The conservation status of pelagic sharks and rays
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- 23rd February 2007
- by thedconceptadmin
- pelagic, rays, sharks,
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Pelagic sharks and rays are a relatively small group, representing only about 6% of the world’s total chondrichthyan fish species and having low diversity compared to the shelf- and slope-dwelling chondrichthyans. They are active, free-swimming species that live in the water column and are not closely associated with the sea bottom. No chimaeras are known to be pelagic.
The pelagic sharks and rays include both “oceanic” and “semipelagic” species. Oceanic species live wholly or partly in ocean basins away from continental landmasses, although some approach the edges of continental and insular shelves and may move close inshore to feed or breed. These species live in one or more of three zones of oceanic habitat: the sunlit epipelagic zone, from the surface to 200m deep; the mesopelagic zone, from 200m to 1,000m deep, where little light penetrates; and the sunless bathypelagic zone, below 1,000m to 6,000m or more.
Semipelagic species penetrate oceanic waters but are concentrated close to continental landmasses over the continental slopes and rises. Many oceanic and semipelagic sharks and rays also enter the littoral zone, that part of the oceans over the continental and insular shelves, from the intertidal to 200m depth. Pelagic sharks are best known from the epipelagic zone. Electronic tagging is providing new data on the lower depth distribution of some of the larger species formerly associated only with epipelagic waters, including whale sharks Rhincodon typus (Graham et al. 2006), basking sharks Cetorhinus maximus (Gore et al. 2008; Skomal et al. 2009) and porbeagle sharks Lamna nasus (Pade et al. 2009). The difficulties involved in collecting specimens from deep pelagic waters, however, mean that less is known about mesopelagic and bathypelagic sharks.Download report