White shark (Carcharodon carcharias) COSEWIC assessment and status report: chapter 2

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Executive Summary

Species information

The (great) white shark (Carcharodon carcharias (Linnaeus, 1758)) is the only living species of this genus. In French it is called ‘grand requin blanc’. It is recognizable in the field by its conspicuously black iris and a sharp contrast between dorsal and ventral colouration changing from dark (grey or black) to white. Genetic evidence combined with satellite tracking information clearly shows that this species is wide-ranging.  Gene flow between Atlantic and Pacific populations is likely restricted but population structure between hemispheres and ocean basins has not been investigated.  There is no known genetic structure in Canadian populations. For the purpose of this report, Canada’s Atlantic and Pacific populations are treated as two separate designatable units.

Distribution

The white shark is widely distributed in sub-polar to tropical seas of both hemispheres, from 60°N to 60°S, but it is most frequently observed and captured in inshore temperate waters over the continental shelves of the western North Atlantic, Mediterranean Sea, southern Africa, southern Australia, New Zealand, and the eastern North Pacific. Worldwide, this species is rare but does occur with some predictability in certain areas. On both the Atlantic and Pacific coast of Canada, white sharks appear to occur sporadically, known from only 46 confirmed or probable records since 1874. White shark records from Pacific Canada consist almost exclusively of strandings on the leeward shores of the Queen Charlotte Islands (Haida Gwaii) during late autumn and early winter months. Off Atlantic Canada, the white shark has been recorded from the Northeast Newfoundland Shelf, the Strait of Belle Isle, the St. Pierre Bank, Sable Island Bank, the Forchu Misaine Bank, in St. Margaret’s Bay, off Cape La Have, in Passamaquoddy Bay, in the Bay of Fundy, in the Northumberland Strait, and in the Laurentian Channel as far inland as the Portneuf River Estuary.

Habitat

The white shark occurs in both inshore and offshore waters, from the intertidal to the upper continental slope and mesopelagic zone. Known bathymetric range is from just below the surface to just above the bottom down to a depth of at least 1,280 m. It occurs in the breakers off sandy beaches, off rocky shores, and readily enters enclosed bays, lagoons, harbours, and estuaries, but does not penetrate brackish or fresh waters to any extent.

Biology

Reproductive mode is ovoviviparous. Gestation period is unknown, but may be about 14 months, inferred from the estimated gestation of the closely related shortfin mako. Litter size varies from 2 to 10 and possibly to 17 with an average of 7, with fecundity increasing with size of the female. Length at birth is assumed to be between 109 and 165 cm, with known length of the smallest free-swimming neonates 109 to 129 cm. Possible white shark pupping areas on the west and east coasts of North America include off southern California and the Mid-Atlantic Bight, respectively. Length of reproductive cycle in the white shark is unknown, but may be more than three years as post-partum females may take a year or more off between pregnancies to rebuild energy stores. Maximum lifetime reproductive output of a female white shark has been estimated to be 45 pups with pup survival considered to be low.

Age and size at maturity in white sharks varies regionally. Males reach sexual maturity at an age of 8 to 10 years and a length of 3.5 to 4.1 m while females reach maturity at an age of 12 to 18 years and a length of 4 to 5 m. Longevity in this species is estimated to be 23-60 years. Generation time has been estimated at 23 years and natural mortality at 0.077 year^–1 and 0.125 year^–1. Intrinsic rate of population increase is estimated at 0.04-0.056.

White sharks are an apex predator with a wide prey base feeding primarily on teleosts, elasmobranchs, and marine mammals, as well as cephalopods, other molluscs, decapods, marine birds, and reptiles.

Biological information from Canadian waters is limited.

Population sizes and trends

There are no estimates of population size in Canadian waters or elsewhere in the world. The species is apparently rare in Canada with only 32 records in the Atlantic since 1874 (and only one in the last decade) and only 14 records since 1961 in the Pacific. Given the low encounter rate in commercial and recreational fisheries in Canada, abundance in Canada has likely always been much lower than in adjacent southern U.S. waters. White shark population trend information is unknown in North American waters. However, there are several locations throughout the world with documented declines in population.

Limiting factors and threats

Humans are the most significant predators of white sharks, taking them as sport fish, commercial bycatch, and for international trade of their valuable body parts. In the Northwest Atlantic, white sharks are taken as bycatch by pelagic longlining operations. In Atlantic Canada there are only two records of white sharks captured in fishing gear since 1990. In Pacific Canada, there are no confirmed records of white sharks caught by fishing activities. Several stranded white sharks on the Queen Charlotte Islands had markings that may have resulted from fishing gear. The white shark’s tendency to investigate boats and other floating objects often brings them to the surface, where they can be easily hooked, shot, or harpooned.

Special significance of the species

The white shark is the quintessential shark species due to its large size, predatory nature and reputation for occasionally attacking humans. The celebrated cultural status of the white shark makes its jaws and teeth particularly sought-after as curios and its fins for Asian delicacies and traditional medicines. Even in the face of protective legislation, the high prices some individuals are willing to pay for white shark parts is an incentive likely sufficiently powerful to stimulate and maintain a clandestine black market trading in such goods.

Existing protection

In the fall of 2004, CITES listed white shark in Appendix II. In 2000, the InternationalWorldConservation Union listed white shark globally as ‘vulnerable’. No federal or provincial laws explicitly protect white sharks in Canadian waters. On Canada’s Pacific coast, hook and line fisheries are prohibited from keeping any species of shark except dogfish, and therefore white shark receives some protection by this regulation.

COSEWIC History

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list.  On June 5^th 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC Membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species. 

Definitions (2006)

Wildlife Species

A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and it is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)

A wildlife species that no longer exists.

Extirpated (XT)

A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)

A wildlife species facing imminent extirpation or extinction.

Threatened (T)

A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*

A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)**

A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)***

A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
** Formerly described as “Not In Any Category”, or “No Designation Required.”
*** Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.