Andre M. Landry

Organohalogen contaminants in blood of Kemp's ridley (Lepidochelys kempii) and green sea turtles (Chelonia mydas) from the Gulf of Mexico.

The threat that exposure to organohalogen (OH) contaminants poses to endangered populations of Kemps ridley (Lepidochelys kempii) and green sea turtles (Chelonia mydas) is not well understood, partly because few OH data are available. Blood samples from live juvenile and sub-adult L. kempii (n = 46) and C. mydas (n = 9) from the Gulf of Mexico and from L. kempii from the southeastern US coast (n = 3) were extracted using microwave-assisted extraction, and analyzed by large volume injection gas chromatography-mass spectrometry for 85 polychlorinated biphenyls (PCBs), 25 organochlorine pesticides (OCPs) and 27 polybrominated diphenyl ethers (PBDEs). Plasma chemistries, hematology and immune responses were also assessed. Concentrations of SigmaPCBs (geometric mean, range: 3190 pg g(-1), 227-21590 pg g(-1) blood), SigmaDDTs (geometric mean, range: 541 pg g(-1), 161-4310 pg g(-1) blood) and OCPs in L. kempii from the Gulf were comparable to those reported in L. kempii from the Atlantic. SigmaPBDEs were detected in all samples (geometric mean, range: 146 pg g(-1), 19.5-1450 pg g(-1) blood), with PBDE 47, 99, 100, 153 and 154 being the predominant congeners. SigmaPCBs, SigmaDDTs and Sigmachlordanes were one order of magnitude lower in green turtles, and SigmaPBDE concentrations were lower by half due to trophic level differences. L. kempii from the southeast USA had higher percentages of highly chlorinated PCBs indicating exposure to Aroclor 1268. Blood urea nitrogen was positively correlated to Sigmachlordanes, and SigmaPCBs were inversely correlated to creatine phosphokinase in L. kempii. These data help establish baseline contaminant concentrations in live L. kempii and C. mydas.

Kemp's Ridley Sea Turtle (Lepidochelys kempii) Age at First Nesting

Abstract Kemps ridley sea turtle (Lepidochelys kempii) age at first nesting is the age at which an individual female successfully nests for the first time. This commentary recommends determination of the statistical distribution of age at first nesting, estimation of central tendency, and variability of age at first nesting, and application of these estimates in future age-based and life stage–based demographic modeling, as substitutes for parameter estimates based on age at sexual maturity or age at first reproduction. We hope that our commentary will encourage discussion and research on age at first nesting and its application to demographic modeling of the Kemps ridley population.

Novel Use of a Shark Model to Elicit Innate Behavioral Responses in Sea Turtles: Application to Bycatch Reduction in Commercial Fisheries

Abstract Sea turtle bycatch in commercial fisheries is a serious global problem. An estimated 250,000 loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles are taken each year as incidental catch by the pelagic longline fishing industry. Studies have examined various deterrents for their potential to repel sea turtles from the vicinity of fishing operations; visual deterrents such as shark models/silhouettes and gillnet illumination have shown the most promise. However, given the difficulty of directly observing sea turtle behavior in the wild, laboratory trials are crucial for characterizing the sea turtle response to shark models. The present study examined the response of 42 captive-reared juvenile loggerhead sea turtles to a shark model in a controlled laboratory setting. Loggerheads exhibited defensive behavior toward the shark model, taking significantly more time to bite squid bait beneath the shark model than that for squid beneath a control object (sphere) and bare squid. Also, the turtles approached the shark model less often and exhibited more defensive carapace turns toward the shark model. Although the shark model in this study elicited avoidance behavior in loggerhead sea turtles, further research is needed to identify plausible applications, which would reduce sea turtle bycatch while maintaining target fish catch rates. It may be possible to develop a “Childrens Day Koinobori kite” (a three-dimensional kite) in the shape of a shark that would unfurl and “fly” underwater and could possibly clip to main or float lines in commercial fisheries.

An Assessment of Green Turtle (Chelonia mydas) Stocks Along the Texas Coast, with Emphasis on the Lower Laguna Madre

Abstract The in-water status of green turtles (Chelonia mydas) in the northwestern Gulf of Mexico has received comparatively little attention in the management and conservation of this species in US waters. We addressed this void via entanglement netting surveys at 3 estuarine areas (Lavaca-Matagorda Bay, the Aransas Bay complex, and the lower Laguna Madre [LLM]) to assess trends in the relative abundance, distribution, and size composition of green turtles in Texas inshore waters during 1991–2010. Overall catch per unit effort (CPUE) in the LLM (1.5 turtles/km-hr) was significantly higher than that observed in the other 2 estuaries and corresponded to general climate patterns and seagrass areal coverage along the Texas coast. Yearly CPUE of green turtles from the LLM exhibited a significant exponential increase from 1991 to 2010, despite variability in capture rate during recent years. Mean straight carapace length (SCL) of green turtles was statistically similar across the 3 study areas and indicative of dominance by juvenile individuals (LLM mean  =  42.2 cm SCL). Historical green turtle size data in the LLM also reveal an overall decreasing trend in mean SCL and shift toward an increased percentage of smaller individuals (30–39.9- and 40–49.9-cm SCL size classes). Also, sighting frequency of postpelagic green turtles at the Brazos-Santiago Pass jetties within the LLM during 2009 was roughly 9 times that reported for comparable months during 1992–1993. These results are indicative of enhanced recruitment of neritic green turtles to the northwestern Gulf of Mexico, most likely due to elevated nesting productivity at beaches in Mexico, Florida, the Caribbean, and the western Atlantic. Overall, the lower Texas coast serves as an important developmental foraging habitat for an increasing population of juvenile green turtles in the northwestern Gulf of Mexico.

Variability in age and size at maturation, reproductive longevity, and long-term growth dynamics for Kemp's ridley sea turtles in the Gulf of Mexico

Effective management of protected sea turtle populations requires knowledge not only of mean values for demographic and life-history parameters, but also temporal and spatial trends, variability, and underlying causes. For endangered Kemp’s ridley sea turtles (Lepidochelys kempii), the need for baseline information of this type has been emphasized during attempts to understand causes underlying the recent truncation in the recovery trajectory for nesting females. To provide insight into variability in age and size at sexual maturation (ASM and SSM) and long-term growth patterns likely to influence population trends, we conducted skeletochronological analysis of humerus bones from 333 Kemp’s ridleys stranded throughout the Gulf of Mexico (GOM) from 1993 to 2010. Ranges of possible ASMs (6.8 to 21.8 yr) and SSMs (53.3 to 68.3 cm straightline carapace length (SCL)) estimated using the “rapprochement” skeletal growth mark associated with maturation were broad, supporting incorporation of a maturation schedule in Kemp’s ridley population models. Mean ASMs estimated from rapprochement and by fitting logistic, generalized additive mixed, and von Bertalanffy growth models to age and growth data ranged from 11 to 13 yr; confidence intervals for the logistic model predicted maturation of 95% of the population between 11.9 and 14.8 yr. Early juvenile somatic growth rates in the GOM were greater than those previously reported for the Atlantic, indicating potential for differences in maturation trajectories between regions. Finally, long-term, significant decreases in somatic growth response were found for both juveniles and adults, which could influence recruitment to the reproductive population and observed nesting population trends.

Swimming performance of captive-reared Kemp's ridley sea turtles Lepidochelys kempi (Garman)

Swimming performance of Kemps ridley sea turtles Lepidochelys kempi (Garman) was evaluated over a 6-month period to determine whether an exercise regine increased swimming capacity in captive reared turtles. Three experimental treatments included: (1) turtles exercised twice weekly and exposed to a weekly stamina test; (2) turtles subjected only to a weekly stamina test; and (3) non-exercised controls exposed to a single stamina test at the end of the study. No statistically significant difference in swimming capacity was detected between treatments 1 and 2, although treatment 1 turtles achieved higher performance levels than those from treatment 2. However, treatment 1 turtles exhibited fewer breaths/min (BRM) and foreflipper strokes/min (FSM) during stamina tests than did treatment 2 turtles. In contrast, control turtles (treatment 3) were unable to achieve the minimum swimming performance level. These results indicate that the swimming performances of exercised turtles significantly improved during captive rearing. The possible effects of an exercise regime on post-release survival potential are discussed.