Turtle! Turn and migrate to the SE Pacific!

By Dave Armstrong - 20 Nov 2014 10:21:0 GMT
Turtle! Turn and migrate to the SE Pacific!

Would you be happy to be trailed around by snorkelers or hit by jet skis every time you surfaced? The green turtle is already endangered, but seems to be coping with these trials in one area of the SE Pacific in this heartening study; Green turtle image; Credit: © Shutterstock

The green turtle is often forgotten in the midst of critically-endangered species and those that live in restricted habitats.Chelonia mydas needs suitable areas to gather in the South Pacific as well as beaches to lay eggs. The age of individuals after they distribute themselves as neonates determines where they aggregate, according to a new study .

Ximena Velez-Zuazo, Javier Quiñones and their colleagues work largely at the University of Puerto Rico-Rio Piedras and Shaleyla Kelez ecOceánica in Perú, but it is the Peruvian coast where the turtles have been found. They publish this paper, Fast Growing, Healthy and Resident Green Turtles ------- in PLOS ONE.

The juvenile oceanic phase of many turtle life stories lasts for years. The green turtle follows this up with this paper’s specific juvenile, sub-adult and adult neritic (coastal) phases that have critical requirements. Feeding in sea-grass beds and even mangroves is well-known for this species, but mixed bottoms and reefs are also used, as long as food is available to colour that green body! They spend a lot of time in these neritic areas, allowing our researchers access to data here that is invaluable in countering their endangered status.

The SE Pacific has large numbers of turtles compared to elsewhere. Northward upwelling waters characterised by the Humboldt Current provide habitat from central Chile to northern Perú. Towards Ecuador, the water is warmed by the tropics and is less productive or suitable. Nesting rookeries occur on the northern equatorial coast, although some believe that migration is restricted by surface temperatures.

Peruvian habitats could be important feeding grounds for the species. Gut contents show that the northern and south-central diets differ. The food resources obviously vary for these 2 populations or within the life history of the turtle. The paper suggests that recruiting juveniles occur in the development habitats in the south while the northern habitats are frequented by all 3 of the age-groups studied.

The big news is the occurrence of 2 aggregations at the upwelling Humboldt-Equatorial site. The study here compares (1) population parameters at each site such as size frequencies, growth rates, and sex ratios in adults, and (2) time of residency. The sites were El Ñuro which was an ecotone or transitional site in northern Peru and the upwelling site of Paracas in central Peru.

228 turtles were captured and examined (including 51 recaptures.) They must have enjoyed the experience. 1 tagged individual was found dead at El Ñuro and one other, while some extra interest was generated with the capture of one Olive Ridley sea turtle (Lepidochelys olivacea) El Ñuro turtles were heavier and larger and resident for longer periods, ranging up to 107cm in length. Paracas individuals grew to 84.5cm - on average, 15cm shorter.

As a first for the SE Pacific, this research is absolutely invaluable. It proves that juveniles inhabit the “feeding-up” upwelling zone at Paracas. These animals were benthic in habit. El Ñuro had mainly sub-adults in residence. Happily, these figures on the population provide the highest values reported in the east of the ocean. They also illustrate well that the theory of development habitats holds true. Despite a big by-catch problem, the green turtle seems relatively safe there because of the rich Humboldt Current. Chrysaora plocamia is the large jellyfish preyed upon here in the summer, while for some potential algal foods, Caulerpa sp is very common in El Ñuro, despite the sparse seaweed abundance there. Fish and squid discards near a pier were also suspected as a potential food source. More studies are obviously required on precise diet, but it can’t be denied that these chelonians are growing faster than others in this cooler, richer environment.

The prospects for beleaguered Caribbean green turtles could be enhanced by this study of healthier population. However the emphasis in this case is on improving the lot of this species in the SE Pacific. It is endangered, by by-catch, jet skis, ingestion of plastics and even snorkelling tourists, although high populations of people can be encouraged to admire the beast, work in the ocean and be educated into compliance on protection. More on our vast and growing collection of turtle information can be found here on the green and all the other species.