Image Processed Vertical Distribution of Water Temperature at the Squid Jigging Stations with a Good Catch in the Japan Sea

Abstract

A fishing information system to estimate the level of catch prior to starting the actual operation is the key to realizing efficient operation planning. The vertical distribution of water temperature is one of the most probable factors having a close relationship to the level of catch. In the present report, the condition for a good catch was established as a yield of 3, 000 squids per operation. 50 stations were selected from 416 jigging station records during the period from 1982 to 1988 in the Japan Sea. The vertical distributions of water temperature were computer-processed into digital images, and their similarities to each other were calculated. The characteristics among the digital images of good catches were examined by the group average method of cluster analysis.
As a result, 41 digital images out of 50 of good catches were grouped into 16 small clusters of mutually high intra-cluster similarity, and then into 3 large ones which had a relation to the area division in the Japan Sea. 6 clusters consisted of the stations in the same area within 30 calendar days. 5 were of the same area in different years but within 30 calendar days. 3 were of the same area but different years and extending over more than 30 calendar days. Only 2 were of different years in the different areas.