An economic model to assess biosecurity management strategies for marine fish farms in Hong Kong SAR

We developed an economic model for small-scale saltwater grouper net-pen farms in Hong Kong SAR of the People's Republic of China to compare economic scenarios based on implementing different biosecurity mea-sures on farms. Our model estimated the probability of reducing endemic infections and their spread within farms. The economic outcomes of interest, including net returns and the margin of safety ratio, were evaluated under different levels of mortality (12%, 23%, and 46%), and different numbers of initial fish stock (20 K and 100 K) on farms. Our results showed that adding a strategy for prompt removal of dead fish and early treatment of disease on farms could reduce the risk of loss, but having a comprehensive biosecurity plan on a typical marine fish farm in Hong Kong was only economically advantageous when a high percent mortality (46%) was expected on the farm, and when the farm was stocked with a high number of fish (100K). Our model may explain why small-scale saltwater net-pen farmers catering to local live markets, do not adopt comprehensive biosecurity plans. According to results from scenarios specific to Hong Kong, our model suggests these plans are expensive and only pay off when expected mortalities are quite high.