Bronze Whaler Shark: Carcharhinus brachyurus

Family: Carcharhinidae
Common name(s)

Bronze Whaler Shark, Copper Shark, Narrowtooth Shark.

Identification

Bronzy to olive-grey dorsal colouration with horizontal pale band along flank. Origin of first dorsal fin level with (or slightly anterior to) free rear tip of pectoral fin. Free rear tip of first dorsal fin noticeably short. Second dorsal origin slightly posterior to anal fin origin. No interdorsal ridge. Pectoral fins long. Fins sometimes dusky towards tips and posterior margin.

Size

Maximum length 305cm. Size at birth 59-70cm.

Habitat

Warm-temperate and subtropical seas. From inshore to far offshore on continental shelves. Found from the surface to at least 100m depth.

Distribution

The bronze whaler shark has a wide ranging but patchy distribution. It is relatively common around the coast of southern Australia New Zealand, and seasonally abundant in South Africa. It is also found off West Africa and in the western end of the Mediterranean but is absent from the northwest Atlantic.
It is found on both sides of South America and very rarely in the north eastern Pacific from southern Mexico to southern California.
It is also present around Japan and along the coast of China and Korea.

Conservation Status

NEAR THREATENED

Carcharhinus brachyurus is a large coastal shark with low productivity. Although widespread, regional populations appear to be discrete, and movement of individuals between them is thought infrequent or absent, and it does not appear to be naturally abundant anywhere. C. brachyurus is assessed as Vulnerable in East Asia due to intensive fisheries and the apparent widespread collapse of fisheries for large coastal sharks. Coastal multispecies fisheries in the region are likely to continue to depress the population by taking pregnant females and juveniles. Coastal nursery areas in this region are also at risk from development and pollution.

Catches appear to be stable in Australia. In New Zealand, although there may have been some reduction in population size due to fishing, C. brachyurus is apparently still common throughout its range. Management of this species in New Zealand, Australia and South Africa is simplified by having most, if not all of the population resident within each nation’s EEZ, and the species is assessed as Least Concern in these regions. However, it is assessed as Data Deficient in the East Pacific, where there is no information and it appears to be uncommon or rare.

Throughout its range, it is known to be exploited by fisheries, but landings are grouped together with other Carcharhinus species, meaning any population declines are likely to go unnoticed, and its coastal nursery areas are potentially vulnerable to development and pollution. This, together with life history characteristics that make it especially vulnerable to overfishing has led to the global assessment of C. brachyurus as Near Threatened. The situation must be monitored as this species could soon qualify for a threatened category, on the basis of population declines due to fisheries exploitation, in other areas.

Citations and References
Duffy, C. & Gordon, I. (SSG Australia & Oceania Regional Workshop, March 2003). 2003. Carcharhinus brachyurusThe IUCN Red List of Threatened Species 2003: e.T41741A10551730. https://dx.doi.org/10.2305/IUCN.UK.2003.RLTS.T41741A10551730.en. Downloaded on 24 September 2020.

Reproduction

A viviparous species with yolk-sac placenta. 13-24 pups per litter. Gestation is approximately 12 months. Mating occurs biannually. Bronze whalers are relatively late maturing sharks. Males mature around 13yrs. Females mature around 20yrs.

Diet

Diet mainly consists of small schooling fishes. Bronze whalers in South Africa predate heavily on pilchards (Sardinops sagax).

Behavior

Bronze whaler sharks congregate in large numbers in the South African winter months to feed on migrating sardines that are corralled into bait balls by pods of common dolphins. Although there is no evidence that the sharks consciously cooperate with the dolphins to herd the fish, they may inadvertently help to pin the bait at the surface by attacking bait balls from below.
A migratory species but with little exchange between isolated populations.

Reaction to divers

Shy around scuba divers but surprisingly bold in baited situations.

Diving logistics

Near South Bimini Island in The Bahamas, blacknose sharks are often encountered during Caribbean reef shark feeds at Triangle Rocks and Southern stingray feeds at Gun Cay. The depth at both sites is less than 6m. These dives are only offered by land-based operators because most liveaboards are too large to approach those dive sites.

Andros Island is reputedly another good place in The Bahamas to find blacknose sharks; moving in and out of the mangroves with the tide. However, I did not encounter any when I was there.

Further south in the Caribbean in Sint Maarten, the reef shark feed organised by Dive Safaris (local operator) used to attract a handful of blacknose sharks but they became less frequent over time. It is unclear if they were fished out or if competition with the attending Caribbean Reef Sharks became too great.

Similar species

Dusky Shark Distinguished by longer free rear tip on first dorsal fin and pronounced interdorsal ridge.