St. Eustatius Sea Turtle Conservation Programme - Annual Report 2006
The St Eustatius Sea Turtle Conservation Programme was initiated in 2001 due to concerns that the island’s sea turtle populations were being threatened due to habitat degradation and destruction. The pro gramme is managed by St Eustatius National P arks Foundation (STENAPA), which is the main environmental non-governmental organization on the island.
The Sea Turtle Conservation Programme is affiliated to the Wider Caribbean Sea Turtle Conservation Network (WIDECAST) and adopts its monitoring and tagging protocols.
Since monitoring began, three species of sea turtles have been confirmed nesting on the island; leatherback (Dermochelys coriacea), green turtle (Chelonia mydas) and hawksbill (Eretmochelys imbricata). There was an unconfirmed nesting by a fourth species, the loggerhead (Caretta caretta), in 2004.
Five nesting beaches have been identified; Zeelandia Beach, Turtle Beach, Lynch Bay, Oranje Bay and Kay Bay. Zeelandia Beach is the primary nesting beach, and the only place where all three species nest regularly; the other beaches are used occasionally by green and hawksbill turtles.
Daily track surveys are carried out on Zeelandia Beach and Turtle Beach throughout the nesting season. Weekly track surveys were carried out on Oranje Bay following the report of a hawksbill track on 1 June. The other nesting beaches were monitored sporadically. Every track is identified to species; categorised as a false crawl or a nest; all nest locations are recorded for inclusion in the nest survival and hatching success study.
- Track surveys were conducted daily from 20 March to 24 November; a total of 232 morning surveys were completed.
- Leatherback nesting activity occurred from 17 March – 14 June; 10 nests and two false crawls were observed; all emergences were on Zeelandia Beach.
- Green turtles were recorded from 27 May until 18 September; 34 nests and 57 false crawls were encountered; nesting was on Zeelandia Beach, Turtle Beach and Kay Bay.
- Hawksbill turtles were observed from the 3 June until 19 September. Six nests and two false crawls were recorded; hawksbills used Kay Bay (3 nests), Zeelandia Beach (1 nest) and Oranje Bay (2 nests).
Night patrols are only conducted on Zeelandia Beach due to limited personnel and minimal nesting on other beaches; patrols run from 9.00pm – 4.00am. Each turtle encountered is identified to species; tagged with external flipper tags and an internal PIT tag (leatherbacks only); standard carapace length and width measurements are taken; nest locations are recorded for inclusion in the nest survival and hatching success study.
- Night patrols were conducted from 12 April –06 October; 127 patrols were completed, totalling 812.75 hours of monitoring.
- One leatherback, three green turtles and one hawksbill turtle were encountered during patrols; all were tagged by the Programme Co-ordinator.
- One remigrant green turtle returned to nest in the 2006 season. This green turtle was first observed on 19 July.
- One green turtle and one hawksbill turtle during the night patrol were selected for satellite transmission in 2006. This has been the second consecutive year that the Dutch Caribbean Nature Alliance Satellite Tracking Project has been conducted and successfully accomplished.
Average carapace measurements for females nesting in 2006:
- Leatherback: Curved carapace length (CCL) = 158.7 cm; Curved carapace width (CCW) = 114.8cm
- Green: CCL = 107.0 cm; CCW = 64.9cm
- Hawksbill: CCL = 85.5 cm; CCW = 75.0 cm.
All marked nests were included in a study of nest survival and hatching success. During track surveys they are monitored for signs of disturbance or predation; close to the expected hatching date the observers record signs of hatchling emergence. Two days after hatchling tracks have been recorded the nest is excavated to determine hatching and emerging success.
- 50 nests were marked: 10 leatherbacks, 34 greens and six hawksbill nests.
- 21 nests were lost during the incubation period; 15 green nests and six hawksbill nests were presumed to be washed away during high tides in October; one leatherback nest was washed over by the tide for three days causing inundation; All hawksbill nests were presumed to be lost, with one hawksbill nest inundated before being moved on 18 October.
- Mean incubation period for leatherbacks was 64.3 days, for greens 51.1 days and for hawksbills was indeterminable since none survived.
Excavations were performed on 20 nests; six leatherbacks, 13 greens and one hawksbill.
- Average egg chamber depth varied between the three species: leatherback = 68.6 cm, green = 54.4cm and hawksbill = 48.2cm.
- Mean clutch size for each species: leatherback = 76.2 yolked + 34.2 yolkless eggs; green = 101.2 eggs and hawksbill = 131 eggs.
- Hatching success was greater for green nests than either hawksbill or leatherback: 51% compared to 0.00 % and 21.1%, respectively.
- Leatherbacks hatching success improved from the 2005 season, increasing from 3.5% to 21.1% in 2006.
- All hawksbill nests were lost for the 2006 season. This was due to a culmination of reasons. Mostly because of laying in Oranje Bay and Kay Bay which has a limited area available for nesting and those areas washed away by high tides later on in the season. The one nest laid on Zeelandia was inundated for an unknown period of days before being relocated causing nest failure.
- Emerging success was lower for leatherback than greens; 15.3 % compared to 46.4 %, respectively.
- Very little predation was observed and a few deformed embryos were recorded; one nest had several hatchlings with deformed carapaces; one had an incomplete skull and no eyes present while another green hatchling had two sets of jaws. One green turtle egg contained twin embryos, and 11 albino green turtle hatchling was also found. Ten were found from one nest.
- Six nests were relocated during the 2006 season; one hawksbill nest, one leatherback nest and four green turtle nests. The hawksbill nest was laid on 7 September but due to the risk of erosion from freshwater run-off from the surrounding cliff, was relocated 19 October. The eggs appeared to have been affected by the run-off.
- The leatherback nest was immediately relocated whilst being laid. Unfortunately, the eggs were unfertilised.
- Of the four green turtle nests that were relocated; two hatched, one was washed away and one failed to hatch.
- In future years the practise of relocating nests laid in erosion zones to safer sections of the beach will continue.
On 27 September, a dead hawksbill turtle was encountered by the Programme Co-ordinator on Turtle Beach during a morning survey. At the current time, the Co-ordinator was lacking the equipment to perform a proper necropsy, but the turtle was moved and a necropsy was performed later. A rudimentary necropsy to determine the cause of death. Unfortunately no definitive answer as to the cause of death was determined from the necropsy.
A satellite tracking project was initiated in 2005 by the Dutch Caribbean Nature Alliance (DCNA) which was continued in 2006. This research was an inter-island collaboration between STENAP A and the Nature Foundation St Maarten. Dr Robert van Dam was the lead biologist, providing expertise and training in satellite telemetry methodology.
- Two transmitters were successfully deployed on nesting females; one on a green turtle (“Grace”) that nested on Zeelandia on 17 September, the other was a hawksbill (“Lisa”) that nested on Zeelandia on 7 September. The turtles’ names were taken from two competitions that were organised for students for the “Name the Turtle” Competition in 2005.
- The green turtle initially went off towards St Kitts, but then headed back towards Statia and returned to nest once more (29 September). The night patrol found her after nesting as she was returning to the ocean. They double-checked to make sure the transmitter was properly attached and it was. She then moved in between St Kitts and Nevis in presumably near-shore waters of the island. We suspect that she is in foraging grounds. As early as December, Grace has travelled a total distance of 1700 km.
- Lisa was the first hawksbill observed nesting on St Eustatius for the 2006 season. The last observed hawksbill was in the 2004 season. She took off from Statia, and headed straight to St Barts. She remained around the uninhabited islands between St Barts and St Maarten for over two weeks before moving to Anguilla for a few days. In late September she started moving again, and travelled to the US Virgin Islands where she stayed until approximately 7 October. Then the hawksbill started out for open water and appeared to head back towards Anguilla but veered to the uninhabited islands between St Maarten and St Bartholomew again in mid October. Lisa moved just off the southeast point of St Maarten but returned to the uninhabited islands around 10 November where she has been since.
Beach erosion continued on Zeelandia Beach in 2006:
- Many of the numbered marker stakes were lost due to high tides. Approximately, twenty were replaced.
- A new method of beach mapping and erosion was undertaken this year. Data were collected in July and November and compared within the year. 64% of the stakes had recorded a positional change from the cliffs that were less than 50cm from their July positions. Only one stake recorded more than 2m cliff erosion from its July location. Although the data does not suggest extensive cliff erosion, the data points to possible steady erosion. Preliminary data stills needs multiple year analyses before any tangible conclusions can be made.
- Sand mining compounds the erosion problem at the northern end of Zeelandia Beach. Despite being an illegal activity, it occurred throughout 2006, in the gully and on the beach.
- In addition to the illegal sand mining, the Executive Council of the Island Government agreed to a one-year policy of sand mining to curb the sand shortage for construction on St Eustatius. This policy started 11 October and will be a temporary solution that will be monitored with certain steps placed to minimise the impact on Zeelandia Beach. None of the preparation steps agreed to have been implemented but the Executive Council has already permitted one sand mining operation to proceed on 1 November.
- Four major cliff falls and four minor cliff falls were recorded from June to October.
- Monitoring of erosion will be a priority for 2007. A suggestion for 2007 is to monitor erosion rates and water table to see if there is a correlation.
Several different community activities were conducted in 2006:
- A puppet show was organised for local schools and the after school programme to teach about water quality with a turtle, Scout, as the main puppet in the theme.
Ten beach clean-ups were conducted on Zeelandia Beach. A total of 16 trucks full of rubbish bags were removed, including a partial radiator, water heater, large rope, fishing nets, oil barrel, a plastic barrel, four large batteries and several car batteries. Unfortunately it was difficult to attract support from the local community despite visits to schools to notify classes.
The Sea Turtle Conservation Programme was featured in regular articles in the local press and on the radio. The STENAPA quarterly newsletter included several features about the research activities conducted in 2006 and the new website contains several pages dedicated to the programme, with a focus on the Sea Turtle Satellite Tracking Project 2006.
Staff participated in several regional and international meetings in 2006:
- The Programme Co-ordinator, Emma Harrison attended the 26th International Sea Turtle Symposium in Crete, Greece 3 – 8 April, 2006 and the WIDECAST Annual General Meeting.
- The Programme Co-ordinator travelled to Puerto Rico from 11 – 19 March, to participate in the in-water monitoring programme of juvenile green and hawksbill turtles at foraging sites close to Culebra Island. The purpose was to receive training in a protocol for conducting in-water capture of turtles, possibly implementing the techniques on Culebra Island to the St. Eustatius in-water monitoring programme.
- On 16 August, STENAPA held its first Annual Public Meeting upstairs at the government guesthouse. At the Annual P ublic Meetin g, Dr Harr ison, gave a presentation on the Sea Turtle Conservation Programme.
- In September, the Programme Co-ordinator was the opening night speaker of the “Sea & Learn on Saba” event. The work of the Sea Turtle Conservation Programme was presented to international biologists, tourists and local residents. The focus of the presentation was satellite tracking and its role in the conservation of Caribbean Sea turtles.
Several recommendations are made for the 2007 season:
- Continued participation of volunteers, from Working Abroad and the STENAPA Intern Programme. To extend volunteer participation, and arrange a dedicated Sea Turtle intern(s) for the upcoming 2007 season.
- Monitoring of nesting beaches to continue: daily track surveys on all beaches and night patrols of the primary nesting beach.
- Further development of the research programme: expand the focus of the programme by implementing an in-water survey of juvenile turtles and continue the satellite tracking project. There is a proposal to extend the satellite tracking to leatherback turtles for 2007.
- Monitoring of erosion should also become a priority. In addition, monitor the water table at Zeelandia beach to determine if the subterranean water levels are causing possible egg failure but more importantly accelerating possible beach erosion.
- As well as the monitoring of erosion, continue to monitor the sand mining approved by the Executive Council of the Island Government and develop alternatives, including instigating a study to assess sustainability of sand mining and impact to the beach nourishment process.
- Include schoolchildren in carrying out beach cleanups. Arrange a contest to see who can collect the most rubbish and award a prize to the winner of the competition.
- Integrate The Ocean Conservancy’s International Coastal CleanupTM Campaign with monthly beach cleanups. The Ocean Conservancy organizes a worldwide annual cleanup on 16 September.
- Revitalize the in-water turtle sighting surveys with the local diving centres. This information will he lp make more informed decisions regarding the in-water monitoring programme.