From the Ontario Ministry of Natural Resources and Forestry - October 15, 2018

The MNRF fish culture program has expertise in rearing many fish species under indoor conditions. We've been doing it for more than 40 years. But surprisingly, Ontario's favourite sport fish, the walleye, hasn't been one of them. In fact, the "summer fingerling"-size walleye that we stock have all been grown in outdoor ponds at White Lake (southeastern Ontario) and Blue Jay Creek (Manitoulin Island) fish culture stations. This works well and requires little labour. But it has two distinct drawbacks:

• it requires lots of land yet produces relatively small numbers of fish; and,
• the inability to control the environment means that production levels depend on weather conditions.

For many years, we've had difficulty meeting our stocking targets for summer and fall fingerlings. We wanted to do better. There were two ways we could increase capacity:

• construct more outdoor ponds; or,
• develop the expertise and specialized rearing space to grow newly-hatched walleye indoors in tanks.

The time was right to bring the early rearing phase of our walleye culture program indoors. We'd produce more fish in less space and gain control over environmental conditions.
 

Major challenges

It wouldn't be easy. Culturing newly-hatched walleye fry indoors in tanks presents major challenges. Fry are voracious eaters. They'll resort to cannibalism if they don't get enough of the right feed. They're also very sensitive to light. If conditions aren't perfect, they won't feed properly and will die.

The "recipe" for successfully culturing newly-hatched walleye fry in indoor tanks has been known for nearly 20 years. But only two or three U.S. agencies do it successfully. In 2012, MNRF asked experts at those agencies for their advice.

At White Lake fish culture station we developed a flow-through water system similar to the one used by the U.S. experts. Flow-through systems work best when you have lots of water that is naturally the right temperature at the right times of year.

The system at Blue Jay Creek fish culture station was based on a recirculating design. Though recirculating water systems are more complex, they operate with far less "new" water than flow-through systems, and achieving optimal water temperatures is easy and relatively inexpensive. If we mastered the "recipe" for a recirculating system, we could potentially raise newly-hatched walleye indoors at any of our nine fish culture stations.

It's taken several years for staff to master the techniques developed by our U.S. counterparts and adapt them to recirculating systems. Sometimes our efforts led to success, sometimes to disappointment. One lesson we learned is that newly-hatched walleye fry are much less forgiving than salmon and trout fry. Getting even the smallest detail wrong can turn success into disappointment in a matter of hours.

Outcomes

The good news for Ontario anglers? Despite the challenges, our results are getting better and better. The goal of meeting our walleye fingerling stocking targets is finally within reach.

Now, North American fish culture practitioners are coming to Ontario for the secrets to growing newly-hatched walleye fry in recirculating systems.

We extend our thanks to the Canada-Ontario Agreement for financial support and to the anglers and hunters whose licensing dollars have helped us develop our expertise and meet the challenges of raising walleye indoors.