EFFECTS OF DIET AND REARING UNIT SIZE ON THE INTENSIVE CULTURE OF NEWLY-HATCHED WALLEYE Sander vitreus IN A RECIRCULATING AQUACULTURE SYSTEM AT ONTARIO'S BLUE JAY CREEK FISH CULTURE STATION

Timothy D. Drew*, P.F. Methner, R.W. Zheng, J.L. Smith, S.V. Krause, and K.K. Loftus
 
White Lake Fish Culture Station
Ontario Ministry of Natural Resources and Forestry
25900 Highway 7, Sharbot Lake, ON K0H 2P0
tim.drew@ontario.ca

Staff from Blue Jay Creek Fish Culture Station have been extensively culturing walleye larva in fertilized ponds at their substation for more than 20 years in order to support stocking efforts. The station stocks its walleye 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 weeks post hatch). In recent years, the demand for both SPF and FF has increased beyond Blue Jay's production capacity.  In response, staff began to explore the intensive culture methods pioneered by Summerfelt and colleagues. The success of these methods relies on a balance of turbidity, light, rearing unit, temperature, diet, and feeding regime.  Of particular importance is the addition of clay during the first few weeks post hatch to maintain elevated turbidity levels.  When applied correctly, the methodology can routinely result in over 50% survival to the SPF stage.

Due to space and temperature constraints at Blue Jay Creek, staff developed one of the first recirculating aquaculture systems for the intensive culture of newly-hatched Walleye in North America. This presentation summarizes some of the challenges faced, and progress made, over three years of effort.  The challenges included difficulties maintaining optimum temperatures and turbidity levels, low oxygen levels, ammonia spikes, system clogging and fish health issues possibly related to the challenge of disinfecting the water between passes during the high turbidity phase.  

Over a three year period, staff overcame many of these challenges while also evaluating the effect of tank size and diet on growth and survival (Fig.1).  Results to date are promising (Fig. 2).