Research

Tagging

White Sharks: "Columba"

»Columba's movements
»Collaborative research
»The tagging procedure
»What we aim to learn

Columba heads north for spring, south for summer

Columba, a 3.5 metre female white shark fitted with a satellite tag on 29 June 2006, traveled some 3800 kilometres from Port Lincoln, South Australia to Exmouth Gulf, Western Australia. She remained in deep water approximately 100 km north-west of Exmouth Gulf from mid-September to early October, and has since been heading back towards the Great Australian Bight. She has transmitted about 140 positions via the ARGOS satellite system in the five months since she was tagged.

Track of Columba, 3.5 metre white shark, from 29 June - 17 November 2006
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“Columba is the first shark we have directly tracked by satellite that has moved up the WA coast,” Barry Bruce of CSIRO says. “We have known for some time that white sharks move up the WA coast as far as the Carnarvon-North-West Cape region, but we do not know why they do this, nor do we have a good detailed track of how they get there.”

Columba's Movements

Columba’s movements were confined to shelf waters across the Great Australian Bight until she reached Cape Leeuwin. There she turned north and tracked along the slope seaward of the continental shelf, in waters of 500–1000 m, for much of the trip to Exmouth.

Temperature data from the satellite tag suggest she dived to depths of 600–800 m (6–9°C waters) during this period. This diving behaviour is similar to that of white sharks previously tracked up the WA coast using pop-up archival tags.

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“We have some good information on diving behaviour from other tag types suggesting that they make deep water excursions during the trip,” Mr Bruce says. “This appears to match with what Columba is doing both in position (often near the edge of the shelf or over the slope) and in the temperatures that the tag has reported during her dives.”

The reason white sharks visit this region is unknown. Although the presence of humpback whales has been suggested, whale specialists believe Columba is too far offshore for interactions with humpback whales.

Collaborative research

Columba was tagged as part of collaborative research between CSIRO and the South Australian Research and Development Institute (SARDI). She was named after St Columba’s Memorial School at Yorketown, SA. Poor weather meant that she was the only shark fitted with a satellite tag during the tagging trip in late June.

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The tagging procedure

Columba, who from her length is estimated to be approximately 10 years of age and 500kg in weight, was fitted with a satellite tag, a short-term acoustic tracking tag, and an acoustic identification tag. Small tissue samples were also taken from her dorsal fin for genetic studies. Acoustic identification tags transmit a unique code that can be logged by acoustic listening stations set on the ocean floor. Columba’s acoustic tag is expected to have a two-year lifespan.

She was acoustically tracked from the vessel for about four hours after being tagged, allowing the scientists to monitor her behaviour and ensure she was not adversely affected by the tagging procedure.

The acoustic tracking tag was attached using a corrodible link so that the tag would be shed after about three days. It was found at Point Turton, SA, (about 100 km from where she was tagged), and returned to CSIRO in early September.

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What we aim to learn

Information about Columba’s journey and tissue samples taken from her will be combined with existing data on white sharks, primarily from CSIRO tagging efforts in SA, to provide information on:

• movement patterns;
• risk of encounter and how to minimise that risk;
• integrated ecological studies (including predator/prey interactions);
• population links between Australian white sharks and those in other areas of the world; and
• estimates of population size.

“This track is consolidating our picture that white shark movements are not random but follow patterns with visits common to particular places at particular times of year. Some sharks also appear to follow common routes when they travel,” Mr Bruce says.

“Documenting these places, the reasons for sharks going there and the routes that they take may provide us with information we can use to minimise interactions between sharks and people.”

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Last updated 12/11/08