New Perspectives on the Pelagic Stage of Sea Turtle Development

Abstract

: An original difficulty in accepting the idea of a pelagic diwelopmental period for sea turtles was to explain bow food could be found in reliable supply in the open ocean The uncertainty that this introduced was removed when I belatedly came to appreciate the prevalence and diversity of convergences where downwelling gathers and aligns buoyant material, including the dispersed food mources of the surface waters. Thus, it now seems clear that an essential factor in the survival of young sea turtles–and of other elements of the epipelagic; open‐ocean fauna as well–is the accessibility of a front; where inanimate debris and any floating animal or plant will be gathered to. This new evidence of complexity in the lost‐year ecology of sea turtles has important implications for their conservation and management. It is now obvious that when young cultured sea turtles are released in so‐called bead‐starting projects, the release sites ought to be chosen with the greatest care. Shores located at a distance from any major current or its eddy ought to be avoided. It is also necessary to avoid release localities where the convergence habitat may carry heavy loads of pollutants. Results of the present work reveal an urgent need for further study of sea turtle life cycles, with special attention to their developmental ecology The growing evidence for a more protracted pelagic stage, during which the juvenile turtles are passive migrants in fronts that are increasingly invaded by debris and toxic wastes, emphasizes the need for a better understanding by marine biologists of the organization of the driftline habitat and the behavioral ecology of its occupants Until these studies of the oceanography and biology of driftlines are done, we are bound to remain peculiarly ignorant of the ecologic organization of three‐fifths of the surface of the earth.

Oceanic survival and movements of wild and captive-reared immature green turtles (Chelonia mydas) in the Indian Ocean

“…Primary production in the western tropical Indian Ocean is generally low (Humbert-Droz and Jullien, 1983), but food for marine animals accumulates along thermal fronts, convergence and divergence areas (Yoder et al, 1994). These zones also concentrate various floating objects, algae (Carr, 1987) and debris (Nichols et al, 2000), which provide shelter for marine animals. More generally, high abundances of large pelagic species are often associated to hydrological discontinuities in the ocean, like fronts, eddies and upwellings (Fonteneau et al, 2000;Herron et al, 1989;Olson and Polovina, 1999;Power and May, 1991).…”

“…Mature individuals periodically migrate between breeding and foraging sites that may be thousands of kilometres apart. Immature green turtles (Chelonia mydas) leave the nesting site as hatchlings and live in the open ocean at least a year, sometimes associated with algae rafts (Carr and Meylan, 1980;Carr, 1987). During this pelagic stage, they are mostly carnivorous.…”

“…Between 3 and 5 years of age, they move to coastal habitats, becoming omnivorous and then herbivorous (Bjorndal, 1985). The spatial distribution and migration patterns of immature sea turtles are thought to depend upon environmental factors like oceanic fronts and gyres (Carr, 1987;Polovina et al, 2000). However, movements of immature turtles are poorly understood, as they can only be observed when they depart their place of birth, or when they are incidentally caught by offshore fisheries (Polovina et al, 2000).…”

Population structure and conservation implications for the loggerhead sea turtle of the Cape Verde Islands

“…Relatively little is known about the location of posthatchling and small pelagic juveniles during the subsequent ''lost years'', where they may circulate in oceanic gyres and drift with currents (Bolten 2003). However, loggerhead turtles born at Florida (USA) rookeries are known to inhabit the pelagic zone of the North Atlantic gyre system for several years (Carr 1986). Next, an unknown proportion of juvenile turtles recruits to neritic habitats closer to their natal beaches, a behaviour known as juvenile natal homing (Bolten 2003;Bowen et al 2004), while others continue to feed in the high seas (Musick and Limpus 1997).…”

Geo-political genetics: Claiming the commons through species mapping

“…Hatchling turtles have been particularly problematic. Following their emergence from the nest and a 2-3 day 'swimming' frenzy to take them beyond coastal waters, hatchlings disappear for several years (called 'the lost year' ), when it is believed they passively drift in pelagic oceanic currents (Carr 1987). After an unknown period of time, they return inshore to foraging grounds as juveniles, where they can be more easily found and studied.…”