Review of the Effects of Rearing Density on Survival to Adulthood for Pacific Salmon

Abstract

Since 1975, 20 brood years of coho salmon (Oncorhynchus kisutch) and 15 brood years of chinook salmon (O. tshawytscha) have been used in experiments to determine the effects of rearing density on survival to adulthood. Results from these experiments were compiled and standardized to determine if there were significant relationships between rearing density and percent yield to adulthood or number of adults produced per rearing pond. For coho salmon, the number of adults per pond increased with increased rearing density for 15 of 20 brood years. For chinook salmon, increased rearing density increased adult yield per pond in only 4 of the 15 brood years. In 7 of 20 brood years of coho salmon, increased rearing density resulted in a reduced percent survival to adulthood. For chinook salmon, increased rearing density produced a reduced percent survival in 14 of 15 brood years. These results suggest some major differences between the responses of coho salmon and chinook salmon to rearing density. The implications for hatchery rearing and management are discussed.