With a few unexpected early encounters in August everyone was eagerly awaiting the official start of the whale shark season. The chilly water we have been embracing bought in millions upon millions of microscopic plankton, which form the main food source for the whale sharks. After swimming around in all that soupy planktony water we were hoping to be rewarded with a whale shark sighting.
From September 1st, the Marine Conservation Society Seychelles (MCSS) run snorkelling excursions with these gentle giants. As the ‘go to’ people for everything marine-related at the resort, the WiseOceans Marine Educators coordinate with MCSS to offer the Four Seasons Resort guests this incredible opportunity. Each day a small microlite circles Mahe (weather permitting of course) and, if any sharks are seen, the boat departs in the afternoon full of researchers and excited guests. The afternoon is then spent in the ocean with one of the world’s most awe-inspiring creatures.
The season started with a bang – groups of four, five, possibly even six whale sharks were sighted in the first three days. Just imagine swimming alongside a creature five times your size or seeing a large dark shadow emerge through the water. That rush of adrenaline and shiver of excitement cannot be described. One Four Seasons guest even watched a whale shark swim across the edge of Petite Anse bay from her villa; what a sight huh?! Then overnight there was a complete transformation. The sharks were gone! Since early September we have had no further sightings and the question on all the guests’ minds (and ours) is where have they gone?
Let’s get back to basics. What do we know about whale sharks? As the largest fish in the ocean, we know surprisingly little. Whale sharks inhabit tropical and warm waters across the globe. In the Seychelles we are unsure where our population is coming from and where they go afterwards; research has tracked the whale sharks heading in almost all directions away from here. These colossal fish migrate here to feed in the plankton-rich waters. Possibly they move along to the next destination with a large food offering, or maybe somewhere to mate and breed; both of which are yet to be documented. Although they spend a large proportion of their time filter feeding near the surface of the water, they have the ability to dive to depths of over 1000m. All this moving around and diving to deeper water makes research incredibly difficult.
Common research methods include photo identification and tagging. Photographic identification uses an image of a particular area of an animal which is unique and doesn’t change over time – like our human fingerprints. For whale sharks a shot of the spot pattern behind the gill slits is used. Catalogues of images have been created and at the start all images were compared and matched by eye; but with advances in technology a variety of pattern matching computer programme have been made to make the task a little easier. This method allows us to see if the same individuals are returning to the same places at the same time each season, or if they are sighted elsewhere. Tagging is a bit more technologically advanced. These satellite transmitting devices allow us to remotely monitor the whale sharks and their behaviour. There are variations in types of tags and the data they provide. Most often the tags used are attached to the sharks alongside the dorsal fin and provide us with data on track movement, depth and dive profiles, as well as water temperature and salinity. With continued research efforts maybe we will one day understand the mystery of the disappearing whale sharks.
Note: With limited sightings this year, all these photos are from the 2013 season.
UPDATE September 2015: *Due to low numbers of whale shark sightings over the last three years the Marine Conservation Society of Seychelles (MCSS) are not running snorkelling excursions for the public in 2015. Please keep an eye out on future blog posts for news regarding any change to this decision*