Holiday snaps of turtles traversing the passages around Rarotonga are being used with image recognition technology to identify sea turtles and get a better handle on their movements around the Cook Islands.
The project is the brainchild of Te Ipukarea Society (TIS), a Rarotonga-based conservation organisation that runs numerous projects aimed at protecting Cook Islands’ land and marine environments and biodiversity.
The Society has amassed a database of turtle photos submitted by tourists to the Cook Islands, as well as locals, tour and dive operators, and the Cook Islands Ministry of Marine Resources.
Green turtles are most abundant in the waters surrounding Rarotonga, followed by Hawksbill turtles, says Alanna Smith, TIS’s Director.
“Very little is actually known about our turtle population. The turtles seem quite happy hanging around our passages, but there’s a question mark over the extent to which they move around and the size of the population.”
Sea turtles are important to the Cook Islands economically, environmentally and culturally. Everyday, turtle tour operators take dozens of paying tourists out around the Ava’avaroa passage at the south of Rarotonga where turtles are most abundant. A turtle experience, which is usually undertaken at low tide for safety reasons, can cost up to $160 per person.
Visitors return with underwater photos and stories of stunning encounters with the graceful and curious turtles. But the Cook Islands currently has no regulations governing turtle tourism. Sea turtles are also considered key indicator species in many coastal ecosystems and hold a strong cultural importance in the Cook Islands.
Te Ipukarea Society’s Alanna Smith and Kelvin Passfield Photo: Peter Griffin
“The turtles are generally very placid and tame,” says Smith, who has worked for Te Ipukarea Society on a wide range of conservation projects since 2015 and has degrees in conservation biology and environmental management completed at New Zealand universities.
They’ve got used to the paparazzi and people being around them, but there are no rules around how many tourism operators can operate there. If you wanted to start a business, you could do so tomorrow,” Smith adds.
That’s gradually changing, with the Cook Islands’ National Environment Service exploring options for regulating tourism activities, including issuing licences for operators.
The NES’s draft Environment Management Plan for the southern sea passages of Rarotonga, addresses matters such as turtle conservation.
TIS and Te Puna Vai Marama (Cook Islands Centre for Research) have been working jointly on public consultation for the draft plan.
Around the Pacific, island nations are looking to sustainable tourism to provide income for their communities as pressure mounts on fisheries, which form the main source of revenue for many island nations.
A Hawksbill turtle known as CRHB-022 has been matched in 13 photos from between 2016 and 2023. Source: Te Ipukarea Society
In March, Cook Islands News reported that the country’s fisheries revenue was projected to double after the signing of the Tuna Treaty between the United States and Pacific Island States. But climate change poses real threats to the sustainability of tuna fisheries in the Western and Central Pacific region. Scientists project that as the ocean warms, some tuna species will shift eastwards out of the exclusive economic zones of nations like the Cook Islands, threatening the flow of fishing revenue. Sustainable tourism may be leaned on to help fill the gap.
TIS’s turtle conservation project, which has been running for just over a year, set out to gather intelligence about the distribution and health of the turtle population. It is a crowd-sourced citizen science project, which relies on turtle photos being uploaded to TIS.
The project uses the free, open source computer-aided photo-identification system, I3S, which has been employed for turtle, shark, and whale tracking projects around the world.
Photos submitted to TIS are geo-tagged and entered into a database. Only images of the left side of the turtle’s face are used to standardise the images. Positive matches, based on comparing images of the distinctive markings on the turtle’s face, are then used to plot a turtle’s movements and to yield data on the state of the turtle’s health.
Smith says the I3S system is around 90% accurate in identifying turtles, though the facial recognition is less effective on Hawksbill turtles than green turtles. The facial recognition project is already yielding some useful results.
Uploading older photos from tour operators and comparing them with recent uploads confirms that Rarotonga has a mainly resident turtle population that is present year-round and based mainly around the Ava’avaroa, Rutaki and Papua passages in the tidal southern lagoon at Vaima’anga.
The turtles congregate around key passages through the reef that surrounds much of the island but also travel between them.
A turtle nesting suitability survey completed in 2015 found no evidence of nesting around Rarotonga. While 15km of beach was categorised as suitable for nesting, most of this was in close proximity of resorts and in areas of high recreational use by tourists and tourist operators.
“Artificial lighting from resorts, proximity of roads to beaches and people walking on the beaches at night could also pose another issue for nesting females as they respond negatively to white light as they are adapted to sight underwater,” researchers working with the Pacific Regional Environment Program (SPREP) found.
Alanna Smith photographs a rehabilitated turtle Source: Te Ipukarea Society
So if turtles are not hatching around Rarotonga and joining the local population, where are they coming from? There are a couple of theories, says Smith.
“Realistically, there’s been no turtle nesting here for 30 – 40 years. So these turtles could be making their way here from nesting locations elsewhere in the Cook Islands or beyond,” she says.
“There’s also a theory that some of the hatchlings from our northern group atolls were brought here as pets and then were released.”
That would explain why Rarotonga has a stable population of largely male turtles that numbers in the high dozens or low hundreds. The next goal for Te Ipukarea Society is to extend the project to the outer islands, including nesting areas like Mauke, Takutea, and Atiu in the south, and Suwarrow in the north. Turtles have been spotted all over the Cook Islands.
Gathering more photos taken in other locations could help confirm if and when turtles travel between Rarotonga and other islands. A grant secured from UNESCO will allow Te Ipukarea Society to broaden its focus to gathering photos in the outer islands. Researchers from other parts of the Pacific are able to query the turtle image database to check for migratory turtles.
With the sea grasses turtles normally feed on absent from Cook Islands waters , their alternative food sources appear to include algae and black sea cucumber, says Smith. A key factor determining whether turtles will nest on an island or beach, is the nearby availability of food.
“We’ve had a turtle biologist provide some feedback after examining the images and the suggestion is that some of them are malnourished. The turtles are generally small.” Collecting DNA samples from turtles would offer scientists insights into their genetic diversity, health, and help in efforts to trace their origin.
The IS3 image recognition software at work. Source: Te Ipukarea Society
Kelvin Passfield, TIS’s Technical Advisor, has lived in Rarotonga since 1988 and says the turtles have only been resident in reasonable numbers around Rarotonga in recent years.
“For quite a long time, no one really saw turtles,” he says.
TIS was seeing more evidence of turtles having run-ins with boat propellers.
“We’ve also seen signs in the outer islands of the turtles being tangled in fish aggregation devices (FADs). We’d like to see more progress on the use of biodegradable FADs so discarded ones aren’t a hazard to sea turtles and other marine wildlife.”
Passfield, who for over 30 years has worked on conservation and environmental management projects around Asia Pacific, says the turtle tracking project is generating valuable insights that will help local communities and tour operators preserve the turtle population.
“This is really about starting the dialogue around whether we can better protect the passages where they reside, and go to that next phase of conservation and protection.”
