Journal entry 2

The MCSS has had a slow 2011 whale shark season. The official season is September 1st- October 31st however whale sharks are seen before and after those dates. In September we were only able to take clients on the boat for 10 days out of the entire month. Us interns have been able to go out on the boat a bit more, but it hasn't been everyday. Even before the season started there were two fatal shark attacks on a different island in the Seychelles, which initially had MCSS worried that would affect the amount of tourists wanting to swim with whale sharks. Even though whale sharks are plaktivores are harmless, the idea of swimming with a sharks after sharks attacks is never good for business.

However, the greatest challenge our whale shark encounters has faced has been the weather and the plankton. Because the Seychelles are situated around the equator, they lie in an Intertropical Convergence Zone (ITCZ), better known as the "doldrums" to sailors. Basically it has something to do with the trade winds from the northern and southern hemisphere colliding and rising at the equator which creates more clouds, more rain, etc. It used to be that the ITCZ was shaped like a band that would move the storms northwest across the islands half the year, and then move the band southeast across the islands the other half of the year so that for the most part there were noticeably wetter and dryer seasons (however since the islands are very mountainy the island does tend to create it's own weather sometimes) but now instead of a "band" of weather, it's shaped more more like "whisps" or "fingers" so the stupid clouds will pass over the island and it will rain, then the clouds will pass it will be sunny, then in the same day it'll rain again when the clouds pass over again. When it rains our microlight pilot can't get up and without the aerial support it's usually not worth the trip out with clients.

But rainy weather hasn't been the only whale shark problem. We've had awesome clear days where the microlight pilot has been able to go up but he just hasn't spotted any shark. So what does this mean? Where are the whale sharks! Well, GVI (another volunteer organization) has been doing plankton tows to measure the amount of plankton in the water. And they do plankton tows at 5 m, 10, m and 15 m below the surface, so they can measure the amount of plankton in that entire part of the water column. This plankton tow is something I was able to do last week as well, and it requires a lot of muscle power! The plankton levels haven't been too unusual for this time of year. But whenever we've done our plankton tows, which we only do surface plankton tows, we were coming up with low levels of plankton (which is also obvious because the visibility in the water was pretty good; if the we had a lot of plankton then the visibility would be low). So what this could mean is that the whale sharks were here, they're just haven't been at the surface where we could see them. Or maybe the whale sharks were just beyond our aerial survey zone. Towards the end of September, the whale sharks have started feeding at the surface so we've been having more whale shark encounters! I've been able to witness the whale sharks go up and down through the water column and felt the stinging plankton prick my legs. A small price to pay to swim and ID these spotty beauties. So now that the plankton is here, so are the whale sharks!

Some of the other science we do during these whale shark encounters (besides getting whale shark photo ID shots) is using a secchi disk to get a sense of the water visibility and we also use a CTD that takes measurements of the conductivity (which is more or less a measurement of salinity), temperature, and depth. So the CTD is lowered from the boat at a steady rate and a reading is taken every two seconds. Once the CTD information is downloaded it's easy for the MCSS to get an idea of the water conditions and see any thermoclines that are present.