Ecological Studies on the Alaska Pollack in the Adjacent Waters of the Funka Bay, Hokkaido-III
Seasonal variations of Hydrographic conditions
1979 Volume 45 Issue 9 Pages 1137-1142
Details
1979 Volume 45 Issue 9 Pages 1137-1142
In the previous papers, the distribution and migration in feeding and spawning seasons of adult Alaska po11ack, Theragra chalcogramma (PALLAS), in the adjacent waters of the Funka Bay, Hokkaido were examined.
However, the relationship between the habits of adult Alaska pollack and environmental conditions throughout the year is not clear. For this reason, the authors investigated water temperature, salinity, food organisms and biological factors of fish once a month from February 1974 to February 1975 six definite stations.
This paper deals with the examination of the seasonal variations of water mass in this area.
1. The Tsugaru warm current (salinity more than 33.8‰ as an indicates of presence) enters this area through the mid-water layer in June and occupies the widest sphere in November. In December the current falls off and disappears in January.
2. The surface layer water of the Oyashio current (salinity less than 33.2‰) occupies most of the surface and mid-water layers in February and gradually declines from March. In June this water is thrust toward the coastal area by the inflow of the Tsugaru warm current and almost disappears in November.
3. The bottom layer water of the Oyashio current (temperature less than 3.5°C and salinity less than 33, 7‰) occupies about 200-450m in depth near the bottom in February, but the range gradually decreases with the inflow of the Tsugaru warm current and shows the minimum range during December and January.
