PACIFIC ROCKFISH MANAGEMENT: ARE WE CIRCLING THE WAGONS AROUND THE WRONG PARADIGM?

摘要

West Coast rockfishes are managed with traditional fishing-mortality and spawning stock biomass-based control rules, the objectives of which are to maintain a specific biomass of mature females regardless of their size or age. The implicit assumption is that larvae produced by all females are equivalent in their probability of survival, but recent research on black rockfish indicates that larvae of older mothers are far more likely to survive than those of younger females. Using a simple deterministic equilibrium model that incorporates the influence of maternal age on larval survival, I compared population age structure, fishery yield, effective larval output, and recruitment for four different management strategies: status quo, slot limit, marine reserves, and reduced fishing mortality. Results of these simulations indicate that a 35% reduction in fishing mortality would achieve increases in effective larval output and yield comparable to a 20% marine reserve option. If recruitment is proportional to effective larval output, a 20% marine reserve would increase yield at equilibrium by 9% relative to the status quo. These results suggest that managing for age structure can increase both resilience and yield.