Difference of Frequency of Transfer Between Several Types of Fishes in Underwater Fence Net Model Experiment

抄録

In the series of experiment, we have done and doing, to see the fish behavior toward various sorts of characters of fishing nets, scince these are a sort of model experiments in tank, we should select the fish species to use as to be small size proportional to that of the model net and as to alive actively through out the period of experiments.
Moreover, as the actual commercial fishing net is usually deviced so as to catch a certain kind of fish mainly, in model experiments we should select a minuature fish which can fairly represent the habit of it.
On the other hand, so various kinds of fish have so various peculiarities according to the range of living and habit of swimming, and about it also we are adding more knowlege in recent days by ultra sonic fish locater and others.
Set nets, including pound net and others, a group of fishing net kinds usually called “Teichi-ami” here, having long fence net or leader attached to the pocket or box, can catch any sort of fish which pass through the area where the net is set, though main turget is some narticular fish.
In the course of studies on the screening effect of fence net, usually using “medaka”, Aplocheilus (Oryzias) latipes, the common rice paddy minnow, as the minuature fish for model experiments, we became to anxious that if other fish species which has other sort of habit is used what result would be, obtained. And we thought such a knowlege would adds some to the deductive interpretaion of the result of this sort of model experiment.
The fence net or leader of set nets is usually spread out from the bottom up to the surface of water, however the screening effect of it would differs according to the fish kind in various parts of the net, if it is considered to be devided according to the stratum in depth of water. Especially, in recent years, set net is deviced to sink below the water surface to avoid the rough wave of the surface caused by stormy weather, so fence net, as a part of it, also has possibility to be set underwater, having its float line or cork line beneath the water surface.
Therefore, in the following experiments in tank, as the under water fence net a nylon film (opaque) of various hights was set at the middle of the tank, and the passing rate was observed about several kinds of fish having different habit of living.
The first serries of the experiments was done by the hand of Keikichi KONDO, (Research student) and the latter part was done by Masakazu YAO (now a member of Tohoku Region Fisheries Research Institute) as a graduation thesis when he was a student, and the plan and the compilation was made by Yoshio HIYAMA.