A Surplus Production Analysis of Cape Horse Mackerel (Trachurus capensis) Midwater Trawl Fishery in Namibia

This paper examines the optimal yield and stock development of the Cape horse mackerel (Trachurus capensis) fishery. Surplus production analysis based on the Gordon–Schaefer bioeconomic model was applied to the Cape horse mackerel (Trachurus capensis) midwater trawl fishery in Namibia, using empirical yearly data from 2009 to 2020. Effort is measured as trawling duration and catch per unit of effort (CPUE) is measured as catch per hour trawled. The findings support model theories and concepts that maximum economic yield, Y_MEY, is estimated to be 327,091Mt, lower than maximum sustainable yield, Y_MSY, at 342,115Mt, and the respective corresponding effort is estimated to be 23,455 and 29,673. There is a small margin between the two static reference points, and therefore, overfishing can cause sudden decline in profits. The results suggest that effort exerted in 2020 was sufficient to achieve maximum economic yield, however, that was not attained due to an irresponsive fishing allocation. The use of bioeconomic modelling informs fisheries management on determining optimal fleet sizes and fishing effort that can give Namibia an advantage to maximise benefits from Cape horse mackerel (Trachurus capensis) resource.