Survival and Condition of Cold-Banked Juvenile Walleyes

Abstract

Over their broad latitudinal distribution in nature, Walleye Sander vitreus have adapted to survive long winters in ice-covered lakes and for more than 5 months when water temperatures are less than required for growth (10°C). Thus, our hypothesis is that hatchery-reared fall-fingerling Walleyes may be maintained in hatchery confinement at low temperature for relatively long intervals with minimal requirement for feed and maintenance, i.e., cold banked (CB). Little information has been published, however, on survival and condition of CB fish to judge its merits. In this study, survival and condition of three cohorts (N = 1,538) of feed-trained juvenile Walleyes (181–192 mm total length, 47–58 g) are described after overwintering for 125–153 d in indoor culture tanks that were supplied with lake water of ambient winter temperature and pelleted feed. The mean for survival of three tanks of CB fish in each cohort was 85.8, 91.7, and 98.6% at corresponding mean water temperatures of 7.6, 8.3, and 6.8°C, where the lowest temperature ranged from 3.3°C to 4°C. The difference in mean length, weight, and condition from start to finish was small and statistically significant in only 1 of 3 years. Accelerated growth was observed in recaptured CB Walleyes 2 and 3 years after they were stocked into an 8-ha lake. The findings of this study suggest that cold banking can be used to hold Walleyes overwinter for subsequent spring stocking, with minimum loss of stock, or for holding back stock in a commercial facility for grow out.

Received March 6, 2013; accepted June 1, 2013

ACKNOWLEDGMENTS

We thank the McGraw Wildlife Foundation board of directors for their support in this project. Kyle Rumpel, Lucas Brown, and Karl Klimah, summer interns from University of Wisconsin–Stevens Point, assisted with culture.