人工藻場プラント周辺の魚群行動について〔人工魚礁近傍の魚群生態に関する基礎的研究-5-〕
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概要
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Artificial seaweed farm plant, experimental floating reef made of steel, had been anchored by two chains at the depth of fourty-three meters off Tajima in the Japan Sea, from August 1979 to October 1982. To find out the behavioral character and the gathering factor of fishes around the plant, investigations were carried out by direct observation, by some automatic recording instruments and by the echosounder, four times. (1) Around the plant, twenty-three kinds of fishes were found. Most of them belonged to the young stage, and some adult fishes appeared sometimes. (2) It seemed that the young fishes settled just near the plant in spring or summer like those that appeared with floating algae, and lived until autumn or winter. (3) Adult fishes were seen to gather around the plant temporarily on their migration. (4) Distribution and activity of fishes around the plant varied with the life stage of each kind of fish, and the distributed area became wide as they grew. (5) Young fishes (22 kinds except Epinephelus awoara) belonged to all the day dependant type to the shelf. (6) Adult fishes (Seriola aureovittata, Trachurus japonicus and Navodon modestus) belonged to daytime dependant type. Navodon modestus distributed under the shelf in the daytime, in a range of about thirty meters horizontally from the end of the shelf. (7) Some fishes (Epinephelus awoara and some of Oplegnathus fasciatus) moved vertically between the shelf and the bottom along the anchor chain of the plant.
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