深海底延縄における残餌に関する研究

概要

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Since a bottom long line lies on the bottom of the sea for many hours, the bait is damaged by objective fish, small fish, a crustaceans, a cephalopods or the like and the hooked rate decreases with the lapse of time. Authors investigated the percentage of remaining bait and hooked rate of the deep sea bottom long line (the used number of hooks; 16500) 33 times to obtain the following results.1. It was concluded that squid bait had high percentage of remaining bait and was much better in bait retentivity compared with saury.2. There was a marked tendency that percentage of remaining bait was low in the water area showing a high hooked rate and the hooked rate is low in the water area showing a high percentage of remaining bait.3. The percentage of remaining bait in deep sea (200 ?? 900m) decreases with increase in depth but the reduction rate became extermely low in deep region over 600m. It is considered that percentage of remaining bait shows the relative distribution density of the benthos in that water region.4. From the percentage of remaining bait along a vertical line, it is said that the range of the vertical migration behavior of predator is very narrow.5. The difference of the hooked rate between a squid and saury was not confirmed.
日本水産學會の論文