Wildlife of Pakistan


 Fishes

( Sharks )


 

Black Tip Reef Shark
(Carcharhinus Melanopterus)

 

PHOTO CREDIT: The shark trust

 

Description and Biology:

Description: A rather small shark (under 1.6m) with conspicuous, black-marked fin tips. Snout rather short and rounded with prominent nasal flaps; eyes oval; no interdorsal ridge; 1st dorsal fin medium-sized (height 8 - 11.4% of TL) with its origin above or just posterior to the inner corner of the pectoral fins; 2nd dorsal moderately large with a short rear tip, anal fin of similar size and positioned directly below. Upper teeth rather narrow, generally oblique, with serrated margins and enlarged serrae and cusplets at the bases. Colour light grey-brown dorsally, fading to white ventrally; darker horizontal band invading the white flanks. Tip of 1st dorsal and lower caudal fin marked with conspicuous black blotches, surrounded into the fin interior with white; other fins with less marked black or dark apexes; trailing edge of caudal fin often clearly lined in black.

Size: Exceptionally to 180cm TL; mostly under 160cm TL; size at birth 33 to 52cm.

Biology: These sharks are active swimmers, generally near the bottom but sometimes visible cruising at the surface in very shallow, wading-depth waters; either singly or in small, loose aggregations. Preys upon a wide range of smaller demersal or inshore bony fish, including jacks, mullet, sea breams and smaller groupers; also octopi, squid, cuttlefish and occasionally shrimps. Activity levels increase markedly at night and tagging studies in Pacific waters suggest that these sharks may inhabit the same microsites for at least 2 years. Viviparous. Litter size 2 - 5 pups, generally 4 or less; gestation period perhaps as much as16 months. Females mature at 96 - 112cm TL; males between 91 - 100cm. (all above information from The Shark Trust).

Habitat and Distribution:

A coastal or littoral shallow-water species typically associated with coral reef communities; it tends to occur in clearer waters in bays and along the margins or sandy flats of shallow banks, also around islets and headlands, over rocky or sandy substrate and often adjacent to drop-offs or channels to a maximum depth of 100m but more commonly in depths under 20m. Found throughout the Arabian Sea.

 

 Great Hammer Head Shark
(Canis Aureus)

 

 

PHOTO CREDIT: The shark trust

 

Description and Biology:

Description: A large or very large (to over 500 cm) distinctive hammerhead shark with an angular head measuring 23 to 27% of TL; its anterior margin conspicuously straight and with a shallow median indentation. Tooth count 17 on each side of upper jaw; 16 or 17 in lower (discounting small symphyseals); teeth strongly serrated. First dorsal fin noticeably tall, with an acute, pointed apex and strongly falcate in shape; its origin opposite or just posterior to the pectoral axil and free rear tip not extending rearwards to above the pelvic fin origins. Posterior margins of pelvic fins concave and strongly falcate. Second dorsal fin fairly tall compared to congeners, its height 4.7-6.5% of TL with its posterior margin concave and the inner margin rather short, equating to about the fin height; free rear tip not extending to the precaudal pit. Anal fin marginally larger, strongly concave and originating anterior to the second dorsal origin. Pectoral fins moderately falcate in shape, their anterior margins measuring 13.4 to 18.4% of TL. Dorsal colour dark brown-grey or bronzy-grey, fading to white ventrally. Ventral apices of pectoral fins plain, not dusky; apex of second dorsal fin somewhat dusky in juveniles.

Size: Maximum perhaps in excess of 550cm and possibly over 600cm; most adults to 350-450cm TL; size at birth ca. 65 cm. First Mediterranean example measured ca. 300 cm and weighed ca. 120kg (Boero & Carli, 1977).

Biology: A large, voracious species - and one of the largest predatory sharks - occuring both as a coastal and semi-oceanic pelagic inhabitant of continetal and insular shelves; ranging from the surfline to well offshore at depths from the surface down to 80m or greater. Great hammerheads are highly nomadic, with poleward summertime migrations in parts of their global range. They are predators upon a wide variety of (primarily demersal) bony fish and elasmobranchs, particularly groupers and dasyatid stingrays (a favoured prey-item, consumed complete with tail-spines), but also jacks, clupeids and flatfish; other elasmobranch prey included smoothhounds (Mustelus spp.), skates, guitarfish and Rhinoptera spp; invertebrates taken by these sharks include crabs and cephalopods (squid). Reproduction is viviparous, with a yolk-sac placenta; litter-sizes range between 6 - 42 young. Gestation period is 11 months. Females mature at ca. 210-250cm and males at ca. 225-269cm. (all above information from The Shark Trust).

Habitat and Distribution:

Found throughout the Arabian Sea.

 


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