Wednesday, January 21, 2009

Dispatches from Djibouti.... 4. Satellite tagging, plankton sampling and more

The team is getting the hang of things now and a daily routine has developed that seems to keep everyone happy and to fit in with both the boat’s schedule and the aims of the programme...

Daniel and David are the early-birds with Daniel eager to get out for an early morning whale shark session while David seems welded to the computer, matching spots on big fish... so there is usually a pre-breakfast run for the early morning team followed by two boats on the main morning survey, an extended break over lunch during which time cameras are downloaded and ‘wet’ data-sheets transcribed onto ‘dry’ permanent copies and checked, prior to the afternoon session.

The amount of data being collected is quite phenomenal and making sure it is in order and properly checked has become the priority with Katie and Luke working with each of the recorders to make sure that this side of things does not fall behind. Our new recorders were doing a sterling job with young Morgan finding that shark spotting was equally as taxing as cetacean photo IDs but with Luke and Katie’s help she was keeping the ‘French’ boat’s data in order.

The photo ID has had to take a back seat as it can only be done once the photos have been matched to each encounter record.... also there’s heaps of ID’s to fingerprint and match and this does take time; as we approach the end of the first week we already have in excess of 80 new sharks photo identified and added to the database as well as several resightings of sharks identified from previous years going back to 2003 when the programme first started in Djibouti.

The first satellite tag deployed on a very cooperative 6 m male shark

The first of the satellite tags was also to be deployed at the end of the week and the modified MK 10 PAT tag from Wildlife Computers was made ready to go on its voyage of discovery... the trouble was that David wanted to put it onto a large shark (larger than 5 m) and with eager camera teams waiting to film the process it had to be a very slow moving shark, in fact preferably one that wasn’t moving at all so that everyone could get their photos!

So with this in mind the teams set out in the afternoon to find a shark to meet David’s exacting needs which seemed to be a bit of a tall order as most sharks being found were around 3 metres in length.However, finding slow sharks proved not to be a problem as the afternoon feeding aggregation was kicking off nicely and many sharks were already into vertical feeding mode where they stay stationary for several minutes at a time just gulping in great mouths full of plankton....

Fortune was smiling and a 6 metre male shark was found placidly vertical feeding off Acacia Beach who didn’t even flinch as David attached the tag.... in fact the shark ignored the whole process and just continued gulping which seemed a little ungrateful! So the first tags is out and alive and we hope to start to get regular updates from the tag as well as its full story when it pops off in three months time.

Talking of gulping plankton, the team has been busy trying to find out exactly what the sharks are gulping by running surface plankton tows and conductivity, temperature and depth profiles.... these too had to be modified from the standard five minute tow to a much shorter two minute tow as the volume of plankton being collected was simply too much to process and we had a limited number of plankton sample pots! What was very apparent was the high number of arrow worms (chaetognaths) and sea-butterflies (pteropods) present which are regarded as prime whale shark food in the Seychelles; and while we don’t yet know the species of the arrow worms these guys were huge compared to those found in Seychelles and so it’s no wonder the sharks here seem to be in vertical feeding mode so often.... all will be revealed when the samples get to the lab!

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