrew Hafs

Abstract

Yellow Perch Perca flavescens are important as forage for other species and for sport fishing in many northern lakes. However, estimating post-larval Yellow Perch populations can be difficult because of many environmental factors that cause unexplained variation. The objective of this study was to help reduce unexplained variation by determining a post-larval Yellow Perch population density estimate on Blackduck Lake, MN, provide guidance to help determine the number of trawls required for trawling-based recruitment indices to achieve varying levels of precision, and test for the effects of wind speed and direction on post-larval Yellow Perch spatial variability. This study estimated a density of 0.45 fish/m' (0.58 SD) during the sampling period (26 Jun - 07 Jul 2017). It was determined that between 10-15 trawls produced a precise density estimate; however, trawls should be taken over multiple days in varying wind speeds to avoid over/under estimation. Trawling should also be performed in-line with wind direction to ensure non-bias estimates are calculated from both upwind and downwind sectors. This study determined wind speed and direction had a significant influence on the distribution of post-larval Yellow Perch, as more fish were caught in the downwind sector until winds reached 15 kmph. At 15 kmph, fish densities were equal in the upwind and downwind sectors of the lake. Wind did not have a significant influence though on how post-larval Yellow Perch were distributed by total length. During high wind events, more fish were found in the upwind sector of the lake, suggesting that post-larval fish are being moved laterally out of non-towable areas. From the results of this study it appears Yellow Perch must continually relocate back into shallow areas after each high wind event moves them out of the non-trawlable areas, until they are strong enough to resist the wind.

Recommended Citation

Hauschildt, Steve, "Spatial and Temporal Variability in Post-Larval Yellow Perch Density" (2019). Biology Graduate Theses. 8.
https://pines.bemidjistate.edu/thesis-biol/8