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 Oncorhynchus gorbuscha and to examine the relationship between the migration and 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 migration. 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 with day-length, and pink salmon tended to migrate fast around the summer solstice. This result suggests that the photoperiod is an important factor related to the spawning migration of pink salmon.