Graduate Student Theses

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Now showing 1 - 5 of 10
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    Habitat Preference of the Daggerblade Grass Shrimp Palaemonetes pugio and Whether Field Preference is Correlated with the Trematode Parasite Microphallus turgidus
    (2018-05) Kirkham, Jessye Sue; Curran, Mary C.; Guidone, Michele; Ebanks, Sue C.; Department of Marine Sciences
    Daggerblade grass shrimp Palaemonetes pugio reside in brackish estuarine systems and are thus exposed to the parasitic trematode Microphallus turgidus. The purpose of this study was to determine if the infection of P. pugio by M. turgidus was different across months and between two sites near Savannah, GA, and to determine habitat preference of infected P. pugio between the invasive red alga Gracilaria vermiculophylla and substrate-free open space in the laboratory. Trematode density was significantly higher in October-December 2016 and February 2017 (11.0-13.3) at one site and was significantly higher December 2016-January 2017 (10.1-10.3) and August-October 2017 (10.8-12.6) at the other site. In the laboratory, 76% of shrimp preferred tank edge locations whereas only 20% preferred G. vermiculophylla. Only 4% consistently selected the substrate-free open space. A wide range of factors such as food availability, presence of predators, interspecies competition, and abiotic conditions perhaps influence changes in parasite density and habitat preference.
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    Examining Stock Structure of Common Bottlenose Dolphins (Tursiops Truncatus) through Photo-Identification and Genetic Analyses
    (2018-04) Griffin, Emily Kathryn; Cox, Tara M.; Hoskins-Brown, Dionne L.; Rosel, Patricia E.; Balmer, Brian C.; Department of Marine Sciences
    Cetaceans range over large distances resulting in complex patterns of population structure. The coastal ecotype of common bottlenose dolphins (Tursiops truncatus) often consists of distinct groups that exhibit localized adaptations on small spatial scales that result in fine scale genetic structuring. Sex-specific home range patterns are common in cetacean species and may differ between geographic locations. The purpose of this study was to couple long-term photo-identification data with genetics to examine stock structure and to measure home range size of male and female common bottlenose dolphins in the estuarine waters around Savannah, GA. The study area was categorized into three segments: a) a north region, b) a buffer region, and c) a south region. Remote biopsy sampling was conducted in September 2015 and February and March 2017. No significant difference was found when regions were compared by sample location only (n=69). After animals without ≥10 sightings (n=45) were excluded from analysis, a significant difference in FST was found between the north versus buffer (p=0.0147). When the animals with ≥10 sightings were placed in the location with 50% or more of their sightings, a significant difference in in FST was found between the north versus buffer and north versus south (p=0.0018 and p=0.0164). With the addition of sighting history data, stronger subdivision was found between populations. No significant difference was found in minimum convex polygon home range size of males (105.34 ± 49.28 km2; n=24) and females (109.83 ± 53.29 km2; n=57) or in kernel density home range size. The addition of supplemental data, such as photo-identification, to a genetic analysis, can provide additional insight into stock structure. Methods used in this study could be employed by future studies to improve understanding of the complex stock structure of common bottlenose dolphins in estuarine waters.
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    Temporal Trends in Abundance and Habitat Preferences of Deep Reef Fishes Off The Coast of South Carolina, USA
    (2017-04) Yeckley, Sean Paul; Sedberry, George R.; Hoskins-Brown, Dionne L.; Pride, Carol J.; Department of Marine Sciences
    ROV and submersible video footage recorded in 1985, 2002, and 2010 from hard bottom habitat known as the Georgetown Hole or Charleston Lumps located NE of Charleston, SC in depths ranging from 175 – 300 m were reviewed to assess temporal trends in demersal fish abundance and bottom habitat preferences for key species. The main purpose of this long-term assessment of deep reef fish abundance and bottom habitat associations was to determine if deep reef fish populations have recovered since the development and implementation of the snapper/grouper fishery management plan (1983) and its various amendments. The major finding of the study was that Snowy Grouper and Blueline Tilefish were found in higher densities above low relief hard bottom areas than over high relief hard bottom. Snowy Grouper were observed to inhabit low relief hard bottom regions in significantly higher densities (18 fish/1000 m3) than over high relief hard bottom regions (3 fish/1000 m3) (P = .0001). Blueline Tilefish were found in the highest densities within low relief areas (5 fish/1000 m3) and mixed hard/soft bottom regions (6 fish/1000m3). The density of Snowy Grouper Hyporthodus niveatus increased from 2 fish per 1000 m3 in 1985 to 7 fish per 1000 m3 in 2010 and Blueline Tilefish Caulolatilus microps density increased from 0 fish in 1985 to 3 fish per 1000 m3 in 2010 so both populations are gradually rising. The density of Yellowfin Bass Anthias nicholsi decreased from 144 fish per 1000 m3 in 1985 to 56 fish per 1000 m3 in 2010. Yellowfin Bass preferred high relief habitat where they were found in the highest densities. Yellowfin Bass density decreased over low relief hard bottom from 199 fish per 1000 m3 in 1985 to only 15 fish per 1000 m3 in 2010. Abundance of Snowy Grouper and Blueline Tilefish have both increased from 1985 to 2010 predominantly within low relief bottom regions where they have significantly lowered prey populations of Yellowfin Bass and restored a balanced deep reef ecosystem.
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    Differences in Habitat Utilization and Temperature Preference between Male and Female Atlantic Stingrays Dasyatis Sabina within the Herb River near Savannah, Georgia, and Incorporating Stingray Data into a K-12 Classroom Activity
    (2016-08) Webb, Sarah Fae; Curran, Mary C.; Cox, Tara Kaltenberg, Amanda; Department of Marine Sciences
    Atlantic Stingrays Dasyatis sabina are ecosystem engineers and benthic predators inhabiting coastal waters along the eastern coast of the United States. These stingrays are seasonal residents of the Herb River near Savannah, Georgia. The purpose of this study was to determine differences in habitat utilization and temperature preferences between sexes across a 14-month study. Stingrays were surgically implanted with acoustic transmitters and a mean percent usage of receiver location was calculated, then mapped. Both male and female Atlantic Stingrays were present in all months of the study (67.5±32.51% and 79.6±28.45% of d, respectively). A few female stingrays had temperatures that were 1-6°C warmer than other stingrays for brief periods during reproductive months. It is possible that female stingrays are exhibiting maternal thermophily but only during brief periods of time. There is suggested evidence of the Atlantic Stingray exhibiting maternal thermophily in a natural setting on a fine scale.
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    Environmental Reservoirs and Mortality Associated with Shrimp Black Gill
    (2016-11) Price, Ashleigh Rene; Frischer, Marc E.; Curran, Mary C. Ebanks, Sue A.; Department of Marine Sciences
    The Georgia commercial penaeid shrimp fishery has experienced a significant decline in landings since 2000. The cause of the decline is unknown, but coincided with the emergence of a new ciliate infection that causes tissue melanization, called Black Gill (BG). Shrimp Black Gill (sBG) occurs primarily from August through November and is absent during February and March. The absence of shrimp Black Gill during the winter indicates that the sBG ciliate is likely reintroduced annually through a reservoir. The effects of sBG on the shrimp host are unknown; though it has been hypothesized that sBG causes mortality in shrimp. The first focus of this study was to investigate the hypothesis that the sBG ciliate uses a reservoir(s) or second host when sBG is not observed in shrimp. The second focus of this study was to determine if BG causes mortality in shrimp during the months when BG prevalence is generally highest. A survey of crustaceans, water, and sediment was conducted to identify potential reservoirs. Samples were analyzed using a molecular diagnostic assay, followed by phylogenetic analysis of the 18S rRNA gene to determine ciliate identities. Five species of crustaceans were identified as potential reservoirs of the sBG ciliate. Water and sediment were not found to harbor the sBG ciliate. Laboratory experiments were conducted to determine if sBG causes mortality in shrimp by measuring BG prevalence, mortality, growth rate, and molting frequency. A significant mortality event occurred when over 80% of shrimp died. This study provides the first evidence that the sBG ciliate uses multiple species of crustaceans as reservoirs and that sBG causes direct mortality in shrimp. While many questions remain, this research indicates that sBG has contributed to the decline of Georgia’s shrimp fishery and informs future management decisions about the fishery.