The Quad Cities Spray Canal Project has operated since 1984 to produce advanced sport fish fingerlings for stocking Pools 13 and 14 of the Mississippi River. Walleye were produced extensively in a 57 acre canal around the Quad Cities Nuclear Generation Station. Target production has been 175,000 walleye fingerlings per year. Over time the canal became less suitable for fish culture due to extensive sedimentation and deterioration of the canal liner. A recirculating aquaculture system (RAS) was installed in 2022 for the production of walleye fingerlings. Starting with the 2023 production season the old canal was abandoned and walleye were raised from fry to fingerling in the RAS system.
The RAS system consisted of three circular self-cleaning larval tanks 96” in (244 cm) diameter, 54” (137 mc) tall, with an operating volume of 5.7 m3 each. The tanks had black interior walls and light grey flooring. A cleaning arm on the wall and floor would sweep waste to a collection trough where it could easily be siphoned out of the tank. Two spray bars were mounted over the tank to provide surface spray to break up any oils on the surface and allow walleye fry to inflate their swim bladders. The recirculation system consisted of a drum filter with 60 micron screens, a 2,839 L (750 gal) divided filtration sump, a 2 cubic meter moving bed bioreactor (MBBR), a 121” (307 cm) tall by 48” (122 cm) diameter degassing tower, an 18KW inline titanium heater, a 960 watt UV Sterilizer and an Oxygen Cone supplied by a liquid oxygen tank.
Each tank was stocked with 150,000 fry 3 days post hatch, for a rate of about 26 fry/liter. Initial temperature was 15.7 oC and was gradually increased to about 21 oC over the culture period. Light was maintained at 50 Lux, 24 hours per day. Concentrated preserved Nanochloropsis algae was added to the sump twice per day, 800 ml per addition, to maintain turbidity and reduce cannibalism. Each tank was equipped with two Arvo Tec feeders, and fish were fed every 5 minutes, 24 hours per day. Fry were started on Otohime B2 feed and progressed through Otohime C1, C2, and Bio Vita fry 1.2mm. Mortalities were counted daily and feeding rates were adjusted daily.
A total of 239,968 walleye fingerlings were harvested from the three RAS tanks in 2023. This represents a 53.3% return. A total of 258,669 fingerlings were harvested in 2024 representing a 57.4% return. Production targets were met in both seasons. Potential problems and pitfalls will be discussed.