Dec 12, 2023

Bronze Whaler Shark

Getting its name from its olive, bronze-grey coloration, these sharks are often mistaken for dusky or spinner sharks. Let's dive in and learn more about this fascinating species!

FAMILY: Carcharhinidae

SCIENTIFIC NAME: Carcharhinus brachyurus

COMMON NAMES: Narrow tooth shark, Bronze whaler, Cocktail shark, Cocktail whaler, and Copper shark.

TYPE: Fish

IUCN Red List Status: Vulnerable (assessed 2020)

SIZE:

Bronze whalers grow over 10ft (3.3m) in length and weigh over 600lbs!

Females tend to be larger than males. Size at maturity for males is around 6ft and 7ft for females. Sources differed on exact maturity ages but it's estimated that males mature around 10-13 years old, while females mature around 12-15 years old.

Interestingly, there is regional variation within this species as size-at-maturity is smaller in Argentina than in South Africa and Australia. Bronze whalers are also known to be social animals, often found in groups of hundreds or even thousands! These large schools are usually made up of individuals of the same sex and size which may suggest a social hierarchy; they have even been reported to hunt cooperatively surrounding schools of fish and attacking from various angles.

DID YOU KNOW:

The upper teeth are sexually dimorphic, the males having proportionately longer and more hook shaped teeth than the females and juveniles.

AVERAGE LIFE SPAN:

Generally, sharks are slow growers. Meaning it takes them longer to reach sexual maturity which is why their populations have a difficult time rebounding from various human-caused threats. Bronze whalers are no exception, in fact, it takes up half their life to reach sexual maturity with a believed maximum lifespan of around 30 years!

This species is viviparous and is known to mate in the spring and summer. Females are thought to breed every other year (biennial reproductive cycle)

After a gestation period of about 12months, females give life birth to a litter of 7-26 pups, measuring about 2ft (59-70cm) when born. This species commonly uses inshore bays as nursery areas.

DISTRIBUTION:

These sharks a patchy yet wide-ranging distribution area as they are at least seasonally migratory following various prey events like the sardine run of South Africa in June/July.

They can be found in the Atlantic, Mediterranean, and eastern Pacific oceans and are commonly seen in southern Africa, Australia, New Zealand, and Japan, Brazil, Argentina, and have also been reported in the Gulf of Mexico.

DID YOU KNOW:

Bronze Whalers are the only species of requiem shark in the genus Carcharhinus that live in temperate rather than tropical waters.

Bronze whalers are commonly seen in a variety of marine habitats- from shallow bays, harbors, brackish water and estuaries to inshore and continental shelf areas to depths of 328ft (100m) where they hunt schooling fish.

DIET:

Bronze whalers are a fast-moving shark species that have been reported to leap out of the water-fitting since their prey are often super fast schooling fish, frequently within the surf zone closer to shore. Their teeth are triangular and serrated which allows them to easily slice through prey, which consists of a variety of fish, squid, crustaceans as well as scavenging dead or dying animals.

These sharks feed on pelagic, shoaling fish like sardines and mullet as well as cephalopods, smaller sharks and ray species (adults are more likely to hunt elasmobranchs).

Bronze whalers use a variety of feeding techniques to capture their prey. They are known to use ambush tactics, chasing and biting, and scavenging. This species is known to feed at night, which may allow them to avoid competition with other predators.

CONSERVATION:

Bronze whalers have been implicated in a number of bites to humans, particularly spear fisherman. According to the International Shark Attack File, the bronze whaler shark has been implicated in fifteen attacks since 1962, one of which resulted in a fatality. It is considered a potentially dangerous shark to humans.

This species is often targeted for its high-quality meat and fins. It is also commonly taken as bycatch in bottom trawls, by line gear, gillnets as well as by sports fishermen recreationally. It's suspected that this species has undergone a population reduction of 30–49% over the past three generation lengths (71 years) due to levels of exploitation. Additionally, under-reporting is likely due to the fact these sharks are commonly misidentified as other species like Dusky or Spinner sharks.

Unfortunately, there are no species-specific conservation measures in place for the bronze whaler shark.