Thursday, July 2, 2009

Tagging whale sharks in China….. part 2

The story so far (see previous post)..... David (MCSS Chairman and whale shark researcher) has flown to China to assist the the Ocean Park Conservation Foundation (OPCF) and the Fishery and Fish Harbor Administration of the South China Sea in satellite tagging two whale sharks that are currently in a sea-pen but about to be released...

The sea-pen the sharks were in was a 20 metre round aquaculture pen of around 6 metres depth, attached to the owner’s fishing boat by a long rope which had been used to tow the pen several miles to its current location.

Visibility was all of 2 metres so finding the sharks was not actually as easy as we had at first thought! However, after a few minutes it became apparent that the sharks were doing laps around the pen along the bottom netting and so staying in one place let you get them once per circuit.

Suzanne Gendron and David prepare to enter the sea-pen, with some feelings of uncertantity it would seem! Photo David Lai

And there were in fact three sharks in the pen, a fisherman had brought in another shark the night before which showed some nasty cuts and abrasions and so this third shark would get transferred back to the main pen for recuperation.

All the sharks were males, the new injured shark was around 3.5 metres as was one of the releasees, while the other was a little larger at around 5 metres. After a brief discussion with the ‘owner’ of the sharks Mr LAI, it was apparent that he didn’t think much of our idea of using a tail rope to restrain the sharks saying that this really upset them, it would be much easier to use a flat net to strand them at the surface where they would go quiet….

As none of us had ever tried to restrain a whale shark (or any shark over three metres!) and Mr LAI seemed to know what he was talking about we decided to let him try. The shark swam into the net and six crew members rapidly pulled the net tight like a trampoline and lo and behold one whale shark was duly stranded on the netting and lay there remarkably calmly with an occasional, rather resigned sweep of his tail….

Just as Mr. LAI predicted the shark just sat in the net waiting patiently... Photo David Lai

This in fact was the biggest shark so we attached one of the Wildlife computer anchored PATs, set to pop off at 6 months, to the base of his dorsal fin and let him go to see how he would react. Once the net dropped he happily swam off and continued doing his laps around the pen!

Next one up was the second releasee and this one was similarly very compliant: so this one got two PATs, one set for 3 months and one for 12 months and then he likewise joined his marathon training partner doing circuits once more. The third shark was the injured shark and this one also was similarly very complacent about being stranded in a few inches of water; this gave us time to have a good look at his injuries and some rather odd skin discolouration. We were also able to clip off a section of frayed skin tissue from a deep gash on his caudal keel for genetic analysis. Hopefully Mr LAI’s high protein whale shark feed would have him sorted and ready for release in a short while!

This just left us the fin-mount splash tag which needed to be attached by two bolts through the dorsal fin, so not an easy job and one that has not been attempted on a whale shark before, although these tags have been used this way with excellent results on salmon sharks and great white sharks. Well we knew we could restrain the sharks and that they were fairly complacent, but drilling two holes through the dorsal fin? There was only one way to find out!

How many people does it take to fit a fin-mount SPLASH tag to a whale shark.... a lot less than you would think! Photo David Lai

So shark number one (the biggest one!) was rounded up once again and beached onto the trampoline, this time with Suzanne and David cradling him on their laps and holding him against the side of the pen so that the dorsal was clear of the water and close enough to drill. Once again the shark was incredibly cooperative and only flicked his tail twice during the drilling process. The tag was attached with special stainless steel bolts with an aluminium cap on the tag end that would corrode off in about five months and so release the tag from the shark and allow the mounting bolts to fall out… In less than four minutes the tag was securely mounted with two bolts properly tightened and looking very smart on his dorsal fin!

And here it is one SPLASH tag fin-mounted onto a whale shark... now we just need to see if it will cooperate and swim at the surface! Photo David Lai

He swam off a bit faster this time so he had probably had quite enough of this trampoline netting game for one day and Suzanne and David followed him around for quite a while to make sure he was alright and the tag was indeed as secure as it looked…. it was!

So one hour and forty minutes of very unusual tagging activity resulting in the first ever direct fin-mount of a tag to a whale shark…. The overnight crew were briefed to keep an eye open for any odd behaviour, we were worried that the sharks might try to ditch their new jewellery by tangling it on the pen netting sides but our fears were unfounded and the sharks and tags were all present and correct the next morning for the big release.

The big release was preceded by the ‘End of Season Ceremony’ where Suzanne and David were both interviewed by numerous newspapers and TV channels and Suzanne had to take the stage as the representative of our scientific collaboration…. Quite an impressive ceremony with gold canons firing paper confetti and all sorts!

David being interviewed by Dragon TV as Suzanne awaits her turn.... where were the 'hand-maidens' in the red satin dresses at the tagging? Photo David Lai.

For the release itself, this was a rather less flamboyant affair as the sharks had not been trained to do the ‘Free Willy’ breach over the pen wall and simply slipped quietly away through the opened pen to continue the journey that had been interrupted a few months ago… hopefully the larger shark with the Splash tag won’t spend the next three months swimming along the bottom and will come back to the surface occasionally so we can get some position fixes on him… if he does we will put a tracking map up on this blog for you to follow…. We know the tag is working as we got a location from it through the Argos system while we were bolting it to his fin!

So a remarkable two days in China, the first satellite tags ever put onto whale sharks in Chinese waters and the first ever Splash tag bolted to a whale shark’s dorsal fin!

1 comment:

Mayukh said...

Dear all,

We are in trouble and need your help.
We are attempting to rescue whale sharks from fishing nets. The crux is that by the time our rescue team arrives, the whale sharks almost always die due to suffocation from getting strangled in nets. Our urging to immediately release the sharks by cutting the nets have failed due to bureaucratic reasons. Unfortunately releasing the whale sharks also take away the opportunity to tag them and get other bits of data.
My question is, is there a way to restrain the accidentally caught sharks without killing them, i:e by cutting open the nets? so that we still have time to go an tag them and collect morphometric data.

Please do let us know of ideas how whale sharks can be safely restrained for implantation of tags.