Expedition blogs and news from the Shallow Marine Surveys Group

Hawksbill success!

We have been continuing our efforts to capture and tag hawksbill turtles from the Georgetown pier during the evenings. Finally, we were rewarded for our efforts when the team managed to recapture the large hawksbill that had been too heavy to lift onto the pier on the previous attempt.

This time, we were better prepared for such a large animal, the biggest hawksbill recorded in Ascension to date, and with the assistance of ropes and a higher tide managed to lift the turtle onto the pier. Sam and Nicola Weber, from Ascension Island Conservation, were able to take measurements and a  biopsy for DNA analysis.

[caption id="attachment_502" align="aligncenter" width="584"] The team of divers manage to bring the turtle alongside the pier where it could be lifted out of the water to be measured.

Sadly, this particular turtle has had a previous encounter with humans and we found a large fish hook embedded in its face. Because the hook exited very close to the orbit of the eye the decision was made to leave the hook in place to rust out, rather than risk further injury to the animal's eye by forcefully extracting the hook.

[caption id="attachment_503" align="aligncenter" width="584"] Sam Weber measuring the carapace length of this very large (for Ascension Island) hawksbill turtle.

Unfortunately the same turtle has been seen on a subsequent night and we noticed that now a plastic bag has become entangled with the hook and may be causing some distress and discomfort to the turtle. If we manage to capture the animal again we'll attempt a removal of the hook. If not, hopefully both the plastic bag and hook will come away in time.

[caption id="attachment_504" align="aligncenter" width="584"] The fish hook can be clearly seen embedded. The turtle's sight appeared unaffected for now and with time, the hook should rust out.
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Hawksbill tagging underway (well, nearly)…

[caption id="attachment_392" align="alignleft" width="300"] Sam Weber instructing volunteer turtle catchers on the finer points of the art.
Image: W Dimmlich

Attempts to capture and tag some of Ascension Island’s elusive hawksbill turtles (Eretmochelys imbricata) got underway during two night dives at the Pierhead in Georgetown this week. Best known for its globally important nesting population of green turtles (Chelonia mydas), Ascension Island also has a small resident population of critically endangered hawksbill turtles about which very little is known. Hawksbills do not nest on Ascension and from their sizes it appears that most individuals are sexually immature juveniles or sub-adults, but the nesting population(s) from which they originate and the migratory pathways which bring them to the Island remain a mystery. By fitting metal flipper tags carrying a return address and taking tissue samples for mitochondrial DNA analysis we hope to answer some of these questions, as well as adding to scarce data on growth rates and residence times at Ascension. But first we have to catch them!

[caption id="attachment_393" align="alignleft" width="584"] A young hawksbill is spotted in the shallows near the pier.
Image: P v West

[caption id="attachment_394" align="alignleft" width="584"] As it swims close to the shore Dion Poncet prepares to leap.
Image: P v West

[caption id="attachment_396" align="alignleft" width="584"] Unfortunately a near miss and the turtle can be seen just escaping Dion's outstretched hand.
Image: P v West

Every evening, as many as 5-6 hawksbill turtles gather around Georgetown Pier where artificial lighting and fish discards allow them to continue foraging late into the night, making this the perfect place to start our tagging campaign. After an unsuccessful attempt earlier in the week, a crack team of elite military divers including Simon Browning, Simon Plummer and Phil Thomas managed to capture one of the largest hawksbills yet seen on Ascension - too large unfortunately, as it proved too heavy to land in the conditions at the Pierhead! Nevertheless, spurred on by their progress so far the team are planning a return visit this week and we will post an update soon.

[caption id="attachment_397" align="aligncenter" width="584"] Success! It takes Phil and two Simons to finally capture a hawksbill and shepherd it back to the pier.
Image: P v West

Contributed by Sam & Nicola Weber
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Team Members Sam and Nicola Weber

[caption id="attachment_175" align="alignleft" width="300"]Nicola Weber Dr Nicola Weber
University of Exeter & Ascension Island Government

Nicola and Sam Weber are Darwin Post-Doctoral Research Fellows at the University of Exeter and Ascension Island Government. They are based on Ascension where they are responsible for coordinating a Darwin Initiative project that will produce the first Biodiversity Action Plan for the Island. The project, which began in July, will bring together partner organisations from the UK, Sweden and Ascension to produce a series of Species Action Plans (SAP) for priority species that identify current threats and develop targeted strategies for their conservation. Prior to starting their present posts, Sam and Nicola were running an Overseas Territories Environment Programme project, which aimed to update population size estimates for nesting green turtles on Ascension Island and produce a revised management plan for this species.

[caption id="attachment_176" align="alignleft" width="225"]Sam Weber Dr Sam Weber
University of Exeter & Ascension Island Government

Sam first visited Ascension in 2007 as a PhD student at the University of Exeter to carry out research on the reproductive ecology of green turtles, and has been trying to find ways to come back ever since! Prior to starting his PhD, Sam also completed an MSc in Biodiversity and Conservation at the University of Exeter. He is a keen recreational diver and is looking forward to surveying some of the remoter corners of Ascension’s coast as a part of the SMSG team. Nicola has a BSc (Hons) in Marine and Environmental Biology from the University of St Andrews where she carried out her dissertation with the Sea Mammal Research Unit studying the energetics of grey seals. She also learnt to dive here in the cold Scottish waters where she gained her BSAC Dive Leader qualification. After completing an MSc in Conservation and Biodiversity at the University of Exeter, she remained there to carry out her PhD where she deployed proximity loggers to study the movement and contact patterns of the European badger and the implications that these have for the spread of bovine tuberculosis.

Within this group expedition to Ascension Island, Nicola and Sam will be assisting with dive surveys where needed, but in terms of research they will be focussing primarily on the critically endangered hawksbill sea turtles that are found in the near-shore habitats around Ascension. The hawksbills at Ascension are probably juveniles using it as a staging post before recruiting to adult feeding grounds in West Africa or Brazil, but compared to their more famous cousins the green turtles, very little is known about them. With the help of the SMSG team, Sam and Nicola are hoping to expand the flipper-tagging programme for hawksbills on Ascension to answer fundamental questions on population size, residence time and growth rate. They will also be taking DNA samples to help determine which nesting population(s) the juveniles around Ascension originate from, and collecting observational data on diet and distribution around the Island.

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