There are very few shark species that make me personally nervous to dive with. This week’s Feature Species is one of those that make the short list: the Shortfin Mako (Isurus oxyrinchus). The shortfin mako, whose name is taken from the New Zealand Maori word for “shark”, is the ultimate ocean cruiser (Parker, 2008). This shark large bodied, with a spindle-shaped body that makes it highly streamlined in the water (Skomal, 2016). It has short pectoral fins, a low dorsal fin and short second dorsal fin, with a lunate caudal fin- meaning the lobes of the tail are almost perfectly even- this allows the shortfin mako to accelerate to incredible high speeds to catch its favorite prey: tuna (Skomal, 2016). While no one really knows exactly how fast a shortfin mako can actually swim, it is estimated they can maintain swimming speeds of 30-35 miles per hour and reach bursts of 60 miles per hour (Skomal, 2016).
Mako Bites Camera and Takes Bait Dragged Behind Boat
NSU Guy Harvey Research Institute Expeditions (2014 June 5). Mako Shark Bites Camera [Video Clip]. Retrieved from https://www.youtube.com/
And of course the shortfin mako is packing some serious heat in the teeth department! With 30 teeth piercing per row in each jaw, the mako’s bite is no joke. In fact, the mako’s bite is so impressive that the teeth in the lower jaw remain visible, even with the jaws are closer (Tricas, Deacon, Last, McCosker, Walker, Taylor, 1997). These teeth are over 1 inch long and hooked back into the mako’s mouth. While larger adult mako’s have been known to feed on marine mammals, their teeth are not serrated. Instead they have smooth edges with wide triangular bases that tapper to a sharp point, ideal for snatching up slippery bluefish and tuna (Parker, 2008).
A mouthful of awesome teeth isn’t the only thing that mako one incredible shark. They are warm-blooded. Unlike other species of sharks which are cold blooded and rely on the surrounding water temperature to thermoregulate their bodies, the sharks in the family Lamnidae, which includes the Great White (Carcharodon carcharias) and the shortfin mako, are warm-blooded – sort of. These endothermic sharks have a modified circulatory system that allows them to elevate the temperatures of certain organs (such as the eyes, brain, heart, stomach, and trunk muscles) through a process called counter-current heat exchange. The arteries and veins run parallel over the trunk muscles. The incoming cold blood in the veins is warmed by the outgoing warm blood in the arteries (Frederico & Hassall, 1998).
While this counter-current heat exchange process does not allow for the internal body temperature to remain at a constant temperature -as demonstrated by figure (a) above in the bluefin tuna- it does allow for selected organs to be kept at temperatures above the surrounding sea water (Frederico & Hassall, 1998). While sharks in the Lamnidae family gain the benefits of being warm blooded, like greater speed and power from these warmer trunk muscles than their cold blooded counter parts, they also have to constantly supply a higher metabolism that comes with it. So these sharks must feed often to sustain themselves (Parker, 2008). They have also developed longer and wider gills than other sharks to suppler their larger respiratory needs (Stevens, 1997).
With awesome jaws, a body built for speed, and a warm blooded core ready to supply the energy at any moment, the shortfin mako is one serious apex predator! But this predator is being threatened by the fisheries industry. A new study conducted by Nova Southeastern University’s Guy Harvey Research Institute (GHRI), the University of Rhode Island and other colleagues has shown that the fishing mortality rate of the shortfin mako is nearly 10 times higher than previously estimated in the North Atlantic (Byrne, Cortés, Vaudo, Harvey, Sampson, Wetherbee, & Shivji, 2017). With overfishing continuing to threatened more elasmobranchs every year, it is crucial that citizens, conservationists, scientists, policy makers and governments come together to better manage and enforce fisheries policies throughout the world.
Guy Harvey Research Institute Shortfin Mako Research
Harvey, G. [Guy Harvey]. (2016 April 26). The incredibly fast Shortfin Mako Shark! [Video Clip]. Retrieved from https://www.youtube.com/
Length: Maximum length of 13 feet (3.95 m)
Weight: Up to 1,100 lbs (500 kg)
Habitat: Continental and island shelves and slopes; coastal and oceanic waters
Depth: Surface to 2,500 feet (762 m)
Reproduction: Ovoviviparous and oophagous (intrauterine cannibalism)
Gestation: 15-18 months
Litter Range: 4-25 pups after intrauterine cannibalism
Home Range: Worldwide, tropical to cool temperate waters
Diet: Oceanic fishes, sharks, invertebrates, large individuals also feed on marine mammals
IUCN Status: Vulnerable
(Skomal, 2016; Cailliet, 2009; Parker, 2008)
Hope you enjoyed the shortfin mako as much as I did! While I do say that the mako makes my short list of species I’m wary about diving with, there is a small chance I may get to dive with one when I travel to Mexico in November. More to come on that adventure! Be sure to check out last week’s Feature Species (one of my favorite!) the Spotted Eagle Ray (Aetobatus narinari) if you missed it!
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 finactics!!
Featured Image Source
Conlin, M. (Photographer). (2011 April 11). Shortfin mako shark (Isurus oxyrinchus). https://commons.m.wikimedia.org/wiki/File:Isurus_oxyrinchus_by_mark_conlin2.JPG
Angela, P., Angela, A., & Recchi, A. L. (1998). Sharks!: Predators of the sea. Philadelphia, PA: Courage.
Byrne, M. E., Cortés, E., Vaudo, J. J., Harvey, G. C. M., Sampson, M., Wetherbee, B. M., & Shivji, M. (2017, August). Satellite telemetry reveals higher fishing mortality rates than previously estimated, suggesting overfishing of an apex marine predator. In Proc. R. Soc. B (Vol. 284, No. 1860, p. 20170658). The Royal Society.
Cailliet, G.M., Cavanagh, R.D., Kulka, D.W., Stevens, J.D., Soldo, A., Clo, S., Macias, D., Baum, J., Kohin, S., Duarte, A., Holtzhausen, J.A., Acuña, E., Amorim, A. & Domingo, A. 2009. Isurus oxyrinchus. The IUCN Red List of Threatened Species 2009: e.T39341A10207466.
Frederico, L., & Hassall, G. (Eds.). (1998). Reader’s Digest Explores: Sharks (1st ed.). Reader’s Digest.
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. D. (Ed.). (1997). Sharks (6th ed.). New York: Facts on File.
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.