Cafe Scientifique: Giants of the Sea

In conjunction with the traveling exhibition A Glass of the Sea's run in Nuvali, Sta. Rosa, WWF researcher David David shared his long-term research on whale sharks for a Cafe Scientifique session on November 21st. 

Before delving into the details of the research, David briefly discussed the biology of whale sharks. First, they are commonly misconstrued as marine mammals like whales and dolphins because of their name. (They are named as such because of their size.) They are actually cartilaginous fishes - like other sharks and rays.

A few characteristics can help you to distinguish the whale shark from a typical whale. Whale sharks' tail fins are oriented vertically, while whales' tail fins are oriented horizontally. This gives them different swimming patterns, as shown in the figure below. 

Whale sharks also have gills, while whales have lungs. Instead of nostrils, they breathe through blowholes on the tops of their heads. Male and female whale sharks can be distinguished by the presence of claspers in the former, used for fertilization. 

Whale sharks are an old species, having been around for hundreds of millions of years. They are also related to other large filter-feeding sharks such as the megamouth shark and the basking shark. It is particularly interesting how they manage to accumulate such biomass given that they consume plankton. The volume of food they must consume must be enormous!

Whale sharks can be found in a variety of sites in the Philippines, and threats to their populations include collisions with boats and their propellers, being hunted for their fins, and when they are caught as by-catch in nets. Their fins can sell for more than $10,000 on the black market, so partially finned sharks have been found. With their fins callously removed before they are returned to the water, the sharks are crippled and have difficulty swimming. 

Their liver oil is also traditionally harvested, along with their meat. Because of these threats, laws have been generated for their protection. These national laws include: FAO 193, the Philippine Fishery Code of 1998, RA 9147, and AO 282

WWF-Philippines' whale shark research began in Donsol in 2007, as a collaboration with WWF-Denmark. The objective of the project is to create a network of marine protected areas in the Coral Triangle to protect the migration routes, feeding and breeding sites of sea turtles, manta rays, and whale sharks. 

The researchers can locate sharks by tagging them - much like our fingerprints, whale sharks' spot patterns are unique and can be used to identify a specific shark. With online projects like Wildbook, photographs of whale sharks' spots can help to locate where they are. 

Currently, there are 909 whale sharks recorded in the Philippines - the 3rd largest population in the world. Invasive tagging can also be utilized, attaching satellite tags to the sharks so the scientists track their movements real-time. 

David also showed how the satellite tagging project enabled them to map the routes of whale sharks over a period of 6 months in Burias Pass, Ticao Pass, and Masbate Pass. Traveling whale sharks can also reach as far north as the Babuyan Islands and even Kao-Hsiung, Taiwan, and as far south as Indonesia. Their sightings are correlated with increases in plankton populations, such as from November to January. 

So what can we do to sustain whale shark ecotourism? For one, we can maintain Marine Protected Areas - with these, the populations of reef fishes can increase by 700% in terms of biomass! 

By the end, the talk inspired some of the audience members to even want to volunteer for WWF's research projects - a demonstration of how science communication can inspire in the public an interest to not only learn about, but also to engage in science. 

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  1. Great and simple post you shared. Whale Sharks has such a mythology about it, but it really is just making a common sense! Thanks for pointing that in your post.

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