The Relation of Temperature to the Seaward Migration of Young Sockeye Salmon (Oncorhynchus nerka)

Abstract

The period of seaward migration of young sockeye from Cultus lake each spring is inversely correlated with temperature conditions prevailing during the months immediately preceding. Correlating temperature readings of the outflow stream with date when twenty per cent migration occurred, a statistically significant correlation of −0.85 was obtained for February and March and −0.77 for January to March. Using air temperatures, coefficients of −0.91 for January to March and −0.74 for February and March were found. Commencement of migration coincides with vernal rise in lake temperatures. Under normal conditions, with low winter minimum, there appears to be a threshold migration temperature approximating 4.4 °C. (40°F.) but in seasons when lake temperatures are not depressed to this level a slight rise stimulates migration. Progress of migration is largely influenced by prevailing weather conditions and their effect upon temperature trends. Cessation of migration appears to be related to the setting-up of a "temperature blanket" which inhibits migration from the lake of sockeye still resident therein. These latter, showing small growth during their first year, remain in the lake until the following spring and then are among the first to migrate.