Studies of Hawksbill Turtles and Green Turtles Advance in the Hawaiian Islands

National Park Service project leader Laren Kurpita and a NPS volunteer observe a tagged, nesting hawksbill turtle at Pohue, Hawaii.  
               The tag was applied by PIFSC scientist Kyle Van Houtan.
National Park Service project leader Laren Kurpita and a NPS volunteer observe a tagged, nesting hawksbill turtle at Pohue, Hawaii. The tag was applied by PIFSC scientist Kyle Van Houtan.

Research on sea turtles in the Hawaiian Islands is being directed at both species that nest in the archipelago, hawksbill turtles and green turtles. The population of hawksbill turtles nesting in the Hawaiian Islands is very likely the smallest distinct population of sea turtles on earth. Since monitoring of the population began in the early 1990s, researchers have never observed more than 20 females nesting in any season. In August 2013, PIFSC biologist Kyle Van Houtan traveled to the Volcanoes National Park on the Big Island of Hawaii and successfully deployed a satellite transmitter on one nesting female hawksbill and removed fouling barnacles and severe fishing line entanglements from another. He met with local National Park Service project leaders over three days to develop plans for future research that will lead to a better understanding of the hawksbill population.

Studies of Hawaiian green turtles also advanced, but along a somewhat different path than expected. Damage to the U.S. Fish and Wildlife Service field station at Tern Island, French Frigate Shoals (FFS) in the Northwestern Hawaiian Islands, caused by a micro-storm in December 2012, prevented the annual survey of nesting green turtles at East Island, FFS. Systematic, nighttime surveys of East Island nesters had been carried out each year since 1973. But the storm damage rendered the facility unsafe for habitation this year. In lieu of the usual month-long survey of green turtle nesters at East Island, biologist Joseph Spring was dispatched on the July 2013 expedition of the NOAA Ship Oscar Elton Sette whose main purpose was to monitor and study Hawaiian monk seals across the NWHI. While the monk seal research was underway, Spring, a cooperating scientist working with the PIFSC Marine Turtle Research Program (MTRP), carried out brief daytime surveys of green turtles at 9 NWHI islands/islets including East Island and Tern Island at French Frigate Shoals; Laysan Island; Lisianski Island; Southeast Island at Pearl and Hermes Atoll; Sand Island and Eastern Island at Midway Atoll; and Green Island and Sand Island at Kure Atoll. The last daytime survey of nesting activity in the NWHI was conducted in May 2007.

The 2013 daytime survey provided a reduced but valuable look at nesting activity at East Island, the main rookery for green turtles in the Hawaiian Archipelago. Overall, nesting activity was documented on six islands in five of the major locations visited. Results of the survey indicated that at least 85% of green turtle nesting activity in the NWHI occurs at French Frigate Shoals with more digs (pits + nests) observed there than at any other location surveyed. When compared to the long term monitoring trends, the 2013 nesting season activity level at French Frigate Shoals was estimated to be of medium magnitude.

During the 2013 survey of green turtle nesting in the Northwestern Hawaiian Islands, this nester was observed crawling on Tern 
               Island, French Frigate Shoals.
During the 2013 survey of green turtle nesting in the Northwestern Hawaiian Islands, this nester was observed crawling on Tern Island, French Frigate Shoals.

In addition to the studies of green turtle nesting activity in the NWHI, MTRP stranding response staff have continued efforts to enhance survival of green turtles in the main Hawaiian Islands, recording the 808th turtle rescued, rehabilitated and released back into the ocean since the program's inception in 1990. This turtle was entangled in life-threatening fishing line that had been strangling the turtle's body and a front flipper. The turtle was encountered by members of the public in Kailua Bay on Oahu who carefully removed the fishing line, promptly released the turtle and watched it swim away vigorously. This is the best outcome for a turtle that interacts with fishing line. In some cases, a flipper is so severely damaged that amputation by a veterinarian is required (62 cases recorded by MTRP since 1990). To date, green turtles make up 96% of rescues, followed by small numbers of hawksbills, olive ridleys and one case of a loggerhead turtle. Most of the turtles rescued were stranded on Oahu (63%), followed by the Big Island (19%) and Maui (11%). Causes of live stranding have been determined and classified into 13 categories. So far, the most common cause is line strangulation (274 of the 808 turtles or 34% of the total) followed by interaction with fishing hooks, usually involving a hook stuck in the body of a turtle without actual entanglement by fishing line (128 cases, or 16% of the total). The third most frequent cause for a rescue is entanglement in fishing net, either from coastal recreational fishing or net debris originating from the high seas (105 instances, or 13% of the total).

A fisherman removed hook and line from a lightly hooked green turtle before releasing it.
A fisherman removed hook and line from a lightly hooked green turtle before releasing it.
Major causes of stranding by Hawaiian green turtles
Cause No. of turtles %
Line Strangulation 274 34
Fishing hooks 128 16
Entanglement in fishing net 105 13
Other 201 13
Total 808
Source: PIFSC MTRP database.