Fall 2009

Rick Goetz explains how fertilized yellow perch eggs are used in his genetic research project. Photo: Carolyn Rumery Betz.
UW Sea Grant Research

Breeding Yellow Perch to Meet Consumer Demand

By Carolyn Rumery Betz

The beer-battered walleye on the menu at Friday night’s fish fry looks tempting, but nothing satisfies like the mild taste and firm flesh of deep-fried yellow perch. But perch served in Wisconsin restaurants may come from Lake Erie or Canada; the only commercial yellow perch fishery on Lake Michigan is limited to Green Bay. Because of a decline in yellow perch natural reproduction between 1988 and 2000, the Wisconsin Department of Natural Resources imposed a severe limit on yellow perch harvest to allow the fish to recover.

Growing yellow perch in indoor aquaculture facilities may help meet the consumer demand, according to researcher Frederick Goetz, a senior scientist at Milwaukee’s Great Lakes Wisconsin Aquatic Technology and Environmental Research (WATER) Institute. Goetz is using Sea Grant funding to develop fast-growing, disease-resistant perch with good reproductive capacity.

Raising fish in captivity requires a broodstock—sexually mature male and female fish with known genetic characteristics—from which to breed. This is not possible when the grower has to start each year with fish from the wild with unknown characteristics.

To create the first-generation broodstock, Goetz selected yellow perch from the Perquimans River in North Carolina, the Choptank River in Maryland, and Lake Winnebago in Wisconsin. He is interested in genetic variations within and across each of the three geographic regions because great genetic variation across the population is more likely to yield desirable traits.

Goetz bred the fish in the wild and brought about 20 sets of fertilized eggs from each site back to his lab. Once the eggs hatched, the researcher embedded tiny microchips into 2,400 fish in order to track which parents produced which offspring. He is able to track the genetic structure of the offspring—called the parental stock. As they mature, the parental stock are measured for length, weight, protein content, and filet yield.

The Atlantic fish grow more rapidly than the Midwest fish, but Goetz believes that the fish from Lake Winnebago may possess other desirable characteristics, such as disease resistance.

Goetz selected the top 30 to 40 percent of the fastest growing and largest fish from the parental stock to produce the second generation. Using electric lights programmed to mimic sunrise, daylight, sunset, and night, the fish are subject to light and temperature conditions characteristic of their home environments. By manipulating light and temperature periods, researchers can trick the fish into changing their natural reproductive cycles, allowing them to reproduce year-round instead of only in the spring.

“The commercial grower wants fast-growing fish with good, consistent filet yields,” he said. This manipulation may allow fish farmers to provide a steady supply of fish to supermarkets and restaurants.

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