Production-scale methods for intensive culture of walleye fry

to date, hatchery production of fingerling walleyes Stizostedion vitreum from intensive culture systems has been limited by fry survival during the first ?I d after hatching. Recent tests of new intensive culture methods for walleye fry have shown promise, although production has been inconsistent at loading rates above 20 fry/L. The objective of this study was to test the feasibility of intensively rearing walleye fry on brine shrimp Artemia sp, at production levels with loading rates 2-3-fold greater than those in current use. After 23 d of intensive culture, our system produced more than 333,000 advanced fry (17-18 mm total length) from initial loading densities of 40 and 60 fry/L. Fry were reared on live brine shrimp in circular tanks and with equipment typically used in the hatchery production of other game fish. Fry mortality during the experiment was low, except for days 8-11, when cannibalism was prevalent. Increased feed rates and removal of cannibals were methods used to control cannibalism during this 4-d period. Growth of fry was slightly higher (4.5%) at 40 fry/L than at 60 fry/L, but yield was substantially higher (37.8%) at 60 fry/L. Survival was not significantly different between densities. Estimated production costs for labor and feed were less than US $0.01/advanced fry. Our findings demonstrate the feasibility of intensively rearing walleye fry at production levels when they are fed brine shrimp.