bronze whaler shark

Bronze Whaler Shark | Sharks Info

The Bronze Whaler Shark (Carcharhinus brachyurus) also known as the Copper Shark (or narrow tooth shark) from the family of the Requiem-sharks (C Archarhinidae). It is the only member of its type, that occurs in temperate climates. It is widespread, with a number of separate populations in the Northeast Atlantic and Southwest Atlantic, southern Africa, the Northwest and Eastern Pacific, Australia and New Zealand and scattered reports in equatorial regions.

Bronze Whaler Shark Description

The Bronze Whaler Shark is characterized by its narrow, hook-shaped upper teeth, the lack of prominent ribs at the back-fins and the simple bronze-coloring. As a large species, which can grow up to 3.3 m long, it can be difficult to distinguish it from other, larger sharks. It feeds on cephalopods, bony fish and other cartilaginous fish. It is a floating predator and is known to hunt in large groups and use their numbers to their advantage, although they remain lonely most of the time. The females are found most years with the males and carry out seasonal hikes.

The Bronze Whaler Shark has a slender, streamlined body with an arched head profile. The muzzle has long pointed nostrils that precede a low skin lobe.

The round, large eyes are equipped with a nictating membrane and a protective third eyelid. The mouth is short, with fine furrows at the corners, and contains 29-35 upper teeth in one row and 29-33 lower teeth in another row. The teeth are toothed with a single narrow tip on the upper teeth, which have a characteristic hook shape that is angled at the corner of the jaw while the lower teeth stand upright. The upper teeth are long, narrow, curved and serrated in adults, females and young.

The pectoral fin is large, pointed, wrinkled and sickle-shaped. The first dorsal fin is high and points to the apex, with a concave trace at the edge of its origin, located at the tip of the pectoral muscles. There is a ridge along the dorsal fin. The second dorsal fin has a smaller, lower position than the anal fin. Five pairs of gills are slits, each slightly longer.

The tail fluke develops a lower lobe and a deep abdominal notch at the top of the upper lobe. The species is bronze to olive grey with a metallic sheen of pinkish cast iron and darkened tips and edges, but not all colours fade to matte grey or brown on death. The underside is white and stretches along the flanks in distinctive bands.

The Bronze Whaler Shark can reach a maximum length of 3,3 m and a weight of 305 kg. It is often confused with other large species of Carcharhinus species, particularly the dusky shark (C. obscurus), but can be identified by its upper tooth shape that is missing, weak interdorsal ribs and missing obvious fin markings.

Bronze Whaler Shark Habitat

The Bronze Whaler Shark is found in brackish rivers, estuaries, shallow bays, harbours and offshore waters at depths of 100 metres or more. Off the coast of South Africa, the species is associated with annual sardine runs involving millions of South African pilchards (Sardinops sagax). The Bronze Whaler Shark is the only member of its genus to occur in temperate and tropical waters with temperatures between 12 ° C and 54 ° F.

Bronze Whaler Sharks occur in surfing zones along the continental shelf and in the open ocean and dive to depths of 100 m or more. The species enters shallower habitats, including bays, shallows and harbours, and inhabits rocky areas and offshore islands. It is tolerant of small changes in salinity and has been found in estuaries and lowlands of large rivers.

Distribution

In the Atlantic Ocean it is found in the Mediterranean, Morocco, the Canaries, Argentina, Namibia and South Africa (with two separate populations). It is rare in Mauritania, the Gulf of Guinea and the Gulf of Mexico. They are found in the Indo-Pacific, in the East China Sea and Japan (with the exception of Hokkaido). They have also been spotted in southern Russia, South Australia (Sydney and Perth) and further north to New Zealand (not Kermadec Island, although there are unconfirmed reports from the Seychelles and the Gulf of Thailand). In the eastern Pacific, the species occurs in northern Chile, Peru and Mexico (until conception in California, including the Gulf of California). It is also present in parts of Argentina and South Africa, but is rare in many areas whose range is defined by confusion with other species. It is widespread among disjointed regional populations, with no exchange between them.

Populations of Bronze Whaler Sharks in both hemispheres conduct seasonal migrations in response to temperature changes. They are also affected by reproductive events, prey availability and movement patterns that vary by sex and age. The adult males remain in the subtropics most of the year, but in late winter and spring, they migrate to higher latitudes. This is so they can meet and mate with postpartum females before spreading to coastal nurseries.

Adult females and juveniles hibernate in the tropics before migrating to the high latitudes in spring. Pregnant females migrate to the coast to give birth in the nursery. Young sharks inhabit coasts in waters less than 30 m deep, while adults are more likely to be found near the coast in spring and summer, and large aggregations have been observed in shallow waters.

Bronze Whaler Sharks are philopatric and return year after year to the same area. During the migration, individual sharks were recorded travelling up to 1,320 km.

Bronze Whaler Shark Reproduction

Like other sharks, the copper shark is viviparous and develops embryos that feed on placental compounds formed from exhausted yolk sacks. Females give birth to litters of 7 to 24 puppies every two years in coastal breeding areas with a gestation period of 12 to 21 months. The species grows slowly, with males and females only reaching maturity at the age of 13 – 20 years.

Conservation

The population size of the species is unknown, but the IUCN Red List classifies it as an endangered species. This is mainly due to its low growth and reproductive rate, which is vulnerable due to its low population. Its numbers are expected to decline in some areas. Copper sharks rarely attack humans and rank tenth in the number of unprovoked attacks on humans. The species is highly valued in commercial and recreational fisheries throughout its range and is used as a food source.

They are prized as wild fish and caught as bycatch in many different fisheries. For example, they are often caught together with other highly prized species such as tuna and swordfish. However, there is no catch data for this group of sharks, which means that the population decline is often overlooked. Requiem sharks are used for their flesh, fins, oil and skin.

The International Union for Conservation of Nature (IUCN) classified the species as endangered in 2003. Due to its low growth and reproductive rate, the species is vulnerable to population decline. Coastal nurseries are also at risk from development and pollution. Worse for species are the majority of animals affected by invasive fisheries pollution and habitat destruction in coastal areas and are likely to be young, pregnant and female mammals.

Marine aquaculture is also a potential threat to nurseries in New Zealand. The effects of human development are considered to be greatest in parts of the Mediterranean and East Asia. Designated conservation measures protect this species in Australia and New Zealand.

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