Spawning Substrate Size, Shape, and Siltation Influence Walleye Egg Retention

Abstract

We compared Walleye Sander vitreus egg retention among varying rock treatments placed in a hydraulic flume to test the influence of spawning substrate shape and size on egg retention and the influence of substrate siltation on egg adhesiveness. Egg loss from suboptimal spawning substrates has been hypothesized as a substantial source of mortality during the incubation period. To investigate the influence of substrate size and shape on Walleye egg retention, known numbers of Walleye eggs were pipetted onto rock substrate in a hydraulic flume and exposed to flowing water conditions. Eggs scoured from the substrate during each trial were collected and enumerated. Egg retention was higher in angular crushed limestone than in round glacial till and greater in coarse gravel than in larger size-classes, under all water velocity regimes. Angular coarse gravel had the highest egg retention rate (mean ± SD, 66.9 ± 3.7%), and round very coarse gravel had the lowest egg retention rate (47.0 ± 3.1%) of all the rock size and shape treatments. Substrate siltation significantly influenced egg adhesion. Clean rocks had a mean ± SD egg retention of 35.9 ± 36.6%, whereas fine-sediment-covered rocks did not retain any eggs throughout the course of the experiment. Differences in substrate size, shape, and siltation between Walleye spawning sites may contribute to variation in egg retention rates. Using angular gravel during the creation of Walleye spawning habitat and maintaining clean spawning substrates (through scouring effects and habitat restoration) may decrease mortality associated with egg entrainment and redistribution.

Received June 13, 2012; accepted December 12, 2012

ACKNOWLEDGMENTS

This project was funded by the Fish Enhancement, Mitigation, and Research Fund, administered by the U.S. Fish and Wildlife Service, Cortland, New York. The authors would like to thank Steve LaPan, Mark Babenzien, and Dave Gordon from the New York State Department of Environmental Conservation for aiding in fish collection for the study. Thank you to Theodore Endreny for providing use of State University of New York–College of Environmental Science and Forestry's hydraulic flume and technical support. We would also like to thank Stephen Stehman for his substantial help with statistical analysis, Kevin Kapuscinski and two anonymous readers for review of a previous version of this manuscript, and the students and staff of the Thousand Islands Biological Station for assisting with data collection.