[PDF] Population Sex Ratio Of The Kemps Ridley Sea Turtle Lepidochelys Kempii eBook

Author : Elizabeth Bevan (Biologist)
Publisher :
Page : 128 pages
File Size : 48,77 MB
Release : 2013
Category : Lepidochelys kempii
ISBN :

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The Kemp's ridley (Lepidochelys kempii) sea turtle neared extinction during the mid-1980s, but due to intense conservation efforts its population is now gradually recovering. Hatchling sex ratios and natural predation on nests and hatchlings have been monitored at Rancho Nuevo, Mexico to optimize this species' recovery. Sand and nest temperatures were evaluated for the 2009-2012 nesting seasons in the egg corrals and on the nesting beach. Temperatures were cool during the start of the nesting seasons (i.e. below pivotal temperature), and gradually rose and were at or above pivotal temperatures by mid-May. Temperatures remained warm for the remainder of the nesting seasons, except when tropical weather systems impacted the area and lowered incubation temperatures. Thus, a female bias was predicted from 2009 -2012, but some nests early in the nesting season or those subjected to tropical weather systems during the middle third of incubation 2012 nesting seasons in the egg corrals and on the nesting beach. Temperatures were cool during the start of the nesting seasons (i.e. below pivotal temperature), and gradually rose and were at or above pivotal temperatures by mid-May. Temperatures remained warm for the remainder of the nesting seasons, except when tropical weather systems impacted the area and lowered incubation temperatures. Thus, a female bias was predicted from 2009 -2012, but some nests early in the nesting season or those subjected to tropical weather systems during the middle third of incubation were predicted to produce males. The nesting beach was also warm (suggesting a female bias) but it was cooler than the egg corrals. Sex ratios for the egg corrals and nesting beach were recalculated using incubation temperatures that were raised by 1 degree C to hypothetically simulate the effects of increasing global temperatures on hatchling sex ratios. Increases in sand temperatures due to global climate change could result in extreme female biases for the egg corrals and the nesting beach. Subsets of in situ nests from arribadas in 2011 and 2012 were monitored for predation throughout incubation and hatching success was determined following emergence. Predation on in situ nests was low and hatching success relatively high. Additionally, survival of hatchlings during seafinding was evaluated for in situ nests in 2012 and results suggest relatively high survival rates. Evaluation of predation data supports the concept that arribadas may achieve predator satiation, thus enhancing nest and hatchling survival. Leaving arribada nests in situ may be an effective conservation strategy. These sex ratio and predation studies provide data to facilitate an effective transition from the use of egg corrals back to the use of the natural nesting beach as the Kemp's ridley recovers.

Author : Erin E. Seney
Publisher :
Page : 168 pages
File Size : 50,64 MB
Release : 2008
Category : 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.

Author : Erin Elizabeth Seney
Publisher :
Page : pages
File Size : 10,15 MB
Release : 2010
Category :
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.

Author : Sarah Holland Stephens
Publisher :
Page : pages
File Size : 24,47 MB
Release : 2003
Category :
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.

Author : National Research Council
Publisher : National Academies Press
Page : 174 pages
File Size : 30,63 MB
Release : 2010-10-07
Category : Science
ISBN : 0309152550

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All six species of sea turtles found in U.S. waters are listed as endangered or threatened, but the exact population sizes of these species are unknown due to a lack of key information regarding birth and survival rates. The U.S. Endangered Species Act prohibits the hunting of sea turtles and reduces incidental losses from activities such as shrimp trawling and development on beaches used for nesting. However, current monitoring does not provide enough information on sea turtle populations to evaluate the effectiveness of these protective measures. Sea Turtle Status and Trends reviews current methods for assessing sea turtle populations and finds that although counts of sea turtles are essential, more detailed information on sea turtle biology, such as survival rates and breeding patterns, is needed to predict and understand changes in populations in order to develop successful management and conservation plans.