Effects of Salinity on the Survival and Growth of Pre-Smolt Coho Salmon (Oncorhynchus kisutch)

Abstract

Salinity tolerance of juvenile coho salmon (Oncorhynchus kisutch) increased markedly during the period from approximately [Formula: see text] months after emergence from the gravel to the onset of the smolt transformation, except for a decline in the fall. In January, salinity tolerance ceased to limit dispersal to the sea. The limiting effects of high salinities on survival were less for larger fish than for smaller individuals and were substantially reduced by a period of exposure to dilute salinities. Growth rate, food intake, and gross food conversion efficiency had the highest values at salinities of 5–10 ppt throughout the pre-smolt period. The results are discussed in relation to the feasibility of using saltwater impoundments as a management tool in increasing coho production.