Did you know that live ain’t easy in the open ocean? Nutrients are relatively scarce: little fish tend to stick together and to larger swimming objects like big fish or flotsam and jetsam (that’s why fish magnets work so well), but predators don’t have it easy, too. Finding worthwhile prey is like looking for a needle in a haystack, and if you do have found it it can see you coming from miles away. You have to use every opportunity to prevent starving.

One of the species living solely offshore is the oceanic whitetip shark. This medium-sized species of requiem shark is highly opportunistic, aggressive and persistent – it has to be. Normally slow moving to conserve energy, it is capable of surprising bursts of speed and feeds from everything including whale carcasses and faeces.

Oceanic Whitetip Shark.png
The original uploader was OldakQuill at English Wikipedia – Transferred from en.wikipedia to Commons., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1984721

Oceanic whitetips prefer waters between 68 °F -20 °C- and 82 °F -28 °C- and inhabit the upper layer of tropical and warm temperate seas to a depth of 490 ft -150 m (occasionally diving to depths of up to 2,000 ft -600 m). Climate change may explain why one was found off Sweden in 2004.

The largest specimen of Carcharhinus longimanus ever caught measured 13 ft -4 m-, but usually oceanic whitetips are up to 11.5 ft -3.5 m- long. The term longimanus translates from Latin as “long hands”, referring to their long wing-like pectoral fins. They reach sexual maturity at 69 in -1.75 m- for males and 80 in -2 m- for females. The shark is oviviparous, after one year up to 15 young are born at a length of about 24 in -0.6 m.

From the time they are born until they reach a length of about 4 ft -1.2 m-, juvenile oceanic whitetips lack the eponymous white tips, in fact, all their fin tips are black or dusky. This seems to be an anti-predator strategy, since the white tips on most of the fins of the adult appear from a distance like a small school of little fish, making it possible to lure and ambush prey.

But it uses many different advantages and strategies to survive. It travels with female short-finned pilot whales (but not male, because they are bigger and could easily make a meal of even a full-grown oceanic whitetip), who share a similar size and coloration, to rely on the whales’ echolocation abilities to find schools of squid at depths of up to 2,000 ft -600 m-, but also to hide behind and ambush other predators. It is active both day and night and uses its acute sense of smell in a peculiar way: it holds its snout tip above the sea surface for several seconds at a time, thus sampling the air. Since currents in the sea transport dissolved chemicals away from their source relatively slowly, but certain compounds can be rapidly carried long distances by wind, this may enable these sharks to locate the source of an attractive odor like a whale carcass more quickly than other species, making it the front of the line to this tremendous and vital caloric windfall.

That way they are first at locations of shipwrecks or downed aircraft, too, and are known to prey on survivors. That’s why famed oceanographic researcher Jacques Cousteau described the oceanic whitetip as the most dangerous of all sharks. But the case of one particularly infamous oceanic whitetip in Egypt in 2010 (featured in a Shark Week episode called “Rogue Sharks”) should be regarded differently, since accumulating evidence revealed this shark to have been conditioned to being hand fed. If you are used to associate a diver with an easy supply of food in its fanny packs, is it really the attack of a rogue shark to target the divers’ buttock and thigh regions in the hope of obtaining a meal in the highly overfished Red Sea? Or are the bitten people unfortunate victims of one or more irresponsible humans training a starving dangerous shark like a dog?

Once extraordinarily abundant, fishing pressure due to their fins, meat and liver oil caused the numbers of the oceanic whitetip to decline steeply. Nowadays the IUCN regards it globally as vulnerable and critically endangered in the Northwest and Western Central Atlantic areas. Since March 2013 fishing and commerce of oceanic whitetip are under regulation.

Sources: herehere and here

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