On the fraction of habitat allocated to marine reserves

The case for marine reserves is strengthening, and both deterministic and s tochastic calculations show that fisheries management using reserves may ac hieve harvests comparable with management without reserves. Thus, depending upon the metric used, reserves need not disadvantage harvest. Reserves pro vide a buffer that increases the chances of sustainability of the stock, an d thus the fishery. In this paper, I develop methods (deterministic and sto chastic) that allow one to determine how much habitat needs to be set aside as reserve, once societal decisions concerning the goals of reserves are m ade. The answer to the question: "how much habitat needs to be allocated to reserves" is not a simple single number. Rather, it is a procedure that ca n be employed once biological, operational and social information are provi ded. The methods also apply to reserves used to aid stock recovery.