The Oceanic Fisheries Programme of the Secretariat of the Pacific Community (SPC) and the Marine Research Laboratory of CSIRO (Australia) are working together on a bigeye tuna tagging project in the Coral Sea off Australia's north-east coast.
So what's new, you might ask?
What's new is the type of tag placed on - or rather IN - the fish.
The conventional tagging method used in the past involved attaching a numbered tag to the fish, releasing the fish at sea and waiting for it to be possibly caught by a fisher. But, as precious as the data gathered in this way ( data on growth, migration, mortality) may be, they provide no information about the fish's behaviour: feeding times, depth habits, etc.
Technological progress and, in particular, the miniaturization of electronic components, have made it possible to fit several sensors linked to a data storage memory into a container the size of a disposable cigarette lighter
This "spy" is placed inside the tuna's stomach by means of minor surgery, which does not affect the fish's normal life
Once the fish has been released at sea, the spy will record the temperature of the fish and of the seawater, the depths the fish swims at and the surrounding light measurement for a number of years, several times per hour. When the fish is recaptured, the tag's memory will be downloaded onto a computer and will reveal a previously-secret slice of an oceanic tuna's life: when it fed, what temperature it preferred, what depth it swam at and where it really went over the period (see analysis - pdf 149k)
Mainly because of its high market value in Japan, bigeye tuna is subject to very intense fishing pressure throughout the tropical Pacific. The information yielded by electronic tags will make it possible to better manage this precious natural resource in the future.
161 tags have now been placed out of a planned total of 200. Seven tagged fish have been recaptured so far (15 March 2002), 6 off the east coast of Australia, and one north off coast of New Caledonia
But the tuna concerned may migrate throughout the whole western tropical Pacific. It is worth a mention that a large reward (Au$250) will be offered to anyone returning any of these tags to SPC or CSIRO. So, to your marks!!!