Effect of smolt size on postrelease survival of hatchery-reared masu salmon Oncorhynchus masou

The relationship between mean weights of hatchery-reared masu salmon Oncorhynchus masou smelts at release and the subsequent recovery rates by coastal commercial fisheries in Hokkaido, northern Japan, was investigated using the maximum likelihood method. A strongly positive correlation was observed, showing smelts with a mean of 32.6 g obtained an approximately 20-fold recovery rate of those with a mean of 14.8g. The model with log-transformed independent variable (Y-i=-11.237+4.239 ln X-i) was selected as the most parsimonious model to represent the release size (X-i) and recovery rate (Y-i) relationship.