RV: Leatherback Population Structure (Atlantic), and other recent papers
- Colegas, a través de Widecats se está circulando el presente trabajo científico sobre las tortugas tora del Atlántico y su estructura poblacional.
De: Dr. Karen L. Eckert [mailto:keckert@...]
Enviado el: viernes, 15 de marzo de 2013 01:06 p.m.
Para: Karen Eckert Ph.D. - WIDECAST Executive Director
Asunto: Leatherback Population Structure (Atlantic), and other recent papers
Dear WIDECAST family, Please enjoy this latest publication co-authored by Dr. Benoit deThoisy, WIDECAST Country Coordinator in French Guiana! Hugs, Karen
Here are 3 other recent leatherback papers of interest:
Tapilatu RF, Dutton PH, Tiwari M, Wibbels T, Ferdinandus HV, Iwanggin WG, Nugroho BH (2013) Long-term decline of the western Pacific leatherback, Dermochelys coriacea: a globally important sea turtle population. Ecosphere.
PDF: http://www.seaturtle.org/PDF/TapilatuRF_2013_Ecosphere.pdf (668.3KB)
The leatherbacks nesting at Bird's Head Peninsula, Papua Barat, Indonesia, account for 75% of the total leatherback nesting in the western Pacific and represent the last sizeable nesting population in the entire Pacific.
Sporadic nest counts at Jamursba Medi Beach at Bird's Head have indicated a declining trend from the 1980s through 2004, although a relatively high amount of nesting has recently been documented at Wermon Beach, located 30 km east of Jamursba Medi. We used expanded year-round nesting surveys from
2005 to 2011 at these two primary nesting beaches to obtain more robust estimates of the nesting population size and to evaluate long-term nesting trends. We found a 29% decline in nesting at Jamursba Medi and a 52% decline at Wermon from 2005 through 2011. We found that the estimated annual number of nests at Jamursba Medi has declined 78.3% over the past 27 years (5.5% annual rate of decline) from 14,522 in 1984 to 1,596 in 2011. Nesting at Wermon has been monitored since 2002 and has declined 62.8% (11.6% annual rate of decline) from 2,994 nests in 2002 to 1,096 in 2011. Collectively, our findings indicate a continual and significant long term nesting decline of 5.9% per year at these primary western Pacific beaches since 1984.
Mark-recapture with PIT tags, initiated in 2003, resulted in the tagging of
1,371 individual nesting females as of March 2012. Observed clutch frequencies ranged from 3-10 per season with a mean of 5.5 ± 1.6 and, based on nest counts, provide an estimate of approximately 489 females nesting in 2011. The persistent and long term decline we report for the Bird's Head leatherback population follows other dramatic declines and extinctions of leatherback populations throughout the Pacific over the last 30 years. These findings highlight the urgent need for continued and enhanced conservation and management efforts to prevent the collapse of what might be the last remaining stronghold for leatherbacks in the Pacific.
Fiedler FN, Sales G, Giffoni BB, Monteiro-Filho ELA, Secchi ER, Bugoni L
(2012) Driftnet fishery threats sea turtles in the Atlantic Ocean.
Fisheries are recognised as a major threat to sea turtles worldwide. Oceanic driftnets are considered the main cause of the steep decline in Pacific Ocean populations of the leatherback sea turtle Dermochelys coriacea. The world's largest leatherback population nests in West Africa and migrates across the Atlantic Ocean to feed off the South American coast. There, the turtles encounter a range of fisheries, including the Brazilian driftnet fishery targeting hammerhead sharks. From 2002 to 2008, 351 sea turtles were incidentally caught in 41 fishing trips and 371 sets. Leatherbacks accounted for 77.3% of the take (n = 252 turtles, capture rate = 0.1405 turtles/km of net), followed by loggerheads Caretta caretta (47 individuals, capture rate = 0.0262 turtles/km of net), green turtles Chelonia mydas (27 individuals, capture rate = 0.0151 turtles/km of net) and unidentified hard-shelled turtles (25 individual, capture rate = 0.0139 turtles/km of net) that fell off the net during hauling. Immediate mortality (i.e., turtles that were dead upon reaching the vessel, excluding post-release mortality) was similar among the species and accounted for 22.2 to 29.4% of turtles hauled onboard.
The annual catch by this fishery ranged from 1,212 to 6,160 leatherback turtles, as estimated based on bootstrap procedures under different fishing effort scenarios in the 1990s. The present inertia in law and enforcement regarding gillnet regulations in Brazil could result in the reestablishment of the driftnet fishery, driving rates of leatherback mortality to levels similar to those observed in previous decades. This development could potentially lead to the collapse of the South Atlantic leatherback population, mirroring the decline of the species in the Pacific. In light of these potential impacts and similar threats to other pelagic mega fauna, we recommend banning this type of fishery in the region.
Galli S, Gaspar P, Fossette S, Calmettes B, Hays GC, Lutjeharms JRE, Luschi P (2012) Orientation of migrating leatherback turtles in relation to ocean currents. Animal Behavior.
PDF: http://www.seaturtle.org/PDF/GalliS_2012_AnimBehav.pdf (586.8KB)
During their offshore movements, leatherback turtles, Dermochelys coriacea, associate frequently with ocean currents and mesoscale oceanographic features such as eddies, and their movements are often in accordance with the current flow. To investigate how individual turtles oriented their
ground- and water-related movements in relation to the currents encountered on their journeys, we used oceanographic techniques to estimate the direction and intensity of ocean currents along the course of 15 leatherbacks tracked by satellite during their long-distance movements in the Indian and Atlantic Oceans. For all individuals a non-negligible component of active swimming was evident throughout the journeys, even when their routes closely followed the currents, but overall the turtle water-related orientation was random with respect to current directions. For turtles in the North Atlantic, the ground-related movements largely derived from the turtles' active swimming, while in the Indian Ocean currents contributed substantially to the observed movements. The same pattern was shown when distinct parts of the routes corresponding to foraging bouts and travelling segments were considered separately. These findings substantiate previous qualitative observations of leatherback movements, by revealing that turtles were not simply drifting passively but rather swam actively during most of their journeys, although with a random orientation with respect to currents. Our analysis did not provide any indication that leatherbacks were able to detect the current drift they were exposed to, further highlighting the navigational challenges they face in their oceanic wanderings.
Also, see http://www.newswise.com/articles/view/599650/?sc=sptp
Dr. Karen L. Eckert
Wider Caribbean Sea Turtle Conservation
1348 Rusticview Drive
Ballwin, Missouri 63011 USA
Tel: (314) 954-8571
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