ワカサギ刺網における漁獲の飽和について

概要

論文の詳細を見る
The maximum catch per unit of gillnet (unit had about 131, 000 meshes) for Wakasagi (pondsmelt) Hypomesus transpcificus nipponensis was estimated from the catch data of experimental fishings. Each fishing operation was designed to have different soaking time of the gear with the repetition of haulinjg, in which the distribution of the enmeshed fish was recorded before the gear was reset into the water with the catch intact. The distance between each enmeshed fish was measured from the record in each haul and the catch-loss which dropped off from the mesh was checked comparing with the position of each enmeshed fish in the former hauling. The results obtained here are summarized as follows; 1) Variation of catch with different soaking time from one hour to four hours showed the realized maximum number as more than 150 individuals. 2) The ratio of loss number to the enmeshed fish amounted to over 20%, and higher percentage of this ratio was observed within one hour after the fish was enmeshed. 3) The influence of the enmeshed fish seemed to decrease the efficiency of the neighbouring meshes within 7cm. 4) Potential catch per unit in this type of gillnet was estimated to be approximately 1, 000 individuals.