Porbeagle

Lamna nasus

SARA Status
No Status
NS
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

SARA Status

  • No Status NS
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX
COSEWIC Status
Not at Risk
NR
Special Concern
SC
Threatened
TH
Endangered
EN
Extirpated
EX

COSEWIC Status

  • Not at Risk NR
  • Special Concern SC
  • Threatened TH
  • Endangered EN
  • Extirpated EX

Description

The Porbeagle is 1 of 5 shark species belonging to the mackerel shark family (Lamnidae). Other sharks in this family that are found in Canadian waters include the white shark (Carcharodon carcharias), salmon shark (Lamna ditropsis) and shortfin mako (Isurus oxyrinchus).

Distinctive characteristics of Porbeagle include:

  • Dark bluish-grey to bluish-black colour on its back with white colour underneath
  • Pale or whitish tip on the lower trailing edge of its first large triangular dorsal fin
  • Heavy secondary keel underneath the longer primary keel on its tail
  • Stout head, pointed snout and large black eyes
  • Small smooth-edged narrow teeth with lateral cusps at the base of each tooth

Life History

Adults can attain a size of over 3 meters (10 -12 feet) but usually average between 1.5-1.8 m in length and about 135 kg. They have an average life expectancy of 30 to 40 years. Age and growth rate has been confirmed in this species, indicating that growth rings in the vertebrae accurately indicate age for at least 26 years. The Porbeagle has a heat regulating mechanism that raises the body temperature 3 to 8℃ above the surrounding water temperature. This allows the shark to be active and strong swimming in the cooler waters it inhabits. Unlike many other sharks the Porbeagle must swim at all times in order to breathe. The Porbeagle undertakes extensive annual migrations in the North Atlantic from Massachusetts up along the Scotian Shelf to Newfoundland. Mature females migrate south to the Sargasso Sea (between Bermuda and Cuba) to give birth to their pups.

Diet

The Porbeagle feeds mainly upon pelagic fishes such as herring, lancetfish and mackerel; however, they also eat cod, redfish, haddock, squid and shellfish. They do not feed upon marine mammals.

Reproduction

The Porbeagle is ovoviviparous, retaining the developing young within the brood chamber before giving birth to live young. The developing sharks obtain nutrients by consuming other fertilized eggs in the oviduct (oophagy). Young are born in the late winter and spring. The females can have between 1-5 pups, but generally produce 4 pups that are between 60 to 75 cm long at birth. Female Porbeagles reach sexual maturity at a size of about 217 cm (age of about 13 years), while the males are mature at about 174 cm (age 8).

Habitat

The Porbeagle is a pelagic shark that is found in temperate waters throughout the Northern and Southern hemisphere. In the North Atlantic, 2 distinct populations have been identified. The first occurs in the Northeast and the second occurs in the Northwest. The Northwest Atlantic population is widely distributed in both inshore and offshore waters and ranges from Northern Newfoundland and Labrador to New Jersey (and possibly South Carolina). The distribution of Porbeagle is limited primarily by temperature, as 50% of its time is thought to be spent in waters between 8 and 13℃. Mature females migrate south to the Sargasso Sea between Cuba and Bermuda to pup in the late winter or spring, while mating occurs from September to November on the Grand Banks in the offshore of southern Newfoundland and at the entrance of the Gulf of St. Lawrence. Porbeagle has a continuous distribution in Canadian waters ranging from northern Newfoundland and Labrador to the Gulf of St. Lawrence and around Newfoundland to the Scotian Shelf and the Bay of Fundy.

Threats

This species’ life history characteristics, including a late age of maturity and a small number of pups per litter (average of 4 per litter) make it particularly vulnerable to overexploitation. Overfishing, in the form of directed fishing and bycatch in non-directed fisheries, has been identified as the most important threat facing Porbeagle. Although directed fisheries for Porbeagle are suspended they continue to be caught as bycatch in multiple fisheries in Canadian and international waters. Although some Porbeagle is retained, most incidentally caught Porbeagle in Atlantic Canada is required to be returned to the water in a manner that causes the least harm. Mortality rates for Porbeagle in Atlantic Canadian fisheries are uncertain, but have been estimated at 110 t per year. Although more recent estimates in population size are not available, population recovery has been predicted to occur over the next several decades if mortality rates are kept at this low level.

In addition to threats posed by fishing activities, other human related activities could pose a potential threat to Porbeagle habitat. These activities include noise associated with offshore petroleum exploratory seismic surveys, marine pollution caused by offshore petroleum exploration or development spills, and large scale marine development projects.

Further Information

In 2014, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assessed the western North Atlantic population of Porbeagle as endangered. This population experienced a decline in abundance in the 1960s after it became targeted by the fishing industry. In the 1980s the population partially recovered before another collapse occurred in the 1990s. The exploratory directed fishery for Porbeagle was suspended in 2013, and no licences have been issued since that year. Due to these reduced catch rates, Porbeagle numbers are thought to have remained low but stable up to 2009, the last year that population size was estimated. At this time, the total population size was estimated to be between 197,000 to 207,000 individuals, including approximately 11,000 to 14,000 spawning females. This represents a decline in total abundance of 73 to 78% and 84 to 88% of total individuals and spawning females respectively since 1961.

Fisheries and Oceans Canada is currently undergoing a process to determine whether or not the western North Atlantic population of Porbeagle should be added to the List of Wildlife Species at Risk as endangered under the Species at Risk Act (SARA).

More information on the SARA process, as well as supporting documents, can be found on the Species at Risk Public Registry.

If you see a shark in Canadian waters, please report your sighting or incident.

Porbeagle shark

Porbeagle shark. Illustration: Jeffrey C. Domm.

Porbeagle shark. Illustration: Jeffrey C. Domm.

Scientific name: Lamna nasus
SARA Status: No Status
COSEWIC Status: Endangered
Regions: Maritimes, Gulf, Newfoundland, Quebec

Region map

Region map, Atlantic Ocean

Regions: Northwest Atlantic Ocean

Did you know?

Porbeagle is the only shark of its genus in the Northwest Atlantic Ocean. Primary and secondary keels on the tail fin and lateral denticles in the teeth help to differentiate this species from the shortfin mako shark.

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