センスイ カンサツ ニヨル ジンコウ ギョショウ ノ ジッタイ ニツイテ VIII : カゴシマケン ホクサツ カイイキ ノ バアイ

During the period from August to September in 1980, diving observations were carried out on the eight Artificial reefs set at the sea-fronts off Akune city and Izumi city, both of which were situated in the Northern districts of Kagoshima Prefecture; with the following results obtained. (1) In both of the reefs set at the two sea-fronts, the method adopted by us, was the one in which the chief attention was paid to make the total bottom-area as wide as possible. And in ease of those set at the sea-front off Akune, the mean bottom-area per one Concrete block was noted to be 190 m^<2>; and in case of those at the sea-front off Izumi, it was 54 m^<2>; and in both the places the distances among the respective blocks were fixed to be uneven. (2) At the sea-front off Akune, the mean valued rate in which the Concrete blocks are made to be submerged in to the sea-bottom was 9 cm/year. (3) Comparing the densities of the fish schools gathering around the reefs, we noted that in case of the sea-front off Akune, the densities of the middle and small size fishes were depending upon the school of Apogon semilineatus while in case of the sea-front off Izumi, the density of the school of Apogon semilineatus was thin and those of the middle and small size ones were thick. (4) Comparing the compositions of the sand grain diameters on the bottom grounds of the two places, those of the sea-front off Akune were noted to be more complicated than those of the sea-front off Izumi, both of which were made of sand and silt mixed, or, of silty matelials only. As to the size of the sand grain diameter of the bottom ground, a propensity was noted that the smaller is the distance from the reef, the larger is the size of the sand grain diameter.昭和55年8月より9月に至る期間,阿久根市と出水市の沖合海域に設置してある8個所の人工魚礁において潜水観察及び採泥を実施した結果下記のような結果を得た。 1) 両海域の魚礁はいずれも設置底面積を広くとる方式を採用している。コンクリートブロック1個当りの平均所要海底面積は,阿久根市沖合が190㎡,出水市沖合が54㎡となり,いずれも分散が大である。2) 阿久根市沖合のコンクリートブロック魚礁の埋没の速さを推算すると,平均9cm/年となる。 3) 阿久根市沖合の魚礁には,ネンブツダイと大型魚が多く蝟集しているが,出水市沖合の魚礁には,ネンブツダイと大型魚が少なく,中型魚が多く蝟集している。4) 底質の粒度組成を比較すると,出水市沖合は阿久根市沖合より複雑な分布を示し砂・泥及び泥の底質部が広い。また魚礁周辺の底質は魚礁に近づく程粒径が大きくなる傾向がみられる