Sharing a fish resource - Bioeconomic analysis of an applied allocation rule

Political and economic factors usually determine the harvest shares allotted to heterogeneous fisher groups harvesting upon the same fish stock. Given that the fishers harvest upon different segments of a fish stock with, for instance, cannibalistic tendencies, the shares allotted may have considerable effect upon the well-being of the stock and the economics of the fishery. This paper analyses an existing allocation rule defining harvest shares allotted to two vessel groups (trawlers and coastal vessels) in the Norwegian cod fishery. We apply a model with two interacting age groups within a single fish stock, where the interaction has both biological and economic implications. Requiring a first best approach to an optimal stock size results in no harvest in the first years studied. In order to ensure harvest amounts close to the historic harvest, we design a second best model giving optimal biological shares in the build-up phase of the stock, and bioeconomic optimal shares at the optimum fish stock level. The second best model recommends that for an increasing stock size the trawlers should obtain decreasing shares. We find that the actual allocation rule functions in a manner opposite to the second best model, since this rule allocates an increasing share to the trawlers for an increasing stock size.