Some refinements of the assessment of the South African squid resource, Loligo vulgaris reynaudii

Abstract

A biomass dynamic model making use of an observation error estimator has been used over recent years to assess the status of the squid resource, Loligo vulgaris reynaudii, off the coast of South Africa. This assessment has indicated the resource to be at a low level and the risk of collapse under the current level of fishing effort to be high. Accordingly, past scientific management advice has been that effort should be reduced. This assessment is refined here to take account of both observation and process error, and a number of sensitivity tests related to assumptions made in the original model are conducted. Bayesian analyses to take full account of estimation uncertainty are also undertaken. The results from the respective analyses are reported, and it is shown that changing the “hockey-stick” stock–recruitment function of the original model to a Beverton–Holt form opens the possibility that the resource is under less risk from the current level of effort than has been supposed.