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Shark Tagging update
october 2003
Sasha Thompson – AQWA’s Marine Biologist – has just returned from an incredible experience tagging sharks in southern Western Australia. This is her exciting story…
I have just returned from the third shark tagging expedition with scientists Dr John Stevens and Mr Barry Bruce from CSIRO Marine Research. This expedition, which was part of an AQWA Research Foundation funded project to study the movement patterns of white sharks in southern Australian waters, was an enormous success. Six white sharks were tagged using three different types of tags. Two of these tags were satellite-tracking tags. The scientists are currently waiting to see if the tags are working properly and, if this is the case, this will allow AQWA members to follow the sharks’ progress via our website.
Tagging was conducted just south of Tooregullup Beach in Doubtful Island Bay. Doubtful Island Bay is half an hour by boat or 1.5 hours by 4WD from Bremer Bay, in Western Australia’s Great Southern Region. Tooregullup Beach is the location in which nine adult sperm whales recently beached themselves. Although this was an unfortunate event, the whale’s bodies have attracted white sharks to this area. More than twelve white sharks were seen over the three days of the expedition.
During the first day, two PAT (pop-off archival transponding) tags were fitted. The first PAT Tag was fitted to a 3m female. This tag will record information about the sharks movements and swimming behaviour for four months, after this time it will detach from the shark, float to the surface and transmit its data via satellite to the CSIRO researchers. The second tag was fitted to a 2.5m female and will collect data for six months.
Despite only one standard ID tag being fitted on the second day, there was constant action. To lure sharks to the boat, fish oil and burley were regularly added to the water and large salmon were dangled from lines and a float off the back of the boat. As a white shark approached, the line was pulled in bringing them towards the boat. The trick was to pull the line in faster than a 4 m Great White swims! While John pulled in the line, Barry got the tagging pole into position. For satellite tags, this pole has a compressed gas cylinder, a trigger, an emergency release, and an area between which the dorsal fin needs to be placed. Getting the tagging pole into position was tricky as ideally the Great White would swim towards you, however, most sharks approached from the side.
On numerous occasions the pole and tag were in position over the dorsal fin but the trigger could not be pushed to attach the tag. Two times, half of the satellite tag was brushed off the pole and fell to the sea floor. Worth over $5000 each, we had to try and find where the tags had landed and scoop them up with a net and two poles! Luckily visibility was excellent and the bottom not too far down – enabling Geoff Campbell (skipper of the vessel we were on), to retrieve both tags. Retrieving the tags was made more interesting by the number of Great Whites swimming by!
By Day three, John and Barry had redesigned the trigger and found a way to link the two parts of the tag together – preventing it from being pulled off. During the morning there were a few unsuccessful attempts; from 11am until about 3pm no sharks approached the boat, but then in the afternoon, two sharks in quick succession approached the boat and were successfully tagged. The first shark to have a satellite tag fitted was a 2.5m female, the second a 2.3m female. At this size they are still juveniles. (Males mature at 3.5m and females at 4.5 – 5.0m).
We don’t know enough about the biology or behaviour of the Great White to understand why we mainly saw them at this site in the morning and late afternoon. Now that we may be able to follow the movements of the two white sharks fitted with satellite tracking tags on a regular basis, we hope to learn a lot more about these magnificent creatures.
Sasha Thompson
AQWA Community Education Manager
The AQWA Foundation