Spring Consequences of Overwinter Conditions for First-Year Saugeye

We used reservoir and laboratory studies to examine first-winter survival and growth of saugeye (female walleye Sander vitreus X male sauger S. canadensis) stocked into Ohio reservoirs.  In reservoirs, saugeye mean length increases during first-winter; however it is unclear whether growth or size-dependent mortality underlies this phenomenon.  In low prey systems, warm winters could increase starvation by intensifying energetic demand, making survival dependent on energy reserves.  Furthermore, survivors emerging from winter in poor energetic condition may experience reduced spring foraging success and growth.  In reservoirs, we estimated individual growth of tagged fish to distinguish between growth and size-dependent mortality.  To determine if accumulated energy reserves are sufficient to survive unusually low winter prey availability, we held two groups (starved and fed) of reservoir-captured saugeye from November through mid-June in outdoor pools.  Finally, to quantify indirect effects of winter, we used survivors from pools in spring foraging trials.  In reservoirs, we found no evidence of size-dependent mortality and saugeye of all sizes increased in length.  In pools, overwinter mortality was zero and spring foraging trials revealed that even starved fish can resume feeding once prey become available.  Our results suggest first winter does not influence recruitment of saugeye in Ohio reservoirs.