Sharks are found in every ocean on Earth, especially roaming around the high seas.
Open ocean shark species consist of upper-pelagic sharks and deep sea sharks.
Upper-Pelagic sharks live in the Epipelagic and Mesopelagic zones where sunlight penetrates deep and allows life to grow. These ocean wanderers travel across vast ‘ocean deserts’ in search for food.
Go deeper, and you’ll find deep sea sharks that exist in the Bathypelagic zone – in complete darkness. These sharks have been found at depths of more than 3700m!
Open Water Life
Open water pelagic sharks such as mako sharks, blue sharks, oceanic white tips and hammerheads tend to be extremely fast swimmers. Makos can reach speeds of more than 60mph, and have very streamlined bodies which enable them to use as little energy as possible when swimming through the water.
As well as speed they have incredible noses, even for a shark! Due to the large distances they may face between meals, they can smell prey from great distances and in small volumes. Some species are able to smell blood at one part per 10 billion, the equivalent of one drop in an Olympic sized pool! Others can smell small volumes from several hundred meters away.
Living In The Dark
Deep sea sharks, such as goblin sharks, frill sharks, demon catsharks, sixgill sharks, and ghost sharks have some incredible adaptation for living in deep water.
For example the swell shark absorbs the tiny amount of blue light that filters through the water column and emits it as fluorescent green light! Scientists are not entirely sure why but theorise it may be a form of communication with other sharks. Other species have elongated bodies that help deal with the high pressure in the depths.
Unfortunately open ocean sharks are some of the most threatened.
Due to high rates of commercial fishing in the open ocean these sharks are caught far too often as bycatch with tens of millions hauled in every year on longlines.
Illegal Shark finning supported by a demand for shark-fin soup is a massive problem that plagues sharks all over the world. 100 million sharks are killed every single year for their fins alone, and a good portion of this illegal activity happens on the high seas.
Blue sharks are the most abundant but also the most heavily fished shark in the sea. Fishermen will catch these sleek ocean predators by setting miles of longlines across the sea. These lines can stretch 60 miles long and contain 300,000 baited hooks, catching every living predator in the area.
Of the 62 open ocean pelagic shark species 32% are classed as threatened, 6% endangered, 26% vulnerable and 24% near threatened.
Although severe overfishing threatens sharks on the high seas, there are conservation efforts happening worldwide to help protect these incredible animals.
The UN is meeting currently to discuss a worldwide treaty protecting the high seas. The high seas comprise nearly two thirds of the world’s oceans and are currently unprotected as they are international waters. This means there is no limit on fishing and no laws on bycatch.
People around the world are joining together to fight the demand for shark fin soup in society. Nations need to work together from both angles to stop the fishing of sharks. People need to be educated on the problem so that their cultures can adapt to a more sustainable world. And bans on the sale of shark fins need to be better enforced around the world.