Population sex ratio of the Kemp's ridley sea turtle (Lepidochelys kempii) : problems in population modeling /
The Kemp's ridley (Lepidochelys kempii) is the most endangered sea turtle species in the world and has been the focus of intense recovery efforts in the United States and Mexico. The objectives of this research were to 1) establish testosterone radioimmunoassay sexing criteria for L. kempii; 2)...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2000.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=731990021&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | The Kemp's ridley (Lepidochelys kempii) is the most endangered sea turtle species in the world and has been the focus of intense recovery efforts in the United States and Mexico. The objectives of this research were to 1) establish testosterone radioimmunoassay sexing criteria for L. kempii; 2) estimate a sex ratio for the L. kempii population; 3) develop a preliminary population model for L. kempii; and 4) assess the impact of various sex ratios on L. kempii population dynamics. This study utilized radioimmunoassay (RIA) determination of blood plasma testosterone (T) concentration in conjunction with limited laparoscopy to sex captured L. kempii. These data yielded a plasma T sexing criteria for L. kempii of [] 12 pg/ml for females and [] 18 pg/ml for males. The sexing criteria applied to all L. kempii for which blood was obtained resulted in 134 females, 95 males and 10 indeterminable (1.5F:1.0M). The capture lot included 20 headstand L. kempii, including 2 males and 18 females, resulting in 132 wild females and 99 wild males (1.3F:1.0M). These results and scientific literature were used to develop a preliminary population model for L. kempii. The final model was used to assess the impact of various population sex ratio values upon Kemp's ridley sea turtle demography. Two scenarios were tested using the model. One in which proportion of adult males in the population have no effect on hatchling production and another where productivity is a function of the relative abundance of adult males. Under the first scenario, the model suggests that a greater proportion of females in the population dramatically enhances hatchling production, yielding a 271% increase in predicted nests after 50 years with a sex ratio of 3F:1M and an 81% decrease with 1F:3M. The second scenario, in which reproductive output is a function of male availability, was approximated by assuming a linear relationship between increasing proportion of males and reproductive success. Strong female bias (3F:1M) resulted in a 20% decrease in the population while a male bias (1F:3M) yielded a 62% decrease. The greatest rate of reproductive return was achieved with a sex ratio of 1.28F:1M (56.2% female). |
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| Item Description: | Vita. "Major Subject: Wildlife and Fisheries Sciences". |
| Physical Description: | xii, 124 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 96-119). |