Asian Diver – March 2018

b

BLUE SHARK

LONG PECTORAL FINS

In order to travel long distances across

the open ocean in search of prey, this

species has a slender body and extremely

long pectoral fins that are approximately

the same length as the distance between

the snout and the posterior gill slit

COUNTERSHADING

The blue shark takes its name from

its distinctive indigo blue colour on the

top of its body that gradually becomes

lighter towards the edges and bright

white on the ventral side. This contrast

in colours is known as countershading,

and provides camouflage for the shark

in the open ocean

SCIENTIFIC CLASSIFICATION

Kingdom : Animalia

Phylum : Chordata

Class : Chondrichthyes

Subclass : Elasmobranchii

Superorder : Selachimorpha

Order : Carcharhiniformes

Family : Carcharhinidae

Genus : Prionace

Species : P. glauca

Maximum Size

Average size

Maximum Weight

4 metres

3.35 metres

205 kilograms

CONSERVATION STATUS

Extinct Threatened Near Threatened

EXEWCRENVUNTLC

Long Pectoral Fin

Indigo Blue Colour

Newborn pups measure around

35–44

centimetres

REPRODUCTION

Blue sharks are viviparous: They gestate

live young via a yolk sac placenta for 9–12

months before giving birth to up to 80

pups in one litter. The length of each pup

at birth is between 35–44cm. Courtship

is believed to involve aggressive biting,

and females have adapted to this by

developing skin three times thicker than

the male

HABITAT

This oceanic shark is sometimes found

close inshore when the continental

shelf is narrow. In temperate seas it

may approach the surface where it

can be observed by divers and fishermen,

but in tropical waters it tends to

seek deeper water with cooler

temperatures in its preferred range of

12–20 degrees centigrade

TOURISM

Although they prefer to stay at depth, blue

sharks can be attracted to the surface with

bait. It may sometimes take hours of

waiting patiently before they arrive, but

when they do, they will normally stay

around the boat for hours and investigate

divers very closely. Great places to

encounter this species are South Africa,

Mexico, Rhode Island, California and the

Azores Islands

GEOGRAPHICAL DISTRIBUTION

With a worldwide distribution in both

temperate and tropical waters, blue

sharks roam the vast expanse of the open

ocean and are highly migratory.

Western Atlantic: Newfoundland, Canada

to Argentina

Eastern Atlantic: Norway to South Africa

including the Mediterranean

Indo–West Pacific: East Africa to

Indonesia, Japan, Australia, New

Caledonia, and New Zealand

Eastern Pacific: Gulf of Alaska to Chile

Area of distribution

Pacific Ocean

Atlantic Ocean