May 27

Everyone remembers their first encounter with a whale shark, just as we all remember that first kiss, but experience has taught me that each encounter is in some manner just as unique as the first time.

When I first began diving the northern islands of Wolf and Darwin in the late 1980´s, we really had no idea of the species that we were going to find. Already Darwin´s Arch had begun to get the reputation as being the best dive site in Galapagos. Within days of my arrival to these distant shores I heard rumours of schooling hammerheads, Galapagos sharks and the strangely named ¨Pez Gato¨ or ¨catfish¨ as the fishermen referred to whale sharks. I later learned that the white spots on a whale shark where likened to those of the jaguar. Perhaps some of the fishermen had spent some of their formative years in the Ecuadorian Amazon jungle!

1 Whale Shark with Creole fish - Jonathan Green

Whale shark with creole fish © Jonathan Green

As time progressed we became aware that the whale sharks were aggregating on a seasonal basis, much more frequent during the cold garua season between June and November. The larger animals were thought to be males, although as with many shark species the female whale sharks are larger on average than males. It was only when we began actively checking for male claspers that it became apparent that most of the sightings were actually of females.

By the beginning of the new millennia I was already convinced that most of those whale sharks that passed by Darwin were not only adult females, but that they were also pregnant! Their distended abdomens appear to confirm this, but how could we get solid scientific evidence? It’s not so easy when they average over 10 m in length and weigh upwards of 20 tons. Researchers working with other large pelagic sharks such as tigers and great whites are able to capture the animal and carry out certain medical procedures in a controlled environment, much as we do with humans. The shark is winched onto the deck and immobilised and although there are strict time limitations, blood samples may be taken and an ultrasound test carried out.

1 Whale Shark - Jonahtan Green

Whale shark © Jonathan Green

This is simply not possible given the size and nature of the whale shark, so how do we propose to do this? Certainly a challenge as this has never been tried before. Blood samples have been taken from captive whale sharks, but never ¨on the fly¨. Picture a diver with no means of propulsion but his fins and leg muscles, chasing down an animal the size of a single decker bus with a 4 knot current in a thousand feet of water! Sound exciting?

Next season we hope to have members from the Georgia Aquarium join us in the field to attempt taking a blood sample from a whale shark in the wild, for the very first time. They already have extensive data of the blood chemistry of captive juvenile female whale sharks that are not pregnant. By comparing the blood chemistry of a female in the wild that we are 90% certain is pregnant, we may be able to determine how close to birthing she is. We also hope to try the worlds first underwater ultrasound using a waterproof prototype unit that is self contained and can record video and still images. Perhaps this will give us an indication of the stage of development of the embryos, as well as numbers of pups. Each encounter with a whale shark provides us with more information.

Alan Purton

Whale shark © Alan Purton

Developing new techniques in order to answer some of the many questions that still remain about their natural history has always held great appeal, for it is that voyage of discovery and the resulting data that may help protect whale sharks in the future, wherever in the world they roam.

If you would like to learn more about the project in Galapagos and how you can get involved, visit whalesharkappeal.co.uk.

Comments are closed.