This week’s featured species is one really awesome shark that is all too often overlooked. The Porbeagle shark (Lamna nasus) is a member of the Lamnidae family. The Lamindae family only has 5 species within it, but they are powerhouse sharks including:
- the Shortfin mako (Isurus oxyrinchus)
- the Longfin mako (Isurus paucus)
- the Salmon shark (Lamna ditropis)
- the Great White (Carcharodon carcharias)
- and the Porbeagle shark (Lamna nasus)
The porbeagle is a large, warm blooded, fusiform bodied shark that is often mistaken for the great white. While the porbeagle only reaches lengths of 12 feet (3.6 m) at maximum length, compared to the great white’s potential 20 feet (6.1 m) or more, it is easy to see why these two species can be easily confused for one another from a boat (Parker, 2008).
The porbeagle does have several distinguishing characteristics that separate it from its Lamnidae family members. The porbeagle has 2 keels on its caudal fin, like the salmon shark, that helps propel the porbeagle to great speeds quickly (Tricas, et al., 1997). In fact, like the other members of the Lamindae family, the porbeagle is one of the fastest sharks in the ocean (Parker, 2008). They have even been documented jumping completely out of the water (Parker, 2008).
But the most distinguishing feature of the porbeagle is a large white smudge on the back edge of their dorsal fin (Parker, 2008). This white smudge is present on porbeagles, but are not found on any other member of the Lamindae family.
Unlike its mammal feeding cousin, the porbeagle feeds primarily on oceanic fishes and invertebrates (Skomal, 2016). Their teeth have one large central cusp with two smaller secondary cusps on either side. The edges are completely smooth and the large central cusp is slightly hooked. These teeth are better suited for puncturing and holding slippery prey than the serrated teeth of the great white (Whitenack & Motta, 2010).
Porbeagle shark populations have been declining in the last 100 years, like many species of elasmobranchs. The porbeagle’s story is the perfect example of how long it can take for an elasmobranch population to rebound from exploitation from over fishing. In the 1960’s, the porbeagle was harvested by the Norweigans in large numbers off Canada and New England. In the peak of the harvest in 1964, nearly 18 million pounds of porbeagle were landed (Skomal, 2016). If you consider the average weight of the porbeagle is 200 pounds, this means nearly 90,000 sharks in a single year! In 1967, the population of porbeagles in Canada and New England collapsed. Harvested were low in the 1970’s and ’80’s while the population tried to rebound. In the 1990’s the Canadians began to harvest them with a strict limit of 2.2 million pounds per year (Skomal, 2016). The population recovery halted, and then began to decline once again. Currently, it is still legal to harvest porbeagles, however the yearly limit has been decreased to 400,000 pounds. It is estimated that only 11% of the original porbeagle biomass remains. They are considered Critically Endangered in the North Atlantic and the Mediterranean (Stevens, et al., 2006). Additional conservation and management are needed for these sharks, and recovery with proper management could take decades. If you are ever fortunate enough to come across the porbeagle shark, count yourself lucky. They are truly a magnificent sight.
Nick Eachus (Eachus, N.) (2011, November 30). Porbeagle Shark, North Sea, 07/11/11 [Video Clip]. Retrieved from https://www.youtube.com/
Authority: Bonnaterre, 1788
Family: Lamnidae, 5 species
Length: Maximum of 12 feet (3.65 m)
Weight: Up to 550 lbs (249 kg)
Habitat: Continental and island shelves and slopes, coastal and oceanic waters
Depth: Surface down to depths of 3,000 feet (914.4 m)
Gestation: 8 – 9 months
Litter Range: 3 – 6 pups
Home Range: Cool temperate waters of North Atlantic and southern hemisphere
Diet: Oceanic fish and invertebrates
IUCN Status: Critically Endangered in Mediterranean and North Atlantic; Endangered in Northwest Atlantic; Vulnerable everywhere else
(Stevens, et al., 2006; Parker, 2008; Skomal, 2016)
Thanks for stopping in and checking out this week’s Featured Species. If you missed last week, be sure to check out the gorgeous Lemon shark. As always, your comments are welcomed! Let me know what species you’d love to see featured next.
The new Ocean For Sharks Shop is open! There’s handmade ocean inspired plush animals, canvas paintings, and of course my children’s book, Winifred the Wondrous Whale Shark, available in print and PDF. Be sure to stop by. Remember proceeds benefit shark research and conservation with a donation to Project AWARE!
Remember you can make a difference for marine ecosystems by calling your Congress man or woman and tell them that you care about the quality of our waters! Sharks, rays, and other marine organisms cannot speak or be represented in Congress. They need your voice. Get involved and stand up for sharks. Until next time finatics.
Featured Image Source
Perrine, D. (Photographer). (n.d.). A porbeagle shark [Digital Image]. Retrieved from http://www.pewtrusts.org/en/research-and-analysis/analysis/2014/11/06/time-to-protect-bluefin-tuna-and–porbeagle-sharks-from-illegal-trade
Parker, S. (2008). The encyclopedia of sharks (2nd ed.). Buffalo, NY: Firefly Books Ltd.
Skomal, G. (2016). The Shark Handbook: The Essential Guide for Understanding the Sharks of the World. (2nd ed.). Kennebunkport, ME: Cider Mill Press.
Stevens, J., Fowler, S.L., Soldo, A., McCord, M., Baum, J., Acuña, E., Domingo, A. & Francis, M. 2006. Lamna nasus. The IUCN Red List of Threatened Species 2006: e.T11200A3261697.
Tricas, T. C., Deacon, K., Last, P., McCosker, J. E., Walker, T. I., & Taylor, L. (1997). The Nature Company Guides: Sharks and Rays. (L. Taylor, Ed.). Hong Kong: The Nature Company, Time Life Books.
Whitenack, L. B., & Motta, P. J. (2010). Performance of shark teeth during puncture and draw: Implications for the mechanics of cutting. Biological Journal of the Linnean Society, 100(2), 271–286.