Short-term Rearing of Pink Salmon (Oncorhynchus gorbuscha) Fry: Effect on Survival and Biomass of Returning Adults

Publisher Website
Google Scholar
Abstract
Survival of pink salmon (O. gorbuscha) fry could theoretically be improved if they were reared to a larger size before being released into the estuary. Three lots of 1975-brood pink salmon fry, reared from eggs in a hatchery, were cultured in floating estuarine raceways for 30, 60 and 90 days before being released into the Little Port Walter estuary on Baranof Island, southeastern Alaska [USA]. An unfed control lot was released after emergence. Four groups of 15,000 fry each were differentially fin marked. Total marine survival for the 4 lots was computed from recoveries of marked adults in the Little Port Walter vicinity in 1977. Survival from release to return was lowest for the control lot (3.1%); increased for fry reared for 30 and 60 days (4.6 and 5.2%, respectively) and decreased for fry cultured for 90 days (4.3%). Mortalities in lots cultured for 60 and 90 days significantly reduced the numbers of fry released in these groups. Mortalities were associated with the marine diatoms Chaetoceros spp. Mean length and weight of returning adults declined with increased fry-rearing time. Compared with the control lot, adults from fry cultured for 30 days had 39% more biomass: adults from fry cultured for 60 days had the same biomass; and adults from fry cultured for 90 days had 45% less biomass. Culturing fry for 30 days in the raceways significantly increased the number and biomass of returning adults.