On the Fish Gathering Effect on the Artificial Reefs ascertained by the Diving Observation XIV : At the off Sea of Eguchi Ura in the Satsuma Peninsula

In November of 1983, diving observation were carried out on the artificial concrete block reef submerged at the Eguchi Ura off the Fukiage Beach in Kagoshima prefecture, with the following informations obtained. (1) The observed artificial reef was a concrete blocked one consisting of a square windowed regular hexahedron, the length of each frame measuring one meter or one and a half meter, respectively. The setting-in conditions were to be assorted into three sorts of figure, namely one-headed hill-shaped figure, two-headed hill-shaped figure and the scattering-block-shaped figure. The sort of the fish gathered around the reefs are; Saurel Trachurus japonicus Crimson sea bream Evynnins japonicus Threeband sweetlips Plectorhynchus cinctus Chiken grunt Parapristipoma trilineatum Flat fish Palalichthys clivaceus and Squid Sepioteusthis lessoniano. The reef around which the most numerous gathering fish were observed was the two-headed-hill shaped concrete block constructed with the respective one meter long frames. (2) From the above mentioned results it was assumed that at the sea-front where the water depth was within the range from 25~30 meters, and the topography of the bottom was flattened, the most effective reef setting was fixed to be in the following condition, namely, firstly, the two headed-hill-shaped reefs with the height of 4 meters were set-in at the center, and around it were arranged a lot of reefs having the different scales and constructions.鹿児島県吹上浜の江口浦沖に設置されているコンクリートブロック魚礁について,昭和58年11月,潜水観察を実施した結果,次のような知見を得た。(1) 観察した魚礁は,1辺の長さが1mと1.5mの正六面体角窓付コンクリートブロック魚礁で,その形態は1山型,2山型及び分散型である。主な蝟集魚はタイ類,マアジ,イサキ,コショウダイ,ヒラメで,最も魚群が多く観察された魚礁は1m角の2山型コンクリートブロック魚礁であった。(2) 本研究の結果から,水深が25~30mの平坦な海底地形の海域において魚礁を設置する場合は,高さ4mの2山型魚礁を中心とし,その周囲に種類と構造の異なる魚礁群を配置する方法がより効果的であると考えられる