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Division: Sport Fish
Title: Growth, survival, and costs of rearing game fish in floating net pens at Harding Lake, Alaska, 1990
Author: Clark, J. H., T. R. Viavant, C. Skaugstad, and T. R. McKinley
Year: 1991
Report ID: Alaska Department of Fish and Game, Fishery Data Series No. 91-2, Anchorage, Alaska, USA.
Abstract: Arctic char Salvelinus alpinus, Arctic grayling Thymallus arcticus, lake trout Salvelinus namaycush, rainbow trout Oncorhynchus mykiss, and sockeye salmon Oncorhynchus nerka were stocked into and subsequently reared in floating net-pens at Harding Lake, Alaska, during the summer of 1990. Fish were reared between five and 11 weeks and were fed a commercially available semi-moist pelletized diet. Fish were sampled every two weeks to estimate mean length and weight. Arctic grayling and sockeye salmon stocked into net-pens as sac fry exhibited the highest growth (18 percent and 15 percent in length per week, respectively), and they also exhibited the lowest survival (less than 10 percent). Arctic grayling and rainbow trout stocked into net-pens as fingerlings grew 11 percent and 10 percent in length per week, respectively, and the survival for these two groups of fish exceeded 99 percent. Rainbow trout stocked into net-pens at an average length of 128 millimeters grew an average of 6 percent in length per week, and exhibited a survival of 99 percent. Rainbow trout stocked into net-pens at an average length of 215 millimeters grew an average of 3 percent in length per week and none died. Arctic char fingerlings grew an average of 5 percent in length per week and survival exceeded 99 percent. Lake trout fingerlings grew 3 percent in length per week and had a survival of almost 98 percent. Conversion factors and average growth increments per temperature unit (degree-day) for pen reared fish were generally similar to such statistics for the same species of fish when reared in Alaskan hatcheries. Lake trout were an exception exhibiting lower growth and less efficient conversion factors. Construction costs for the net-pen facility totaled $26,000. Costs of operating and maintaining the facility totaled $39,000. Assuming a five year amortization rate for construction costs, the cost of the 1990 net-pen rearing project was estimated to be $44,200. A total of 1,231 kilograms of fish were stocked into net-pens and a total of 4,178 kilograms of fish were released from the net-pens. Thus 2,947 kilograms of fish were produced at the facility at an average cost of $15 per kilogram.