Simulating Red Tide Flow into a Bluefin Tuna Fish Cage Using Computational Fluid Dynamics Analysis

Abstract

Red tides are major problems for fish aquaculture as they can cause massive mortality. To prevent fishery losses due to red tides, this study simulated the movement of red tide plankton around a fish cage using particle-based computational fluid dynamics (CFD). A scale model of a fish cage with a net height of 0.95 m and diameter of 1.0 m was used. A fish cage with a tarp in the surface zone was also studied in terms of whether it prevented the red tide from entering the cage.

The flow velocity inside the fish cage without the tarp was slightly lower, while the tarp drastically decreased the velocity inside the fish cage. Based on the simulated transport of the red tide, the inflow ratio (number particles entering the fish cage/all particles) was calculated. The inflow ratio of the fish cage without the tarp was about 100%, and was lower in the fish cage with the tarp. A tarp length three times the red tide depth was required to reduce the inflow ratio to 20%.

Using the proposed simulation, we can estimate the transport of red tide plankton and determine the effects of the red tide on aquaculture. The simulation could help fish cage designers. We believe that our method will contribute to efficient fish aquaculture.