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This tagging project is part of the Foundation's broader study into the population dynamics of Great White sharks in South Australian waters. With more tags planned for the future, this project will attempt to determine where the sharks migrate to when they leave the Neptune Islands and Dangerous Reef, our areas of operation; to pinpoint possible breeding grounds that are so far completely unknown in this area of the world; and to determine if sharks follow the same migratory routes or travel on differing paths depending on age and sex.
A sub-adult female white shark tagged by the FSRF at Dangerous Reef in the Spencer Gulf was seen to visit the Neptune Islands and reside in and around the Gulfs for a period of two months before then undertaking a migration to Shark Bay off the coast of Western Australia, a journey of over 3500km in only 64 days. Moreover, the results showed that the shark travelled in waters up to 376m deep. The visitation to the Neptune Islands could indicate that this site is a stopping point for migrating white sharks. Another female tagged by us travelled on the same route, with her tag popping off near Exmouth and Ningaloo Reef, a distance of roughly 4200km from the start point. It was calculated that she travelled this distance in only 62 days.Another Australian study showed a 2.4m male white shark to have travelled nearly 3000km from the waters off Victoria to the northern coast of New South Wales (CSIRO 2001), whilst similar migrations have been found to occur in Californian white shark populations. Furthermore, a transoceanic migration recorded using satellite technology has proven that females as well as males are philopatric, disproving a previous study that suggested only males to be roving.
Even more astonishingly, a recent South African project showed an epic journey of a white shark from the southern tip of South Africa to Western Australia and back. On the 7th of November 2003, a circa 3.8m female Great White Shark was tagged with a PAT (Pop-up Archival Transmitting) satellite tag in an area known as Haibaai near Dyer Island, Gansbaai, Western Cape, South Africa. On the 28th of February 2004, the PAT tag released itself from the shark at the pre-programmed date. The pop-up location indicated that this shark travelled in 99 days to a location 2 km from shore and 37 km south of the Exmouth Gulf in Western Australia about 11,000 kms from her tagging site. Moreover, this shark was then identified using a photographic identification database on the 20th of August 2004, around Dyer Island in South Africa – a round trip of over 20,000km!
In 2005, satellite tags were deployed on 4 sharks at the Chatham Islands in New Zealand. To everyone’s surprise, three of the Chatham Islands’ white sharks tagged travelled to faraway places never imagined by scientists. One shark moved over 1,000 km in a north-easterly direction to a site devoid of any islands or land masses in the middle of the South Pacific Ocean. The other two sharks made even greater voyages travelling almost 3,000 km to tropical islands NW of New Zealand. A great white shark tagged off Stewart Island set a world diving record as it crossed the Tasman Sea to the Great Barrier Reef, reaching a depth of 1000m. Three four-metre-plus great whites tagged off the Chathams in 2007 also surfaced in Tonga for a midwinter feast of humpback whale calves. It is a mystery as to why sharks are making these long migrations and what they are feeding on during these trips, especially when at such depths. Thus future tagging programs could yield invaluable results. We aim to raise funding for more satellite tags to determine the migration patterns and pathways of sharks from the Neptune Islands, and whether there are sex, size or seasonal based differences in these migrations. It could enable us to pinpoint possible mating grounds. It will also help us to determine the site fidelity of certain sharks, since there are a handful of sharks we observe at the Neptunes on a yearly basis while others are seen once and never again. Temperature data worldwide suggests that white sharks are observed in waters with a maximum temperature of 22ºC, and a minimum temperature of around 4ºC. While they may be encountered in warmer waters, it is likely that the sharks spend the majority of their time in deeper, cooler waters in these areas. Since the tags also record temperature and depth, further tagging efforts could give us an insight into the amount of time white sharks are spending in the oceans depths and at the limits of their temperature tolerances.
Jammie, a 3.3m female shark, was tagged on the 5th of August 2005, at North Neptune Island. On 21st January 2006, after 154 days, her tag popped off and transmitted the results to the satellite.
The pop-up location was pinpointed off the coast of Western Australia, near Exmouth and Ningaloo Reef, a distance of roughly 4200km from the start point. However, the shark remained around the tag point for all of September and October and did not begin to travel west until late November. Therefore, she travelled this distance in only 62 days, making an average distance of 68km per day.
The greatest fluctuations in depth and water temperature occurred near the end of her journey. Throughout her journey, she descended to depths of around 80m, making regular excursions to the surface also. It was only in the final 7 days of her journey that she swam into waters deeper than 100m, with the maximum depth recorded being 139m. She also swam in waters that ranged from 8.5°C to 26.5°C.
Although Jammie did penetrate into relatively deep waters, most of her time was spent in waters shallower than 50m, with the highest frequency of readings being between 0 and 10m depth. She only travelled off the edge of the continental shelf in the final days of her journey, accounting for the deeper readings recorded during this time.
On July 12th 2003, we implanted one a Pop-Up Satellite tags on a 3.5m female shark named “Ticka” at Dangerous Reef. Ten days later, she was spotted swimming around Boston Bay, near Port Lincoln, but, after that, no more sightings were recorded. However, on December 2nd, her tag popped off, floated to the surface and began transmitting data to the satellite.
The pop-up location was pinpointed off the coast of Western Australia, just northwest of Shark Bay, with the nearest point of land being Carnarvon, a trip of over 3800km. This resulted in the shark travelling an average of 62km per day. However, since the shark remained in the gulf waters and did not start travelling west until late September, she actually covered this distance in 66 days, an average of 58km per day.
From July 12th until at least August 18th, Ticka remained in the Spencer Gulf and surrounding area, staying in relatively shallow waters (less than 40m). The data during this period was averaged over a 24-hour period and showed that the shark spent the hours of 23:00 to 07:00 in waters deeper than 10m. Ticka spent from 12:00 to 22:00 above 10m, with much of the late afternoon and early evening (16:00 to 19:00) in even shallower waters (above 5m). The mean water temperature for every hour remained relatively stable, at 12.2°C to 12.7°C. Interestingly, the time period when the shark was in the coolest waters (in late evening) correlated with the shallowest depths.
Once Ticka had left the Spencer Gulf, her mean hourly movements were much different then when in the gulf. Between the hours of 21:00 and 07:00 Ticka descended to depths of 30m or more and then generally spent the daylight hours in shallower waters, with the shallowest mean depth experienced at 18:00. In contrast to her behaviour whilst in the gulf, the mean depth for each hour was always deeper than 20m (with only one exception at 18:00), so she appeared to spend less time close to the surface. The water temperature readings followed a similar pattern, with the shark swimming in cooler waters at night and warmer waters during the day. This would be expected since deeper waters would be colder than those closer to the surface.
Ticka appeared to make regular excursions to the surface, mostly frequently at 09:00 and 17:00. However, only 28% of recordings were at less than 10m, as opposed to 50% when in the gulf. In fact, 39% of all depth recordings were at greater than 30m. Thus, Ticka spent equal time at less than 20m as she did in waters greater than 20m deep.
There were 6 readings of over 300m, all between the hours of 00:00 and 05:00, and all were made in the final month of the journey, as she rounded the southwest corner of Australia and proceeded up the wets coast towards her final destination. 31 readings of depths over 100m occurred mostly during the night, between 21:00 and 07:00 (25 out of the 31 readings), all between November 6th and November 30th 2003.
During these deep dives, the temperature dipped as low as 8.8°C, whereas the surface water temperature at these times were between 18°C and 21°C.
Tagging work is also being conducted on the white sharks' cousin, the mako shark by fellow South Australian researchers:
"We are currently investigating the migration paths and critical habitats of shortfin makos in Australian waters. Between March and June 2008, we deployed satellite tags on shortfin mako sharks (Isurus oxyrinchus) (1.7-2 m) from commercial fishing vessel Rahi Aroha in the Great Australian Bight. Two makos were fitted with Wildlife Computers 'splash' tags, which relay regular summaries of water temperature and dive depth data via the ARGOS satellite network. In March and April 2009, we deployed a further three Wildlife Computers satellite tags on makos of ~1.8, 2.4 and 3 m. This was also done with the assistance of commercial fishers from Port Lincoln. The tag on the 3 m shark was a pop-up satellite tag. In May 2009, two satellite tags were deployed on Shortfin Makos off the Bonney or Limestone Coast off South-eastern South Australia. These included a 1.7 m male named 'Zura' and a 2.15 m male named 'Home Strait'. In November, the final satellite tag to be deployed on shortfin makos in 2009 was deployed during a CSIRO field-trip from fishing vessel Lucky-S in the gulper shark spatial closure area in the eastern Great Australian Bight. 'Lucky the mako' was a male of 1.7 m, total length. Currently (updated 13 July 2010) there are still three satellite tagged makos reporting regular position, temperature and depth information."
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