The great white shark

Carcharodon carcharias

Photo courtesy of Bob Semple, Bedford Institute of Oceanography

White shark captured off PEI in 1983

White shark captured off PEI in 1983. Photos courtesy of Jack Woolner and Tom Hurlbut.

White shark captured off PEI in 1983

White shark captured off PEI in 1983. Photos courtesy of Jack Woolner and Tom Hurlbut.

Tooth from the lower jaw of a white shark.

Tooth from the lower jaw of a white shark.

Description

The white shark is also commonly known as the great white shark. It is a large, robust, torpedo-shaped shark with a moderately long, conical snout. The upper and lower lobes of the caudal fin are about even in size, and its large serrated triangular teeth are virtually symmetrical. It has a strong keel on the caudal peduncle, but no secondary keel. Despite its name the white shark is only white on its underside; the top of the shark varies from lead grey to brownish grey to black.

Range

The white shark has a worldwide range along the continental margins of all temperate seas and part of the tropics. It is rare in Atlantic Canadian waters, but sightings or captures are reported every 2-3 years. Great whites have been caught in the Bay of Fundy, off of southwest Nova Scotia, eastern Nova Scotia, southern Newfoundland and in the Gulf of St. Lawrence. A 5-meter (17') white was caught off of PEI in 1983. Based on the growth bands in the vertebra, this shark appears to have been about 17 years old. A small (10' or 3 metre) white shark was caught in a fishing weir in the Bay of Fundy near Economy in 2011; the shark was conclusively identified by its jaws and teeth.

Habitat

The white shark inhabits coastal and offshore waters of the continental shelf. Periodically it will wander into bays and harbours. This shark also inhabits waters around oceanic islands. The great white shark occurs in surface waters and down to a depth of 1280 meters (4,240 feet). It can easily tolerate temperature differences from sub arctic conditions to inshore tropical areas and probably has one of the widest habitat ranges of any fish.

Life History

The white shark is a solitary predator that can grow up to 6.6 meters (21 feet) in length. Although this is the largest confirmed report of a white shark, indirect evidence suggests that there may be specimens off of southern Australia which are 8 meters (26 feet) in length. Average specimens measure 4.6 m (15 ft) and weigh in excess of 680 kg (1 500 lbs). Age and growth for this species is not well known but they are believed to be slow growing and attain large sizes with a relatively long life span. The white shark does carry out migrations but its movements in the North Atlantic are unknown. Tagging studies have shown that some whites were capable of traveling 190 km in 2.5 days. They tend to be found in Canadian waters during the months of August and September.

Diet

The white shark preys mainly upon a variety of fishes and marine mammals. Fish such as salmon, hake, halibut, mackerel and tunas are common prey, as are marine mammals such as harbor porpoises and harbor seals. However whites also eat other sharks, sea turtles and seabirds. They may also scavenge opportunistically upon blubber from dead whale carcasses. Examination of the stomach contents of one great white caught off Deer Island, New Brunswick revealed three porpoises. The metabolic rate is slow and it is believed that a 30 kg piece of blubber could sustain the animal for a period of 1.5 months.

Reproduction

This shark is ovoviviparous. Females give birth to 2 to 14 live pups and may only produce 4 to 6 litters in a lifetime. The gestation period is not known, but may be more than a year. Female white sharks reach sexual maturity at a length of 4-5 metres (12 to 14 years of age), while males mature at 3.7 - 4.1 metres (9-10 years old). Circumstantial evidence suggests that the New York Bight, between Cape May and Cape Cod, may be a mating area for white sharks. Offspring are thought to be greater than 100 cm long at birth, with the smallest free living white shark being 108 cm in length.

Interaction with People

The white shark is considered one of the most dangerous sharks because of its large size, the fact that it enters shallow waters, its feeding habits and aggressiveness, and the fact that it has attacked humans. It is rare in Canadian waters, but is reported every 2-3 years. Although there have been 4 accounts of white sharks attacking boats in Canadian waters in the past 120 years, none have occurred in the last 45 years. They are rarely encountered by commercial fishermen and rarely caught recreationally due to their scarcity, size and ability to bite through regular tackle. Due to their dangerously low numbers in world oceans, COSEWIC listed the white shark as an endangered species in Canada in 2006. DFO carried out a  Recovery Potential Assessment on white sharks in 2006.

Distinguishing Characteristics

  • Serrated triangular teeth
  • Lobes of caudal fin of about equal size
  • Caudal keel
  • Black spot may be present at axil of pectoral fin
  • Lunate tail