Department of Marine Biosciences, Faculty of Marine Science, Tokyo University of Marine Science and Technology, Minato, Tokyo 108-8477, Japan
Occurrence of transmission of a fish disease among culture ponds and risk analysis were computed using a simple simulation model of a one-dimensional pond distribution. We assumed three types of fish transportation ((1) directional exchange, (2) directional on-way transportation and (3) random transportation among tanks) and three defense strategies against the invasion of the disease. Numerical simulations suggested that the strategy which avoids the transportation (3) is more effective to inhibit the spread of disease, and disease-induced mortalities were detected even at lower numbers, so transportation among ponds should be stopped as fast as possible.