Growth and survival of newly emerged and juvenile coho salmon (Oncorhynchus kisutch) reared at different salinities

Abstract

Newly emerged coho salmon (Oncorhynchus kisutch) from 40 families of a coastal-spawning population were reared in fresh water and seawater for 144 d after ponding. Growth and survival were, on average, higher in fresh water than in seawater, but juveniles from some families had higher or equivalent survival in seawater compared with fresh water. Heritability (sire variance component) of survival and length ranged between 0.30 and 0.35. The transfer of juveniles from fresh water to 15‰ seawater after 70 d of rearing in fresh water had little effect on their subsequent growth and survival. In a second experiment, newly emerged fry from a coastal- and an interior-spawning population had the same survival in fresh water, but survival was higher for the coastal population than for the interior population in 15 or 25‰ seawater. Rearing environment had no effect on survival for the coastal population, but as rearing salinities increased, survival for the interior population decreased. Within a population, length, weight, and instantaneous growth rates for length and weight decreased with increased rearing salinity. The growth and survival of some juveniles in a saline environment were comparable to those observed for juveniles reared in fresh water, indicating that the marine environment provides a suitable rearing environment for some coho salmon.