According to a study, the number of sharks at coral reefs worldwide has decreased significantly. They die out “functionally.”
Scientists led by Aaron MacNeil of Dalhousie University in Halifax, Canada, reported in the journal Nature that sharks were often no longer found during field research. Reef sharks are “functionally extinct” in many places, the researchers write. They hardly played a role in the local ecosystems.
Shark spotting with underwater videos
Scientists attempted to spot sharks using more than 15,000 bait underwater video stations on 371 coral reefs in 58 countries. No sharks were found on about a fifth of the reefs (19 percent), and so did 63 percent of all video stations.
In 34 countries (59 percent), the number of sighted sharks fell by more than half from the number expected. This includes, for example, Colombia, Qatar and Sri Lanka. In the Dominican Republic, despite 120 video stations on four reefs, not a single shark was seen.
Overfishing is a major cause
The decline in reef sharks affects much of the tropical oceans, the team concludes. The trend is strongly related to factors such as the population density in the area and the size and proximity of markets. In general, the main cause of the decline is overfishing.
The researchers found positive developments in countries that campaign for the protection of sharks, for example with protected areas. This is the case in Australia, the US, the Bahamas and the Maldives.
The news about sharks can sometimes be more positive: in January it was announced that a new shark species had been discovered, the walking one. Literally, this shark has legs. Scientists found the new species and presented their findings in Marine and Freshwater Research. The new shark species is quite young for evolutionary concepts: ‘only’ 2 million years ago the walking fish developed. If you think ‘that’s quite long’: the shark has been moving through the waters of the globe for 400 million years. In comparison, the dinosaur was born about 240 million years ago.
Also read: 15-year-old Australian surfer bitten by shark
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