Genetic Analysis of the Kemp's Ridley Sea Turtle (Lepidochelys Kempii) and Estimates of Effective Population Size

Genetic Analysis of the Kemp's Ridley Sea Turtle (Lepidochelys Kempii) and Estimates of Effective Population Size
Author: Sarah Holland Stephens
Publisher:
Total Pages:
Release: 2003
Genre:
ISBN:

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The critically endangered Kemp's ridley sea turtle experienced a dramatic decline in population size (demographic bottleneck) between 1947 and 1987 from 160,000 mature individuals to less than 5000. Demographic bottlenecks can cause genetic bottlenecks where significant losses of genetic diversity occur through genetic drift. The loss of genetic diversity can lower fitness through the random loss of adaptive alleles and through an increase in the expression of deleterious alleles. Molecular genetic studies on endangered species require collecting tissue using non-invasive or minimally invasive techniques. Such sampling techniques are well developed for birds and mammals, but not for sea turtles. The first objective was to explore the relative success of several minimally invasive tissue-sampling methods as source of DNA from Kemp's ridley sea turtles. Tissue sampling techniques included; blood, cheek swabs, cloacal swabs, carapace scrapings, and a minimally invasive tissue biopsy of the hind flipper. Single copy nuclear DNA loci were PCR amplified with turtle-specific primers. Blood tissue provided the best DNA extractions. Additionally, archival plasma samples are shown to be good sources of DNA. However, when dealing with hatchlings or very small individuals in field situations, the tissue biopsy of the hind flipper is the preferred method. This study's main focus was to evaluate whether the Kemp's ridley sea turtle sustained a measurable loss of genetic variation resulting from the demographic bottleneck. To achieve this goal, three alternative approaches were used to detect a reduction in Kemp's ridley's effective population size (Ne) from microsatellite data. These approaches were 1) Temporal change in allele frequencies, 2) An excess of heterozygotes in progeny, and 3) A mean ratio (M) of the number of alleles (k) to the range of allele size (r). DNA samples were obtained from Kemp's ridleys caught in the wild. PCR was used to amplify eight microsatellite loci and allele frequencies were determined. Data from only four microsatellites could be used. Although the reduced number of loci was a limiting factor in this study, the results of all three approaches suggest that Kemp's ridley sustained a measurable loss of genetic variation due to the demographic bottleneck.

Population Dynamics and Movements of the Kemp's Ridley Sea Turtle, Lepidochelys Kempii, in the Northwestern Gulf of Mexico

Population Dynamics and Movements of the Kemp's Ridley Sea Turtle, Lepidochelys Kempii, in the Northwestern Gulf of Mexico
Author: Erin E. Seney
Publisher:
Total Pages: 168
Release: 2008
Genre: Lepidochelys kempii
ISBN:

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The Kemp0́9s ridley sea turtle, Lepidochelys kempii, is recovering from devastating declines that reduced nesting activity from a single-day estimate of 10,000- 40,000 females in 1947 to fewer than 300 during all of 1985. Nesting beach monitoring is crucial to estimating population size and reproductive activity, but in-water data are essential for understanding population dynamics and evaluating management strategies. Hook-and-line, stranding, and nesting records, satellite telemetry, and diet analyses were used to characterize ridley population dynamics and movements in the northwestern Gulf of Mexico during 2003-2007. Recreational hook-and-line captures comprised approximately one third of non-nesting encounters along Galveston and Jefferson Counties, Texas. The hook-and-line dataset displayed similar geographical and monthly trends to that of strandings, but was devoid of pelagic-stage, subadult, and adult ridleys. Coastal and bay waters along the upper Texas and western Louisiana coasts were utilized by immature ridleys during warmer months. Nesting occurred along Galveston Island on both armored and unarmored beaches. Inter-nesting females exhibited fidelity to Galveston during nesting season and subsequently migrated to federal waters offshore Louisiana. Crabs were important components of benthic-stage (>25 cm SCL) ridley diet, while worm tubes were targeted by some individuals. Short satellite track durations for immature ridleys precipitated examinations of biofouling, attachment protocols, and turtle excluder device (TED) interactions. Antifouling paints drastically reduced fouling of transmitters. A less-rigid neoprene attachment method was developed to increase transmitter retention on fast-growing juveniles, but further trials are necessary. Transmitters were not damaged or lost during TED trials, but turtle escape times increased when transmitters wedged between TED bars. Projected population growth will increase numbers of Kemp0́9s ridleys utilizing the Gulf of Mexico and interacting with human activities. Future research should examine year-round distribution and abundance of all life history stages and further characterize recreational hook-and-line capture, nesting activity, movements, and diet. Education efforts targeting the beach-going public, beach residents and workers, and the recreational fishing sector should be employed to promote sea turtle reporting and minimize negative interactions. State and federal managers should examine anthropogenic impacts within the region and determine the need for mitigation and/or regulations to promote continued species recovery.

Population Dynamics and Movements of the Kemp's Ridley Sea Turtle, Lepidochelys Kempii, in the Northwestern Gulf of Mexico

Population Dynamics and Movements of the Kemp's Ridley Sea Turtle, Lepidochelys Kempii, in the Northwestern Gulf of Mexico
Author: Erin Elizabeth Seney
Publisher:
Total Pages:
Release: 2010
Genre:
ISBN:

Download Population Dynamics and Movements of the Kemp's Ridley Sea Turtle, Lepidochelys Kempii, in the Northwestern Gulf of Mexico Book in PDF, Epub and Kindle

The Kemp0́9s ridley sea turtle, Lepidochelys kempii, is recovering from devastating declines that reduced nesting activity from a single-day estimate of 10,000- 40,000 females in 1947 to fewer than 300 during all of 1985. Nesting beach monitoring is crucial to estimating population size and reproductive activity, but in-water data are essential for understanding population dynamics and evaluating management strategies. Hook-and-line, stranding, and nesting records, satellite telemetry, and diet analyses were used to characterize ridley population dynamics and movements in the northwestern Gulf of Mexico during 2003-2007. Recreational hook-and-line captures comprised approximately one third of non-nesting encounters along Galveston and Jefferson Counties, Texas. The hook-and-line dataset displayed similar geographical and monthly trends to that of strandings, but was devoid of pelagic-stage, subadult, and adult ridleys. Coastal and bay waters along the upper Texas and western Louisiana coasts were utilized by immature ridleys during warmer months. Nesting occurred along Galveston Island on both armored and unarmored beaches. Inter-nesting females exhibited fidelity to Galveston during nesting season and subsequently migrated to federal waters offshore Louisiana. Crabs were important components of benthic-stage (>25 cm SCL) ridley diet, while worm tubes were targeted by some individuals. Short satellite track durations for immature ridleys precipitated examinations of biofouling, attachment protocols, and turtle excluder device (TED) interactions. Antifouling paints drastically reduced fouling of transmitters. A less-rigid neoprene attachment method was developed to increase transmitter retention on fast-growing juveniles, but further trials are necessary. Transmitters were not damaged or lost during TED trials, but turtle escape times increased when transmitters wedged between TED bars. Projected population growth will increase numbers of Kemp0́9s ridleys utilizing the Gulf of Mexico and interacting with human activities. Future research should examine year-round distribution and abundance of all life history stages and further characterize recreational hook-and-line capture, nesting activity, movements, and diet. Education efforts targeting the beach-going public, beach residents and workers, and the recreational fishing sector should be employed to promote sea turtle reporting and minimize negative interactions. State and federal managers should examine anthropogenic impacts within the region and determine the need for mitigation and/or regulations to promote continued species recovery.

Biology and Conservation of Ridley Sea Turtles

Biology and Conservation of Ridley Sea Turtles
Author: Pamela T. Plotkin
Publisher: JHU Press
Total Pages: 382
Release: 2007-03
Genre: Nature
ISBN: 9780801886119

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Here Plotkin and her colleagues reveal the nature of these species and the steps needed to make sure they remain a permanent part of the marine environment.