Barrows, F.T.
Abstract:
Walleye is a very popular game fish and highly prized for the quality of its flesh. The meat can be characterized as firm, mild tasting, white fillets. Walleye are native to the North central region of North America where most of the interest in the culture of the species is centered. At one time there was a substantial commercial fishery for walleye, but currently only Native Americans can harvest walleye commercially in the U.S. There is also a commercial supply of frozen walleye fillets from Canada, but both of these sources are very seasonal. Although there seem to be many small aquaculture firms rearing walleye for the fillet market, the level of production appears fairly minor relative to apparent demand. Walleye have been spawned and fry released into the wild for the last 100 years. Eggs and milt are easily hand stripped from mature adults collected over spawning beds. Hormone induced spawning can be accomplished to ripen adults out of season. Fry have traditionally been reared in fertilized ponds. After the primary food of larval walleye (zooplankton) is depleted by the growing walleye there are several options. Fish are then either supplied with minnows, stocked into the wild, or transferred to hatchery tanks and fed formulated feeds. Research is progressing in feeding formulated feeds to walleye while still in the fry-rearing ponds. Survival of pond-reared fingerlings that are switched to formulated feeds was usually less than 30%. The survival rate, however, seemed to be affected by many factors including but not limited to water temperature, diet formulation and type, fish size and body fat content of the fingerlings. The advent of specialized larval feeds has greatly increased the overall survival of pond-reared fish when they are switched to formulated feeds. Development of improved rearing techniques and larval diets now allows for the successful culture of larval walleye using only formulated feeds in tanks. Survival rates of 60 to 70% have been observed in production hatcheries. A primary reason for commercial aquaculture of walleye is the present market for the flesh and the high price of fillets. The mild, firm texture of the meat may compete well with other species already available. The low fat content of the fillets has a positive effect on frozen shelf life. A major disadvantage of the species is the undomesticated nature of walleye, which results in the fish being very susceptible to stress, and subsequent reduction of growth. The time required to rear a marketable fish is still not well defined, which is another major disadvantage. Research is needed to increase the growth of fingerling fish and clearly define the time required to produce marketable fish economically.
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