Study of characteristic of feeding habitat of juvenile chum salmon and their food environment in the Pacific coastal waters, central part of Hokkaido [Japan]
2005
Seki, J.(National Salmon Resources Center, Sapporo (Japan))
This study is to investigate the ecological characteristics of juvenile chum salmon and the behavior of zooplankton during spring and early summer in the Pacific coastal waters off the coast of Hokkaido. The coastal waters were covered with the Coastal-Oyashio in early spring, and surface temperatures increased to 10 deg C in early-mid June and above 13 deg C in July. Juvenile chum salmon scattered extensively at surface temperature 8 deg C, and the fish abundances decreased when over 13 deg C. Instantaneous growth rates of fish were -0.0025 to 0.0138 in the coastal waters. Zooplankton biomass peaked from late May to early June. Cold-water zooplankton species dominated at all times. Four types of diel vertical migrations of zooplankton were recognized. The mean distances between peaks of zooplankton number were almost 80 to 140 m. Zooplankton body lengths decreased in later periods. Due to the increased water temperature, zooplankton biomass and growth rate of fish in this area, it is desirable for fish to be released at fork length 56 mm at a surface temperature of 5 deg C.
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