Aquaculture-fisheries interactions

Abstract

Assuming externalities from aquaculture to fisheries, we use a Verhulst-Schaefer model of fish population-dynamics and production, coupled with an aquaculture production model, to investigate effects on open-access and rent-maximising fisheries. Externalities are modelled by letting carrying capacity, intrinsic growth rate or catchability coefficient in the fishery depend on aquaculture production. We find that the different externalities can give opposite effects on steady state fishing effort, yield and stock, even for only “negative” externalities. With the catchability externality, increased unit cost of fishing can imply reduced aquaculture production in social optimum, under reasonable assumptions. We also look at allocation between the industries under three different management regimes for coastal areas: 1) Aquaculture has a primary right of use; 2) Optimal management of aquaculture and fishery; 3) Fishers have a primary right of use, but may allow marine farming, possibly against payment.