メダカ群集の大きさと網地の遮断効果について
1955 年 21 巻 3 号 p. 154-158
詳細
1955 年 21 巻 3 号 p. 154-158
It is presumed that fish behavior against a fishing net, is more or less influenced by the sociality of a school of fish. In the present experiment, the habits of the Japanese minnow (Orizias latipes) are tested as they pass through various kinds of meshes (0.5, 1.0, 1.5 and 2.Ocm.) individually, and in schools of 3, 5 and 10 fishes respectively.
In solitary, the fish is very cautious, and if the mesh is smaller than 1.0cm. it does not approach the net. But when the mesh is larger than 1.5cm. the fish readily approaches and goes through the net.
Fishes forming a school, however, do not take so much care of the net as solitary, and approach the net although the mesh is small. The intercepting effect of a net disappears when the mesh is 1.0cm. for schools of 5 and 10 fishes, and 1.5cm. for a school of 3. It is also observed that the leader fish of a school is apt to pass the net more quickly and easily than a fish left alone in any kinds of meshes.
