The AfriOceans M-SEA Programme Shark Releases 2005 Report
Sharks: Maxine, Val and Sam
The Maxine Research Project, a component of the M-Sea Programme, a unique shark conservation initiative of the AfriOceans, was initiated to investigate the behaviour of ragged tooth sharks (Carcharias taurus) released from Two Oceans Aquarium to the wild. Maxine, the first shark to be released, was intended to act as an icon to generate public interest in sharks and their need for conservation. A major part of the initiative was the broader education and awareness initiative that links to the research. The education initiative is broad based and includes filming documentaries for television, web page based information and other education and awareness initiatives.
The research project aims to investigate how sharks released from captivity re-integrate into the wild population and to determine if their behaviour after release is similar to that of wild individuals. Maxine was the first of several releases from Two Oceans Aquarium. Because knowledge of the behaviour of ragged tooth sharks is limited, the programme aims to increase our knowledge base by tagging wild caught individuals and studying their behaviour in comparison to the released sharks.
Ragged tooth sharks are widely distributed (Compagno 2001), but in several areas they are under threat from exploitation. They became the first protected species in 1984 following targeted hunting in Australia. Worldwide, the status of ragged tooth shark populations has come under mounting pressure. They are considered critically endangered off the coast of South America and on the East Coast of Australia where around 300 individuals remain. The apparently larger and more stable population off the West coast is considered endangered. Off Africa it is considered near threatened, while off South Africa the IUCN Red List them as vulnerable.
The first detailed information on the biology and behaviour of ragged tooth sharks off South Africa was published by Bass et al. in 1975. They found that juveniles are found on the south-eastern Cape coast, and that adults are found in KwaZulu-Natal. Pregnant females occur in the northern part of KwaZulu-Natal from about December to March and they showed that the females move south and pup in the Eastern Cape during spring. The distribution of the nursery areas was confirmed by Smale (2002) who suggested that the pupping season is more extended and may last from about September to December. They are important inshore apex predators that feed on small teleosts, elasmobranchs and cephalopods, such as squids (Bass et al. 1975, Smale 2005).
Although broad scale information on behaviour of raggedtooth sharks is known from fishing catches and net entanglements in KwaZulu-Natal, details of behaviour in the wild are lacking. The current study aims to address this shortcoming, with particular focus on the movements of released animals and wild sharks moving northeast from the western Cape at the end of summer.
Each of the study animals was measured and, in the case of the released individuals, weighed. They were fitted with Wildlife Computers Pop up archival transmitting satellite tags (PAT4), and Vemco ultrasonic tags, which have a lifespan of up to three years. The signal from these tags will be picked up by base stations (receivers) placed at different points along the South African coast should the animal pass within 300-500 metres. Hallprint ‘spaghetti tags’ were also attached for long-term identification.
Maxine was equipped with two PAT4 tags with different release dates, while subsequent animals had one PAT4 tag each. Released animals were subjected to veterinary checking prior to release, then trucked to Struis Bay, where they were transferred to a large boat transport tank with oxygenated seawater, and released near Saxon Reef, near Arniston. Film crews documented all stages of capture and release of the animals.
Maxine was displayed in the Two Oceans Aquarium, Cape Town, for nine years prior to release. She was tagged with a spaghetti tag coded PEM 2303, a VEMCO coded 69KHz tag number 769, and two Wildlife Computers PAT4 tags attached at the base of the first dorsal fin. One was programmed to release on 15 June and the second on 15 September 2004.
Maxine’s total length was 278 cm, 202 cm PCL and she weighed 192 kg. She was in exceptionally good condition. Calculating the mass of an average wild-caught female of her length revealed that she would have been expected to weigh 146 kg – so she was approximately 46 kg heavier than would be expected from a wild animal, a result of her being well fed in the Two Oceans Aquarium. She was released on 18 March 2004 off Saxon reef, 34°41’S, 20°15′ E off Struis Point, just south of Arniston in the Western Cape.
The tag that was programmed to release on 15 June 2004 (28243) was not detected by the ARGOS system at the expected time. It was thought to have been faulty or unable to transmit to the ARGOS satellites because it was trapped under water, or because it was thrown up onto a beach before it could transmit its position and data to the satellite.
Unexpectedly, in the period 6 – 9 February 2005, this tag (#28243) transmitted data to the ARGOS system. It transmitted good locality data with an estimated accuracy of approximately 150-350 m of the true position. The tag apparently moved little during these 4 days. This position (33 o 42.3′ S, 25 o 58.98′ E) is approximately 11 km east of Sundays River mouth in Algoa Bay and approximately 570 km from the point of release (roughly 539 km straight line distance).
Sundays River beach is part of a very long sandy beach that extends up to Woody Cape (close to Bird Island). It forms part of the Addo Elephant Park Marine Protected Area and therefore has restricted access. The authorities were notified of the tag’s position and requested to watch out for it when patrolling or working in the area. It has not been located to date, despite the rangers looking for it while on patrol of the beach on quad-bikes, and a careful search of the site on foot.
Maxine’s second tag was programmed to release on 15 September 2004, but it was detected on 11 July 2004 at 34°.210 S (= 34° 12.6′ S) 23.445° E ( = 23° 26.7′ E) approximately 6 NM SSE of Cape Seal, Plettenberg Bay, in water approximately 97 metres deep. The tag came off approximately 2 months early. Distance between release point and tag “pop-up” position – 161 nautical miles or 298 km. This is the minimum distance travelled.
On release, Maxine went to approximately 10 m then swam above the thermocline. She was observed and photographed underwater by SCUBA divers for about an hour, until the weather deteriorated.
There were insufficient data to generate a track, but some information on her depth range and temperatures experienced were obtained.
Summarised data from the archival tag showed that she spent most time at less than 10 m depth. The large proportion of data from 0 m is probably an artefact possibly caused by malfunction of the tag. No evidence was collected of her movements into waters deeper than 30 m (Fig 1.)
Melinda Braun of Willife Computers examined the tag information and observed that the quality of the data suggests damage to the aerial, and further commented:
” something odd occurred on 01July. From 01-06July, the depth sensor showed erratic, negative readings. This might have been caused by trauma to the pressure sensor. The temperature stayed in the 16.4 to 16.6°C range, which seems to indicate that the tag remained in water.”
The temperature range encountered by Maxine was between 13 o C and 20.2 o C (Fig 2). She spent most of the time, 65%, at 16-18o C and 30 % of the time at 18.1-20o C (Fig. 2).
Val was held at Two Oceans Aquarium for 7 years before being released. She measured 295 cm total length, 215 cm precaudal length when caught from the predator tank and she weighed 210 kg.
She was transported and released using similar methods as those used for Maxine. She was released near the west corner of Saxon Reef 34° 41′ S, 20° 15′ E (= 34.0667° S, 20.25° E) on 4 April 2005.
She had a PAT4 tag (ARGOS PTT 34050, PAT ID code #517) that was programmed to release on 4 August 2005. She had a VEMCO ultrasonic coded tag No. 782 and an orange spaghetti tag No. PEM 2901 and had been injected with oxytetracycline for age determination, should she be caught and killed by fishing gear in future.
The satellite tag was programmed to release on 4 August at 20:00 and the first data was recorded by ARGOS on 5 August at 03:21, indicating that the release was successful and Val is presumed to be healthy. ARGOS was unable to provide even an approximate locality of the release. Although a fair amount of data was received from the tag it was all corrupted. Thus no useful information was received on the depth, temperature or probable track (estimated from light level fluctuations and compared to time of dawn and dusk recorded by the tag).
This shark was a wild shark caught by the team from the boat RUSVIC. It was caught, and measured at a precaudal length of 230 cm (otal length calculated to be 308 cm). She was tagged with an ultrasonic tag No. 783, a spaghetti tag No. PEM 2902 and a PAT4 tag PTT No. 33921 and released on the same day: 5 April 2005. The PAT tag was programmed to release on 8 August at 20:00.
The first ARGOS satellite data was collected at 05:02 am on 2005-08-09, so the release was successful and data was transmitted. The information received was of large volume and very high quality and has proved to be the most comprehensive data set of any of the four tags released during the Save Our Seas Foundation M-Sea Programme scientific research project so far.
The first high quality position was 31.626 oS, 29.619o E. This is 31o 37.62’S, 29o 37.14′ E, approximately 5.7 km east of the mouth of Mzimvubu mouth, or roughly off Port St Johns (in the former Transkei) in about 60 m. The time and temperature at depth information is excellent and it shows that Sam swam at depths of <10 m to about 100 m depth. This is high quality and new information.
The depth range covered by Sam in the period 2-10 June was from <10 m to nearly 80 m (Fig. 3). Most of the time she was in depths of 1-10 m and 11-20 m. In the period 15 – 20 June, she ranged deeper and spent more time at 51-80m and little time in water shallower than 30 m (Fig. 4). In the period 10-19 July she spent most time in shallow water < 20 m (Fig. 5), and rarely ventured deeper. In the period 29 July to 3 August she spent most time at 50-90m and little time shallower than that.
The temperature ranges encountered by her in the period 2-10 June were largely from 16 to just over 20o C (Fig. 7). A similar range was encountered in the period 11 June to 20 August (Fig. 8).
The light level changes at dawn and dusk allow an approximate position of Sam to be calculated. A large number of data were received for her movement track but interpretation has yet to be completed. Preliminary interpretation of the positions suggest that she had moved to a position near Port St Johns by 2 June and that she moved between this location to possibly as far north as the area off Durban in July before returning south to the northern part of the Eastern Cape later in July. These position estimates should be regarded as very tentative for the moment.
The quantity of data collected from the first three PAT4 tags (Maxine’s two and Val’s one tag) did not meet all the scientific teams expectations, but the information quality and quantity received back from Sam’s tag was excellent. Discussions with colleagues overseas using the same type of tags has revealed that disappointment on information received back form this technology is not unique to this programme. Other workers studying pelagic species have experienced a 50% loss of data. However, high quality data can be collected and transmitted by these tags on ragged tooth sharks and this is confirmed with the data received from Sam.
Sam’s movement towards the northern part of the Eastern Cape (the former Transkei region) was not unexpected. She had probably spent the summer in Cape waters, when females move to drop their two pups. She may have pupped during the 2004/5 summer, but we do not know this for certain. She was large and at about 3 m total length and would have been sexually mature.
Although there are records of ragged tooth sharks being caught in deep waters, Sam’s data has revealed a) pattern of using both shallow and deep waters, probably in hunting and other activities. Information from feeding studies have shown that these sharks include deep water species, such as hake and kingklip in their diets, and clearly hunting in deep water is part of the strategy used by this opportunistic predator. Whereas this shark is normally thought of as an inshore species, these results show that this understanding needs revision. Hopefully it will be possible to repeat this study with additional animals to deepen our understanding of space use by this ecologically important coastal predator, and a species favoured for observing and photographing by SCUBA divers.
Although each of the three sharks was tagged with ultrasonic tags, none have yet been detected on the stations in Algoa Bay. This may be because the stations are shallower than sites used by these large individuals. Unless they were within 300 – 500 m of any station, they would not be detected.
This project is a first for tagging and releasing sharks from an aquarium with sophisticated electronic tags in South Africa, and apparently worldwide. Further information may yet be obtained if any of the tags are recovered, because the archived raw data may be downloaded from the tag into computers for decoding. If this is achieved, a host of detailed information may become available because considerably more data is stored in the tag than is transmitted to satellite.
The M-Sea Programme hopes to continue to raise funds for the tagging and releasing of the remaining three large sharks at the Two Oceans Aquarium over the next few years. The Two Oceans Aquarium will continue to fund the tagging of wild sharks with each captive shark that is released. This technology can produce new insights into the behaviour of animals in the wild about which very little is known.
With more VEMCO listening stations in the sea along the coast, information may yet be collected from these sharks should they come within range. This would augment the information gathered to date and contribute to a better understanding of these sharks in the wild.
Overall bringing science to the public in a compelling and exciting way will continue to remain the prime object of the M-Sea Programme, always with the aim of improving perceptions and through research assist in the conservation of one of our planets most magnificent predators.
Other related research projects
The status of several research projects on this species is listed below to provide a more comprehensive understanding of the current status in South Africa.
Ongoing or recently completed research on ragged tooth sharks.
1. Biology of ragged tooth sharks. Researchers at Natal Sharks Board continue to investigate the biology of individuals caught in the inshore bather protection nets along the coast of KwaZulu Natal. This work is headed by Geremy Cliff who has an extensive data base gathered over the past 3 decades.
2. Age and growth and validation is being investigated by Malcolm Smale of Port Elizabeth Museum at Bayworld. Both have used tetracycline to verify ring deposition patterns and will collaborate in assessing age and growth of this species.
3. Population dynamics of ragged tooth sharks in South Africa is being investigated by Matt Dicken in his PhD thesis under supervision of Tony Booth (Department of Ichthyology and Fisheries Science, Rhodes University) and Malcolm Smale. Part of the data being used is from the Sedgewicks/ORI/WWF tagging data base set up by the Oceanographic Research Institute (Durban) with assistance of Natal Sharks Board and by the research data set from the Eastern Cape developed by Malcolm Smale.
4. Movement and behaviour of ragged tooth sharks has been investigated by Malcolm Smale in the Eastern Cape nursery grounds for the past two years. At present 25 individuals have VEMCO ultrasonic pingers. Ten base stations are set up between Cape Recife and East London and these are downloaded periodically to investigate site fidelity and movement patterns.
5. Ultrasonic work on this species in KwaZulu-Natal has to date focussed on Aliwal Shoal where a project headed by Vic Peddemors with Mieke van Tienhoven have been investigating the influence and impact of sharks by divers. This work is currently being written up as a PhD thesis.
6. A preliminary study of mating aggregations was undertaken in the summer of 2003/4 by Geremy Cliff, Mieke van Tienhoven and Vic Peddemors at Sodwana. On listening station was placed at ¼
7. mile reef and the other listening station at 9 mile, and five sharks were tagged with ultrasonic tags. An expansion of the above programme is being investigated with the collaboration of colleagues in KZN and Malcolm Smale in a meeting in January 2005.
8. Genetic project comparing South African and Austalian sharks has been completed (MacQuarie University Researchers and Vic Peddemors).
This project is a multi-institutional, multi-funded research project that has benefited from the generosity of the Save Our Seas Foundation in collaboration with AOCA and the Two Oceans Aquarium. In addition a team of dedicated aquarists demonstrated their ability to capture, transport and release the large sharks successfully, and capture and release another, wild individual. The team of photographers, divers and researchers made this project as successful as it has been to date. The assistance of several others, including Mike Meyer (M&CM), and Matt Dicken (Bayworld) is gratefully acknowledged.
Bass, A.J., D’Aubrey, J.D. and N. Kistnasammy 1975 – Sharks of the east coast of southern Africa. IV. The families Odontaspididae, Scapanorhynchidae, Isuridae, Cetorhinidae, Alopiidae, Orectolobidae and Rhiniodontidae. Invesl. Rep. Oceanogr. Res. Inst. 39: 1-102.
Compagno, L.J.V. 2001 – Sharks of the World. An annotated and illustrated catalogue of shark species known to date. Volume 2. Bullhead, mackerel and carpet sharks (Heterodontiformes, Lamniformes and Orectolobiformes). FAO Species Catalogue for Fishery Purposes, No. 1. Vol. 2. Rome, FAO. 269 p.
SMALE, M.J. 2002 – Occurrence of Carcharias taurus in nursery areas of the Eastern and Western Cape, South Africa. Mar. Freshwater Res. 53: 551-556.
SMALE, M.J. 2005 – Feeding of ragged-tooth shark (Carcharias taurus Rafinesque, 1810) in the Eastern Cape, South Africa. Afr. J. mar. Sci. 27 (1): 331-335.