Tuesday, September 22, 2015

The results are in! Role on Djibouti 2016

It is now official! Djibouti 2015 was another epic expedition! The two five-day monitoring sessions netting us a total of  323 encounters with a total of 55 individual sharks, all identified by photo ID. 
A happy little Djibouti shark, with friends!
Of these, 34 were sharks we had seen before in previous years while 21 were new to the programme,  that is close to 62% of site faithful sharks which we believe is the highest level in any aggregation currently studied. Not unsurprisingly the majority of the sharks we saw were male with only 3 female sharks found compared to 51 males (one individual was a bit too speedy and we did not get a reliable gender on it).

Most sharks were found either off the Foreign Legion Camp at Arta or 30 odd kilometres away in the far end of Ghoubet el Kharâb, the almost land locked ‘lake’ at the very end of the Gulf of Tadjourah.  

 The locations of our January 2015 encounters

Interestingly two sharks found in Ghoubet were seen two days later off the Camp, having made the 31 km swim down!
The 31 km swim undertaken in two days by two sharks!

Things are shaping up well for Djibouti 2016: once again we will be running two weeks starting on Saturday Jan 9th to Friday 15th and Jan 16th to 22nd aboard the MV Deli. The trip costs are Euro 1270 for divers and Euro 1150 for snorkelers, sharing a cabin with full board and inclusive of the last (Friday) night at the Djibouti Sheraton hotel. Divers have the option of doing a minimum of 2 dives per day depending on how much whale shark watching they want to do. Also available, but not included in the cost, is a land trip to Lac Assal on the Saturday after the expedition, a trip well worth doing!

Those interested in participating please contact Dolphin Excursions directly on excursions@dolphinservices.com.

Our thanks to Savi for the photo ID work, number crunching and map production!

Tuesday, September 15, 2015

Whale sharks,El Niño and Indian Ocean Dipole....

Well the Seychelles whale shark season should be well underway by now but only one whale shark has been sighted and that was in July over on Praslin. 

In El Niño years there are fewer whale sharks off Ningaloo in Australia as the water temperature drops, due to a weak  Leeuwen, and conversely in La Niña years, the warm Leeuwin current is stronger and warm Ningaloo’s waters attracting more whale sharks.

Where are our faithful Seychelles sharks?
The situation in Seychelles is not the same as at Ningaloo as there is no warming current involved; currently Seychelles waters are 1.0°C warmer than usual which is the normal El Niño pattern. This year is the strongest El Niño since the 1997-1998 episode which caused such devastation to corals in the Indian Ocean and around Seychelles when it combined with a positive Indian Ocean Dipole phenomena.  At the moment the Dipole is showing a +0.4°C increase so not yet major but worrying over the coming few months.From a whale shark perspective the best ever year for in Seychelles was in 2010 which was a significant Negative Dipole year which was -1.60°C below the normal and this was also a La Niña year. 

The Indian Ocean Dipole record for the last 10 years, 2010 was great for whale sharks!
So it seems that Seychelles’ normal South East monsoon water temperatures (25-26°C) are just about right for whale sharks but any increase in temperatures and the waters are simply too warm for them; slightly cooler waters are even more attractive. This is somewhat problematic as Indian Ocean mean Extended  Reconstructed Sea Surface Temperature (from NOAA) is estimated to have increased by about 0.75°C over the last 100 years. 

 100+ years of rising Sea Surfaces Temperatures in the Indian Ocean (NOAA)
Also, positive Dipole years have become far more frequent in the last 50 years (1 in every 6.3 years compared to 1 every 17.3 in the previous century). Add to this that water temperatures in the Western Indian Ocean are higher in positive Dipole years and all in all it is not a promising scenario for whale sharks around Seychelles!

But we're still here and looking!