What are Whale Sharks?
Whale sharks are a type of Chondrichthyes, meaning that it is closely related to sharks and rays. More specifically, they are the only member of the Rhincodontidae family that is not extinct, and they live primarily in warm tropical waters. Whale sharks commonly grow up to 40 feet long, with a mouth of 5 feet wide!
Why are they endangered?
Scientists estimate that the Indo-Pacific population of whale sharks has reduced by 63% in the past 75 years, and the Atlantic population is thought to have to decreased 30%. Because populations are continuing to decline, whale sharks have been classified as vulnerable.
The major current threats that affect whale sharks include hunting, by-catch in nets, poorly managed tourism, and boat strikes.
How is their decline affecting ecosystems?
Over the past decade, research on whale sharks has increased substantially. Despite this effort, still little is known about the ecology of whale sharks. There is still lots of research to be done!
However, because whale sharks have a wide distribution and tend to migrate towards areas with rich plankton abundance (because that is their primary food source). The abundance of plankton shifts regularly based on environmental conditions, so whale sharks are therefore an extremely useful indicators of healthy oceans. If we see declines or shifts in where whale sharks are present, it can tell us if there are any issues occurring in those areas (i.e. pollution) that may have negatively affected plankton abundance.
What is being done to recover populations?
International Law: Whale sharks are listed in the “Highly Migratory Species” section of the United Nations Convention on the Law of the Sea (UNCLOS), which includes them in the conservation and management of international seas. They are also listed as part of the Bonn Convention for the Conservation of Migratory Species of Wild Animals (CMS), which identifies them as a species that would benefit from international conservation agreements.
Hunting: Most fisheries for whale sharks were closed due to the reduction in catch as populations declined. However, there are still active fisheries (i.e. China), which is thought to be the largest threat to whale sharks in the Indo-Pacific. Management focus against fishing focuses on the enforcement of fishing restrictions, and education programs for fishermen. In 2002, whale sharks were listed under the Convention on International Trade in Endangered Species (CITES), which requires all exports from countries be from sustainable fisheries.
By-Catch: Whale sharks are often used as indicators of plankton-rich waters, which is also where valuable fishery species (i.e. tuna) tend to migrate towards. So far, restrictions on mesh size, net length, and no-fishing zones have been implemented to avoid accidental catch of whale sharks. Fishermen in areas where whale sharks are present are also being trained in the safe release or proper maintenance of fishing equipment to reduce injury to whale sharks when interactions do occur.
Tourism: A common form of whale shark tourism is the “swim with the whale sharks” tours. This is where people pay to be taken out to a boat so they can view and/ or swim with whale sharks. This is great way for people to get excited about oceans; however, it is really important that tourist companies follow good practices as to not disturb the natural behavior or potentially injure the whale shark! For example, there are laws requiring boats to stay a certain distance from the animals to reduce stress and the potential for boat strikes. If you choose to book an exciting adventure like this, please be sure your tourism agency follows good practices, and report any agency that puts the animal in any potential harmful situations!
Boat Strikes: Key habitats for whale sharks, such as coastal feeding locations or movement corridors, have been established to protect whale sharks in these areas. This reduces boat traffic, tourism, and fishing in these areas.
What does the future hold?
Although whale shark populations are still declining, the increased attention that whale shark conservation has gained by the public and the efforts that have already been made to protect whale sharks makes their future seem bright! 🙂
How can you help?
1. Learn More about Whale Sharks!
“Whale shark (Rhincodon typus) biology and ecology: A review of the primary literature” by J.D.Stevens
2. Volunteer with Whale Shark Research!
3. Report Whale Shark Sightings!
Any suggestions? Comment below!
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