<p> The South Texas Banks are a mesophotic coral ecosystem (30-150m deep). Understanding the community structure, biodiversity and, geographic connectivity of the South Texas Banks is essential with increasing threats from climate change, ocean acidification, invasive species, and pollution. In this study, a remotely operated vehicle (ROV) was used to examine the fish communities at five of the South Texas Banks: Big Adam, Hospital, Mysterious, North Hospital, and Southern. Reef fish were identified to the lowest possible taxon and enumerated from ROV transect video footage. A total of 3,838 demersal and pelagic fishes were recorded representing 61 species in 22 families including invasive <i>Pterois volitans. Bodianus pulchellus, Holocentrus adscensionis, Priacanthus arenatus,</i> and the Gobiidae family were the only fishes observed at all five banks. Habitat suitability models were created that highlight the rich biodiversity found on the South Texas Bank, which will warrant for future research and conservation efforts.</p>

<p> Natural and sexual selection shape animal communication signals according to the demands of social context and the environment, which results in enormous variation in signal properties. My dissertation uses the electrocommunication signals of South American weakly electric knifefish to compare signal structure across several closely related species, with particular emphasis on signals that are extreme or unusual. Weakly electric fish continuously generate an electric field using an electric organ discharge (EOD). During short-range social interactions, fish produce chirps by rapidly and transiently increasing EOD frequency. I used recordings with playbacks of conspecific signals and hormone manipulation to characterize the sexually dimorphic chirp duration of <i>Parapteronotus hasemani</i>, a species of electric fish with high-frequency, long-duration chirps and huge variation in male morphology. I also described signaling behavior in <i>Distocyclus conirostris </i>, a species of electric fish with a low-frequency EOD and an unusual asymmetrical behavioral response to &ldquo;jamming&rdquo; created when EODs of similar frequencies interact. Next, I compared across species to examine how signal properties (EODs and chirping) interact to influence each other&rsquo;s detection and evolution. Certain signal parameters such as chirp frequency modulation and EOD frequency difference have substantial effects on chirp conspicuousness. Contrary to expectations, there was little support for a strict co-evolution in which a species&rsquo; chirps are most conspicuous on their own EOD waveforms. Thus, although EOD properties influence chirp conspicuousness, other factors such as the social or physical environment also likely shape chirp structure. Additionally, I show that EOD waveform may differ in perceptibility based on the EOD waveform complexity of the interacting fish. I consider how chirp conspicuousness could drive the evolution of sexually dimorphic chirps (such as those produced by <i>P. hasemani</i>), and I raise questions about whether low-frequency EODs (such as those produced by <i>D. conirostris</i>) contain sufficient information for fish to detect conspecific EOD frequencies using the neural mechanisms described in fish with high-frequency EODs. Taken together, these results show how the properties of multi-component signals shape each other and impact signal detectability. Finally, my dissertation concludes with a description of an innovative approach to teaching scientific communication skills in a highly structured undergraduate introductory biology lab.</p>

<p> As eel populations decline worldwide, research tools for scientists and managers to better understand eel populations and dynamics will be vitally important. This research focuses on the relatively understudied silver phase eel, the sexually mature adult life stage that will make the single spawning journey to the oceanic spawning grounds. A non-lethal index of eel maturity was designed based on external measurements and was able to correctly classify individuals into one of seven maturity classes 83% of the time overall, yielding similar results to other non-lethal indices. Habitats above and below barriers to migration, at varying levels of watershed urbanization, and different distances from the ocean were compared in terms of eel maturity, size, age, and parasite parameters. Two methods of bioelectrical impedance analysis (BIA) were evaluated in their ability to estimate eel lipid concentration, a key factor in eel maturity and successful spawning.</p>