Inferred Adult Foraging Grounds of Two Marine Turtle Species Nesting at Amami-Oshima, Japan

Oki, Katsuki; Hamabata, Tomoko; Arata, T.; Parker, Denise M.; Ng, Connie Ka Yan; Balazs, George H.

doi:10.2744/ccb-1337.1

Cited by 7 publications

(11 citation statements)

References 31 publications

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“…Previous studies have also indicated the importance of the ECS for nesting females of loggerhead turtles (Hatase et al, 2002b), as well as for males and subadults (Kobayashi et al, 2011;Saito et al, 2015). Most loggerheads, particularly those migrating to the southern ECS, showed site fidelity towards narrow foraging areas and did not change locations throughout the tracking period (Hatase et al, 2007;Japan Fisheries Resource Conservation Association, 1999;Oki et al, 2019;Saito et al, 2015;present study). Moreover, the turtle Oki-3, showed site fidelity towards her summer foraging spot across the years.…”

Section: Implications For Conservation Management Of North Pacific Lo...mentioning

confidence: 60%

Latitudinal cline in the foraging dichotomy of loggerhead sea turtles reveals the importance of East China Sea for priority conservation

Okuyama¹,

Watabe

Takuma

et al. 2022

Diversity and Distributions

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Aim: Quantifying the importance of habitat areas for conservation of highly migratory marine species with complex life histories can be challenging. For example loggerhead turtles (Caretta caretta) nesting in Japan forage both oceanically and neritically after their reproductive period. Here, we aimed to quantify the proportions of turtles using these two contrasting habitats (foraging dichotomy) to suggest priority conservation areas.Location: North Pacific Ocean. Methods:We examined the occurrence of foraging dichotomy at three nesting sites (Ishigaki, Okinoerabu Islands and Ichinomiya) based on stable isotope analysis of the egg yolks for 82 turtles and satellite tracking of post-nesting migration for 12 turtles.Moreover, we used the data of three other sites from previous studies (Yakushima Island, Minabe and Omaezaki).Results: Two neritic foraging grounds (East China Sea and the coastal area of the Japanese archipelago), and an oceanic ground (North Pacific Ocean) were identified.We found a latitudinal cline with respect to the occurrence of foraging dichotomy; >84% of the females nesting at southern sites (Ishigaki and Okinoerabu Islands), 73% at middle sites (Yakushima Island and Minabe) and <46% at northern sites (Omaezaki and Ichinomiya) were neritic foragers; the proportion of oceanic foragers increased at northern sites. Based on the annual number of nests in the entire nesting region of Japan, satellite tracking and the latitudinal cline of foraging dichotomy, we estimated that 70% and 9% of annual nesting females in Japan utilize the neritic foraging habitat in the East China Sea and the coastal area of the Japanese archipelago, respectively, and that and 22% utilize the oceanic habitat of the North Pacific Ocean. Main conclusions:The East China Sea represents a critical foraging habitat for the North Pacific populations of endangered loggerhead sea turtles. Our findings emphasize the need for international management to ensure their protection.

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Section: Implications For Conservation Management Of North Pacific Lo...mentioning

confidence: 60%

Latitudinal cline in the foraging dichotomy of loggerhead sea turtles reveals the importance of East China Sea for priority conservation

Okuyama¹,

Watabe

Takuma

et al. 2022

Diversity and Distributions

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show abstract

“…All seven loggerhead turtles mainly used the northern part of the East China Sea, which is a suitable habitat for the species owing to being shallow, with a sea depth of less than 100 m and having an annual SST over 20°C [ 5 , 60 ]. Additionally, in this region, small islands such as Jeju Island, Tsushima Island, and Okinawa Island provide core foraging areas for loggerhead turtles [ 5 , 22 , 61 , 62 ]. Furthermore, despite the few records of loggerhead turtles in the East Sea, KOR0092 and KOR0151 periodically used the East Sea in this study.…”

Section: Discussionmentioning

confidence: 99%

“…Both adult loggerhead and green turtles are known to forage mainly in shallow coastal waters, where the depths reach between 20 and 50 m [ 50 , 66 ], although some turtles prefer open oceanic habitats [ 4 , 70 ]. In Korean waters, more loggerhead turtles are observed in the East Sea, whereas more green turtles are observed near Jeju Island [ 5 , 34 , 41 ]. Because two loggerhead turtles, KOR0092 and KOR0151, stayed in the East Sea for long periods, the values of Chla and POC in the foraging areas of loggerhead turtles were greater than those of green turtles.…”

Section: Discussionmentioning

confidence: 99%

“…Despite the increased observation of loggerhead and green turtles at these distribution margins, studies on their habitat use are lacking. Several studies have shown that juvenile loggerhead turtles use the East Sea near South Korea and Japan as a route to the open Pacific Ocean, but few studies have been conducted on adult specimens [ 5 , 16 , 40 ]. In green turtles, some research showed that adults use the sea near Jeju Island [ 41 ], whereas juveniles use the Yellow Sea west of the Korean Peninsula [ 16 ].…”

Section: Introductionmentioning

confidence: 99%

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Habitat use of loggerhead (Caretta caretta) and green (Chelonia mydas) turtles at the northern limit of their distribution range of the Northwest Pacific Ocean

Kim,

Park,

Park

et al. 2024

PLoS ONE

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Verifying habitats, including the foraging and nesting areas for sea turtles, enables an understanding of their spatial ecology and successful planning of their conservation and management strategies. Recently, the observation frequency and bycatch of loggerhead (Caretta caretta) and green (Chelonia mydas) turtles have increased in the northern limit of their distribution range, in the northern part of the East China Sea and East (Japan) Sea. We conducted satellite tracking to investigate the habitat use of seven loggerhead and eight green turtles from June 2016 to August 2022 in this area, where little is known about their spatial ecology. We applied a 50 percent volume contour method to determine their main foraging areas and analyzed 6 environmental variables to characterize their habitats. Loggerhead turtles mainly stayed in and used the East China Sea as a foraging area during the tracking period, while two individuals among them also used the East Sea as a seasonal foraging area. Most green turtles also used the East China Sea as a foraging area, near South Korea and Japan, with one individual among them using the lower area of the East Sea as a seasonal foraging area. Notably, one green turtle traveled to Hainan Island in the South China Sea, a historical nesting area. Our results showed that the two sea turtle species included the East Sea as a seasonal foraging area, possibly owing to the abundance of food sources available, despite its relatively lower sea temperature. Considering that loggerhead and green sea turtles were observed using the northern part of the East China Sea and East Sea more frequently than previously known and that the sea temperature gradually increases due to climate change, conservation and management activities are required for sea turtles in these areas.

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“…Samples obtained from the foraging ground of loggerhead turtles are limited in location, as they are only from Sanriku in Japan. In addition to the coastal area of the Japanese archipelago, the East China Sea is an important foraging ground for loggerhead turtles nesting in the Ryukyu Islands (Oki et al, 2019;Okuyama et al, 2022). However, it is unclear whether this area is also used by individuals from other nesting sites or at other life stages.…”

Section: Knowledge Gaps To Be Filledmentioning

confidence: 99%

Overview of the population genetics and connectivity of sea turtles in the East Asia Region and their conservation implications

Ng,

Ishihara,

Hamabata

et al. 2024

Front. Mar. Sci.

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Understanding the current status and recent development of the population genetics and connectivity of sea turtles is crucial for effective conservation management of the species. Five sea turtle species, green turtle (Chelonia mydas), loggerhead turtle (Caretta caretta), hawksbill turtle (Eretmochelys imbricata), olive ridley turtle (Lepidochelys olivacea) and leatherback turtle (Dermochelys coriacea), are recorded in the East Asia Region situated in the western side of the North Pacific Ocean. We compiled information from 35 published genetic studies on the five sea turtle species, with a focus on green turtle and loggerhead turtle, which are the most studied species (in 30 studies) in view of their commonness and occurrence of nesting populations. We provided an overview of the key methods and findings of these previous studies, addressing two main objectives on genetic structure of the rookeries and their differences compared to other populations, and connectivity of the rookeries and foraging aggregations. By identifying information gaps and conservation needs, we discussed future developments for sea turtle genetic studies and conservation implications in the region.

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Inferred Adult Foraging Grounds of Two Marine Turtle Species Nesting at Amami-Oshima, Japan

Cited by 7 publications

References 31 publications

Latitudinal cline in the foraging dichotomy of loggerhead sea turtles reveals the importance of East China Sea for priority conservation

Latitudinal cline in the foraging dichotomy of loggerhead sea turtles reveals the importance of East China Sea for priority conservation

Habitat use of loggerhead (Caretta caretta) and green (Chelonia mydas) turtles at the northern limit of their distribution range of the Northwest Pacific Ocean

Overview of the population genetics and connectivity of sea turtles in the East Asia Region and their conservation implications

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