Gray reef shark

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Gray reef shark
C. amblyrynchus.JPG

Gray reef shark ( Carcharhinus amblyrhynchos )

Systematics
without rank: Sharks (selachii)
Superordinate : Galeomorphii
Order : Ground Sharks (Carcharhiniformes)
Family : Requiem sharks (Carcharhinidae)
Genre : Carcharhinus
Type : Gray reef shark
Scientific name
Carcharhinus amblyrhynchos
( Bleeker , 1856)

The gray reef shark ( Carcharhinus amblyrhynchos ) is a representative of the requiem sharks (Carcharhinidae). The medium-sized shark inhabits lagoons, channels and outer reefs of tropical regions worldwide. The occasionally used, abbreviated name gray shark is ambiguous and can also refer to the much larger six- gill shark .

features

The shark is 1.5–2.5 meters long, usually 1.85 m long, with the females being significantly smaller and lighter than males. It has a torpedo-shaped body with a broad, round snout. The dorsal fin usually begins at the level of the free end of the pectoral fins; the gray reef shark has no interdorsal ridge . The upper side of the body shows a light to dark gray, more rarely brownish color, the caudal fin has a black border. The first dorsal fin usually has no markings; in populations in the Red Sea and Indian Ocean there is a white rear edge of the first dorsal fin. The underside of the body is clearly lighter in color. Life expectancy is a maximum of 25 years.

distribution and habitat

Distribution areas of the gray reef shark

The gray reef shark is native to the Indo-Pacific (Madagascar, Seychelles, Maldives, Thailand, Australia, Hawaii, Tahiti) and the Red Sea . It lives mainly in lagoons, canals and outer reefs .

The shark prefers the area between the water surface and a maximum of 275-280 meters water depth; the reef he keeps mostly on the outer reef slope ( Outreef ) and in lagoons near strong currents on. The animals were also found on the inner reef slope or over sandy plateaus. Together with the blacktip reef shark, the species shows a microhabitat separation, whereby the gray reef shark inhabits the deeper, the somewhat smaller blacktip reef shark inhabits the flat area of ​​the habitat. If this is missing, the gray reef shark lives in both areas. Together with the whitetip reef shark , both are among the most common species in the coral reefs of Oceania .

Way of life

behavior

The shark is curious, active and usually swims quickly. The social animal sometimes forms schools during the day; schools of juvenile and subadult animals are striking. The gray reef shark can be found during the day, but is more active at night and for prey. Adult animals show pronounced territorial behavior ; the area of ​​the territory is usually around four square kilometers. Intruders are warned by threatening behavior such as rapid swimming with exaggerated movements of the caudal fin, lowering of the pectoral fins, head roll and hump formation ( hunching ); this is followed by a single, usually non-fatal bite. The populations in the Pacific are significantly more aggressive than those of the Indian Ocean and Red Sea.

nutrition

Gray reef shark with clear bite marks on the abdomen during the mating season

The Gray Reef Shark feeds mostly on reef fish such as moray eels , garfish , soldier , butterfly fish and surgeon fish , but also of cephalopods and crustaceans . It usually eats near the ground. A feeding orgy can be triggered by harpooned fish. At night, groups of gray reef sharks were observed, the schooling fish - similar to a pack of wolves - rounded up on a reef wall before the prey were attacked.

Reproduction

Gray reef sharks become sexually mature at the age of seven years and between 130 and 145 cm in size. They are viviparous and have one to six young per litter; these are 40–60 cm long at birth. When mating, it is not uncommon for bites with visible injuries, with the larger males biting the female's fins and abdomen.

Danger to humans

Despite the clearly threatening behavior of adults, attacks by the gray reef shark on humans have been reported. However, this is also due to the frequent, non- pelagic occurrence of the species on reefs.

Endangerment and population development

The Gray Reef Shark is still quite common species. However, the continued IUCN to Carcharhinus amblyrhynchos because of the population decline on since 2000 IUCN Red List and classifies the type since as near threatened ( Near Threatened ) a. The limited coral reef habitat, the loyalty to the location, the slow reproductive cycle of the species and the high pressure from fishing in the majority of its range are considered to be the cause of endangerment . There are no precise data on the development of the populations. It is caught partly as bycatch , partly by hunting specifically for this type of shark - as in the Maldives .

Individual evidence

  1. ↑ a b c d E. Lieske, R. Myers: Coral reef guide Red Sea. 2004, Franckh-Kosmos Verlag, Stuttgart, ISBN 3-440-09356-5 , p. 25
  2. ↑ Mark Carwardine: Sharks. Delius Klasing, 2005, ISBN 3-7688-1601-X .
  3. ↑ a b c d Hai.ch: Gray reef shark (Carcharhinus amblyrhynchos)
  4. ↑ a b c d e f g Ralf Michael Hennemann: Haie & Rochen worldwide . 1st edition. Year Top Special, Hamburg 2001, ISBN 3-86132-584-5 , p. 123 .
  5. ↑ a b Alberto Siliotti and others, Memofish Book - The fish of the Red Sea , Geodia Verlag Verona, 2002, ISBN 88-87177-43-0
  6. ↑ E. Lieske, R. Myers: Coral reef guide Red Sea. 2004, Franckh-Kosmos Verlag, Stuttgart, ISBN 3-440-09356-5 , p. 19
  7. ↑ J. Stafford-Deitsch: Red Sea Sharks. Trident Press, 1999, ISBN 1-900724-28-6 , pp. 19-24, 27-32, 74-75
  8. ↑ IUCN: 2008 Pacific islands Red List for Animals (2008) (PDF; 533 kB)
  9. ↑ Carcharhinus amblyrhynchos in the endangered Red List species the IUCN 2009. Posted by: Smale, MJ, 2005. Accessed on March 3 of 2010.

Web links

Commons : Carcharhinus amblyrhynchos  - collection of images, videos and audio files