Effects of a simulated fishing moratorium on the stock assessment of red porgy (Pagrus pagrus)

Abstract

Much of the information available on the population status of a harvested fish species is obtained from landings data. When fishing restrictions are in place, fishery-dependent data are reduced and assessments rely more heavily on fishery-independent data. Stock assessments of red porgy (Pagrus pagrus) have shown a declining population and have led to a number of management measures, including a moratorium on fishing this species. To investigate how a lack of fishery-dependent data during a moratorium would affect stock assessment results for red porgy, we conducted simulations representing a range of periods of moratorium. As data were removed from the model, stock status indicators and projections became increasingly variable. Projections estimated that a 12-year moratorium would be needed for stock rebuilding, but simulations showed that uncertainty surrounding stock assessment estimates would increase after three years without fishery-dependent data. Unless additional data are collected during periods of strict fishing regulations, it may be difficult to accurately assess the length of time needed for the stock to rebuild and to assess the population status.