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Nagata Y.,Marine Information Research Center | Oguma S.,Hokkaido National Fisheries Research Institute | Nagase K.,Nemuro City Fisheries Research Institute | Aikawa K.,Nemuro City Fisheries Research Institute | Hakata I.,Nemuro City Fisheries Research Institute
Mer | Year: 2010

The Nemuro City Fisheries Research Institute installed bottom temperature sensors off Sanri-hama Beach, Nemuro in in order to know seasonal variations of environmental circumstance of Hanasaki crabs. 8 stations were set along a straight line extended towards offshore. The depths of stations are 5m through 60m. The observations were made from December 28, 2005 through May 13, 2009. In the previous paper (Nagase et al., 2010) showed that temperature and salinity profiles have usually vertically homogeneous both in summer and in winter seasons. The temperature decreases from shore to offshore in summer season, and it increases in winter season. These trends appear to extend into temperature structure in the East Hokkaido Coastal Current (the Coastal Oyashio in winter season and the East Hokkaido Warm Current in winter season). By using the results of STD observation which were obtained 17 times during the observation. In contrast to temperature gradients, salinity gradients in the nearshore region are opposite to those inside the East Hokkaido Coastal Current: salinity increases toward offshore in summer season, and it decreases in winter season. This would be explained by supply of fresh land water was brought from offshore into the region in summer season. In winter season, the fresher Oyashio Water, originated from the sea area off the Kruil Islands, would be brought into the nearshore region from offshore.We examined the seasonal variation of water type of the 50m depth at the most offshore observation station St. 8, and compared with that of the East Hokkaido Coastal Current Water. The water is almost identical to that in the East Hokkaido Coastal Current Water at 50m depth, but some tendency that the phase of the seasonal variation in nearshore region advances to that of the he East Hokkaido Coastal Current Water. Source


Nagase K.,Nemuro City Fisheries Research Institute | Aikawa K.,Nemuro City Fisheries Research Institute | Hakata I.,Nemuro City Fisheries Research Institute | Nagata Y.,Marine Information Research Center
Mer | Year: 2010

The Nemuro City Fisheries Research Institute installed bottom temperature measuring sensors off Sanrihama Beach, Nemuro, in order to know seasonal variations of environmental circumstance of Hanasaki crabs. We set 8 stations along a straight line extended offshore, and the observations were made from December 28, 2005 through May 13, 2009. Depths of stations are 5, 10, 15, 20, 30, 40, 50, and 60m. STD observations were made at the time of replacement of measuring systems or at that of exchange of data loggers. Though some of measuring systems were often lost due to severe storms or due to fishing activities, we could clarify peculiar seasonal variations of temperature structure in the sea under consideration. In "summer season" or in "winter seasons", temperature is basically vertically uniform at each station, except in surface thermocline, but temperature decreases toward offshore in "summer season" and increases toward offshore in "winter season". These horizontal temperature gradients are the same as those in the flow regions of the East Hokkaido Warm Current and of the Coastal Oyashio, respectively. The phases of "summer season" and "winter season" appear to advance by about 3 months than that of the East Hokkaido Warm Current or of the Coastal Oyashio, respectively. Besides, melted water of sea ice which originated from the Okhotsk Sea cannot produce very cold water (say below 0°C) in March or in April. These findings would give valuable suggestion for studies of the East Hokkaido Coastal Current. Source

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