| ||Halsydrus pontoppidani Neill, 1809, (nomen nudum), Fleming, 1817.|
| ||? Tetroras angiova Rafinesque, 1809|
| ||Squalus gunnerianus Blainville, 1810|
| ||Squalus peregrinus Blainville, 1811|
| ||Squalus (Cetorhinus) gunneri Blainville, 1816|
| ||? Scoliophis atlanticus Anon., 1817|
| ||Squalus isodus Macri, 1819|
| ||Squalus elephas Le Sueur, 1822|
| ||Squalus rashleighanus Couch, 1838|
| ||Squalus rhinoceros Mitchell, in DeKay, 1842|
| ||Squalus cetaceus Gronow, 1854|
| ||Polyprosopus macer Couch, 1867|
| ||Cetorhinus blainvillii Brito Capello, 1870|
| ||Selachus pennantii Cornish, 1885|
| ||Cetorhinus maccoyi Barrett, 1933|
| ||Cetorhinus maximus van Deinse & Adriani, 1953, forma infanuncula.|
| ||Cetorhinus maximus normani Siccardi, 1960|
| ||Halsydrus maximus Gunnerus, 1765|
|En - Basking shark, Fr - Pèlerin, Sp - Peregrino.|
3Alpha Code: BSK Taxonomic Code: 1060100301|
|Scientific Name with Original Description|
|Squalus maximus Gunnerus, 1765, K. norske Vidensk-selsk. Sck. Trondh., 33, pl. 2. Holotype: apparently none. Type Locality: Trondhjem, Norway.|
Trunk fusiform and moderately stout. Head moderately long but much shorter than trunk; snout moderately long, pointed and conical, not depressed, flattened and bladelike; eyes small; mouth large and arcuate, ventral on head,
gill openings extremely large, extending onto dorsal and ventral surfaces of head, all anterior to pectoral fin bases; gill rakers present on internal gill slits, in the form of hairlike modified dermal denticles with extremely elongated crowns;
teeth very small, hooklike, not blade-shaped, and in over 200 rows in either jaws; several rows of small anterior teeth in upper jaw, separated from the laterals by a broad gap.
First dorsal fin large, high, erect and angular; second dorsal and anal fins moderately large but less than half size of first dorsal, with broad, non-pivotable bases; pectoral fins long and moderately broad, much shorter than head in adults; pelvic fins smaller than first dorsal fin but larger than second; caudal fin lunate, upper lobe moderately long but less than one-third length of rest of shark, lower lobe nearly as long as upper lobe. Precaudal pits present, caudal peduncle depressed and with strong lateral keels.
|fieldmarks: The great size, enormous gill slits that virtually encircle the head, dermal denticle gill rakers, pointed snout, huge, subterminal mouth with minute hooked teeth, caudal peduncle with strong lateral keels, and lunate caudal fin distinguish this shark from all others.|
|Coastal and amphitemperate.Western Atlantic: Newfoundland to Florida; southern Brazil to Argentina. Eastern Atlantic: Iceland, Norway and western Barents Sea to Mediterranean and Senegal; western Cape Province, South Africa. Western Indian Ocean: Eastern Cape Province, South Africa. Western Pacific: Japan, the Koreas, China; Australia (New South Wales, Victoria, Tasmania, South and Western Australia), New Zealand. Eastern Pacific: Gulf of Alaska to Gulf of California; Ecuador, Peru and Chile, ?Galapagos Islands.|
|Habitat and Biology|
|A coastal-pelagic shark found in boreal to warm temperate waters of the continental and insular shelves, occurring well offshore and often very close to land, just off the surf zone; enters enclosed bays.This huge, impressive, conspicuous shark is often seen at or near the surface, singly, in pairs, triads or in schools up to a hundred or individuals, basking with dorsal fins out of the water or even with bellies upward, or moving slowly forwards or in short arcs with their mouths open like hoops while feeding. Surface basking in this shark is thought to be correlated with surface concentrations of food plankton and also with courtship and mating. Two, three or more individuals may swim in tandem, in a straight line or in circles, which suggests to some writers that a row of these sharks swimming together may have been mistaken for a single huge 'sea serpent' in the past. [more...]|
Adult, nonpregnant female basking sharks have immense numbers of small eggs in their ovaries. Presumably this shark is ovoviviparous and has uterine cannibalism like other lamnoids, with embryos feeding on the small eggs and possibly smaller siblings, but this remains to be seen. An unconfirmed record of a fetus about 1.7 m long and the above mentioned free-living individual suggests that size at birth may be about 1.7 m, and hence greater than any other known ovoviviparous or viviparous shark.
Age of this shark has been estimated by counting vertebral rings and attempting to correlate them with supposed changes in size of individuals within a population. It has been suggested that birth occurs after a 3 and 1/2 year gestation period, and that two calcified rings per year are laid down until maturity at between 6 to 7 years for males. The biannually calibration of the rings is uncertain and controversial; a yearly rate of ring deposition has been suggested, with possible age at maturity for males doubled to 12 to 16 or more years (D. Pauli, pers. comm.). Whatever the case, the basking shark has proved to be extremely vulnerable to overfishing, perhaps more so than most sharks, and this can be ascribed to its slow growth rate, lengthy maturation time, long gestation period, probably low fecundity, and probable small size of existing populations (belied by the immense size of individuals in their small schools).The basking shark is one of the three types of huge, filter-feeding sharks, the other two being the megamouth and whale sharks. The basking shark may be unique in relying entirely on the passive flow of water through its pharynx generated by swimming for filtration; the other two giant filter-feeders may assist the process of food ingestion by actively pumping or gulping water and food organisms into their pharynxes. The basking shark feeds exclusively on small planktonic organisms trapped on its unique gill rakers, apparently with the help of mucous secreted in its pharynx. Food items include small copepods, barnacle and decapod larvae, and fish eggs. On the average a half ton of material may be present in the stomach of these sharks. While feeding the basking shark cruises with mouth widely open and gills distended, occasionally closing its mouth to ingest its prey. An average adult has been estimated to be capable of filtering over 2000 tons of water per hour assuming a constant cruising speed of about 2 knots. The facts that the basking shark periodically sheds its gill rakers and that plankton densities seasonally fall below levels thought essential to maintain ordinary swimming and metabolic activity in this shark have spawned a controversy over whether or not the species remains active when deprived of gill rakers and high plankton densities. It has been suggested that the basking shark may 'hibernate' on the bottom, perhaps at the edge of continental shelves, until its rakers are replaced and plankton blooms reoccur. Proof of hibernation has never been forthcoming, and an alternate hypothesis has been suggested that the basking shark may turn to benthic feeding when it loses its gill rakers. A possible additional factor is that the massive, oil-filled liver of this species may serve as a metabolic store to supply energy to support a reduced rate of activity (slower swimming in colder, deep water) while gill rakers and plankton supplies regenerate. Estimates have been proposed that, in north European waters, the basking shark drops its gill rakers in early winter and takes about 4 or 5 months to fully replace them.
|Basking sharks have been credited as reaching a maximum total length of 12.2 to 15.2 m, but even if this is correct most specimens do not exceed about 9.8 m. Males mature at about 4 or 5 m and reach about 9 m, females are mature at 8.1 to 9.8 m. Size at birth unknown; the smallest known free-living individual was 165 cm long. The basking shark is the second largest shark, fish-like vertebrate, and elasmobranch after the whale shark (Rhincodon typus ).|
|Interest to Fisheries|
|The basking shark has been the object of harpoon fisheries from small boats off the Norwegian coast, Ireland and Scotland, Iceland, California, Peru, Ecuador, China, and Japan, often sporadically fished due to periodic depletion of basking shark stocks; during the last century they were also harpooned by whaling vessels . The basking shark has also been taken in nets, including bottom gillnets and even bottom and pelagic trawls, and formerly was a problem to salmon gillnetters in the Pacific northwest of North America by fouling gillnets . Catches of basking shark have been reported to FAO only from Northeast Atlantic (Fishing Area 27) by Norway (Portugal reported one single t in 1987, 1994, 1995 and 1996). Norway' catches had two peaks in 1970 (18,700 t) and in 1975 (18,352 t) then steadily decreased; in 1992 they raised again to 3,658 t but in 1995 and 1996 dropped to 108 and 413 t respectively. The total catch reported for this species to FAO for 1999 was 210 t. The countries with the largest catches were New Zealand (129 t) and Norway (77 t).|
The basking shark meat is used for human consumption fresh or dried salted; its fins are used for shark-fin soup; its liver, rich in oil and very large, is extracted for its high squalene content but the liver oil was formerly used for tanning leather for lamp oil; the hide is processed for leather and the carcass is rendered for fishmeal.
The basking shark has been exploited commercially for centuries in several parts of the world mainly for its liver oil, which was used as lighting fuel for lamps in the past, and during this century as a source of chemical compounds. Several localised basking shark fisheries have shown sharp declines recently and in the past. However, the unpredictable nature of the occurrence of this shark which seems to be driven chiefly by oceanographic processes (Sims and Quayle 1998), its poorly known migratory movements, and the total lack of understanding of the size and structure of the stocks make it difficult to separate natural fluctuations in local abundance from the effects of exploitation on the populations. A fishery around Achill Island, in Ireland, operated from 1947 to 1975 with decreasing catches after an initial peak of 1,800 sharks taken in 1952 (Fowler 1996). Parker and Stott (1965) attributed the decline in this fishery during the early 1960s to overfishing of the local stock. Fowler (1996) notes that few basking sharks occur in the area today. Norway has a basking shark fishery that dates back to the 16th century when the dry flesh was used for human consumption. In the 1960s, a high demand for shark livers spurred a great expansion in this traditional fishery and catches of between 1,266 and 4,266 basking sharks per year were made in the period 1959-80 (Kunzlik 1988, Miklevoll 1989a, Bonfil 1994). Presently, under EU regulations, Norway can only take 400 t of basking shark livers per year (about 2,400 t live weight). However, shrinking markets for basking shark oil and an ageing Norwegian fleet together with the erratic distribution of the sharks have constrained the catches and the quota has never been fully taken (Bonfil 1994). The abundance of basking sharks off the coast of California and the effects of fishing on local stocks are also surrounded by uncertainty. Historical accounts of basking sharks point to both low and high abundances in the region. Clark (1887; cited by Castro et al. in press) reported them as very rare off Monterey while Chute (1930; cited by Castro et al. in press) cited reports of up to 500 sharks at a time. A fishery for basking sharks took place off California during 1924-1950 (Phillips 1948). The yearly average catch was about 25 sharks but up to 200 basking sharks were taken in a single year in Monterey Bay (Roedel and Ripley 1950). The California fishery stopped in 1950 when the price of shark liver oil collapsed and basking shark availability decreased (Squire 1967). Squire (1990) provides some data suggesting that the abundance of basking sharks in California is quite variable. Based on aerial survey reports he found that basking shark apparent abundance north of Point Conception was higher before 1970 than recently, in a period when no significant fishing (directly or as bycatch) has occurred since 1950. However, the drop in apparent abundance is concurrent with decreased survey effort in that area over that period. This author suggests that ENSO and other oceanographic anomalies may be an important factor driving the abundance of basking sharks in California. During the 1950s, the Department of Fisheries and Oceans of Canada conducted a basking shark eradication programme in the West Coast of Vancouver Island following complaints of salmon fishermen who lost their nets and catches to basking sharks. Some 110 basking sharks were killed in 1955-56 and local shark populations have not yet recovered to their original levels (Darling and Keogh 1994). Kunzlik (1988) attributes the decline of basking shark fisheries to the inconsistent nature of their seasonal availability and to collapses in the price paid for their livers, and finds no firm evidence to suggest that the species has been threatened, even locally, by exploitation.
Conservation Status : Our poor knowledge of the basic biology of the basking shark precludes the calculation of its intrinsic rebound potential. However, preliminary studies suggest it is a late maturing fish (Pauly 1978) and has few offspring. This points towards a low intrinsic rebound potential which coupled with declines in local abundance suggest a precautionary approach to basking shark exploitation. The IUCN Red List (Camhiet al. 1988) classifies the basking shark as Vulnerableworldwide. Mooney-Seus and Stone (1996) consider this species asData Deficient but stress its potential frailty. The basking shark is protected from fishing in state waters of Florida, all federal waters of the US coasts of the Gulf of México and the Atlantic Ocean, the Isle of Man, and New Zealand. It is proposed for protection in the Mediterranean Sea and British waters (Anon. 1998).
Additional information from IUCN database
Additional information from CITESdatabase
|Siccardi (1960, 1961) suggested that there are four species of Cetorhinus, two from the North Atlantic and Mediterranean (C. maximus and C. rostratus), one from southern Australia (C. maccoyi) and one from the South Atlantic (C. normani). Pending further work, I prefer to follow Springer & Gilbert's (1976) reasoning that there is insufficient evidence at present to separate these species.|
Threat to humans: The basking shark is usually quite tolerant of boats approaching closely to it (to its detriment when harpoon fisheries for it have been mounted), and divers have been able to swim right up to individuals and photograph them without invoking an extreme fright reaction. Basking sharks may approach divers quite closely, possibly out of curiosity, and swim around them. This species is regarded as ordinarily harmless and inoffensive but potentially dangerous if attacked (particularly when harpooned). The immense size and power of the basking shark should invite respect, however. Divers should avoid contact with the skin of this shark, which has large dermal denticles with sharp, hooked crowns that point forwards and sideways as well as backwards; while involved in the dissection of a large basking shark the writer has experienced first hand the lacerations that can result from contact with its skin.
Bigelow & Schroeder, (1948)
D. Pauli, (pers. comm.,1983)
Matthews & Parker, (1950)
Parker & Boeseman, (1954)
Parker & Stott, (1965)
Springer & Gilbert, (1976)
Van Deinse & Adriani , (1953)