Blue Shark
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Worldwide Distribution


Summary
Scientific Name
Prionace glauca
Classification
Phylum: Chordata
Class: Chondrichtyes
Subclass: Elasmobranchii
Order: Carcharhiniformes
Family: Carcharhinidae
Genus and Species: Prionace Glauca
Species Authority: (Linnaeus, 1758)
Range
Circumglobal; Temperate and tropical waters
Occurrence in Canadian Waters
Very Common
Population Trend
Interaction with Humans
High bycatch and discard rate in pelagic longline fisheries
Conservation Status
COSEWIC: Special Concern (2006)
IUCN Global: Near Threatened (2000)
Fisheries Vulnerability: Very High

Description

The blue shark is the most wide-ranging of all shark species, inhabiting all tropical and temperate waters. This shark is also the most common shark species found in Canadian waters, generally living to around 20 years.

It can grow to around 3.8 metres or 12 feet in length and is recognized by its distinctive blue colour and its slim, graceful body with large eyes, long conical snout and pectoral fins.

Habitat

Blue sharks are pelagic species often occurring near the surface where waters depths are greater than 200 metres. They prefer temperatures between 10 and 20 °C and are commonly seen near the surface over deep waters off the coast of Nova Scotia and Newfoundland during the summer and fall.

Distribution

This highly migratory shark occurs in the Atlantic, Pacific and Indian Oceans, and in some cases may travel distances above 9000 km. In Canadian waters, it can be found off southeastern Newfoundland, the Grand Banks, the Gulf of St. Lawrence, the Scotian Shelf and the Bay of Fundy.

Blue Shark Fisheries

Despite the fact that a blue shark fishery exists, it is rarely pursued because of its low market value. A non-restrictive commercial quota of 250 tonnes has been allocated for the blue shark fishery. In addition to this, approximately 10 to 20 tonnes of blue sharks, as well as other sharks, are caught in commercial or community-sponsored shark derby events that are held each year in waters off Nova Scotia, usually during the months of July, August and September. Reported landings of the blue sharks, primarily taken as by-catch in commercial fisheries and shark derbies, have averaged less than 55 tonnes annually since 1990.

A Species at Risk?

The main threat to the blue shark is by-catch in other fisheries. Highly prized for their fins, there is evidence of population decline, with some reports in the order of 60-80% decline in catch rates. In the Canadian tuna and swordfish fishery, experts estimate that 100,000 blue sharks are caught annually, accounting for 47-152% of the fishery's catch. It is estimated that the average total discard mortality is about 2,000 tonnes per year, with dead discards accounting for 1,000 tonnes since 2002. The pelagic longline is not the only fishery that catches blue sharks accidentally. Given that these sharks are taken in other Canadian fisheries, as well as foreign fisheries, impacts to the population cannot be assessed without taking into consideration the cumulative fishing mortality.

Did You Know?

Blue sharks use a form of camouflage called countershading. This means that when seen from the top, the darker shade of blue on its dorsal area blends into the darkness of the water below, and when seen from below, the lighter colour of its ventral area blends into the sunlight from the surface.