The Basking Shark
Cetorhinus maximus (Gunnerus, 1765)
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The basking shark is the only member of the Cetorhinidae family. It is the second largest shark and fish in the world. It is normally observed at the surface where it feeds alone or in a group. The basking shark is found near the coast in northern and temperate waters. In Eastern Canada, it ranges from Newfoundland in the north, to the St. Lawrence Estuary in the west.

Despite its huge size, the basking shark poses no threat to humans. It feeds exclusively on plankton. It is not known where Canadian specimens spend the winter although sharks tagged in New England are known to have swum as far south as Brazil. Various sources state that the basking shark hibernates on the sea floor during winter. This idea was debunked in 2003 when scientists of the Marine Biological Association (UK) discovered that the basking shark actually feeds on plankton at depths up to 900 m during the cold season. It is also the only shark that passively filter feeds, relying solely on forward movement to capture plankton at a speed of approximately 2 knots (3.7 km/h; 2.3 mph).

BASKING SHARK MENU

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


NAMES

Scientific Name: Cetorhinus maximus* (Gunnerus, 1765)
*sea monster with a big nose
Cetorhinus comes from the Greek words "ketos," meaning "sea monster", and "rhinos," meaning "nose". Maximus is latin for "great."

Common Names: Basking shark, elephant shark, bone shark, nurse fish, sunfish, sailfish, hoe-mother, squale pèlerin (Fr.), squale géant (Fr.), éléphant de mer (Fr.), poisson à voiles (Fr.)

(Below) Basking shark off the coast of Ireland. Photo © Ross Beane

SIZE AND APPEARANCE

Maximum length: Up to 12 m (40')
Average length: 6.5 m to 9 m (22' to 29')
Weight: Up to 4 500 kg (9 900 lbs)

The basking shark is the second largest shark and fish in the world, measuring up to 12m in length. Seen from the surface, it often looks like a whale. It can even completely leap out of the water in order to rid itself of parasites. This rare occurence was reported in Percé Bay in July 2001. When it opens its mouth, its head takes on gigantic proportions. Its liver is equal to 25% of its body weight and helps maintain the buoyancy of this enormous fish.

(Below) Basking shark filter feeding on the surface near Percé, Québec (Gaspé Peninsula).
Photo © André Berthelot (All Rights Reserved)



(Below) Basking shark. Photo © Chris Gotschalk (Creative Commons)

DENTITION

Even if it only feeds on plankton, the Basking shark has hundreds of little teeth.

PREY

The basking shark feeds exclusively on zooplankton which consists of small fish and invertebrates. It can filter up to 2,000 short tons (1,800 t) of water per hour.

(Below) Basking shark filter feeding on the surface near Gascon, Québec (Gaspé Peninsula). Photo © André Bédard (All Rights Reserved)



DISTRIBUTION

The Basking shark is found in almost all of the worlds' oceans. Its American habitat extends from the North Atlantic off Newfoundland, to the South Atlantic. In Quebec, the Basking shark is found in the Gulf of St. Lawrence in the summer and fall and it often ventures into the St. Lawrence Estuary. It is frequently observed off the Gaspé Peninsula especially in the Bay of Chaleur. Specimens have even been captured in the dead of winter by trawlers, which may be an indication that a certain number remain in the Gulf of St. Lawrence yearround.

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

REPRODUCTION

Basking sharks are ovoviviparous. Embryos feed on a yolk sac and later on unfertilized ova (oophagy). Gestation is believed to last up to three years. Pups are born fully developed at 1.5 - 2 metres (4.9 - 6.6 ft). Litter size is approximately 6 pups (only one pregnant female has ever been captured) every 2 to 4 years. Mating and birthing are thought to occur in shallow water in the summer.

LIFE EXPECTANCY

May live up to 100 years.

ATTACKS

Attacks on humans attributed to the basking shark are virtually nonexistant. In fact, most known incidents have involved humans getting too close and getting hit by the caudal fin (tail).

FISHERIES

The basking shark is not hunted in Canada or the U.S. and many directed fisheries in the world have closed. A few fisheries still exist in Asian markets where the basking shark is hunted for its liver oil, meat, cartilage and fins. Large numbers are also caught as by-catch and for the illegal fin trade.

STATUS

Shark, Basking | Cetorhinus maximus | Pacific population
Status: Endangered
Last Examination and Change: April 2007 (New)
Canadian Occurrence: Pacific Ocean
Status Criteria: A2a; C1

Reason for Designation: This shark species is the only extant species in the family Cetorhinidae. It occurs circumglobally in temperate coastal shelf waters, and exists in Canada as two geographically isolated designatable units – Atlantic and Pacific. The species is vulnerable to incidental fishing mortality because of its low intrinsic productivity. Females do not mature until 16 to 20 years old, gestate between 2.6 and 3.5 years (the longest known gestation period for any vertebrate), and produce litters of only about 6 “pups”. These sharks are especially susceptible to entanglement in fishing gear and collision with boats because of their large size, surface behaviour and fearlessness around boats, and because their coastal distribution overlaps fishing and boating areas. Prior to 1970, large aggregations of these sharks were seasonally common in Pacific Canada, but only 6 sightings have been confirmed since 1996. This dramatic reduction in abundance is attributed to directed fisheries for liver oil (1941-1947) and an eradication program (until 1970) that killed hundreds, perhaps thousands of individuals between 1945 and 1970. The minimum historical population reconstructed from documented kills was at least 750 individuals, whereas the current population is virtually nil, implying a rate of decline exceeding 90% within < 2 generations. The species is believed to migrate seasonally between Canada and California, where regional aggregations were also severely depleted by historic fisheries. Rescue from outside Canada is unlikely.

Status History: Designated Endangered in April 2007.

Click HERE to go to COSEWIC's web page on the basking shark.

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

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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.

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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