ホソトビの回遊と産卵生態に関する研究-III : 産卵場における魚群の行動について

概要

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In the Japan Sea, all kinds of fisheries for flying-fish, Cypselurus opisthopus hiraii ABE, are operated in the inshore areas; drift nets are operated at 10km or so from the shore, surrounding nets in the inshore areas within 2km, and gill nets within 1km from the shore. The change of the fishing method with the approaching proximity of the shore is considered to be dependent on the great changes in the behavior of the flying fish there. The present report deals with the behavior of the fish schools after they descend to the sea bottom at gill net fishing grounds. 1) Coefficient of variation in the flying fish catch with gill net is larger than that of drift net and surrounding net. 2) Since a fish school in the sea bottom is in the nature of a condensed mass, the dif-ference between catches of two adjoining gill nets is large. Generally one school is assumed to be composed of about 2000 fish but occasionally, depending on oceanographic conditions, scores of thousands of fish are also found. 3) More fish are caught at the inshore side of a net than on the offshore side, and in most cases they are caught in masses at about 3m from the sea bottom. 4) Fish schools are considered to be inactive and scarecely move at the sea bottom. They float up to the surface early in the morning to migrate offshore.
公益社団法人日本水産学会の論文