EFFECTS OF DIET AND REARING UNIT SIZE ON GROWTH AND SURVIVAL OF NEWLY-HATCHED WALLEYE Sander vitreus GROWN UNDER INTENSIVE CONDITIONS AT ONTARIO'S WHITE LAKE FISH CULTURE STATION AND PROGRESS ON DEVELOPING A CAPTIVE BROODSTOCK

Staff from White Lake Fish Culture Station have been extensively culturing Walleye larva in fertilized ponds for more than 20 years to support stocking efforts. These Walleye are stocked as either summer pond fingerlings (SPF) in mid-July when they typically weigh 0.5 - 1.0 gram (about six weeks post hatch), or as fall fingerlings (FF) when they typically weigh 20 grams (about 21-22 weeks post hatch). In recent years, the demand for both SPF and FF has increased beyond White Lake's production capacity.  In response, staff began to learn about and apply the intensive rearing practices that were pioneered by Summerfelt and colleagues. The success of these methods relies on a balance of turbidity, light, rearing unit, temperature, diet, and feeding regime.  The most critical component of this methodology is the addition of clay during the first few weeks post hatch to maintain turbidity.  When applied correctly, the technique can routinely result in survival rates to the SPF stage in excess of 50%.  

In 2011 and 2012, White Lake staff attempted rearing Walleye intensively without the use of turbidity modifiers.  Survival rates were low.  In response, staff identified experts in Iowa and Wisconsin who had expertise in the application of Summerfelt's methodology (or modifications thereof). Staff's first attempt to apply the methodology in 2013 failed; however they have seen steady improvements in survival and growth since that time (Fig. 1). This presentation describes the results of those efforts and summarizes the findings from diet and tank size trials.  

The presentation also describes the effects of diet and tank size on growth and survival (Fig. 2) and of efforts to develop captive broodstocks.