Porbeagle Shark

Lamna nasus

Atlantic mackerel shark, Beaumaris shark, blue dog, bottle-nosed shark, requin maraîche,

requin-taupe commun

INTRODUCTION

The porbeagle is a member of the mackerel sharks, which includes the white shark, the mako, and the extinct megalodon. These sharks share the same general shape, which oftens leads to misidentification, especially when observed from a boat. Contrary to recent news headlines associating the porbeagle's presence with global warming, this shark has been a regular visitor to the St. Lawrence Gulf and Estuary for thousands of years. All mackerel sharks are very fast swimmers capable of lightening bursts of speed. The porbeagle's closest relative is its North Pacific cousin, the salmon shark (Lamna ditropis).

AUTHOR: Jeffrey Gallant

LAST MODIFIED: October 24, 2016

VIDEO: Porbeagle shark in St. Margaret's Bay, Nova Scotia. Images © SHARCC

NAMES

Scientific name: Lamna nasus* (Bloch & Schneider, 1801)

Lamna: Greek = voracious fish

nasus: Greek = nose

*voracious fish with a "powerful" nose

 

Common name: Porbeagle shark: Porbeagle is derived from the Cornish "porgh-bugel." It is a combination of "porpoise" which refers to its appearance, and "beagle" for its hunting abilities.

 

Other names: Atlantic mackerel shark, Beaumaris shark, blue dog, bottle-nosed shark, requin maraîche (FR.), requin-taupe commun (FR.)

AUTHOR: Jeffrey Gallant

LAST MODIFIED: October 24, 2016

ABOVE: Porbeagle shark caught in a weir in La Malbaie, Quebec, in 1936.

Photo: Library and Archives Canada

SIZE AND APPEARANCE

Maximum length: 3 m (10 -12 ft)

Average length: 1.5-1.8 m (5 - 6 ft)

Average weight: 135 kg (300 lbs)

Maximum weight: Over 225 kg (500 lbs)

 

The first dorsal fin has a white patch on the trailing edge while the second dorsal fin is practically non-existent.

 

Like its more famous cousins, the porbeagle has a laterally flattened caudal keel, but it is the only mackerel shark with a secondary caudal keel. Its colour is dark bluish-gray to brown above, and white below.

AUTHOR: Jeffrey Gallant

LAST MODIFIED: October 23, 2016

DENTITION

The porbeagle's teeth are smooth and bladelike with lateral cusplets.

AUTHOR: Jeffrey Gallant

LAST MODIFIED: October 23, 2016

DISTRIBUTION (QUEBEC AND MARITIME PROVINCES)

In Canada, the distribution of the porbeagle shark extends from Newfoundland & Labrador to the Bay of Fundy. It uses the entire water column on the continental shelf from the surface to the bottom (to 366 m / 1,200 ft). Juveniles are found further inshore.

 

ST. LAWRENCE: The presence of Lamna nasus in the St. Lawrence Gulf and Estuary is neither recent nor is it related to climate change.

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AUTHOR: Jeffrey Gallant

LAST MODIFIED: October 25, 2016

PREY

The porbeagle shark is an opportunistic predator that mostly feeds on fish (91%) (Joyce et al., 2002) and invertebrates. Its diet varies depending on season and depth. Its diet of fish consists mostly of pelagic species except in the fall when it moves into shallower water in pursuit of coastal species.

 

Verified stomach contents: Cod, flounder, herring, longnose lancetfish, lumpfish, mackerel, redfish, sandlance, spiny dogfish, wolffish, crabs, gastropods, shellfish, squid.

 

Note: The porbeagle does not actively feed on marine mammals.

AUTHOR: Jeffrey Gallant

LAST MODIFIED: October 24, 2016

VIDEO: Porbeagle shark in the North Atlantic

REPRODUCTION

According to the Canadian Shark Research Laboratory (DFO), 50% of male porbeagles are mature at a fork length of 174 cm (age 8), while females do not mature until a fork length of 217 cm (age 13). Females give birth to their pups (average of four per year) in the Sargasso Sea (between Bermuda and Cuba) in the spring. The porbeagle shark is aplacental viviparous with oophagy: that the developing embryos are retained within the mother's uterus and subsist on non-viable eggs.

AUTHOR: Jeffrey Gallant

LAST MODIFIED: October 24, 2016

LIFE EXPECTANCY

Up to 40 years. The oldest porbeagle aged in the northwest Atlantic was 26 years (Francis et al., 2008).

AUTHOR: Jeffrey Gallant

LAST MODIFIED: October 23, 2016

ATTACKS

Attacks on humans attributed to the porbeagle shark are extremely rare with only one incident recorded in Canada. On December 5, 2000, a diver was charged by and then towed by a porbeagle shark while fishing for sea urchins. The incident took place in the Bay of Fundy at a depth of 16 metres and the diver was unharmed.

VIDEO: A porbeagle shark bites a scuba diver's camera near Eastport (Maine), by the border with New-Brunswick.

AUTHOR: Jeffrey Gallant

LAST MODIFIED: October 29, 2016

FISHERIES

The directed fishery for the porbeagle shark in Canada was closed in 2013. Large numbers are still caught as by-catch by other fisheries.

AUTHOR: Jeffrey Gallant

LAST MODIFIED: October 24, 2016

STATUS

Scientific Name: Lamna nasus

Other/Previous Names: Porbeagle Shark

Taxonomy Group: Fishes

Range: Atlantic Ocean

Last COSEWIC Assessment: May 2014

Last COSEWIC Designation: Endangered

SARA Status: No schedule, No Status

 

Click HERE to go to the COSEWIC profile page on the porbeagle shark.

AUTHOR: Jeffrey Gallant

LAST MODIFIED: October 24, 2016

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