Latin name

Carcharhinus brachyurus

Other names

Bronze whaler,narrowtooth shark.

Identification

It has a slender, streamlined body with a slightly curved profile behind the head. The muzzle is long and pointed, with leathery wrinkles in front of the nostrils. The round, large eyes have a protective blinking membrane. The mouth is short, with thin furrows running along the corners. There are 29-35 teeth in the upper row and 29-33 in the lower row. The teeth have serrated edges terminating in a single narrow spearhead; the upper teeth, which are characteristically hooked, are progressively inclined towards the corners of the jaw, while the lower teeth are upright. The upper teeth of adult males are longer, narrower and more curved, and the serrations covering their edges are shallower than those of adult females and immature males. There are five pairs of long gill slits.

Features of fish fins

The pectoral fins are large, pointed and crescent-shaped. The first dorsal fin is high, with a sharp tip and a concave posterior margin, and its base is approximately level with the tips of the pectoral fins. The second dorsal fin is small and low and lies opposite the anal fin. The ridge between the first and second dorsal fins is usually absent. The caudal fin has a well-developed lower lobe and a deep ventral notch near the tip of the upper lobe. The caudal peduncle has a depression. 

Fish colouring

Dorsal colouration from bronze to olive-grey, with a metallic sheen and sometimes a pink tinge, fins darkening towards the tips; these sharks lose colour quickly after death to a dull grey-brown. The belly is white, with the whiteness extending down the sides. The Copper Shark is easily confused with other large species of the genus Carcharhinus, especially the Dark Shark Carcharhinus obscurus, which is distinguished by the shape of its upper teeth and the absence or sparseness of the interdorsal and dorsal fin ridges. 

Distribution

It is the only grey shark species that lives predominantly in temperate rather than tropical areas with temperatures above 12°C. The species is widely distributed, but there is little exchange between different regional populations. In the Atlantic, this shark is found from the Mediterranean (including off Morocco) to the Canary Islands, off Argentina, Namibia, occasionally off Mauritania, the Gulf of Guinea and possibly the Gulf of Mexico. In the Indo-Pacific, it is common in the East China Sea, off Japan (except Hokkaido) and south-eastern Russia, in the waters of southern Australia (mainly between Sydney and Perth, sometimes further north) and New Zealand, but not beyond the Kermadec Islands, and there is unconfirmed evidence of sightings in the Seychelles and the Gulf of Thailand. In the eastern Pacific, the copper shark is found from northern Chile to Peru and from Mexico to California, including the Gulf of California. The species is common in the waters of Argentina, South Africa, Australia and New Zealand, and less common elsewhere. These sharks are often confused with other members of the genus Carcharhinus.

Habitat

Copper sharks can be found both in the surf zone and well beyond the continental shelf in the open sea at depths of 100m or more. Sharks of this species often enter shallow waters, including bays, harbours and shoals, and inhabit rocky areas and offshore islands. They are tolerant of low and fluctuating salinities, allowing them to enter the mouths and lower reaches of large rivers.

Size

The maximum length is 3.3 metres and the weight is 305 kg.

Behavior

Immature individuals are found year-round in coastal waters at depths of no more than 30 metres, while adults are usually in the open sea and only regularly approach the coast in spring and summer, when large aggregations of these sharks can be seen in shallow waters.

Populations of these sharks in both hemispheres make seasonal migrations in response to changes in temperature, reproductive cycle or prey availability, with movement patterns dependent on sex and age.

Adult females and juveniles overwinter in the subtropics and generally move to higher latitudes as spring approaches. Pregnant females move towards the coast to give birth in shallow waters. Adult males remain in the subtropics for most of the year, only moving to higher latitudes in late winter or spring to mate with birthing females who leave shallow waters. Individual sharks can travel up to 1,320 kilometres during their migrations. Copperheads return to the same area year after year.

People have often seen groups of narrow-toothed sharks hunting together. The sharks would gather schools of fish into a tight ball and then the predators would take turns swimming through the ball with their mouths open. When chasing schools of tuna and larger prey, the sharks may form a "wing" formation to force them to stay together, with each shark targeting a specific fish and taking turns to attack it. 

Food and feeding habits

This species feeds more often in the lower water column than near the surface, consuming cephalopods including squid (Loligo spp. ), cuttlefish, octopus, bony fish such as roosterfish, flounder, hake, catfish, horse mackerel, Australian salmon, mullet, crucian carp, smelt, tuna, sardine and anchovy, and cartilaginous fish such as catfish (Squalus spp.), rays and pelagics. Cephalopods and cartilaginous fish are more important in the diet of sharks over 2m. Young sharks also consume scyphoid jellyfish and crustaceans. 

Copper sharks do not attack marine mammals, although they have been known to eat the bodies of dolphins caught in fishing nets. Off the coast of Africa, sardines (Sardinops sagax) are the sharks' main prey, making up 69-95% of their diet. Each winter, packs of sharks follow the course of huge schools of sardines that migrate along the coasts of the Eastern Cape province of KwaZulu-Natal. 

Reproduction

Like other sharks of the genus Carcharhinus, Copper Sharks are viviparous: after the embryo has exhausted its yolk supply, the empty yolk sac becomes the placental junction through which the mother provides nourishment to the embryo. Adult females have one functioning ovary on the right side of the body and two functioning uteruses. During mating, the male bites the female as foreplay. In the southern hemisphere, mating occurs from October to December (spring and early summer) when individuals of both sexes migrate to higher latitudes. Births occur from June to January, peaking in October and November.

Females give birth in shallow water, both in open coastal areas and in more sheltered bays and inlets, where they are less likely to be caught in the jaws of larger members of their species. They provide abundant food for the newborn akulates. Such sites are found in New Zealand, the Gulf region, Australia, Japan, South Africa, Rhodes (Greece), Nice (France), Morocco, Rio de Oro (Western Sahara), Rio de Janeiro (Brazil), Buenos Aires and Bahia Blanca (Argentina), Peru, Mexico and San Diego Bay.

Females breed once every two years with a litter of 7 to 24 offspring, averaging 15 or 16. The gestation period is 12 months, although some data suggest 15 to 21 months. Female sharks off the coast of California tend to give birth to fewer pups than females in other parts of the world. Newborns range in size from 55 to 67 centimetres. The copper shark is one of the slowest growing species in the genus Carcharhinus. Off the coast of South Africa, males reach maturity at a length of 2.0-2.4m at the age of 13-19 years, while females reach maturity at a length of 2.3-2.5m at the age of 19-20 years. Maximum lifespan is at least 30 years for males and 25 years for females.

Fishing

Copper shark is commercially fished off the coasts of South Africa, Brazil, Uruguay, Argentina, Mexico, China, New Zealand and Australia. The species is caught by gillnets and bottom longlines, and less commonly by bottom trawls and pelagic longlines. 

Relationship with a person

In False Bay, South Africa, this species of shark often follows fishing boats.

Despite its size and strength, the narrow-toothed shark is not particularly aggressive towards humans in the absence of food and is therefore not considered to be a particularly dangerous species for humans. 

The meat of these sharks is used as food.