Walleye, Sander vitreus. (Photo: Engbretson, Eric/U.S. Fish and Wildlife Service)

Walleye could open new aquaculture opportunities at Wisconsin

UNITED STATES
Saturday, October 21, 2017, 01:50 (GMT + 9)

Researchers from the University of Wisconsin-Madison are carrying out a two-year aquaculture research project intended to compare the production of walleye, a native Wisconsin fish, and saugeye, a natural hybrid of walleye and sauger, in a recirculating aquaculture system and a closed aquaponics system.

As the project, funded by UW–Madison-based Wisconsin Sea Grant and headed by Chris Hartleb and Greg Fischer, reaches the midway point, it is looking more promising by the fish tank.

Both Fischer and Hartleb spent the last year raising saugeye in tanks with low, medium and high densities at each facility at the UW-Stevens Point Aquaponics Innovation Center in Montello, Wisconsin.

These scientists pointed out that so far, the results are encouraging. Walleye in the low-density tanks grew the best, reaching as high as a pound and a half. In the medium density tanks, 93 per cent of the fish reached one pound. The high-density tank was somewhat less successful—70 percent of the fish did not reach a pound.

"The saugeyes grew really well," said Fischer. "We reached our target goal of growing a one-pound fish in less than a year at each of the three densities. We even had some fish up to two pounds."

In addition, it has been noted that Fischer's Northern Aquaculture Demonstration Facility operation and systems experienced no significant issues with maintaining water quality, a common problem that can often derail an aquaculture operation.

“At NADF, we've have been investigating and working on walleyes and their hybrids for food fish use for almost 10 years now and this research is critical to move this species forward for sustainable US aquaculture," Fischer stated.

Currently, nearly 90 per cent of the aquaculture industry in the US is focused on tilapia, which is explained by the fact that the fish grows well in high-density tanks and sometimes returns a good price at market.

Given the fact that tilapia fry can be hit by a disease at the only three nurseries in the US that provide tilapia fingerlings to aquaculture/aquaponics operations, UW-Madison scientists are convinced that walleye farming offers its own economic advantage and it can be the cornerstone of a successful aquaponics operation.

At the Aquaponics Innovation Center the water containing the fish waste is drained, filtered and oxygenated, then pumped into tanks to provide nutrients to a wide variety of greens, from multiple types of lettuce to kale. Hartleb has even taken a stab at growing broccoli.

"Aquaculture is about purifying the water," explained Hartleb. "Aquaponics is about purifying the water to a non-toxic level. It's a closed system, and you're basically Mother Nature. Any change you make shifts everything."

Hartleb's also been charting the water chemistry necessary to keep both the fish and the plants healthy and productive. For instance, walleye are a carnivorous fish, which has an impact on the proper nutrient process.

The only bottleneck that the researchers have pinpointed is the lack of a nursery provider.

"We need a private industry partner to step up to the plate on this aspect of providing biosecure, feed trained, intensively reared fingerlings to support the industry. We know how to do this successfully and can help with training and setup." said Fischer.

The researchers is convinced that if they can continue working with and educating interested fish farmers, walleye and hybrids will be the next big thing for Wisconsin aquaculture.

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