During the summer months pregnant copper sharks migrate to the coastal waters near Swakopmund and give birth to their young. By then, males have already moved there to mate with the females later.
Anglers had noticed for years that at certain times large copper sharks (Carcharhinus brachyurus), also called bronze whalers or “bronzy” in Namibia, occur near Swakopmund and further north. During winter there are usually less sharks of this species in the area and those that are there are usually young ones. A researcher at the Ministry of Fisheries and Marine Resources and an expert on surf fish, Dr Hannes Holtzhausen, looked into this phenomenon after an angler from Germany had landed a copper shark, weighing nearly 80 kilograms and measuring 2.37 metres from nose to tail tip, on 7 December 2003 at Mile 17 south of Wlotzkasbaken. This fish was to be the first of its kind to be fitted with a tracking device to confirm the migrations of that particular cartilaginous species between Swakopmund and Baia dos Tigres, a sheltered bay on southern Angola’s coast. The bay is about 50 kilometres north of the Kunene estuary and 700 km north of Swakopmund.
As part of the BCLME project (Benguela Current Large Marine Ecosystem) initiated by South Africa, Namibia and Angola, the copper sharks were studied by Dr Holtzhausen because this species plays an important role for tourism in Namibia. Furthermore, Namibian surf anglers as well as owners of fishing safari companies had expressed concerns about large numbers of copper sharks being caught in Angolan waters for human consumption. This would have a negative effect on the Namibian bronzy population. Between 1988 and 2003 more than 3600 copper sharks were fitted with a plastic tag in the back next to the dorsal fin, of which 69 were caught again later. In 2002 a total of 151 copper sharks were tagged in Baia dos Tigres, three of which were later hooked at Mile 8 north of Swakopmund. During the same period four sharks had been equipped with tracking devices, but unfortunately problems occurred with the transmitters and after a few days it turned out that these efforts had been in vain. With other transmitters and tagged sharks it could be proven, however, that Namibia’s copper sharks migrate to Baia dos Tigres in Angola and in the summer turn south again and move along the entire coast off the Skeleton Coast and Dorob National Park to Swakopmund.
Copper sharks are one of the slowest-growing shark species. They can reach a length of up to 2.90 m and a weight of 170 kg. According to research their lifespan is close to 30 years and they become sexually mature at around 20 years old. The female gives birth to an average of 16 pups after a gestation period of 12 months. Thus a full-grown female has about 160 pubs during her lifetime. The low number worries experts, because it makes copper sharks very vulnerable in certain areas.
Anglers who catch copper sharks on the Namibian coast take pictures of them and release them back into the ocean. Some years ago several safari companies fitted the sharks caught by their clients with plastic tags provided by the Ministry of Fisheries. The project has since been discontinued, however. One of Namibia’s best-known anglers, Henry Laubscher, who also conducts fishing safaris, says that conditions for hooking a bronzy are highly unpredictable. In some years copper sharks are found close to the coast in large numbers, especially when the Atlantic is a little warmer, but in other years there are hardly any at all. In November last year (2017) Laubscher’s clients caught and released 74 copper sharks within three weeks.
Author: Dirk Heinrich