Order: Lamniformes

Family: Cetorhinidae-Basking Shark

Taxonomy Etymology

• 1 genus, 1 species• Cetorhinus maximus

• Greek, ketos= a marine monster, whale + Greek, rhinos=nose

• Latin, maximus= greatest, largest

Diagnostic Features• Gigantic, 5-10m and possible 12-15m

• Conical snout, large subterminal mouth, laterally distensible jaw

• Gill rakers present most of the year

Fig. 6. Gill rakers from Sarasota basking shark. The longest rakers are about 150 cm.

Fig. 2. The Sarasota basking shark showing the short, pointed snout and huge mouth.

Diagnostic Features

• Many small teeth (5-6mm), very numerous

• Hook like and similar on both jaws

• ~100 teeth per row, 150+ rows in each jaw

• Only 1st 3-4 rows and 6-7 rows in lower jaw functional

(A) Labial, (B) basal and (C) lateral views of basking shark teeth, ex Compagno (1990) NOAA Tech. Rep. NMFS 90,D) Enlarged photo of a portion of jaw,ex Radcliffe (1916) Bull. Bur. Fish. Circ. 822

Fig. 5. Left. A segment of the right lower jaw of the Sarasota basking shark. Right. Some of the lowerteeth, the largest about 4 mm long.

Diagnostic Features

• Enormous gill slits (back of midline to throat)

• Lunate caudal w/ strong lateral keels

General Characteristics• Color: blaskish to greyish brown, may

have lighter patches.

• 2 albino species have been reported (N. Atlantic)

• Skin has sharp dermal denticles

Denticles from outside surface of gill flap of adult female basking shark from Sarasota. Note that the slenderdenticles point in random directions as they doover all skin surfaces of this specimen.

General Characteristics

• 2nd largest fish, average size 22-29 ft.

• Largest measured specimen 32 ft.

• A 30 ft. specimen was reported to weigh 8,600 lbs

Fig. 1. The Sarasota basking shark, 8.8 m long, weighed 1980 kg. The significance of the li ht coloredtip of the second dorsal fin is not known. Basking sharks taken in other areas commonly have someirregular mottling of lighter and darker color. Photo-Neil Sanders, Kiekhaefer Mercury.

Habitat• Coastal/oceanic pelagic shark of continental &

insular shelves (may stay into deep offshore waters in winter)

• Have been sighted from 200-2,000 m, a few sightings from 2,000-4,000 m

Basking shark at the surface showing exposed tip of snout (far right), 1st dorsal fin and upper lobe

of caudal fin.

Distribution• Circumglobal distribution

• Ususally found in boreal to temperate waters (8-14º C/46-57º F)

• Adult female taken alive in Sarasota in 1969 using gill net

Food Habits• Continuous ram filter feeder, feed

exclusively on plankton (crustaceans)

• Shown to feed on zooplankton when concentrations above 0.48-0.70 g/m³ (Sims 1999)

• Captures food with mouth open, stiff gill rakers strain plankton

Biology• Social, seen at surface singly, pairs, triads,

or in schools 100 +

• Highly migratory, follow plankton blooms

• Large schools appear close to shore in summer off Iceland and N. Europe

• Can shed gill rakers, has

been hypothesized that

hibernate in deep waters

Biology• Another hypothesis is that C. maximus

may benthic feed after losing gill rakers

• Massive oil filled liver may serve as metabolic store

• May achieve greatest length (10m) after 50 years (age has been estimated by counting vertebral rings, limited success)

Fig. 8. Transverse section through formalin-preserved vertebrae of the Sarasota shark showing shortdiagonal lamellae and calcified rings

Biology• Maturity for males: 12-16+ years

• Maturity for females: up to 20 years

• Able to breach partly or entirely out of the water to dislodge parasites or commensals (lampreys, remoras, and cookie cutter sharks)

Reproduction

• Almost nothing known

• Believed to be ovoviparous, only one pregnant female catch is known (litter of 6)

• Breeding thought to occur in shore when they aggregates to forage

Reproduction• Females mature at 4-5 m, thought to give birth in

spring

• Adult non pregnant females have had immense #’s of small eggs in ovaries which suggest uterine cannibalism

• Gestation period 1-3 years, 2-3 yrs. btwn. litters

• Size at birth thought to be ~1.5 m

Commercial Value

• Target of harpoon fisheries for centuries for it’s liver oil (burned in lamps), yields 200-400 gallons of oil

• Meat is used fresh or dried-salted for human consumption

Commercial Value

• Fins used for shark fin soup, pectorals and dorsals recently sold for $10,000 and $20,000 (USD) each in 1999

• Also yields squalene, which is used in medicinals and cosmetics, leather, fish meal, and animal feed

FIN IN THE SUN: Basking sharks roam temperate waters worldwide. They stay close to the surface while feeding, a practice that early observers mistook for basking in the sun. Their shallow swimming habits make the sharks easy marks for fishers, who take thousands of the creatures each year. A large, dried shark fin like this one (above), on display in New York’s Chinatown, can fetch more than $16,000 in some parts of the world.

Conservation

• Placed on ICUN Red List as a VULNERABLE species worldwide

• Placed on ICUN Red List as an ENDANGERED species in N. Pacific and NE Atlantic

• Slow growth rate, long gestation, late maturity, low fecundity, & few predators make it extremely vulnerable to overfishing

Bibliography• Carrier, J.C., et. al. 2004. Biology of Sharks and Their Relatives. CRC Press, Boca

Raton, FL. (pp. 68,173,187,488,494).• Castro, J.I. 1983. The sharks of North American waters. Texas A&M University Press,

College Station, TX. (pp.86-88).• Compagno, L.J. 1984. FAO species catalogue. Vol. 4. Sharks of the World. An

annotated and illustrated catalogue of shark species known to date. Part 1- Hexanchiformes to Lamniformes. FAO Fish. Synop. 125(4/1): 88-96.

• IUCN 2007. 2007 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 12 October 2007.

• Sims, D. W. 1999. Threshold foraging behavior of basking sharks on zooplankton: life on an energetic knife-edge? Proc. R. Soc. Lond. B 266: 1437-1443.

• Sims, D., Southall, E. Quayle, V., & Fox, A. 2000. Annual Social Behavior of Basking Sharks Associated with Coastal Front Areas. Proceedings: Biological Sciences. 267 (1455) : 1897-1904.

• Springer, S. & Gilbert, P. 1976. The Basking Shark, Cetorhinus maximus, from Florida and California, with

• Comments on Its Biology and Systematics. Copeia. 1: 47-54.