Is there a single stock of Merluccius paradoxus in the Benguela ecosystem?

Abstract

The deep-water Cape hake, Merluccius paradoxus, is one of two hake species found off South Africa and Namibia. In the past it was assumed that there were separate stocks of M. paradoxus off Namibia, and off the west and south coasts of South Africa, but there were also indications that the assumption might not be true. In this study, the stock integrity of M. paradoxus in the Benguela was investigated using a holistic stock identification approach. The approach involved analyses of the temporal and spatial distribution of M. paradoxus off Namibia and the South African west coast. It also involved an investigation of published characteristics of M. paradoxus such as genetic identification, distribution of eggs and larvae, and of parasites, etc. From this information, it was suggested that the Benguela supports a single stock of M. paradoxus, which spawns on the Agulhas Bank and with nursery areas off the South African west coast and southern Namibia. Adults of the species are widespread throughout the region. If there is a single stock in the Benguela, management strategies and assessment by South Africa and Namibia could need revisiting, for the stock is currently treated as two national entities, and is assessed and managed independently.