Dynamics of the Namibian hake fleet and management connotations: application of the ideal free distribution

Abstract

In order to determine the factors governing the spatial distribution of effort, it is essential to better understand the relationship between CPUE and abundance. In this study the spatial distribution of effort of the Namibian hake trawl fleet is examined by looking at competitive abilities among vessels, spatial allocation of effort, competition between vessels and equalisation of catch per unit effort (CPUE). The Ideal Free Distribution (IFD) was used as the foundation for deriving the tests. The results show that interference competition does not occur among vessels. Nevertheless, the prediction of the IFD of the equalisation of CPUE was confirmed in this fishery and indicates that the number of vessels in a specific area reflects stock density. Since there is no interference competition among vessels, the catchability coefficient (q) is not affected by this factor. Moreover, we infer that the CPUE from the whole area is not distorted as an index of abundance by the way effort is allocated in this fishery.