The citizen science project TurtleSpot Taiwan (海龜點點名), has released its latest research in collaboration with academic institutions. For 14 years, over 7,000 photographic records of 709 individual sea turtles were analyzed. The study revealed that nearly 15% (105 turtles) had suffered injuries. Among them, 10% experienced repeated injuries, and six died. Fishing line entanglements and propeller strikes accounted for one-third of all injuries. The team analyzed 19 wounds across 13 injured turtles and found that it takes an average of 500 to 600 days for a turtle's wound to heal completely.
Fong Chia-ling (馮加伶), co-founder of TurtleSpot Taiwan, urged Taiwan to follow international precedents by establishing "Go-slow zones" in sea turtle foraging hotspots like Xiaoliuqiu, Green Island, and Hengchun. These zones would limit vessel speeds in nearshore waters, strengthen regulations for recreational fishing.
The research paper was published this March in the international journal, Endangered Species Research. This study marks Taiwan's first long-term quantitative analysis of wound recovery in wild sea turtles, highlighting the value and need for long-term data collection through citizen scientists.
7.6% sustained serious injuries and have not yet recovered
The study was a collaborative effort between "TurtleSpot Taiwan," the National Museum of Marine Biology and Aquarium (國立海洋生物博物館), National Sun Yat-sen University (國立中山大學), and Academia Sinica (中央研究院). The results were announced at a press conference on March 9th.
Utilizing a 14-year-long (2010–2024) photo database of 7,233 Xiaoliuqiu sea turtle sightings, as well as a two-year systematic survey of 709 individual turtles, the team identified 105 injured turtles (104 green sea turtles and 1 hawksbill turtle).
Injuries were categorized into seven different types:
- Amputation
- Carapace laceration
- Carapace fractures
- Abrasions
- Foreign object entanglement
- Carapace deformities
- Flipper tears
Fishing line entanglements (17.1%) and propeller strikes (15.2%) accounted for about one-third of the cases, however, for the majority of injuries (67.6%) the cause remains unknown. Eleven turtles were recorded having suffered repeated injuries—10 of them twice, and one three times. Nearly half of the wounds were located on the carapace, the shell’s outer layer (49.7%), followed by the flippers (33.3%), with some injuries also recorded on the head, mouth, or multiple body parts simultaneously.
Among the injured turtles, 73 sustained minor injuries and 32 suffered severe trauma. According to the latest sighting reports, 80% of the turtles' wounds had fully healed, eight were partially healed, and seven had fresh wounds. Fong Chia-ling added that six deceased turtles had suffered severe injuries—three from propeller strikes and three from fishing line entanglement.
Injured turtles average 500–600 Days to recover; some suffer permanent functional damage
The team identified 13 sea turtles that were sighted multiple times after injury, allowing the team to monitor their recovery. Since six of them had more than one wound, the team analyzed a total of 19 wounds to track recovery times.
Out of the 19 wounds, 14 (about three-quarters) were caused by propeller strikes or fishing line entanglements. Propeller strikes cause carapace laceration and fractures, with healing times ranging from 274 to 860 days (average: 527 days). Two turtles developed permanent shell deformities after healing, including kyphosis (hunchback shell) and visible hind limb paralysis.
The recovery period for front flipper injuries due to fishing line entanglements took between 450 and 627 days (average: 538.5 days). One turtle, named "Xiao Qiang," (小強) was found entangled but was too timid to let citizen scientists approach and help. After more than 100 days, photos showed the line cutting deep into its right front flipper. After more than 480 days, the limb was swollen and ulcerated. By day 627, the right front flipper was self-amputated and healed.
"He was under high stress for a long time, and we didn't see him coming close to forage; he probably struggled fighting this wound on its own," Fong said. In the following years, "Xiao Qiang's" swimming and foraging behaviors returned to normal, showing he had adapted to losing the limb.
For five turtles, the scientists were unable to identify the cause of injury. Of these, minor wounds took 193 to 968 days to heal (average: 491 days), while severe wounds took 371 to 860 days (average: 600 days). In stark contrast, sea turtles treated at rehabilitation centers before being released back into the wild take an average of just 121 days to recover (around 4 months).
Compared to other large marine animals, sea turtles heal much slower. Recent international studies have shown that aquatic mammals in the whale family (cetaceans) have evolved unique genetic adaptations and immune cells that regulate inflammation and promote wound healing. For instance:
- Whale sharks (Rhincodon typus) reach 90% healing in an average of 35 days, with severe wounds fully healing within 170 days.
- Reef manta rays (Mobula alfredi) see 95% of tear wounds heal within 295 days.
- Short-beaked common dolphins (Delphinus delphis) can fully heal within 21 to 147 days.
Fong's team analyzed 8 wounds across 5 sea turtles and found that the daily wound healing rate was a mere 0.08% to 1.53%. Minor injuries could achieve 50% healing within 300 days, with some exceptions. One turtle fully recovered from a facial tear caused by a propeller strike in just 275 days, indicating significant variation between individuals. "If a turtle is in good nutritional status to begin with, it might have enough energy to fight off infection," Fong added. "But being struck or entangled might also affect its appetite."
As for severe wounds, the healing progress was less than half even after 375 days, with the slowest case taking 725 days just to reach 50% healing. The team suspects that due to their low metabolic rate, a sea turtle's carapace and scales require 1 to 2 years to regenerate.
The study also emphasized that even if a wound heals, deformities or disabilities (such as a missing flipper) can restrict migration, foraging, mating, or the nesting success of female turtles. Citizen scientists have encountered turtles missing hind flippers. "The nests they dig end up crooked easily. These injuries have permanent impacts."
While past research indicates some turtles can still successfully reproduce after losing limbs, it remains unknown how many successfully nest, mate, or migrate. The long-term consequences of severe injuries is a critical gap that future research can fill.
"We don't want Xiaoliuqiu to go from 'only having sea turtles' to 'only having injured sea turtles'"
Human-induced trauma is the most direct conservation issue for sea turtles. Tracking data from rehabilitated and released turtles shows they are very loyal to their habitats. "If they like a place, they will keep returning. If threats persist in their habitats, it leads to repeated injuries." In this study, six turtles suffered second injuries, with at least three cases caused by propeller strikes.
Past measures to prevent propeller strikes have proven largely ineffective. For example, propeller guards only offer marginal help when boats operate at a minimum speed of 7 km/h, but at planing speeds (12-18 knots) they are entirely useless . Most turtle strikes occur at these planing speeds. Therefore, TurtleSpot Taiwan is calling on the government to follow the examples of the US and Australia by setting up Go-slow zones in turtle foraging hotspots like Xiaoliuqiu, Green Island, and Hengchun, limiting vessel speeds to under 6 knots in nearshore waters to reduce ship strike risks.
How should these Go-slow zones be mapped? International researchers conducted line-transect surveys over two consecutive nesting seasons (2021–2022) along the Atlantic coast of Florida (USA) to estimate the distribution of loggerhead and green sea turtles. They found that vulnerable turtles congregate in nearshore areas and hotspots within tens of kilometers of nesting beaches.
A 2017 study on water depth and turtle protection within the Go-slow zones of Moreton Bay, Queensland, Australia, suggested that designating all shallow waters as Go-slow zones would protect over half of the turtle habitats from vessel interference. Extending buffers to adjacent deeper waters could protect 80% to 95% of turtle habitats.
Fong noted that in Xiaoliuqiu, most injured turtles were found near Baisha Port—the main gateway for tourist boats. Other hotspots include Dafu Port and Shanfu Port, which are popular diving sites. These areas show high overlap between human activity and turtle sightings. Aerial photography could also be used to map foraging hotspots and compare them with human activities to delineate Go-slow zones.
But does the public sector have enough law enforcement capacity? Fong paused to think before saying, "I think it's incredibly difficult." She noted that fishing is banned in Xiaoliuqiu’s protected areas, yet people still go into the water with spearguns. "Reporting it doesn't do much because you have to catch them in the act to enforce the law. And why should the burden of reporting fall on the citizens who happen to see it?"
Some countries use incentive-based approaches. Speed limits reduce fuel consumption and greenhouse gas emissions. Monitoring devices can be installed on vessels to track compliance, leveraging ESG metrics or eco-certifications to provide sufficient incentives for companies and boat operators.
Furthermore, fishing line entanglement remains a thorny issue. Although Xiaoliuqiu has established no-fishing zones and banned gillnets within 3 nautical miles, abandoned recreational fishing lines lack regulation. Fine fishing lines and fishhooks continue to threaten marine life. The team suggests installing recycling bins at popular fishing spots and promoting biodegradable lines to strengthen the management of recreational fishing.
Dr. Allen Chen, Director of the Biodiversity Research Center at Academia Sinica, pointed out that while citizens face fines for touching sea turtles, some divers worry that they might also be penalized for cutting fishing lines off entangled turtles. In response, the Ocean Conservation Administration (OCA) stated that under the Wildlife Conservation Act, the OCA and local governments can authorize rescue teams to handle such rescue operations, meaning there are no legal violations. Moving forward, the law will be amended to consider incorporating training and certification systems for professional rescue and care personnel, thereby strengthening the professional capabilities of rescue teams.
"Xiaoliuqiu only has sea turtles left because the condition of the coral reefs in the ocean isn't great. We don't want human threats to turn Xiaoliuqiu from a place that 'only has sea turtles ' into a place that 'only has injured sea turtles,'" Fong expressed.
Translated by Stella Cammack; Proofread by Jaye Brayboy and Vita Liu (劉祐君).
*Note: This article has been translated between Chinese and English. Proper names and pinyin spellings are provided for reference only.