The Namibian horse mackerel stock -Summary of resource and management
The horse mackerel (Trachurus capensis) stock is distributed from around Tomboa in Southern Angola (16°00’S) and throughout Namibia (Figure 1). The exchange of horse mackerel between Namibia and South Africa is not known but the horse mackerel stocks are considered as separate at least for management purposes. Juvenile fish is manly found inshore of the 200 m isobath and adults manly offshore of this. The mean size increases southwards with largest fish (>35 cm) caught south of the Luderitz upwelling cell. The biomass in this area however is low and there is very little fishing on this part of the stock. The main concentration of fish is found in the north from around 17°00’S - 20°00’S. This is also where the main fishing pressure is. The stock has seasonal differences in distribution but these are not well known. Horse mackerel has a vertical diel migration. The stock is in midwater (juveniles) and closer to the bottom (adults) in aggregated shoals during the day. They lift from the bottom in the evening and descend up in the water column and become more dispersed at night. This is probably a reaction to feeding pattern and predator avoidance. The main part of the juveniles diet consists of zooplankton, and there is increasingly more auphausiids with increasing size. Adult also eats some myctophids and gobies.