Bio-economies of scope and the discard problem inmulitple species fisheries

This paper considers the problem of multi-species fisheries managementwhen targeting individual species is costly and at-sea discards of fish by fishermenare unobserved by the regulator. Stock conditions, ecosystem interaction, technologicalspecification, and relative prices under which at sea discards are acute are identified.A dynamic model is developed to balance ecological interdependencies among multiplefish species, and scope economies implicit in a costly targeting technology. Threeregulatory regimes, species-specific harvest quotas, landing taxes, and revenue quotas,are contrasted against a hypothetical sole owner problem. An optimal plan under allregimes precludes discarding. For both very low and very high levels of targeting costs,first best welfare is close to that achieved through any of the regulatory regimes. Ingeneral, however, landing taxes welfare dominate species-specific quota regulation; arevenue quota fares the worst.[...]