IMPLICATIONS OF HARVESTING STRATEGIES ON POPULATION AND PROFITABILITY IN FISHERIES

The effects of different harvesting strategies on the mean and variation in size of the fish stock and net revenues are investigated. The strategies analyzed are constant catch, constant effort, and constant escapement. A Gordon-Schaefer model affected by cyclical disturbances and stochastic disturbances is applied. Factors explaining the differences between the strategies are the length of the recruitment cycles and the presence of stochasticity. With short recruitment cycles the constant catch strategy somewhat surprisingly produces least variation and highest mean with respect to stock size and net revenue, while constant escapement produces most variation and lowest mean. With longer recruitment cycles or pure stochasticity, constant escapement produces highest average stock size and net revenue as well as lowest variation in the stock size, but not in the net revenue. Constant effort is in most cases ranked between the other two strategies.