Open access is a well-known externality problem in fisheries causing excess capacity and overfishing. Due to global warming, externality problems from CO₂ emissions have gained increased interest. With two externality problems, a first-best optimum can be achieved by using two regulatory instruments. However, solving the open-access externality problem also affects CO₂ emissions. By using a bio-economic model covering Iceland, Norway, Denmark, Sweden, and the Faroe Islands, it is shown that regulations of the open-access externality problem have a large effect on both economic performance and CO₂ emissions, while an additional CO₂ regulation only has minor effects. The second-best solution achieved by only regulating open access reduces emissions by approximately 50% compared to current fisheries, with the exception of Iceland, which already has a well-developed fisheries management system.

JEL Codes: Q22, Q54.