Experimental study and discussion of Fridman's theory in relation to the behavior of fish school encountered by the leader-net of set-net.

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In relation to the behavior of fish school encountered by the leader-net, Fridman's theory is as follows. The fish school of constant concentration is considered as a liquid stream of density ρ=const. Let the volume rate of the liquid in the incoming stream to the leader-net be q, the volume rates in the component of the same direction as yet which is parallel with the leader-net, and that of opposite side be q2 and q1, and the encounter angle be α, respectively, i.e., q1/q2=(1-cosα)/(1+cosα). The author has put forth a new theory on the behavior of the fish passing through the mesh of leader-net. If the fish swimming speed when encountering the leader-net is ν, then the component of swimming speed in parallel with the leader-net is ν cosα, and that in right angle with the leader-net is ν sinα. The volume rate of the liquid passing through the mesh is q3, i.e., q1=k1k1•sinα/2 q2=k2•(sinα/2+cosα) q3=k3•sinα k1, k2, k3; const. This theory is more in conformity with the experimental values than Fridman's.