Evaluation of Closed Areas for Fish Stocks with Maternal Effects in Larval Survival

Recent studies have indicated that the viability of larvae for some species, including Pacific rockfish (genus Sebastes) and Atlantic cod (Gadus morhua), may depend upon spawner age.  These maternal effects imply that the age structure of the spawning population is a management consideration, as older fish would be expected to contribute disproportionately to the viable offspring.  Because even moderate amounts of fishing mortality can dramatically affect spawner age structure, closed areas have been proposed as a management tool that would allow old spawners to accumulate.  In this study, we examine several spatial recruitment models to evaluate the effects of closed areas on yield and recruitment for stocks with maternal effects in larval survival.  Under the assumption of only larval movement between areas, marine reserves do help ameliorate the loss of equilibrium yield associated with maternal effects at high fishing rates.  However, the differences in maximum sustained yield (MSY) and its associated fishing rate (F_msy) between the cases with and without maternal effects due to reduced numbers of old females were generally small.  An effective way to address concerns regarding reduced production due to maternal effects may be to fish at F_msy, where the loss of equilibrium yield associated with maternal effects is reduced.  Because rockfish and cod stocks likely differ in their degree of adult mobility, the sensitivity of these results to adult movement will be considered.