Studies on the floating seaweeds-II : Floating seaweeds found in Iki-Tusima region

Abstract

From July to September, 1957 , the floating seaweeds around the Tusima-Higasi and the Iki Passages were surveyed four times on the facilities of the Fukuoka and the Saga Prefectural Fisheries Experimental Stations. The results are summarized as follows : 1) The species forming the floating seaweeds collected from this area appear almost similar to those of Tuyazaki region in the same season, as reported in the first part of this paper. 2) The relative abundance by weight of major species forming floating seaweeds of this area is also similar to the results obtained from the Tuyazaki materials in the same season (Fig. 5). 3) There was a small quantity of floating seaweeds in the Tusima Higasi Passage where the main stream of the Tusima Current runs through from the western Kyushu area to the Japan Sea. They were rather abundantly observed near the shore, probably along current-rips, as shown in Figs. 1-4. 4) From the results of the present surveys and the current investigations by the drift bottle method which were previously made by the Fukuoka and the Nagasaki Prefectural Fisheries Experimental Stations, there is considerable evidence, as mentioned in the first part of this paper, that the floating seaweeds in this area are not of origin of southern or western Kyushu area.第1報においては津屋崎近海の流れ藻を対象とし, 主として種類相や各種類の重量組成の周年変化について明らかにした(瀬川・沢田・檜垣・吉田1959).すでに述べたように,沖合,とくに対馬暖流の主流に当ると思われる対馬方面の調査も沿岸のものと同様に必要であり,筆者らがこの研究に着手した時から流れ藻の資源的意義,起源などに関する解決をめざして沖合の調査を計画していた. 壱岐・対馬方面での調査としては,1957年7月から9月にかけて計4回の機会を得たが,その結果少なくともその当時の夏から秋のはじめ頃は予想に反して非常に流れ藻の量が少なかつたこと,および種類組成は同時期に津屋崎近海でみられるものと大差なかつたことなどがわかつたので報告する.なお従来海流調査のため各地で海流びんが投入されているので,流れ藻の移動と類似の関係にあると思われるこれらの結果について若干の考察を行いたい.この調査は福岡県水産試験場の玄海丸,および佐賀県水産試験場の舞鶴丸で行つている月次定期海洋観測に便乗して行つたものである.便乗の便宜をいただいた両試験場長ならびに調査に協力いただいた乗組員の方々に謝意を表する