This study investigates the following problems. The first problem is to describe a model of a set-net as a fish/gear-space system. The second problem is to develop a methodfor derivin gprobable swimming paths, and the third is to evaluate the probable swimming paths.
Research was carried out in a water tank using Yamame Onchorhynchus masou ahd Ugui Tribolodon hakonensis. This was a relatively easy means for obtaining data on the ecology of fish and long observation records of fish behavior.
Fish behavior can be termed as an m-th order Markov process. Therefore, the fish/gear-space system was described as an m-th order Markov source.
The probable swimming paths were derived from the joint probability of 3 sequential zones (mesh zones)in this study because fish swimming through 3 or more zones appeared to have a chosen path, or direction, in mind. Those were evaluated by using the entropy as defined by the author.
In conclusion, it appears that the above model, the method for deriving probable swimmingpaths and the evaluating method are applicable for investigating fish behavior in relation to any given fish/gear-space system.