What’s Up With Whale Sharks?

Whale shark at Molokini

Whale shark sightings are on the rise. It used to be that we would see whale sharks occasionally, while diving or underway, usually during winter months. They are a sight to see- with adults clocking in at around 40 ft long, with dark skin and a tribal pattern of white polka dots. Over the past few years, we have been seeing these massive marine species more and more, and not just during winter. Here are some interesting facts on whale sharks, and some research that is being done to track population growth.

Their massive size makes whale sharks easier to spot near the surface

About Whale Sharks

Whale sharks are seen in tropical waters around the world. Just like a humpback whale’s tail is an identifier, the spotted coloration on whale sharks are unique, allowing researchers to catalog them. If you hadn’t guessed already, whale sharks are not whales at all. They just carry that name because of their size. Whale sharks (Rhincodon typus) are the largest shark species known, and also hold the title of largest of any fishes on earth. To maintain their bulk, they travel large distances, feeding on plankton, tiny shrimp and small fish.

Photo: Matthew T Rader, MatthewTRader.com, License CC-BY-SA Whale shark filter feeding

Scientist have been stymied in collecting data on these giant animals because they are among the most widely traveling species. Whale sharks can shift between the open ocean, coastal areas and the deep sea. A 2018 study on a whale shark named Anne traveled more than 12,500 miles across the Pacific in just over two years, including making her way through the Mariana Trench – the deepest place on Earth. Tracking devices are not always effective, as whale sharks often deep dive, going beyond a typical beacon’s 2000m limit.

Females give birth to live young but this has never been observed. No one is certain where  pupping occurs, though we have observed juvenile and adult whale sharks in Maui waters. They can be seen in shallower waters or feeding at the surface.

Are they safe to be in the water with?

A docile filter-feeder, whale sharks are not in the same league as more toothy, predatory sharks. They are not known to pose a threat to people.

Whale sharks are gentle creatures. However, because of their size, divers should be careful in the water. An inadvertent tail smack from a whale shark could be dangerous.

Population

Whale sharks were listed as endangered in 2016, often getting caught in commercial fishing nets, or purposely fished to feed the demand for shark fins in Asia.

Repeated anecdotal accounts do lead researchers to believe whale shark numbers are increasing, at least in Hawaii. The Hawaii Uncharted Research Collective (HURC) is working to find out with the Whale Shark Initiative.

Unusual whale shark facts

Whale sharks have roamed the ocean for more than 70 million years, overlapping their existence with the Tyrannosaurus rex at one point.

Whale shark teeth

The species 300 of rows of teeth are microscopic, filtering out large matter to feed on small shrimp, fish and plankton. A research team documented thousands of shrimp-like creatures living in the mouth of one whale shark, riding along as an in-house cleaning service.

Researchers in Japan also discovered recently that whale sharks have retractable eyes, with 3,000 tiny tooth-like structures called “dermal denticals” surrounding the iris.

Whale sharks move through the water at a relatively plodding pace, allowing other fish to hitch a ride along the way

If you see a whale shark while diving

Showing scale of diver with mature whale shark, and a fish riding on its head. Photo: Crystaldive, Creative Commons

Consider yourself lucky and observe as much as you can. If you have a camera, please document what you can, share your photos with us by using the secure photo upload in the footer of our website homepage at www.lahainadivers.com. Please include the dive location and date and approximate time, and we will in turn share with local researchers.