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While there are only a few dozen of oceanic shark and ray species – animals that spend most of their lives in the open ocean – they are critical for the health of the ocean and the well-being of millions of people who depend on it for food and their livelihoods. These fascinating fishes are essential for so many reasons, from being blue carbon sinks and ocean mixers to inspiring innovation and design! This World Oceans Day, let's learn more about how important these predators are to the big blue, our planet, and people!
Blue Carbon Sinks - Literally!
A large gathering of mobula rays in Baja California, Mexico. © Simon Lorenz / WWF
All living things are essentially carbon-based life forms and store carbon in their bodies. In oceanic sharks and rays, carbon makes up 10%-15% of their body tissues. When these animals die naturally, they sink to the ocean floor, taking all that carbon with them. This way the carbon is trapped in the depths for thousands or even millions of years. Unfortunately, when they are fished, removed from the oceans, and eaten, all that carbon – partly in the form of CO2 (carbon dioxide) – gets released into the atmosphere instead. This in turn contributes to higher levels of atmospheric carbon dioxide, worsening climate change. Researchers who recently described this natural “blue carbon pump” phenomenon suggest that recovering populations of large marine fishes – including oceanic sharks and rays – provides a potential nature-based solution to climate change. With more sharks and rays, and other large fishes, swimming in our oceans, more carbon would be sequestered, helping to buffer climate change impacts! As you see, sharks and rays really are natural blue carbon sinks.
Shortfin mako shark just below the surface at dusk in New Zealand. © naturepl.com / Richard Robinson / WWF
Sharks have always fascinated mankind, and shark skin in particular has long been a source of inspiration for engineers and inventors. Shark skin is covered in tiny scales called denticles, which reduce turbulence enabling sharks to speed their way through the oceans. The shortfin mako shark is the fastest shark out there, and one of the fastest of all marine creatures (reaching top speeds of around 74 kilometres per hour) thanks to the denticles on its fins and the sides of its streamlined, torpedo-shaped body. One well-known application of imitating shark skin is the production of high-tech swimsuits for professional swimmers, helping them to swim faster than ever. However, there is an even more fascinating innovation based on the structure of shark skin! Did you know that a special shark-skin-inspired paint can help airplanes fly more efficiently? This high-tech coating helps to reduce aerodynamic drag, and so reduces fuel consumption, making flying more planet-friendly. Airlines are already starting to use this invention, with one German airline announcing earlier this year that from 2022, their fleet of cargo freighters will be covered in this special paint to support the company’s attempts to become carbon neutral by 2050.
Mixers of the Blue
Basking shark feeding on plankton in the Inner Hebrides, Scotland, UK. © naturepl.com / Alex Mustard / 2020VISION / WWF
The ocean is separated into three layers and some of the oceanic sharks and rays are catalysts in the mixing of those layers, together with other large marine creatures. The basking shark is one example of a large oceanic shark species that helps to mix ocean layers as it carries out vertical migration throughout the day, moving in a "yo-yo" like pattern through the water column. After feeding in the depths, basking sharks swim to the surface, releasing nutrients such as nitrogen and iron by excretion. And you know what depends on such nutrients? Phytoplankton! These microscopic marine algae exist in the otherwise nutrient-poor upper layers of the ocean but can thrive thanks to this nourishment. Phytoplankton is not only the basis of many marine food chains but also produces vast amounts of oxygen. Together with other marine plants, phytoplankton produces at least 50% of all the oxygen in the atmosphere! Oceanic sharks and rays act as important mixers of the blue, and help maintain this natural cycle. Since every other breath we take is thanks to these creatures, they sure are important!
Whale shark in Donsol, Philippines. © James Morgan / WWF
For years, whale sharks and tuna schools have been known to travel together. When scientists looked closer at this fascinating relationship, they have discovered that the sharks and tuna also work together when it comes to finding and catching food, such as small fishes like sardines or anchovies. Tuna travel with whale sharks in the hopes that they will be led to greater food sources. On the other hand, whale sharks benefit from the tuna driving their prey into forming tight bait balls, making it easier for the gentle giants to suck in large amounts of food in short amounts of time. That way, finding food and feeding more effectively becomes easier for both species – a real win-win.
Blue Tourism Icons
Oceanic manta ray at a cleaning station with a diver in Raja Ampat, Indonesia © Jürgen Freund / WWF
The presence of healthy populations of oceanic sharks and rays is an opportunity to develop marine tourism and provide local coastal communities with alternative, more sustainable livelihoods. Indonesia’s region of Raja Ampat is one example where the eco-tourism industry developed thanks to local and foreign tourists coming to see and dive with manta rays and other shark and ray species. In the pre-pandemic times, manta ray tourism generated around USD 140 million per year for 7 different countries! Another oceanic species which is becoming increasingly important for dive tourism is the blue shark. A 2014 study in the Azores, where diving with these creatures is possible, found that tourists were willing to pay more and contribute to conserving blue sharks to ensure that diving with these animals can continue. Blue shark diving provided islanders with jobs and the industry helped to educate local communities and tourists about the importance of this beautiful creature, in turn contributing to its conservation.
Heroes in Danger - and How to Save Them
A school of scalloped hammerhead sharks in the Cocos Islands, Costa Rica © Simon Lorenz / WWF
Sadly, even though these important creatures contribute so much to healthy eco-systems, our planet, and people, they are in grave danger. Global populations of oceanic sharks and rays have declined by 71% since the 1970s due to overfishing. This in turn will have likely affected the ability of these creatures to fulfil their ecological functions such as carbon sequestration or nutrient mixing. As a result of the drastic declines, half of all oceanic shark and ray species are now either critically endangered or endangered – only one or two steps away from extinction. But these animals can be brought back from the brink and we know what must be done!
WWF launched a call for action for oceanic sharks and rays, urging all fishing nations to introduce a set of science-based measures to prevent extinctions and recover the most threatened species before it is too late. There is a narrow window of opportunity that we must seize now if we are to solve the global oceanic shark and ray crisis. This World Oceans Day, learn more about how to save oceanic sharks and rays and help us spread the word!
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