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ANDY MURCH ELASMO GEEK

 

WHAT IS ELASMODIVER?

Not just a huge collection of Shark Pictures: Elasmodiver.com contains images of sharks, skates, rays, and a few chimaera's from around the world. Elasmodiver began as a simple web based shark field guide to help divers find the best places to encounter the different species of sharks and rays that live in shallow water but it has slowly evolved into a much larger project containing information on all aspects of shark diving and shark photography.

There are now more than 10,000 shark pictures  and sections on shark evolution, biology, and conservation. There is a large library of reviewed shark books, a constantly updated 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:

WHAT'S NEW?

Shark picture - green sawfish

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Porbeagle Shark

Porbeagle Shark

 

Porbeagle Shark picture

Photographs copyright Andy Murch. All rights reserved.

 

View all available Porbeagle Shark Pictures

 

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.

Conservation Concerns: Listed by the IUCN as 'Vulnerable'. The porbeagle is a wide-ranging, coastal and oceanic shark, but with apparently little exchange between adjacent populations. Low reproductive capacity and high commercial value (in target and incidental fisheries) of mature and immature age classes makes this species highly vulnerable to over-exploitation and population depletion. This depletion, despite variations in availability of data and degree of depletion between the northern and southern hemispheres, is considered to meet Vulnerable criteria globally. The eastern and western North Atlantic populations have both been seriously over-exploited by directed longline fisheries. Collapse of the Northeast Atlantic population led to intensive target fishing in the well-documented Northwest Atlantic fishery in the 1960s, with most of the virgin biomass removed in just six years. Renewed target fishing in the 1990s led to a further population decline to ~11 to 17% of virgin biomass within the three generation period for this species. Recently improved management in the Northwest Atlantic should now help stocks to recover, however the Northeast Atlantic population has been subject to unrestricted fishing pressure ever since its earlier crash. Data are lacking, but stock depletion is considered to be much greater than in the Northwest Atlantic. Longline tuna and swordfish fleets in the southern hemisphere take a significant partially-utilised bycatch. Only limited trend data are available, including over 90% declines in landings by the Uruguayan longline fleet in the southwest Atlantic.

Citation: Stevens, J., Fowler, S.L., Soldo, A., McCord, M., Baum, J., Acuņa, E., Domingo, A. & Francis, M. 2006. Lamna nasus. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1. <www.iucnredlist.org>.

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: 

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