The open ocean is a desert. You have nowhere to hide, either as prey nor as predator. And you have to catch any prey you can find to prevent starvation. One survival strategy of oceanic pelagic fish is speed, and the champion in it is the Shortfin Mako shark (Isurus oxyrinchus). As the fastest-swimming of all sharks, it is typically clocked at 31 mph -50 km/h- with occasional bursts of speed of at least 46 miles -74 km- per hour to catch really quick prey.

Isurus oxyrinchus by mark conlin2.JPG
By Mark Conlin, SWFSC Large Pelagics Program – http://swfsc.noaa.gov/ImageGallery/Default.aspx?moid=532, Public Domain, Link

The Shortfin Mako lives in tropical and warm temperate waters all around the world. It is highly migratory (albeit seasonal) – tagging proved that a specimen swam 1,322 mi -2,128 km- in 37 days, another one traveled over 1,725 mi -2,776 km across the Pacific (by the way, genetic tests shows that they rarely cross the Atlantic). Its spindle-shaped body, large gills and huge heart and a heat exchange circulatory system named rete mirabile (Latin for “wonderful net”) like the salmon shark that enables the body to be 12.5 to 18 degrees Fahrenheit -7 to 10 degrees Celsius- warmer than the surrounding water allow a high level of activity. But that means the shark needs to consume 3% of its weight each day – in fish.

Like every other species of the family mackerel sharks, the Shortfin Mako is ovoviviparous. Litters of between 4 and 25 live young are born after a 15 to 18 month gestation period, during which they feed on yolk and unfertilised eggs (oophagy). Females are believed to rest for 18 months after birth before conceiving again. They mature at around 17 to 19 years of age and males at around 7 to 9 years. The maximum known age of a Shortfin Mako is 32 years. Altogether, like all apex predators Shortfin Makos have a low reproduction rate.

The Shortfin Mako is one of the most popularly consumed shark species. It is a favored game fish and famed for its fights with spectacular leaps of up to 20 ft – 6m- out of the water. It is also targeted commercially for its high-quality meat (containing high doses of methyl mercury like in all apex predators), fins (shark-fin soup) and liver oil (to make vitamin supplements). It is one of the few known predators of the Swordfish (however, those fight back and in turn can injure and likely kill it). Its predilection for commercially important fish (billfish, tuna or mackerel, but primarily bluefish) makes it a frequent bycatch, too. All in all, the IUCN considers the Shortfin Mako as Vulnerable worldwide and Critically Endangered in the Mediterranean, which seems an important nursery area.

Despite its size (in average around 10 ft -3.2 m- length, but up to 13 ft -4 m- and 2,200 lb -1,000 kg-), speed and strength, the ISAF recorded only one unprovoked fatal attack by Shortfin Makos in 5 centuries. This close relative of the white shark only bits humans when provoked (fighting for its life after being caught), but it can attack boats or spear fishermen if it considers them competitors for prey. When hunting, it does not rely on electroreception but smell, hearing, and most prominently, vision. It is fast-learning due to one of the largest brain:body ratios of all studied sharks.

Sources: here, here, here and here

Advertisements