Distribution and abundance of Cape hakes (Merluccius capensis and Merluccius paradoxus) in relation to environmental variation in the Southern Benguela system

Abstract

Standard Geographical Information Systems (GIS) techniques and Generalized Additive Models (GAM), nonparametric regressions without the assumptions of normality or linearity of traditional regression methods, were used to test the hypothesis that trends in hake (M. paradoxus and M. capensis) distribution and abundance are related to ocean environmental conditions (including bottom temperature, bottom oxygen concentration, sea surface temperature and sea surface minus bottom temperature, as a measure of stratification or mixing) and location (including longitude, latitude and bottom depth). Hake and physical data, from seventeen biomass surveys undertaken by Marine and Coastal Managment between 1984 and 1997 in the southern Benguela ecostystem, were used to test these relationships.