Studies on the Microbiota of Fishes and the Factors Influencing Their Composition

ii In this dissertation, I aimed to characterize the microbiota of finfish including identification of the bacteria present as well as the factors that influence their composition. I examined the microbiota of the skin, gill, gut, and/or blood of 7 marine and 3 freshwater fish species. I looked at the impact of fish species, geographic location, season, DNA extraction protocol, and oil exposure on bacterial community structure. Methods used included ribosomal intergenic spacer analysis (RISA) for identification of patterns in bacterial community structure followed by sequencing techniques to determine the bacteria responsible for observed differences. My research indicated that fish species exerts a stronger influence on fish microbiota structure than environmental parameters. Studies included on the skin and gut indicated a species-specific portion of the microbiota that remained stable across various locations and seasons as well as exposure to varying levels of oil. These results challenge the current paradigm that the microbiota of fishes simply reflects that of the surrounding water. My results als