Dynamics of closed areas in Norway lobster fisheries

A dynamic, age-structured population model was developed to investigate the potential effects of introducing a closed area to a fishery for a species with limited adult mobility and planktonic dispersal of larvae, using biological and fishery information from a Norway lobster fishery in eastern Scotland. Simulated closure of part of the fishing grounds led to a long-term increase in total biomass and recruitment to the fished zone, but the larval subsidy did not compensate for the loss of fishing ground, and fishery yield was reduced under all modelled combinations of closed-area size and prior fishing effort. Concentration of effort in the fished zone and increased recruitment there led to reduced average size, and therefore value, of animals in the catch, as well as increased destruction of biomass by discarding undersized lobsters. Implementation of a closed area also led to oscillations in stock biomass, recruitment, and yield over several years after the closure, particularly with large closed areas and high fishing effort.