This book that contains 38 research articles on marine ecology of Pacific salmon and steelhead trout, is dedicated to the International Year of the Salmon and is the first scientific publication that contributes to the library of the project.

Chum salmon Oncorhynchus keta eggs from the Chitose and Shiriuchi rivers in Hokkaido, northern Japan, were incubated under identical conditions with the aim of comparing vertebral number (V N ) to that reported archived data from the 1950s. The comparison revealed that mean V N of salmon from the Shiriuchi River has remained unchanged for 50 years and is higher than that from the Chitose River. The V N in the Chitose River salmon was found to be significantly higher than that recorded in the archival data. The variation in the mean V N of chum salmon fry collected during different seasons and years in the Chitose River falls within a range that has remained constant, suggesting that the difference between the values obtained in our study and the archival data may be due to differences in the timing of egg collection. These results indicate that the mean V N of chum salmon has been stable for a long period. Incubation experiments under identical conditions are a useful tool for examining changes in genetic structure and detecting the essential properties of populations.

No abstract

Comparison of vertebral number between wild and hatchery-reared population, and eŠect of stock enhancement programs on vertebral number in masu salmon Oncorhynchus masou DAISEI ANDO, 1 KAZUTAKA SHIMODA, 2a KATSUMI TAKEUCHI, 2 ANAI IIJIMA, 3b