Whale sharks in distress – world’s biggest fish disappear without a trace

Rekiny wielorybie

One of the most beautiful and charismatic marine species is being radically devastated by large ocean-going vessels. Impressive whale sharks have found themselves in the limelight following the publication of a recent study by scientists at the University of Southampton. As of 2016. Their population is steadily declining, and according to the IUCN Red List, globally the species already has endangered status. British researchers have identified the areas of highest risk for fatal collisions.

Maritime transport in the role of a serial killer

Whale sharks(Rhicodon typus) inhabit the tropical zones of all the world’s oceans. Measuring up to more than 18 m, these giants need water with a minimum temperature of 21 °C to live – unfortunately, their habitat overlaps territorially with an area of high marine transport. Over the past 16 years, the world’s merchant fleet has doubled in size. As a result, more than 100,000. Ships today traverse the seas and oceans carrying goods from one country to another. Projections say that over the next three decades this number could increase by a further 1,200 percent!

Large container ships not only significantly increase the balance of emissions and pollutants entering marine ecosystems. Up to 75 aquatic species are also subject to the risk of lethal collisions that can seriously shake their populations – these include. whale sharks.

Areas of highest collision risk

A study published in the scientific journal Science of the Total Environment identifies areas where the world’s largest fish are subject to the greatest threat from ships. Their designation was quite a challenge, because unlike marine mammals, whale sharks sink after death – so their bodies sink to the depths without a trace. That’s why Southampton scientists invited 75 marine experts from around the world, whose data allowed them to determine the so-called “maritime experts”. constellations, or groupings of giant sharks.

Although whale sharks have a solitary lifestyle, they regularly gather together to forage for food. It is these constellations that mark where the risk of death from a collision with the hull of a massive metal ship is greatest. The study identified 107 zones in 26 countries around the world, where a total of 13,000 individuals were observed, more than half of the global population. In 39 areas, the peak seasonal presence of whale sharks collides with periods of peak marine transport, which last up to several months a year.

A representative of the Marine Megafauna Foundation (MMF), Dr. Chris Rochner, who took part in the study, points out that in some giant shark habitats, up to several vessels per 1 km have been observed. Around the Mexican island of Isla Mujeres, as many as 56 large transport vessels pass through the constellation each month. The following were also considered the most vulnerable zones:

  • Ecuador’s coast;
  • The northern part of the Gulf of Mexico;
  • Malaysian islands of Kota Kinabalu and Redang;
  • Pintuyan Island in the Philippines;
  • Musandam coast in Oman;
  • Seychelles;
  • zone around Taiwan.

Do whale sharks have a chance to survive?

Identifying the threat is just the first step in the fight to save the world’s biggest fish from extinction. Study leader Dr. Freya Womersley stresses that countermeasures are now needed to reduce the risk of collisions within shark constellations. As a suggestion to policymakers and lawmakers, the researchers prepared a simulation of ship traffic in the Gulf of Mexico.

It turned out that already the 75 percent speed limit. in areas of increased whale shark presence will give them a great chance of avoiding a collision, at little cost to shipping. Regulatory speed limits could be implemented seasonally and would also apply to smaller vessels, which, while they don’t kill, sometimes cause serious injuries.

Modifying the ships’ courses, which would increase their travel time by just 0.5 percent, is indicated as even more reasonable. (with a 1.1 percent route extension), but would help save the lives of many undersea creatures. According to the researchers, whale shark constellations are relatively small and a course change of just 22 kilometers could allow for rapid transport, but without casualties.

So whale sharks can be saved without a huge compromise from the transport industry. For such a global species, however, international cooperation and increased general awareness of the silent and invisible killings beneath the sea are needed.

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