コンクリートの飼育池で水深別に育成したアユの成長
2002 年 50 巻 3 号 p. 377-378
詳細
2002 年 50 巻 3 号 p. 377-378
Growth of ayu, Plecoglossus altivelis, reared at several depths was examined to clarify the effect of increasing the water depth in ayu fishing grounds in which the flow has been decreased artificially, such as in the Shou River. Ayu were reared in concrete ponds from 16 June to 18 September, 2000. Ayu were divided into 3 groups (Group 1, with feeding and a density of 0.9 individuals/m2; Group 2, with feeding and a density of 2.5 individuals/m2; Group 3, without feeding and a density of 0.9 individuals/m2) . In each group replicate samples were reared at 50cm, 30cm and 10cm depths. Initially, they were of the same body weight, but finally the ayu reared at 50cm depth grew to be significantly bigger than those reared at the 30cm and 10cm depths. In Group 3, ayu reared at 30cm were significantly bigger than those reared at 10cm. These differences are considered to be caused by the decrease in the density of individuals/m3, increase of food on the side walls and reduction of stress with depth. The mean depth of rivers increases as the flow increases. These facts suggest that increasing the water flow or creating deeper runs artificially in such rivers as the Shou River would lead to an increase in the number of large individuals of ayu and aid in propagating the ayu resources more effectively.
