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The sea giant is in danger: what threatens the whale shark?

The world's largest fish in danger of extinction: a new international study came to the aid of whale sharks and tries to change the routes of ships at sea

Ayelet Davidi, Angle of the Science and Environment News Agency

The size of a bus, a whale shark. Photo: Miron Segev, Sharks in Israel
The size of a bus, a whale shark. Photo: Miron Segev, Sharks in Israel

Although the largest fish in the world are approx The size of a bus, but contrary to what was expected, there is nothing threatening about them: they swim relatively slowly, are decorated with dots and stripes and feed on plankton - tiny creatures that drift in the current of water. International Whale Shark Day, which takes place every year on August 30, is a great opportunity to showcase this magnificent animal, which despite its enormous size is vulnerable and endangered. An international study that was also conducted here in Israel - in the Gulf of Eilat - examines the dangers facing whale sharks in the world, and suggests ways to protect them.

More than half of the researchers reported collisions with large vessels leading to the majority of fatal injuries. Photo: Miron Segev, Sharks in Israel
More than half of the researchers reported collisions with large vessels leading to the majority of fatal injuries. Photo: Miron Segev, Sharks in Israel

Whale sharks are characterized by a broad and flattened head structure, a white belly and a gray-blue back decorated with white dots and stripes. The special body of the cartilaginous fish The goddess makes them easy to distinguish and popular among bathers and divers. As mentioned, they feed on plankton, and to eat it they swim with their mouths open and scoop up everything that passes their way. They then filter and throw out what is not suitable for them to eat. They usually swim alone in ocean water; But in areas with an abundance of plankton, we can find a grouping of several whale sharks together. These sharks swim for distances of thousands of kilometers and can reach great depths, but spend about half of their lives in the shallow waters because of the greater amount of plankton in these areas.

Great danger for a big fish

The whale shark is defined as a species Endangered. From the beginning of the 20th century there is testimonies About the collision of ships with whale sharks that swim slowly on the surface of the water and do not rush to escape even when a ship arrives. in research A recent study found that strikes from vessels are a major risk factor in whale shark aggregation areas. Later, the researchers mapped the whale sharks' gathering areas against the traffic routes of large ships in the sea to find ways to prevent them from being hit. "The study showed that whale sharks regularly cross busy shipping lanes, where the risk of collision is higher," explains Dr. Adi Barash, a post-doctoral researcher at the Steinhardt Museum of Nature and a participant in the international study on whale sharks together with Shir Bar, a doctoral student at the Institute The inter-university in Eilat as part of the research work of the Sharks Association in Israel. "Therefore, in order to preserve this special species, important local areas must be identified where the vessels can be directed to reduce collisions," Barash explains.

75 researchers from around the world participated in the study who collected information on more than 50 different aggregation sites of more than 13,000 whale sharks. The study provides for the first time an assessment of the risk levels for collisions between vessels and whale sharks. These are deadly collisions that are a constant danger to a population that is already in danger of extinction. Analyzing the results of the collected data, more than half of the researchers reported collisions with large vessels – which lead to most fatal injuries – as a major threat to whale sharks. Moreover, most experts believed that large vessels affect whale sharks in all areas of their habitat (and not just in the areas where they congregate). When focusing on the aggregation sites, the researchers noted that unregulated tourism in certain areas (which could include, for example, motorboat cruises), and collisions with small vessels, are the leading threats to whale sharks.

Each individual has a unique collection of spots and dots that sets it apart from other whale sharks. Photo: Miron Segev, Sharks in Israel
Each individual has a unique collection of spots and dots that sets it apart from other whale sharks. Photo: Miron Segev, Sharks in Israel

Also as part of the research, mapping the density of the ships in each area where whale sharks gather helped to examine the risks of collision. The information obtained shows an overlap between the habitats of the whale sharks and the shipping lanes, and the researchers recommend the implementation of targeted preventive measures in these areas, such as reducing the speed of vessels, changing shipping lanes away from these aggregation areas and enforcing rules that limit access during the peak periods of fish activity. The researchers show that the shark season is usually short, and in limited areas, so it is possible to incite ship traffic from it without a high cost, and even offer alternative routes to some of the sites.

fin print

To learn about the movement of whale sharks, "we observe and photograph whale sharks, and upload the images to an international AI system," she explains. Each detail has A unique collection of spots and dots which distinguishes it from the other whale sharks. An area on the back left side of the whale shark's body was chosen to act as a fingerprint and be a unique identifier for each shark. "The system finds several matches of similar 'fingerprints', then goes through and checks if there is a complete match. If you find a match - you can tell who the whale shark is that visited us. If there is not - he is entered into the system and given a number so that we can identify him and follow his route", she explains.

It is interesting to know that private individuals can also upload photos of whale sharks that they have photographed. That is, each and every one of us, if we are lucky, can contribute to research. "In 2019 when the identification project started, we had 90 sightings by people who saw, photographed and reported to us in the Facebook group led by the Shark Association in Israel. Out of the sightings, there were 45 photos good enough for us to search for identification in the system, and indeed we identified 19 different whale sharks that passed by us in the Gulf of Eilat that season - that's a lot," she says. You can see them mainly in the summer, while the Gulf of Eilat is bustling with life and full of marine activity, and therefore it is important to check there also the level of their vulnerability from vessels, and to work to reduce these interactions.

The collected data highlights the urgent need for coordinated action to preserve this unique species through a joint effort of all relevant parties - local communities, the shipping industry and the appropriate authorities - in order to ensure the continued existence of these huge and impressive fish. "When we started tracking in the Gulf of Eilat, we discovered to our surprise that there is a large turnover of whale sharks here. They come to us for two or three days and continue on their way. That is why it is very important to understand the amount of injuries caused by the boats", she concludes.

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