Abstract
Enhancement strategies for masu salmon Oncorhynchus masou have been developed during the last 20 years in northern Japan. The introduction of age-1 smolts is regarded as the most effective method although age-0 smolts are produced experimentally by accelerated incubation and rearing at the Hokkaido Fish Hatchery. In this study, we estimated recoveries of hatchery-reared age-0 and age-1 masu salmon smolts through a two-stage sampling survey of commercial landings in western Hokkaido, Japan. Recovery rates ranged between 0.1 and 4.5% for age-0 smolts and 0.2 and 3.5% for age-1 smolts. Increased smolt weight at release had positive effects on recovery rates of age-1 smolts, and increases in condition factor had negative effects on the recovery rates of age-0 smolts.
