|Scientific Name:||Cetorhinus maximus|
|Species Authority:||(Gunnerus, 1765)|
|Infra-specific Taxa Assessed:|
Squalus maximus Gunnerus, 1765
|Red List Category & Criteria:||Vulnerable A2ad+3d ver 3.1|
|Reviewer(s):||Musick, J.A. & Cavanagh, R.D. (Shark Red List Authority)|
This assessment is based on the information published in the 2005 shark status survey (Fowler et al. 2005).
The Basking Shark (Cetorhinus maximus) is a very large, filter-feeding cold-water pelagic species that is migratory and widely distributed, but only regularly seen in a few favoured coastal locations and probably never abundant. Most documented fisheries have been characterised by marked, long lasting declines in landings after the removal of hundreds to low thousands of individuals. Its fins are among the most valuable in international trade. Basking Sharks are legally protected in some territorial waters and listed in CITES Appendix II. Compagno (1984a) considers the species "to be extremely vulnerable to overfishing, perhaps more so than most sharks, ...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 global status of the Basking Shark is assessed as Vulnerable, with the North Pacific and Northeast Atlantic stocks, which have been subject to target fisheries, assessed as Endangered. These assessments are based primarily on past records of rapidly declining local populations of basking sharks as a result of short-term fisheries exploitation and very slow population recovery rates.
|Range Description:||Basking Sharks occur in temperate and boreal oceans. In the North Atlantic, the species occurs from the transition between Atlantic and Arctic waters (including the Gulf of Maine, south and west of Iceland and off the North Cape of Norway and Russia) to the Mediterranean, and occasionally as far south as Senegal and Florida. In the North Pacific, around Japan and off the Chinese coast, and from California north to British Columbia. In the southern hemisphere, recorded from South Africa, Brazil to Ecuador in South America, southern Australia and New Zealand (Compagno 1984a). Most records are from surface waters during spring and summer, with some reports from deep water in winter (Francis and Duffy 2002, Sims et al. 2003). A seasonal migration may occur, either from deep to shallow water or from lower to higher latitudes in warmer weather (the latter is not supported by recent UK observations (Sims et al. 2003)). Most records occur within a narrow range of water temperatures: 8°-14°C in the UK, Japan and Newfoundland, but up to 24°C in New England, USA. Records in warmer waters are generally of moribund or stranded specimens. At least some populations are migratory (Sims et al. 2003) and possibly seasonally segregated by sex; the winter distribution of most populations and locations used by pregnant females are unknown, although it seems likely that wintering sharks occur mainly in deep shelf water (Francis and Duffy 2002, Sims et al. 2003). The different morphological characteristics of basking sharks in the Pacific and the North and South Atlantic oceans are not thought to indicate separate species (Compagno 1984a), but geographically isolated populations.|
Native:Albania; Algeria; Argentina; Australia (South Australia); Belgium; Bosnia and Herzegovina; Brazil; Canada; Chile; China; Croatia; Cyprus; Denmark; Ecuador; Egypt; France; Germany; Gibraltar; Greece; Iceland; Israel; Italy; Japan; Lebanon; Libya; Malta; Mauritania; Montenegro; Morocco; Netherlands; New Zealand; Norway; Peru; Portugal; Russian Federation; Senegal; Slovenia; South Africa; Spain; Syrian Arab Republic; Tunisia; Turkey; United Kingdom; United States (California, Florida, Maine, Oregon, Washington); Uruguay; Western Sahara
|FAO Marine Fishing Areas:||
Atlantic – eastern central; Atlantic – northeast; Atlantic – northwest; Atlantic – southeast; Atlantic – southwest; Indian Ocean – eastern; Mediterranean and Black Sea; Pacific – eastern central; Pacific – northeast; Pacific – northwest; Pacific – southeast; Pacific – southwest
|Range Map:||Click here to open the map viewer and explore range.|
|Habitat and Ecology:||
This shark is named from its habit of "basking" on the surface in good weather conditions, usually singly or in small groups, although it also carries out extensive vertical migrations between the surface and deep water on the continental shelf and shelf-edge (Sims et al. 2003). Basking sharks are often associated with surface aggregations of zooplankton (Kunzlik 1988, Earll and Turner 1993), particularly along tidal and shelf-break fronts (Sims et al. 1997, 2003, Sims and Quayle 1998, Speedie 1998), where they feed on small fish, fish eggs and zooplankton by swimming open-mouthed with gill rakers erect and extended across the gaps between the gill arches to form a sieve (Stendall 1933, Matthews and Parker 1950, Van Deinse and Adriani 1953).
The large liver and high squalene levels (Burandeen and Richards-Rajadurai 1986) are characteristic of deepwater sharks. Deepwater pelagic shrimps (from >100 m) found in the stomach of a basking shark in Japan first indicated mesopelagic food sources (Mutoh and Omori 1978). Few sharks are recorded from coastal and surface waters in winter, indicating a migration into warmer regions or deep water, although there are surface records from Monterey Bay in winter (Squire 1990, Baduini 1995). A few winter specimens from the northeast Atlantic had shed their gill rakers, indicating that they were not feeding during this period of low zooplankton abundance. It was suggested that Basking Sharks might rest in deep water in winter (Parker and Boeseman 1954), utilising food reserves in the large liver. Energetics and tagging studies, however, indicate that feeding still takes place at this time and that extensive horizontal and vertical migrations are undertaken throughout the winter, on and near the edge of the Northeast Atlantic continental shelf (Sims et al. 1998, 2003). A New Zealand winter hoki fishery, targeting fish aggregated in deep water for spawning, takes a bycatch of Basking Sharks that may be feeding on the energy-rich eggs (Francis and Duffy 2002), while Sims et al. (2003) suggest that deep-diving sharks may feed on over-wintering copepods.
The reproductive biology of Basking Sharks is considered to be similar to that of other lamnoid sharks (Kunzlik 1988). Pairing takes place in early summer, wounds caused by copulation having been recorded in British waters in May by Matthews (1950). A single functional ovary contains a very large number of small eggs. Ovoviviparity occurs: embryos hatch within the uterus. Other lamnoid sharks exhibit embryonic ovophagy, in which the mother continues to produce infertile eggs on which the embryos can feed; the Basking Shark probably has the same strategy. Estimates for gestation period range from 12-36 months (Parker and Stott 1965, Pauly 1978, 2002, Compagno 1984a). The only record of a pregnant female was made by a Norwegian fisherman, who caught a shark which gave birth to five live young and one still-born, estimated to be between 1.5 and 2 m in length (Sund 1943). This indicates birth at a larger size than any other known ovoviviparous or viviparous shark. The catch from commercial surface fisheries is almost entirely non-pregnant females (e.g. Watkins 1958). It is thought there is likely a resting period of at least a year between pregnancies, and therefore a 2-4 year interval between litters (Parker and Stott 1965, Pauly 1978, 2002, Compagno 1984a). Pregnant females must normally segregate to an area where no fishery takes place (probably in deep water). Lien and Fawcett (1986) recorded twice as many males as females in incidental catches in deeper water around Newfoundland, indicating segregation of the sexes.
The smallest free-swimming individuals recorded are about 1.7-1.8 m (Parker and Stott 1965). However, the young are very rarely encountered until they reach more than 3 m in length. Growth is about 40 cm annually (Pauly 1978, 2002, Watterson in litt.). Males become sexually mature at a length of 5-7 m, age unknown, but possibly 12-16 years. Females are mature at 8.1-9.8 m and perhaps 16-20 years (Compagno 1984a). Pauly (1978) suggested mean age at first maturity for females as 18 years and that a shark of 9.6 m was 31 years old. There are unconfirmed measurements of 12.76 m (a theoretical maximum from Parker and Stott 1965) and 13.72 m (Holden 1974). Theoretically, longevity is about 50 years, though much more work on the age, growth and demographics of this species is needed. It is estimated that the natural mortality is low (M~0.07 per year) (Pauly 2002).
Anon. (2002c) describes historical and modern fisheries. The Basking Shark has been exploited for several centuries to supply liver oil for lighting and industrial use, skin for leather and flesh for food or fishmeal. Modern fisheries yield liver oil, fins, meat and cartilage (Rose 1996, Anon. 2002c). The large liver represents 17-25% of total weight and contains a high proportion of squalene oil (Buranudeen and Richards-Rajadurai 1986). The very large fins fetch extremely high prices in international trade to East Asia (Fleming and Papageorgiou 1996, Lum 1996, Fairfax 1998, Anon. 2002c). Targeted basking shark fisheries entangle them in nets or use non-explosive harpoon guns to take sharks on the surface. Incidental catches are utilised when there is a market for the products and there has been an unutilised "eradication" fishery. Catches have been recorded from Norway, Ireland, Scotland, Spain, Iceland, Canada, California, Peru, Ecuador, China and Japan (Compagno 1984a, Anon. 1999). One fishery in the Northeast Atlantic continues to take small numbers (ICES data, see Anon. 2002c). Most Basking Shark fisheries appear to have collapsed after initial high yields, and this species is considered by Compagno (1984a) to be extremely vulnerable to overfishing - perhaps more so than most other sharks. A small fishery off Monterey Bay, California (Northeast Pacific), produced fishmeal and shark liver oil between 1924-1937. It expanded from 1946 to early 1950s, taking about 200 sharks annually. A drop in market prices for shark liver reportedly made the operation uneconomic. R. Lea (pers. comm.) reports that basking shark sightingsoff central California over the past 20 years are less numerous than in the past. The population may not have recovered from a substantial depletion during the 1940s and 1950s fishery and could still be affected by bycatch. S. van Sommeran (pers. comm.) notes that finned carcasses are occasionally reported.
Basking Sharks are common in the traditional knowledge of indigenous peoples of Vancouver Island, Canadian Pacific. Salmon net fishermen in Barkley Sound, Vancouver Island, complained of damage through accidental basking shark catches in the 1940s. The Department of Fisheries and Oceans instigated a shark eradication programme in the 1950s. Clemens and Wilby (1961) state that Fisheries vessels killed "several hundred" in Barkley Sound up to 1959, to reduce salmon net bycatch. Darling and Keogh (1994) state "Basking sharks are rarely sighted in Barkley Sound today, suggesting that the majority of the population in that area were killed." It seems that this stock of Basking Sharks was significantly depleted over a period of just a few years and has not yet recovered. A summer Basking Shark fishery started at Achill Island, western Ireland in 1947, using set nets to entangle sharks. It peaked in the early 1950s, when 1,000-1,808 sharks were taken each year. In the early 1970s only 29-85 sharks were taken annually, a decline of over 90% in 20-25 years. Re-capitalisation of the fishery in 1973 failed to increase yields locally and it closed in 1975, despite high oil prices. Parker and Stott (1965) and Horsman (1987) attributed the decline and collapse of this fishery to the overfishing of a local stock. Berrow and Heardman (1994) noted that there were still very few observations of basking sharks along the whole west and north-west coast of Ireland in 1993, and Achill Island fishermen reported fewer than 10 sharks sighted annually (Earll pers. comm.). This fishery appears to have depleted the population to such an extent that it has still not recovered some 40 years later. A wide-ranging Norwegian fleet has undertaken the major basking shark fishery in the northeast Atlantic from April to September in most years. Catches were high (>1,000 and up to >4,000) from 1959-1980 (Kunzlik 1988, ICES data, in Anon. 2002c). The Norwegian quota in European Community waters was 800 t (liver weight) in 1982, 400 t (approximately 800-1,000 sharks) in 1985, subsequently reduced to 200 t, 100 t, and to zero in 2001. Because basking sharks are taken by fishing vessels targeting small whales, increased restrictions on whaling activities and ageing vessels have reduced fleet size. The decline in this fishery has also been attributed to the falling value of Basking Shark liver oil, as a result of the competition from deepwater shark fisheries. Landings rose slightly in the early 1990s, when the fishery was being sustained by high fin prices (ICES 1995), but have since declined to very low levels, despite steeply increasing fin values. The majority of fins landed by Norway have been exported to Japan (Anon. 2002c). Since the precise location from which the basking sharks were taken is only identified by ICES sea area, it is difficult to detect and evaluate trends in catches, effort, and hence population, but the declines appear to be related to population trends and driven by fisheries and trade demand (Anon. 2002c). An intensive targeted Japanese Basking Shark fishery, utilising liver oil, shark fin and meat, took place in spring off Nakiri, Shima Peninsula, in the 1960s and 1970s. An estimated 1,200 sharks were harpooned from 1967-1978, peaking in 1972 when more than 60 sharks were sold at market in one day. Catches declined from about 150 sharks in 1975, to 20 in 1976, nine in 1977 and six in 1978. The fishery closed a few years later. In the 1990s, only 0-2 Basking Sharks were being sighted each year off Nakiri during migration (Yano 1976, 1979, Uchida 1995). Basking sharks are sometimes landed and sold after becoming entangled in set nets or pot lines, or caught in trawls, but bycatch (whether landed or discarded) is rarely reported. Exceptions are reports by Lien and Fawcett (1986) on an incidental fishery for basking sharks by salmon and cod set nets and deepwater trawls in Newfoundland, and Francis and Duffy (2002) on incidental capture in deepwater fisheries off New Zealand. Incidental shark catches in Newfoundland increased in 1981 when a market developed for the fins and liver. When there is no market for the sharks' fins and livers, salmon fishermen generally remove their gear from the water to prevent damage when basking sharks are known to be in the area. If there is a market, any sharks caught are killed and landed.
Berrow (1994) estimated that 77-120 sharks are taken annually in the bottom set gillnet fishery in the Celtic Sea. Fairfax (1998) reports that basking sharks are sometimes brought up from deepwater trawls near the Scottish west coast during winter. Bycatch in Isle of Man herring fishery is about 10-15 fish annually and a further 4-5 entangled in pot lines, (K. Watterson in litt.). Local fishermen estimate an unreported bycatch of up to 40 Basking Sharks per year in one large bay in south-west England (C. Speedie pers. comm.). In contrast to these relatively large coastal bycatches, observer data from oceanic gillnet fleets suggest that only about 50 Basking Sharks were among the several million sharks taken annually offshore in the Pacific Ocean (Bonfil 1994). Habitat loss or degradation is not considered to be a serious problem for this species.
Following notes added by Lucy Harrison (email@example.com) via Sarah Fowler May 17th 2010
Later in 2005, the species was listed in Appendix I and II of CMS. Appendix I means that Parties are required to provide strict protection.
In 2006 ICES issued this advice, which is still current:“No targeted fishing for basking shark should be permitted and additional measures should be taken to prevent bycatch of basking shark in fisheries targeting other species. A TAC should cover all areas where basking sharks are caught in the northeast Atlantic. This TAC should be set at zero.”
Norway ALWAYS implements ICES advice (and indeed, unless they take out a reservation, also other MEA measures – unlike many other States). Their basking shark fishery was therefore closed in either 2006 or 2007, I forget which but probably the latter. They are presumably still landing bycatch, because Norway prohibits discards, but fishermen are not paid full market value for catches for which they do not have a license – only enough to cover the cost of bringing home the catch. This means that they will be avoiding basking sharks wherever possible.
Because of the CMS Appendix I listing, basking shark is also an EU prohibited species: “It shall be prohibited for Community vessels to fish for, to retain on board, to tranship and to land the following species in all Community and non-Community waters” Every year, however, we get reports of basking sharks being caught, landed and put on sale illegally in the EU. So, small scale bycatch and utilisation is definitely ongoing even in areas where the species is strictly protected.
Elsewhere: NZ is the only place where there is still a fairly large utilised basking shark bycatch (in trawls over hoki spawning grounds). The fins are exported under CITES license to East Asia. NZ allows finning.
|Conservation Actions:||The Basking Shark is strictly protected under wildlife legislation within 12 nautical miles of the Isle of Man and Guernsey (United Kingdom dependent territories) and in British waters. It is protected in US Federal waters (including the Gulf of Mexico and Caribbean Sea) by a National Marine Fisheries Service rule for Atlantic shark fisheries, which prohibits directed commercial fishing, landing and sale of the species and in Florida State waters. The basking shark is one of several species partially protected through New Zealand's Fisheries Act (1983). Commercial target fishing has been banned since 1991, but bycatch may be utilised. The liver and fins are landed and the fins almost certainly exported. The Basking Shark is listed on Annex II (Endangered or Threatened Species) of the Barcelona Convention for the Protection of the Mediterranean Sea (1976) Protocol Concerning Specially Protected Areas and Biological Diversity in the Mediterranean, but only Malta has legally protected the species. The Mediterranean population is also listed on Appendix I of the Bern Convention for the Conservation of European Wildlife and Habitats, subject to a European Commission reservation. A UK government proposal for an Appendix II listing on CITES was narrowly defeated in 2000, but was followed by an Appendix III listing in Europe later that year. Japan and Norway, the world's two main trading nations, took reservations on this listing. An Appendix II proposal, accepted by the 12th Conference of the Parties in 2002, came into effect at the end of February 2003 (www.cites.org). This requires international trade to be monitored and derived from sustainably managed fisheries.|
|Citation:||Fowler, S.L. 2005. Cetorhinus maximus. The IUCN Red List of Threatened Species. Version 2015.2. <www.iucnredlist.org>. Downloaded on 31 August 2015.|
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