Not just Shark
Pictures: Elasmodiver contains photos of sharks, skates, rays, and
chimaera's from around the world. It began as a simple web based
field guide to help divers find the best places to encounter
different species of sharks and rays but it has slowly evolved into
a much larger project containing information on all aspects of shark
diving and photography. There are now more than a thousand shark
pictures and sections on shark evolution, biology, and
conservation. There is a large library of reviewed shark books, a
constantly outdated shark taxonomy page, a monster list of shark
links, and deeper in the site there are numerous articles and
stories about shark encounters. Elasmodiver is now so difficult to
check for updates, that new information and pictures are listed on
an Elasmodiver Updates Page that can be accessed here:
If you're looking for a
broader range of marine life pictures the following links represent
a new area that contains pictures on other marine organisms and on
marine habitats. This expansion of Elasmodiver is in its first
stages but will eventually include pages on everything from sea
stars to nudibranchs. Creating this portal will take time and for
now it consists of a token offering of fish pictures. Please return
regularly to enjoy the progress.
Common
Names:
Porbeagle Shark,
Beaumaris shark,Blue dog, Mackerel shark.
Latin
Name: Lamna
nasus
Family:
Lamnidae
Identification:
Conical snout. Large black eyes.
Teeth narrowly triangular. Dorsal
fin high with distinct white patch on free rear tip (trailing edge). Caudal fin
crescent shaped with pronounced caudal keel. No second caudal keel on lower
caudal lobe. Dorsal coloration
slate grey. Underside off white.
Size:
Maximum recorded size 3m but may exceed 3.7m. More commonly 2m. Size at birth 60-80cm
Habitat: Coastal
and oceanic in depths of up to 700m.Migratory.
Distribution:
A large but fragile population covers the temperate
North Atlantic Ocean. Smaller isolated populations in the southern hemisphere
around south Australia, southern South America, South Africa, and far southern
Indian Ocean. Southern
populations may be linked by migration.
Diet and Behavior:In
summer moves inshore possibly in search of prey species.
Main diet consists of small bony fishes, dogfish, soupfin sharks (tope) and squid.
Reproduction:
Litter size around 4 pups.
Foetal sharks feed on unfertilized eggs.
Photographs:
Bay of Fundy, Canada.
Similar species:
The Pacific equivalent of the Porbeagle Shark is the Salmon Shark (Lamna
ditropis) which can be distinguished by the dark trailing edge of its dorsal fin, white
pectoral fin bases, blotchy coloration, and second caudal keel on its lower
caudal fin.
The Porbeagle shares part of its range with the Great White Shark and the
Shortfin Mako.
Reaction to divers:
Very difficult to approach. After chumming for many hours we were finally able
to attract two Porbeagle sharks but these left as soon almost immediately.
Porbeagles have been known to approach divers (on one occasion aggressively) but
they remain elusive in baited situations.
Diving
logistics:
There are presently no organized Porbeagle Shark diving charters in North
America. In the UK Richard Pierce runs Blue and Porbeagle cage dives.
Other diving locations submitted by
readers:
References
and further
reading:
Sharks of the World. Leonard
Compagno.
Sharks
and Rays - Elasmobranch Guide of the World. Ralf M. Hennemann. IKAN.
