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Megachasma pelagios

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA CHONDRICHTHYES LAMNIFORMES MEGACHASMIDAE

Scientific Name: Megachasma pelagios
Species Authority: Taylor, Compagno & Struhsaker, 1983
Common Name(s):
English Megamouth Shark, Megamouth Shark

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2005
Date Assessed: 2005-10-01
Assessor(s): Compagno, L.J.V.
Reviewer(s): Musick, J.A. & Fowler, S.L. (Shark Red List Authority)
Justification:
This assessment is based on the information published in the 2005 shark status survey (Fowler et al. 2005).

Megamouth Shark (Megachasma pelagios) is a very large pelagic filter-feeding shark and was perhaps the most spectacular discovery of a new shark in the twentieth century (Compagno 2001). Specimens are very seldom reported, thus the shark is apparently very rare throughout its range, yet likely to be increasingly taken as bycatch in oceanic and offshore littoral fisheries. At the time of writing it was known from less than 20 specimens, though its distribution is thought to be circumtropical and wide ranging. The colouration and catch records of the megamouth shark are suggestive of epipelagic rather than deepwater habitat, as is the composition of its liver oil.
History:
2000 Data Deficient

Geographic Range [top]

Range Description: This species is known from only a few specimens but probably it is circumtropical and wide ranging. Known records are from the following areas:

Western Atlantic: Brazil.
Eastern Atlantic: Senegal.
South-eastern Indian Ocean: Western Australia.
Northwest Pacific: Japan, Philippines, Indonesia.
Central Pacific: Hawaiian Islands (Oahu).
Eastern Pacific: USA (southern California).

A coastal and oceanic, epipelagic and neritic species, it has been found in water as shallow as 5m in a bay and 40 m deep on the continental shelf. It has also been recorded offshore in the epipelagic zone at 8-165 m depth in water 348-4,600 m deep and some have been washed ashore (Yano et al. 1997).
Countries:
Native:
Australia (Western Australia); Brazil; Indonesia; Japan; Philippines; Senegal; United States (California, Hawaiian Is.)
FAO Marine Fishing Areas:
Native:
Indian Ocean – eastern; Pacific – eastern central; Pacific – northwest
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This rare shark is known from less than 20 specimens since its discovery in 1976.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: The only known prey of the Megamouth Shark are epipelagic and mesopelagic euphausiid shrimp, copepods and jellyfish (Yano et al. 1997). The feeding structures of this shark may allow it to feed on other pelagic invertebrates and even small fishes, but so far the stomach contents studied suggest that it primarily targets euphausiid shrimp (Compagno 2001).

Observations made on a live-captured megamouth shark which was later tagged with an acoustic telemetric tag and tracked for two days, suggested it could breathe readily by gill-pumping and was not dependent on constant swimming like other lamnoid sharks. During the tracking period, the shark revealed a pattern of vertical, crepuscular migration in the epipelagic zone. It has been suggested that the Megamouth Shark may follow vertical migrations of euphausiid prey during diel cycles (Compagno 2001).

The mode of reproduction is probably aplacental viviparous with uterine cannabilism or cannibal vivipary suspected in the form of oophagy. A late immature or early adolescent female had two ovaries with many tiny oocytes, while an adult female had numerous larger oocytes. This is similar to the ovaries of other lamnoids.
Systems: Marine

Threats [top]

Major Threat(s): Taken as a rare incidental bycatch of various high-seas and coastal fisheries, including commercial littoral drift gillnets, set fish traps, and pelagic longlines and purse-seines, vulnerable to pelagic gillnets and pelagic trawls. Seldom reported. So far, specimens have been utilised by museums and oceanaria for research and display.

Conservation Actions [top]

Conservation Actions: None.

Bibliography [top]

Compagno, L.J.V. 2001. Sharks of the World. An annotated and illustrated catalogue of the shark species known to date. Volume 2. Bullhead, mackerel and carpet sharks (Heterodontiformes, Lamniformes and Orectolobiformes). FAO, Rome.

Fowler, S.L., Cavanagh, R.D., Camhi, M., Burgess, G.H., Cailliet, G.M., Fordham, S.V., Simpfendorfer, C.A. and Musick, J.A. (comps and eds). 2005. Sharks, Rays and Chimaeras: The Status of the Chondrichthyan Fishes. Status Survey. pp. x + 461. IUCN/SSC Shark Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK.

Itabashi, Y., Yamaguchi, A. and Nakaya, K. 1997. Liver oil composition of the Megamouth Shark, Megachasma pelagios. Biology of the Megamouth shark, pp. 151–159. Tokai University Press, Tokyo.

Yano, K., Morissey, J.F., Yabumoto, Y. and Nakaya, K. 1997. Biology of the Megamouth Shark. Tokai University Press, Tokyo, Japan.


Citation: Compagno, L.J.V. 2005. Megachasma pelagios. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 19 December 2014.
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