First Advisor

Deborah Duffield

Date of Publication


Document Type


Degree Name

Master of Science (M.S.) in Biology






Bottlenose dolphin -- Texas -- Matagorda Bay -- Genetics



Physical Description

1 online resource (v, 96 p.)


A long-term photoidentification study was initiated in response to an unusually high incidence of bottlenose dolphin mortality between Corpus Christi and Matagorda Bays, Texas. Blood samples from 36 captured and released animals were analyzed using three genetic techniques; mtDNA haplotyping, nuclear DNA fingerprinting and electrophoretic analysis of hemoglobin. Two Hinf I mtDNA haplotypes previously described in bottlenose dolphins from other locations within the Gulf of Mexico were discovered. Similarity Indices (SI) were calculated based on nuclear DNA fingerprinting data. These SI values were used as a relative measure of relatedness between two individuals run on the same gel. Means of pairwise similarity indices were determined for the overall sample and various subgroupings. These subgroupings were based on such factors as sex, reproductive condition, mtDNA haplotypes and behavioral characteristics. All but one of the samples had hemoglobin profiles characteristic of inshore dolphins. The one exception was an individual with a hemoglobin profile reflecting an intrusion of offshore alleles into this population. A significant difference was revealed between the mean SI values for subgroupings based on the two mtDNA haplotypes. Further analysis revealed a correlation between this division and an observed behavioral partitioning. These data suggest a division in the samples characteristic of an inshore or locally resident group and an offshore or more migratory group. Differences in learned foraging strategies are proposed as a possible explanation for observed differences in philopatry between the two groups of animals. Inshore and offshore animals are not believed to be genetically isolated based on hemoglobin data previously mentioned and findings from a separate study of chromosomal markers. Evidence for genetic exchange between neighboring communities is found in a review of the literature pertaining to migration capabilities of the species. A clinal distribution pattern of mtDNA haplotypes seen throughout the Gulf of Mexico and along the south-eastern Atlantic seaboard is presented. A potential correlation is drawn between haplotype distribution patterns and major oceanographic features. Studies of specific geographical regions, such as the one undertaken in Matagorda Bay, are deemed useful for the future mapping of population subdivisions and stock definition throughout the Gulf of Mexico.


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