Mixed stock analysis of a resident green turtle, Chelonia mydas, population in New Caledonia links rookeries in the South Pacific

Abstract

Context Migratory species are known to pose a challenge for conservation because it is essential to understand their complex life history in order to implement efficient conservation actions. Aims In New Caledonia, large seagrass habitats in the Grand Lagon Sud (GLS) are home to resident green turtles (Chelonia mydas) of unknown origins. To assess the stock composition in the GLS, 164 foraging turtles were sampled for genetic analysis of ~770 base pairs of the mitochondrial DNA (mtDNA) control region. Methods Foraging turtles ranging in size from 48.0 to 108.4 cm curved carapace length were captured at five different sites within the GLS between September 2012 and December 2013. To provide baseline data for mixed stock analysis, published data from rookeries were used in addition to 105 samples collected at rookeries in the d’Entrecasteaux Islands and Chesterfield Islands in New Caledonia and at Malekula Island in Vanuatu. Exact tests of population differentiation and pairwise FST estimates were used to test for differences in mtDNA haplotype frequencies. Key results These analyses indicated that rookeries in the d’Entrecasteaux Islands and Vanuatu form unique management units and that the Chesterfield Islands rookeries are linked to the Coral Sea management unit. Mixed stock analysis indicated the highest proportion (mean = 0.63) of foraging turtles originate from the d’Entrecasteaux stock. Conclusions The larger contribution is estimated to be from a large rookery from New Caledonia, but smaller contributions are suggested from other rookeries in the South Pacific. Implications Marine conservation policies in New Caledonia need to consider the links between the foraging and nesting populations of C. mydas in New Caledonia and other rookeries and foraging grounds in the Coral Sea.

Spatial and temporal genetic variation among size classes of green turtles (Chelonia mydas) provides information on oceanic dispersal and population dynamics

“…In addition, we increased the sample size from some rookeries and included samples from 3 new rookeries: Browse Island in Western Australia, Cocos (Keeling) Island, and Cobourg Peninsula in the Northern Territory. We also used data from the published literature for rookeries in Palau, Yap, Northern Mariana Islands, Guam, Marshall Islands, American Samoa, New Caledonia and French Polynesia (Dutton et al 2014) as well as additional samples from New Caledonia, the Chesterfield Islands and Vanuatu (Read et al 2015). Additional samples from 32 nesting females collected from Raine Island (nGBR) in 2008 were analysed to assess whether there was temporal variability in the genetic structure of the nGBR nesting population (Table S1 in the Supplement at www.int-res.com/ articles/ suppl/ m543 p241 _supp.xlsx).…”

Seascape Genetics and the Spatial Ecology of Juvenile Green Turtles

“…The maternally inherited mitochondrial (mt)DNA control region sequences have been used extensively in sea turtles [21], and elucidate the connectivity between nesting and foraging areas [22,23]. When the genetic stock structure of breeding populations are known (and sufficiently differentiated), they can be used as a reference to trace back the natal origin of turtles using a mixed stock analysis (MSA) [24,25].…”

Advances in the Application of Genetics in Marine Turtle Biology and Conservation

“…These studies have shown considerable variation in results, with some foraging ground aggregations being composed mostly of turtles from the nearest stock (see Glossary) such as Hawaii, Aru, Gulf of Carpentaria, and the northern and southern Great Barrier Reef Dethmers et al, 2010;Jensen et al, 2016a), while other aggregations include significant numbers of turtles from distant stocks over 2,000 km away such as Palmyra, New Caledonia, Colombia and Japan (Amorocho et al, 2012;Nishizawa et al, 2013;Naro-Maciel et al, 2014b;Read et al, 2015). A similar pattern is evident in the Atlantic basin where transatlantic dispersal has been identified from Suriname to the West coast of Africa and from rookeries in western Africa to the Brazilian coast (Monzón-Argüello et al, 2010).…”

“…Since then, studies including additional beaches in Taiwan (Cheng et al, 2008) and Japan (Nishizawa et al, 2011;Hamabata et al, 2013) have shown population differentiation between rookeries separated by no more than 150 km, identifying six new MUs in the Northwest Pacific. Recent regional analyses of Southwest and South-central Pacific green turtle rookeries also filled a significant gap across a large portion of the western Pacific and identified seven MUs Read et al, 2015). In contrast, in the central and eastern Pacific only five MUs have been identified, with no genetic differentiation detected between neighboring rookeries in the Hawaiian archipelago (>500 km), the Revillagigedo Islands (∼400 km), or between rookeries in the Galapagos and mainland Ecuador (>1,000 km) (Dutton et al, 2014a;Chaves et al, 2017).…”

“…With the advancements defining rookery population structure across the Pacific, an increasing number of foraging grounds have now been analyzed using MSA across northern Australia (Dethmers et al, 2010), Southeast Asia (Jensen et al, 2016b;Joseph and Nishizawa, 2016), Southwest Pacific Ocean (Read et al, 2015;Jensen et al, 2016a), Northwest Pacific Ocean (Nishizawa et al, 2013), Central Pacific Naro-Maciel et al, 2014b), and the East Pacific (Amorocho et al, 2012;Chaves et al, 2017). These studies have shown considerable variation in results, with some foraging ground aggregations being composed mostly of turtles from the nearest stock (see Glossary) such as Hawaii, Aru, Gulf of Carpentaria, and the northern and southern Great Barrier Reef Dethmers et al, 2010;Jensen et al, 2016a), while other aggregations include significant numbers of turtles from distant stocks over 2,000 km away such as Palmyra, New Caledonia, Colombia and Japan (Amorocho et al, 2012;Nishizawa et al, 2013;Naro-Maciel et al, 2014b;Read et al, 2015).…”