Elasmobranchii (sharks and rays) >
Lamniformes (Mackerel sharks) >
Cetorhinidae (Basking sharks)
Etymology: Cetorhinus: cetus (L.), from ketos (Gr.) whale, referring to its size; rhinus, an ancient name for sharks, from rhine (Gr.), rasp, alluding to a shark’s jagged, rasp-like skin. (See ETYFish); maximus: Latin for greatest, being the largest known fish (i.e., non-mammalian aquatic vertebrate) at the time (superseded by Rhincodon typus). (See ETYFish).
Environment: milieu / climate zone / depth range / distribution range
Ecology
Marine; pelagic-oceanic; oceanodromous (Ref. 51243); depth range 0 - 2000 m (Ref. 26346), usually 0 - ? m (Ref. 55197). Temperate; 6°C - 24°C (Ref. 88171); 75°N - 58°S, 111°E - 42°E (Ref. 84930)
Cosmopolitan, frequent in cold to warm temperate waters; rare in equatorial waters (Ref. 48844). Highly migratory species. At risk of extinction by overfishing because of low to very low productivity (Ref. 36717).
Length at first maturity / Size / Weight / Age
Maturity: Lm 895.0, range 500 - 1000 cm
Max length : 1,520 cm TL male/unsexed; (Ref. 247); 980.0 cm TL (female); common length : 700 cm TL male/unsexed; (Ref. 6077); max. published weight: 4.0 t (Ref. 4645)
Dorsal spines (total): 0; Anal spines: 0. Distinguished from all other sharks by the enormous gill slits practically encircling the head; dermal denticle gill rakers; pointed snout; huge, sub terminal mouth with minute hooked teeth; caudal peduncle with strong lateral keels, and lunate caudal fin. Body covered with placoid scales. Blackish to grey-brown, grey, or blue-grey, often with irregular white blotches under the head and abdomen (Ref. 43278). Also Ref. 309, 5983.
The second largest shark, reportedly reaching 1,220-1,520 cm TL (Ref. 247). Thought to live up to 50 years (Ref. 9030, 89083). Semi-oceanic or oceanic species, highly migratory (Ref. 43278). Found on continental and insular shelves, offshore and often close to land, just off the surf zone; enters enclosed bays (Ref. 247). Coastal-pelagic at 1 meter to unknown depths, probably epipelagic (Ref. 58302). Occurs singly, in pairs or groups of 3 or more, or in huge schools (group of up to 100 individuals has been reported) (Ref. 6871, 43278). Prefers water temperature between 8-16 °C (Ref. 88171). Makes extensive horizontal and vertical movements along the continental shelf and shelf edge to utilize productive feeding areas (Ref. 50200). During the summer months, it is found near the surface of boreal to warm-temperate areas (Ref. 43278) feeding on zooplankton by filtering (Ref. 88781). Found in deeper waters during winter (Ref. 6871, 50200, 58302). Undertakes long transoceanic migrations (e.g. from the British Isles to Newfoundland, Canada (Ref. 88824)) and moves between the northern and southern hemisphere in tropical mesopelagic water (Ref. 88825). These migrations have been found to cover distances of over 9,000 km. May form segregations by size or sex (Ref. 88171). Ovoviviparous (Ref. 50449). Regarded as ordinarily harmless and inoffensive but potentially dangerous if attacked (particularly when harpooned) (Ref. 247). In Bay of Fundy, Canada parasitic lampreys have been found attached to the back of basking sharks and sucking their blood (Ref. 83375). Utilized fresh, frozen and dried, or salted (Ref. 9987). Also valued for its liver for oil, fins for soup, hide for leather and carcass for fishmeal (Ref. 247). May be a potential source of anti-carcinoma drugs (Ref. 6034, 6035). Used in Chinese medicine (Ref. 12166). Threatened due to bycatch fisheries (Ref. 83294).
Distinct pairing with embrace (Ref. 205). Courtship behaviour patterns associated with elasmobranch reproduction were documented from an aerial observation which include 'parallel swimming', 'pectoral biting', 'nudging', and 'male on top of female'. Other mating behaviours particular to this species from the same aerial observation include nose-to-tail following; flank approach; close approach involving rostral contact or proximity with the gill, pectoral fin, vent, and dorsum; and echelon swimming (Ref. 37026). Exhibit ovoviparity (aplacental viviparity), with embryos feeding on other ova produced by the mother (oophagy) after the yolk sac is absorbed (Ref. 50449). Estimated gestation period 12-36 months (Ref. 247, 1765, 9030, 88829); TL at birth estimated between 150-200 cm; mating thought to take place during early summer; a female giving birth to young captured in August in Norwegian waters (Ref. 5983). Over a study period of 5 years, courtship-like behaviour was observed off southwest England between May and July, always in surface waters along thermal fronts; because actual mating was not observed, this may occur in deeper water (Ref. 88831). A one-year resting period between pregnancies is thought to occur, resulting in a 2-4 year interval between litters (Ref. 9030, 1765, 88829). Only one pregnant female has been observed giving birth to a litter of 6 pups (Ref. 88830).
Compagno, L.J.V., 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):1-249. Rome, FAO. (Ref. 247)
IUCN Red List Status (Ref. 130435)
Human uses
Fisheries: commercial
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Estimates based on models
Preferred temperature (Ref.
123201): 5.4 - 22.7, mean 11.4 °C (based on 10877 cells).
Phylogenetic diversity index (Ref.
82804): PD
50 = 1.5000 [Uniqueness, from 0.5 = low to 2.0 = high].
Bayesian length-weight: a=0.00389 (0.00180 - 0.00842), b=3.12 (2.94 - 3.30), in cm total length, based on all LWR estimates for this body shape (Ref.
93245).
Trophic level (Ref.
69278): 3.2 ±0.3 se; based on diet studies.
Generation time: 17.7 ( na - na) years. Estimated as median ln(3)/K based on 1
growth studies.
Resilience (Ref.
120179): Very Low, minimum population doubling time more than 14 years (Fec=1-2; Musick et al. 2000 (Ref.
36717)).
Prior r = 0.07, 95% CL = 0.04 - 0.10, Based on 2 data-limited stock assessments.
Fishing Vulnerability (Ref.
59153): Very high vulnerability (86 of 100).
Climate Vulnerability (Ref.
125649): High vulnerability (62 of 100).
Nutrients (Ref.
124155): Calcium = 2.25 [0.46, 11.12] mg/100g; Iron = 0.218 [0.050, 0.684] mg/100g; Protein = 19.3 [16.7, 21.8] %; Omega3 = 0.317 [0.116, 0.875] g/100g; Selenium = 38.4 [9.2, 129.2] μg/100g; VitaminA = 2.24 [0.46, 11.41] μg/100g; Zinc = 0.226 [0.103, 0.441] mg/100g (wet weight);
