Sea sharing or sparing: Should we focus on more habitat protection or no-take marine areas?

Background/Question/Methods

Unsustainable exploitation of the oceans has led to widespread degradation of marine ecosystems. In order to maintain the primary benefits humans derive from the sea, namely food supply and biodiversity that generates other ecosystem services, the ocean is divided into three general management regimes: open–access areas with no restrictions, managed areas that control aspects of gear and fishing effort that damage habitat, and reserved or protected areas that prohibit all extractive uses. Using a theoretical example of a fish stock that depends on habitat type, we explore the conditions under which is it better to spare the sea, by investing more in no take marine reserves, to share the sea by investing in gear management to maintain habitat quality over a larger area, or a mixed strategy. We model the fraction of the seascape in each management regime given a fixed budget and a minimum food supply. Our objective is to create a plausible model with a simple analytic answer for the purpose of allowing people to choose broad policy options.

Results/Conclusions

We explored the range of parameters where no-take marine reserves may be favoured over habitat protection with fishing and vice versa. The relative costs of no-take reserves vs. habitat protection, the growth rate of the fish population, the effectiveness of habitat protection and the amount of self-recruitment all influence this decision. For example, preliminary results suggest that intermediate levels of self-recruitment favour a mixed strategy of some no-take reserves and habitat management areas. Obviously, when the cost of reserving area increases in relation to managing an area to reduce habitat loss, we prefer a management regime that protects habitat. We are working on a simple rule of thumb that determines the optimal management strategy given our constraints.