Fisheries regulations based on yield-per-recruit analysis for the linefish silver kob Argyrosomus inodorus in Namibian waters

Abstract

The most important linefish species, silver kob Argyrosomus inodorus was assessed using two yield-per-recruit approaches, Beverton and Holt and Thompson and Bell. For the Beverton and Holt model, the analysis was run using three different values of natural mortality and depletion of the stock was estimated to be between 14 and 35%. Using the Thompson and Bell method, uncertain values of parameters such as catches, natural mortality and terminal fishing mortality were modelled using Monte Carlo simulations with a pseudo-cohort analysis. For this analysis, it was estimated that the stock was depleted below F SB(40%). In addition, natural mortality versus fishing mortality per age class was investigated and it was found that natural mortality was higher for the first three age classes. Based on the analysis it was recommended that the commercial fishery should be subjected to a total allowable catch, a license system should be introduced, bag limits should be lowered and a maximum size limit be implemented.