This is the first time that a fin-mount tag has been successfully attached to the dorsal fin of a whale shark (see earlier article) and apart from a single location when the tag was attached on the 28th of June, it has been worryingly silent ever since.
David was concerned that perhaps the tag antennae had been damaged while the shark had remained in captivity for a further 12 hours prior to release, even though the Chinese fisheries scientific officer Cui Yun-Chen had confirmed it had looked good…. Seems that he was quite right!
A map of the track of the whale shark tagged with a SPLASH tag; the tag was deployed off Sanya on the 28.06.09 and the last position was on the 31.07.09. Map courtesy www. seaturtle.orgSo what has this shark been doing since it was released of San-Ya on Hainan Island to the South West of Hong Kong a month ago?
We might never really know but the splash tag is sending snatches of data from this period so we might get some indication over the coming weeks. What we have to take into consideration is that the satellites that have the ARGOS platform do not have a global 24 hour coverage and that while this area has in excess of 14 ARGOS satellite passes each day, their footprint is short and so there may be less than 3 hours coverage each day.
That means that even if the shark is on the surface and the tag transmitting all day at best we would get only 12.5% of the transmissions. On the other hand the shark may simply have been staying deep for the last month getting used to being back in the open ocean and not restrained by a sea-pen to shallow sunlight waters.
Whatever the reason, for the last three days we have captured from one to three transmissions each day and so we are forever optimistic of getting more information!
On receipt of the first transmission David and colleagues Suzanne Gendron and David Lai from Ocean Park Conservation Foundation (OPCF) all heaved a collective sigh of relief as OPCF had funded the SPLASH tag. We are sure that Director Zeng Xiaoguang and Mr. Cui Yun-chen from the Bureau of Fishery Management of South China Sea will also be relieved to hear that their shark is alive and doing well!
The SPLASH tag is an advanced satellite tag developed by Wildlife Computers that acts as both a data logger, recording details of depth and temperature the tag encounters, and also as a tracking device that transmits to the ARGOS platforms on NOAA weather satellites.
A proto-type fin-mount SPLASH tag mounted onto an aluminum and plastic collar for attaching with a single bolt by a RamSet gun. Photo courtesy MCSS
These tags have been used to great effect on marine mammals and on some species of sharks where the shark can be restrained to allow the tag to be fitted directly to the dorsal fin; in whale sharks their deployment up to this point has been either on a floating torpedo towed on a tether behind the shark or on a collar mounted to the dorsal fin, neither of which has proven to be very successful.
The SPLASH tag successfully mounted directly to the dorsal fin of the whale shark off Sanya by David, Suzanne and the OPCF & Bureau of Fishery Management team. Photo David Lai OPCF
As such, this tag may indeed be a very important step forward in whale shark research; if fin-mounted SPLASH tags stay on and give enough data in terms of position and behaviour some of the perplexing questions about whale shark migrations may yet be revealed!
Watch this blog for updates of our Chinese adventurer….. guess we should have a name for him so send us your suggestions!