The Porbeagle Shark
Lamna nasus (Bonnaterre, 1788)
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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).





PORBEAGLE SHARK MENU

Names
Size and Appearance
Dentition
Prey
Distribution
Reproduction
Life Expectancy
Attacks
Fisheries
Status
Bibliography

NAMES

Scientific Name: Lamna nasus (Bloch & Schneider, 1801)
lamna: Greek = voracious fish
nasus: Latin = nose

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

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

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 mackeral shark with a secondary caudal keel. Its colour is dark bluish-gray to brown above, and white below.





DENTITION

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

(Below) Porbeagle shark (Lamna nasus) caught off Tourelle, Québec. Image © Exploramer

DISTRIBUTION

The distribution of the porbeagle shark extends from the province of Newfoundland to the state of New Jersey. It uses the entire water column on the continental shelf from the surface to the bottom (to 366 m / 1,200 ft) and <19°C (66°F). Juveniles are found futher inshore.


Provisional distribution map based on research by GEERG. Details on observations (other than year) are available. Map does not include data from the U.S. or Europe. To submit additional sightings or captures, please contact us at: info@geerg.ca

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

Fish: cod, flounder, herring, longnose lancetfish, lumpfish, mackerel, redfish, sandlance, spiny dogfish, wolffish

Invertebrates: crabs, gastropods, shellfish, squid

Mammals: The porbeagle does not feed on marine mammals

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.

LIFE EXPECTANCY

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

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.

FISHERIES

The porbeagle shark is one of only two directed commercial shark fisheries in Atlantic Canada (The other is the spiny dogfish). It is usually caught on longline baited with squid at a depth of 50 to 150 meters. Fishing mostly takes place in the spring and in the fall off Nova Scotia.

STATUS

COSEWIC (Committee on the Status of Endangered Wildlife in Canada)
Porbeagle | Lamna nasus
Status: Endangered
Last Examination and Change: May 2004 (New)
Canadian Occurrence: Atlantic Ocean

The porbeagle shark has declined greatly since Canada entered the fishery in 1991 after an earlier collapse and partial recovery. Fishery quotas have been greatly reduced, and the fishery has been closed in some areas where mature sharks occur. The landings now are comprised mostly of juveniles. Its life history characteristics, including late maturity and low fecundity, render this species particularly vulnerable to overexploitation.

Status History: Designated Endangered in May 2004.

BIBLIOGRAPHY

Benz, G W., Dippenaar, S M., 1998, Putting the Bite on Jaws: Copepods as Enemies of Sharks, Southeast Aquatic Research Institute.

Bigelow, H B., Schroeder, W C., 1953, FISHES OF THE GULF OF MAINE, United States Government Printing Office, Washington.

Borucinska, J. D., Benz G.W., Whiteley, H.E. 1988, Ocular lesions associated with attachment of the parasitic copepod Ommatokoita elongata (Grant) to corneas of Greenland sharks, Somniosus microcephalus (Bloch & Schneider), Journal of Fish Diseases ,21, 415-422.

Caloyianis N., Winter, 2000, Arctic Sharks - Adventures with the Greenland Shark, Ocean Realm.

Francis, M. P., S. Campana, and C. M. Jones. 2007. Age underestimation in New Zealand porbeagle sharks (Lamna nasus): is there an upper limit to ages that can be determined from shark vertebrae? Mar. Freshw. Res. 58:10–23.

Gallant J., Harvey-Clark C., Myers R.A., Stokesbury M.J.W., 2006, Sea lamprey (Petromyzon marinus) attached to a Greenland shark (Somniosus microcephalus) in the St. Lawrence Estuary, Canada, Northeastern Naturalist, 13, 35–38.

Harvey-Clark C., Gallant J , Batt J., 2005, Vision and its relationship to novel behaviour in St. Lawrence River Greenland Sharks (Somniosus microcephalus), The Canadian Field-Naturalist, Volume 119, Number 3. (July–Sept 2005).

Homer S., 1984, Jaws IV : Great white shark netted off Maritime tourist beaches, Equinox Magazine. 14, 127-128.

Joyce WJ, Campana SE, Natanson LJ, Kohler NE, Pratt HL, Jr, Jensen CF (2002) Analysis of stomach contents of the porbeagle shark (Lamna nasus Bonnaterre) in the northwest Atlantic. ICES J. Mar. Sci., 59:1263-1269.

Lineaweaver, T., Backus, R.H. 1970, THE NATURAL HISTORY OF SHARKS, Ed Lyons & Burford.

Martin, R. Aidan., Wallace, Scott., Wallace, COSEWIC Assessment and Status Report on the White Shark Carcharodon carcharias in Canada, COSEWIC COMMITTEE ON THE STATUS OF ENDANGERED WILDLIFE IN CANADA, 2006

Martin, R. Aidan., 2003, Field Guide to the Great White Shark, ReefQuest Centre for Shark Research, Special Publication , 1, 1-185.

Martin, R. Aidan., 1995, SHARK SMART, ed Diving Naturalist Press, Vancouver.

Paccalet, Y., 2003, LA VIE SECRETE DES REQUINS, Ed l'Archipel, Paris.

Pranschke, J. L., 2000, The use of carbon and nitrogen isotope analyses for the determination of carbon source and trophic position of Somniosus microcephalus, Carleton University, Ottawa.

Ridoux V., Hall A.J., Steingrimsson G., Olafsson G., 1998, An Inadvertent Homing Experiment with a Young Ringed Seal, Phoca hispida, Marine Mammal Science, 14, 883-888.

Scott, W.B., Scott M.G., 1988, ATLANTIC FISHES OF CANADA, University of Toronto Press.

Stokesbury M.J.W., Harvey-Clark C., Gallant J., Block B.A., Myers R.A., 2005, Movement and environmental preferences of Greenland sharks (Somniosus microcephalus) electronically tagged in the St. Lawrence Estuary, Canada, Marine Biology.

Templeman, W., 1963, Distribution of Sharks in the Canadian Atlantic, Fisheries Research Board of the Atlantic, Ottawa.

Le naturaliste canadien, Déc. 1960. Université Laval

Les nouvelles du large, (Bulletin no. 7) - GREMM, 18.06.1999

Les nouvelles du large, (Bulletin no. 8) - GREMM, 24.06.1999