Simulating Juvenile Bluefin Tuna Thunnus orientalis Behavior Inside of a Fish Cage

Abstract

The Pacific bluefin tuna (PBT) Thunnus orientalis is an important commercial species. The life cycle aquaculture of PBT has been widely studied in Japan. Collisions or contact with the net cage leads to mortality in juvenile PBT. Therefore, it is important to understand the schooling behavior of juvenile PBT to reduce contact and collisions.

In this study, we developed a fish schooling behavior model based on a Boids model to understand the schooling behavior of PBT. The parameters used to simulate PBT schooling were optimized using a three-dimensional movement track. The optimized model results agreed well with the actual measurements. Next, the proposed model was applied to circular, octagonal, and square net cages. Simulated PBTs swam in a circular pattern inside the circular net cage. In the octagonal and square net cages, schooling behavior was less obvious than in the circular net cage. In addition, the modeled PBT swam nearer to the wall in the octagonal and square net cages compared with the circular cage. Consequently, the collision risk was higher in the octagonal and square net cages.

Using the proposed model, we can simulate the behavior of PBT. Ultimately, a net designer can use the model to assess collision risk. We believe that our model will enhance fish aquaculture.