PINK SALMON MIGRATION IN RELATION TO SEA-SURFACE TEMPERATURE AND DAY-LENGTH IN THE OPEN SEA

Our aim was to describe the migratory process of pink salmon Oncorhync hus gorbuscha and to examine the relationship between the migration an d physical environments (sea surface temperature and day-length). From tag data for 4,876 individuals for the past thirty years, we examined distribution change, migratory speed and day-length during open sea m igration. The open sea distribution was consistent with 4-11 degrees C sea surface waters as found by past studies. Mean migratory speed was 31.5 +/- 27.8 km/day. Migratory speed was significantly correlated wi th day-length, and pink salmon tended to migrate fast around the summe r solstice. This result suggests that the photoperiod is an important factor related to the spawning migration of pink salmon.