basking shark

A very large shark (Cetorhinus maximus) that measures up to about 12 meters (40 feet) in length, feeds on plankton, and often floats near the surface of water.

Cetorhinus maximus

FAMILY

Cetorhinidae

TAXONOMY

Squalus maximus Gunnerus, 1765, Norway.

OTHER COMMON NAMES

French: Pélerin; Spanish and Portuguese: Peregrino.

PHYSICAL CHARACTERISTICS

An unmistakable, huge shark, with extremely elongated gill slits (reaching from the dorsal to the ventral side), a very wide gill region when gills are expanded during feeding, a large, capacious mouth, well-developed gillrakers on the inside of the gills to capture small food particles, very small teeth, elongated pectoral fins, and a large lunate caudal fin. Grayish in color all around. Reported to reach 40–50 ft (12.2–15.2 m) in length, but large specimens are more common at about 33 ft (10 m).

DISTRIBUTION

Worldwide in mainly coastal, cold, temperate waters, most abundant off both sides of the northern Atlantic, but also in warmer, subtemperate regions such as the Mediterranean Sea.

HABITAT

Usually found over relatively shallow, coastal, pelagic waters but can be caught in open seas over deeper waters. Basking sharks appear in regular periods in certain areas (probably to feed) but also disappear in what appears to be regular cycles. Where they "disappear" to is a mystery, and perhaps they "hibernate" or spend periods of relative inactivity on or close to the bottom of the ocean.

BEHAVIOR

Basking sharks have been seen to leap clear out of the water (as have other mackerel sharks). Usually they are observed cruising at about 2.3 mph (2 knots) near or at the surface, with their mouths open during feeding. They are highly migratory, and several individuals may swim in tandem.

FEEDING ECOLOGY AND DIET

A filter-feeding shark, capable of taking in massive amounts of zooplankton. It swims with its mouth open very wide, retaining food items on its gillrakers, which are covered by denticles, giving them a rough texture. The gillrakers are shed periodically, usually in the early winter. Basking sharks feed mostly in the summer months near the surface. They either feed by alternative means when the gillrakers are shed, or remain without feeding, inactive, until they are regenerated. Food is retained in the gillrakers, aided by secretions of mucus in the pharynx, and subsequently swallowed when the mouth is closed.

REPRODUCTIVE BIOLOGY

Basking sharks employ yolk-sac viviparity, giving birth to two to six pups per gestation. The pups are the largest of all shark species, ranging 59–67 in (150–170 cm) in total length. Gestation periods are mostly unknown but are estimated to be very long (more than 1 year). The ovaries produce huge quantities of eggs.

CONSERVATION STATUS

Listed as Vulnerable by the IUCN and protected in the United Kingdom, Malta, United States (East Coast), and New Zealand. Protection is pending in other areas (Mediterranean Sea, South Africa).

SIGNIFICANCE TO HUMANS

The basking shark has been captured in much of its range since the nineteenth century for its oily liver, which may contain up to 500 gal (1,893 l), meat (fresh and dried-salted), and skin, and also for its fins for the abhorrent shark fin–soup industry. Populations of the basking shark have declined significantly in many regions. The basking shark has some importance for the tourism trade, as it can be seen in many places, especially in the northern Atlantic (e.g., Bay of Fundy, Cape Cod, Isle of Man). Harmless, this shark poses no direct danger to people, but deserves respect because of its large size.

For more information on basking shark, visit Britannica.com.

The noun has one meaning:

Meaning #1: large harmless plankton-eating northern shark; often swims slowly or floats at the sea surface
  Synonym: Cetorhinus maximus