Change in length frequency distribution of Namibian hake, Merluccius capensis and Merluccius paradoxus based on survey data of 1999-2002

Abstract

Abstract by author:

There are essentially three species of hake found along the Namibian coast. They are Merluccius capensis, Merluccius paradoxus and Merluccius polli although polli is very scarce and found mainly in Angolan waters and will thus not be dealt with in this project. According to regulations set up by the Ministry of Fisheries and Marine resources, any hake of length 20cm or smaller are considered to be juvenile hake that are not supposed to be caught commercially. Hake of 21cm and longer are of legal fishing size. We want to see how the length frequencies of M. capensis and M. paradoxus have changed over the past four years. For the period of 1999 to 2002, it can be seen that there is a general increase in the biomass numbers of hake, but the overall lengths seem to be decreasing. If the juveniles are also fished in a fishing season, then there will be fewer recruits to build up the fish stocks. This will lead to less fish that can be classified as part of the fishable party of hake stock. If a certain length of fish is being exploited over a long period, it may lead to directional selection and an overall decrease in the maximum lengths of fish caught. This can be seen where no fish are caught of length greater than 80cm while the maximum length of hake is supposed to be 1m and longer