Search

Fisheries bycatch is posited to be a leading cause of decline in abundance of Atlantic leatherback turtles (Dermochelys coriacea). However, although this species regularly interacts with fisheries across its range, movements and postrelease survival of leatherbacks remain largely unstudied. Such research is lacking because sampling opportunities are unpredictable and logistically challenging. Here, movements of 4 leatherbacks equipped with satellite tags following incidental capture in fixed-gear fisheries in Nova Scotia, Canada, are presented, alongside results from previous post-entanglement tracking of 15 leatherbacks tagged throughout the Atlantic Ocean. Mean tracking duration after tagging was 232.58 d (standard deviation 165.61; sample size=19), comparable with what has been reported for fishery-independent deployments of satellite tags on leatherbacks. This result indicates that, provided they are released carefully and completely from fishing gear, many leatherbacks survive entanglement events without apparent long-term effects. [ABSTRACT FROM AUTHOR]

The leatherback sea turtle, Dermochelys coriacea (Vandelli, 1761), has the most extensive range of any reptile, migrating from tropical and subtropical nesting areas to distant foraging habitats, including those in temperate and even boreal waters. This implies flexible thermal functioning. It has been inferred that leatherbacks support active foraging by keeping warm in cold water, rather than becoming lethargic as other marine turtles do. However, data consistent with this view have come from captive turtles in unnatural and stressful conditions. In the present case, foraging leatherbacks were captured at sea off Nova Scotia and their body temperature recorded within 10 min, before such large animals could change their body temperatures appreciably. Mean excess temperature over that of the sea surface (15.0–16.7 °C) averaged 8.2 °C. These results attest to, but underestimate, the capacity of free-swimming leatherbacks to keep warm in northern waters, as data from another turtle that was instrumented to record ocean temperature while diving revealed that leatherbacks foraging in this area at the same time of year may spend 40% of their time diving to waters cooler than the surface. [ABSTRACT FROM AUTHOR]

Typical chelonians have a rigid carapace and plastron that form a box-like structure that constrains several aspects of their physiology and ecology. The leatherback sea turtle, Dermochelys coriacea, has a flexible bony carapace strengthened by seven longitudinal ridges, whereas the plastron is reduced to an elliptical outer bony structure, so that the ventrum has no bony support. Measurements of the shell were made on adult female leatherbacks studied on the feeding grounds of waters off Nova Scotia (NS) and on breeding beaches of French Guiana (FG) to examine whether foraging and/or breeding turtles alter carapace size and/or shape. NS turtles exhibited greater mass and girth for a given curved carapace length (CCL) than FG turtles. Girth:CCL ratios rose during the feeding season, indicating increased girth. Measurements were made of the direct (straight) and surface (curved) distances between the medial longitudinal ridge and first right-hand longitudinal ridge (at 50% CCL). In NS turtles, the ratio of straight to curved inter-ridge distances was significantly higher than in FG turtles, indicating distension of the upper surfaces of the NS turtles between the ridges. FG females laid 11 clutches in the breeding season; although CCL and curved carapace width remained stable, girth declined between each nesting episode, indicating loss of mass. Straight to curved inter-ridge distance ratios did not change significantly during the breeding season, indicating loss of dorsal blubber before the onset of breeding. The results demonstrate substantial alterations in size and shape of female D. coriacea over periods of weeks to months in response to alterations in nutritional and reproductive status. [ABSTRACT FROM AUTHOR]