The AfriOceans M-Sea Programme Scientific Report 2007
Sharks: Bella, Billy, Jeannette and Tamera
This report summarizes the protocols used in preparation of the raggedtooth sharks, “Bella” and “Billy” at Two Oceans Aquarium (TOA) for release back to the wild. It also details the capture and release of two wild-caught sharks in March 2007, and the results obtained to date from two PAT tags.
This was the fourth year of the program. Initiated in 2004, “Maxine” was the first shark released, followed by “Val” in 2005. “Dee” was successfully released in 2006. “Bella” and “Billy” were scheduled for release in March 2007.
“Sam”, the first wild shark that was tagged with a PAT tag under this programme, was caught and released in April 2005. “Lesley” was the wild-caught shark successfully PAT tagged and released in 2006. Additions to wild caught and released animals were again planned for 2007.
“Bella” and “Billy” tagging preparation 6 March 2007
Bella was removed from the 2 Oceans Aquarium predator tank at 09:42 after being darted and sedated with Domitor/Medetomidine Reg No. 92/1.4.3/4. This was the first time this particular drug had been used in this programme. She was moved onto a stretcher while still submerged in the lifting tank. Mike Meyer and Deon Kotze drilled two holes in her first dorsal fin for attaching the PAT tag supporting saddle. The saddle was positioned and fixed in place but without the PAT tag being attached to the saddle.
The stretcher was removed from the tank and the water drained prior to weighing. She weighed 228 kg with stretcher and some water, the stretcher and water weighed 13 and 7 kg, respectively so her weight was estimated by subtraction to be 208 kg. She measured 2 m PCL and 2.715 m TL (straight line, tail bent down).
She was placed in the stretcher on the ground and positioned in a way that her ventral surface was visible. Malcolm Smale cut a 3 cm slit through the abdominal wall after it had been pinched up to avoid cutting internal organs. The VEMCO coded tag was placed in the abdominal cavity and the wound was stitched up using nylon and four stitches. The VEMCO 69 KHz coded ultrasonic tag number was 815. Twenty ml of Hi-tet 120 was injected into the abdominal cavity. She was lifted into the isolation tank and swum around to facilitate her recovery. Antisedan, Reg. No 92/1.4.2/5 was used to counteract the sedative drug.
The whole procedure from removal to weighing till the end of the surgery and placement back in water was 15 minutes – within the normal range of times that this species can be kept out of water under normal conditions.
“Billy” was darted at 11:05 and removed from the tank at 11:54. His dorsal fin was drilled for the saddle placement. Drilling started at 12:02 and he was weighed at 12:09.
He weighed 193 kg with stretcher and his body weight was calculated to be 180 kg. He measured 2.08 m PCL and 2.82 m TL. His claspers were fully calcified (indicating full sexual maturity) and they measured 30 cm (inner length) and 21 cm (outer length). A VEMCO tag was inserted into the abdominal cavity following surgery. The VEMCO tag number was 816. The shark was placed back in water in the holding tank at 12:25, so weighing and surgery took some 16 minutes. He was stabilised and assisted in recovery by assisting him to swim in the tank. He was initially a little unsteady because he had some air internally, apparently at the anterior part of the abdominal cavity.
In the early hours of the morning of Monday, 12th March 2007 Bella was found in the holding tank dead. Billy was swimming in an uncoordinated way. Billy was euthanased on early evening of Monday, 12th March 2007. Following post-mortem and tissue sample analysis, it was found that the sharks had probably died from tissue anoxia. The probable reason for this was that the sharks had not had their gills flushed during surgery and the blood circulation was inadequate while sedated. Anoxia resulted. Protocols have subsequently been developed to avoid repetition of this in future. These fatalities were the first since the inception of this programme. Both the VEMCO tags were removed from the sharks for use with other animals.
Capture and tagging protocols of wild-caught sharks 2007
The TOA team (Michael Farquhar, Vincent Calder, Tinus Beukes, Claire Taylor, Natasha Townsend, Sifiso Ngobese, Derick Neethling), Mike Meyer (MCM) and Malcolm Smale (PEM) met at Struis Bay on Monday 26 March 2007 to tag two wild sharks. Lesley Rochat, Mike and Valerie Fraser joined the team to film the procedure. Two PAT tags were programmed that evening in preparation for the capture and tagging of two wild sharks. The details of each tag set up are provided at the end of this report.
The team launched using Aquarium 1 and Awesome Charters, although the sea conditions were not good because a moderate south-easterly wind was blowing. The team fished for approximately two hours between Struis and Saxon Reef, prior to moving to the west side of Saxon Reef to fish until approximately 16:00. The sea conditions were difficult and although there were 3 raggedtooth shark hook-ups, none were landed because of the poor sea conditions that resulted from the 20 knot wind. The team launched using Aquarium 1 and Awesome Charters, although the sea conditions were not good because a moderate south-easterly wind was blowing. The team fished for approximately two hours between Struis and Saxon Reef, prior to moving to the west side of Saxon Reef to fish until approximately 16:00. The sea conditions were difficult and although there were 3 raggedtooth shark hook-ups, none were landed because of the poor sea conditions that resulted from the 20 knot wind.
On 28 March the team again set off for Saxon Reef at 07:15 and spent several hours fishing there. There were no raggedtooth shark hook-ups, possibly because the water temperature had dropped by 2-3 degrees to an estimated 18° C. The team on Awesome caught one gully shark, one cow shark and one striped pyjama shark but the one raggedtooth hooked managed to break off. Aquarium 1 caught 2 gully sharks and 4 striped pyjama sharks. A humpback dolphin was seen swimming alone in the vicinity at a position of 34° 41.826’ S, 21° 14.439’ E. The team stopped fishing at 13:00 and moved to 5 Mile Bank. Although the water was cleaner and warmer there, there was a current flowing approximately to the west that was too strong to allow the baits to go down. We then moved to Spookdraai, a shallow inshore area immediately east of Cape Agulhas. This area was protected by fringing rocky reef and was calm, very turbid but only about 5 m deep.
The first raggedtooth shark was caught at 15:00 at a position 34° 48.990’ S, 20° 02.096’ E. It was hoop-netted and transferred to Aquarium1, where it was placed in the holding tank. It was disentangled from the line and net and placed into a stretcher. Seawater was pumped into the mouth and over the gills throughout the procedures on the boat.
It was positioned on its back and surgery initiated. A VEMCO ultrasonic tag was placed in the abdominal cavity and the opening sutured closed. The VEMCO 69KHz coded tag number was 818. No PEM spaghetti tag was used on this individual and no oxytetracycline was administered. It measured 203 cm TL, 150 cm PCL and it was an adolescent male (despite the name given – “Jeanette”). Two holes were drilled in the dorsal fin for the saddle, using the same attachment as in previous years, excluding Maxine’s. The tag was difficult to initialise, so the boat moved into deeper waters to set the alternative, depth initiation of the tag (>10 m), by moving to a position 34°49.723’S 20°02.535’E in 14 m of water. It was released at 15:38 and he swam off strongly.
The second shark was caught at the same locality as the first while Aquarium 1 was releasing the first one. It was caught at 16:00 and transferred to Aquarium 1 using the hoop net at 16:15. It was placed in the tank and water pumped into the mouth and over the gills immediately it was there. Although it was hooked in the gill arches, the hook was dislodged. An assessment of the mouth and gills revealed that the hook had not damaged any major blood vessels and there was no bleeding from the gills. A VEMCO coded tag number 817 was placed in the abdominal cavity following surgery. The abdomen was stitched up and the dorsal fin drilled for the saddle attachment. The PAT tag was attached and successfully initiated. The shark was released in deeper water of 13-15 m again to ensure that the tag initiated properly. It was released at 17:23 at a position 34° 49.800 S 20° 03.752E. This female shark was named Tamera, after Lesley Rochat’s daughter, and she measured 252 cm TL and 188 cm PCL.
PAT tag results
Jeanette’s tag surfaced on 17 May 2007 at a position just south of Mpekweni Beach Resort in the Eastern Cape, approximately 36 km north-east of Port Alfred. It was thrown onto the beach nearby at a position of 34.960° S, 34.693° E but it transmitted very little data. Two search teams visited the site to hunt for the tag over two low tides. This was unsuccessful, so limited data were obtained from this tag. The tag was released approximately 684 km “as the shark swims” its point of release. (This was measured as usual as the minimum distance around the coast from the tag and release position to the PAT tag surface position). The tag had been programmed to release on 26 July, so it surfaced more than 10 weeks early. The reason for the premature release is unknown, but possibly she stayed at constant depth (within 2.5 m) for more than 5 days – the time set for premature release.
The limited data obtained from the tag indicated that he spent time between the shallow subtidal to approximately 30 m in waters of 14-20° C. He swam 684 km over 50 days between release and tag pop-off, giving an overall speed of 13.68 km/day.
Tamera’s tag surfaced in Algoa Bay at 33.752° S, 25.776° E on 10 May 2007 roughly 5 km north of St Croix Island, a distance of approximately 562 km from the point of initial release near Cape Agulhas. Her overall swimming speed was approximately 13.07 km/day. The reason for the early release may have been that she spent extensive time with little depth variation, as the tag was scheduled to release much later, on 7 August 2007.
The tag washed ashore at Sundays River mouth and was found and retrieved by Mr Wait of Cradock. He returned the tag to Two Oceans Aquarium and it was sent back to Wildlife Computers to download the extensive raw data stored in memory inside the tag. These data will be analysed in the near future to reveal details of her movements in the environment. The raw data are considerably more detailed than the summaries that are sent by satellite when these tags surface.
The data transmitted from Tamera’s tag via satellite were extensive and of high quality. They showed that she had stayed on the western side of the Agulhas Bank until about 10 April then made her way eastwards to the Eastern Cape.
Although the bulk of her time was spent at depths less than 30 m, she did go as deep as 80 m and appeared to spend prolonged periods at shallow sites of less than 5 m. This behaviour probably resulted in the premature release of the tag. She moved through waters as cold as 10° C and 21° C, with an overall average of about 15° C. The lower temperatures were associated with her entering deep cold waters of the continental shelf.
In conclusion, these two sharks showed similar movement eastwards from Cape Agulhas region in April. In the case of Tamera, she showed a rapid movement eastwards similar to that found with Lesley, the wild shark tagged in 2006. Both Jeanette and Tamera showed similar behaviour patterns to those tagged previously in that they withdraw from the western part of their range in autumn. Their costal habitat was again confirmed with similar depth ranges being used. The considerable data set downloaded from Tamera’s tag will add more detail of our understanding of these sharks when it is fully analysed.
18 September 2007