Basking Shark ( Cetorhinus maximus )


Description

The Basking Shark is the second largest fish in the world, measuring up to 11 meters and 7 tonnes (1). It is characterised by its large gaping mouth containing five gill slits that almost encircle its head (2). The basking shark has an extremely distinctive body shape with its conical, almost pointed snout, up to 2m long dorsal and pectoral fins, and a crescent shaped tail (2). The body is a greyish brown colour, and can be this colour all over or have a paler shade underside (2). The basking shark has declined in recent years by between 50- 70 % (3).

Behaviour

Basking sharks are occasionally seen leaping from the water (2) and spend much of their time at the surface where their main food source, plankton, aggregates (3). They are often seen in pairs and occasionally there have been sightings of groups of up to 100 individuals (2).

Lifecycle

The exact lifespan of the Basking shark is unknown, but experts estimate that it is approximately 50 years. Sexual maturity is reached between 5 to 18 years (4). Basking sharks give birth to live, well developed young that hatch from eggs incubated inside the female (1) every 2- 4 years, with a gestation period of approximately 14 months. New born basking sharks range in size from 1.5- 2 meters (4).

Habitat

Basking sharks inhabit coastal and pelagic temperate waters (4). They are often sighted close to the surface with their mouths open, where plankton aggregates (4).

Distribution

There are approximately 8200 basking sharks left in the world (5) and these are widely distributed and only regularly seen in a few locations (4). There is some debate as to whether the Northern and Southern hemisphere populations may have evolved into different species (2).

Migration

Basking sharks are highly migratory (1) and undertake both horizontal and vertical migrations in order to benefit from the most abundant plankton locations throughout the years (6). Horizontal migrations can cover a distance of up to 3400km and vertical migrations can reach depths of more than 850m (6).

Food

Basking sharks are filter-feeders, consuming small planktonic organisms such as small copepods, larvae, and fish eggs, while swimming forward through the water with their mouths open (4).

Conservation Status

IUCN Red List Status: Vulnerable (Assessed 2000) (4)

Bern Convention Appendix II and III (7)

Bonn Convention on the Conservation of Migratory Wild Animals Appendix I and II (8)

CITES Appendix II (9)

Barcelona Convention Appendix II and III

UNCLOS

UNFSA

References

Description written by Jo Pollett (2009)

(1)   Bloomfield, A. & Solandt, J.-L., 2006. The Marine Conservation Society Basking Shark Watch 20 Year Report 1987-2006. Marine Conservation Society.

(2)   Solandt, J.-L., 2009. Basking Shark – Cetorhinus maximus – Information – ARKive – facts and status. [Online] Available at: http://www.arkive.org/basking-shark/cetorhinus-maximus/info.html [Accessed 19 August 2009].

(3)   Shark Alliance Trust, 2009. Basking Shark Facts. Shark Alliance Trust.

(4)   Fowler, S.L. 2000. Cetorhinus maximus (North Pacific subpopulation). In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1. <www.iucnredlist.org>.

(5)   Fordham, S.V., 2006. Shark Alert. Revealing Europe’s impact on shark populations. Shark Alliance.

(6)   Sims, D.W., 2008. Tracking Fish with Chips: revealing marine fish movements, behaviour and population structure through technology. IMarEST, 13(12), pp.47-58.

(7)   Europe, C.o., 2002. Convention on the conservation of European wildlife and natural habitats: Bern Convention. [Online] Available at: http://conventions.coe.int/Treaty/FR/Treaties/Html/104-2.htm [Accessed 23 July 2009].

(8)   (CMS), C.o.t.C.o.M.S.o.W.A., Effective 5th March 2009. Appendices I and II of the Convention on the Conservation of Migratory Species of Wild Animals.

(9)   UNEP-WCMC, 2009. UNEP-WCMC Species Database: CITES-Listed Species. [Online] Available at: http://www.unep-wcmc.org/isdb/CITES/Taxonomy/tax-species-result.cfm?displaylanguage=eng&Genus=Cetorhinus&Species=maximus&source=animals&Country= [Accessed 19 August 2009].

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