Using monitoring data from in and near marine reserves for fishery management

Monitoring data from inside and outside marine reserves can provide useful information on the size and abundance of harvested fishes under fished and relatively unfished conditions.  A proposed control rule that reduces allowable relative fishing effort as a function of the ratio of fish density outside versus inside no-take marine reserves (as a measure of depletion) was found to be effective at maintaining spawning stock biomass and yield in a management strategy evaluations based on five nearshore California fish species.  Scenarios with fish movement, illegal fishing in the reserve, or post-dispersal density dependence in recruitment required higher density ratio targets, such as 60% of mature fish or 80% of all fish, to avoid stock depletion.  In addition to density data, monitoring data can provide information on fish lengths, which may be informative about fishing mortality rates.  A Bayesian length-based cohort analysis of length frequency in each year inside and outside the Channel Islands marine reserves, both before and after the reserve were established, was able to estimate both natural mortality (M) and fishing mortality (F) rates, which were comparable to rates found in the stock assessment for California sheephead.  There is a need for greater research investment in methods to use marine reserves to inform fishery management.