Fishes

Elasmobranch fishes use electroreception to detect electric fields in the environment, particularly minute bioelectric fields produced by potential prey. A single elasmobranch family (Potamotrygonidae) is composed of obligate freshwater stingrays endemic to the Amazon River. A freshwater existence has imposed morphological adaptions on their electrosensory system due to life in a high impedance medium. Because their electrosensory morphology differs from their marine relatives, freshwater stingrays may demonstrate corresponding differences in behavioral sensitivity. The objective of this study was to quantify behavioral sensitivity of the obligate freshwater stingray Potamotrygon motoro to prey-simulating voltage. The voltage produced by common teleost prey of P. motoro were measured and replicated for behavioral trials. The best response was 10.62 cm, and the smallest voltage gradient detected was 0.005 mVcm-1. This sensitivity is reduced compared to marine species. The conductivity of the medium, more so than ampullary morphology, may dictate sensitivity of the elasmobranch electrosensory system.

Although most batoids (skates and rays) are benthic, only the skates (Rajidae) have been described as performing benthic locomotion, termed 'punting'. While keeping the rest of the body motionless, the skate's specialized pelvic fins are planted into the substrate and then retracted caudally, which thrusts the body forward. This may be advantageous for locating and feeding on prey, avoiding predators, and reducing energetic costs. By integrating kinematic, musculoskeletal, material properties, and compositional analyses across a range of morphologically and phylogenetically diverse batoids, this dissertation (i) demonstrates that punting is not confined to the skates, and (ii) provides reliable anatomical and mechanical predictors of punting ability. Batoids in this study performed true punting (employing only pelvic fins), or augmented punting (employing pectoral and pelvic fins). Despite the additional thrust from the pectoral fins, augmented punters failed to exceed the punting c apabilities of the true punters. True punters' pelvic fins had greater surface area and more specialized and robust musculature compared to the augmented punters' fins. The flexural stiffness of the main skeletal element used in punting, the propterygium, correlated with punting ability (3.37 x 10-5 - 1.80 x 10-4 Nm2). Variation was due to differences in mineral content (24.4-48-9% dry mass), and thus, material stiffness (140-2533 MPa), and second moment of area. The propterygium's radius-to-thickness ratio (mean = 5.52 +-0.441 SE) indicated that the propterygium would support true and augmented punters, but not non-punters, in an aquatic environment. All propterygia would fail on land. Geometric and linear morphometric analyses of 61 batoid pelvic girdles demonstrated that pelvic girdle shape can predict punting and swimming ability and taxonomic attribution to Order.

The Abacoa Greenway is a manmade artificial water system constructed in the late 1990s, and home to an array of aquatic flora and fauna. There has been no previous survey of the species residing in this area; therefore this will be a foundation for future samplings to compare to. The goal of this study was to compile a species list of fishes inhabiting the freshwater systems of the Abacoa Greenway Ranges IV and V, as well as a classification of exotic and native species inhabiting the area. A total of 11 species have been collected and identified between March 2007 and May 2008. Of these three species have been classified as exotic or introduced and the other eight as native species naturally existing in Florida.

Prior to 2000, very little was known about fish biodiversity on the New England Seamount chain. In late 2000, 115 fish species were found on Bear Seamount by the NOAA R/V "Delaware II." Woods Hole Oceanographic Institution conducted two cruises to explore the New England Seamount chain in 2003. This study assessed fish species throughout Alvin submersible dives during these 2003 cruises. Digital video footage was converted to still photographs and video clips using the Macintosh movie program iMovie. Fishes were identified to the lowest possible taxonomic level using keys and literature. The habitat, depth and behavior of observed fishes were compared to the literature available. Geographical distributions of the species were considered. I assessed substrate preference by building a chart that reflects the different sediment regimes that fishes were found on. In all I identified 317 individuals representing 33 different taxa, including two species with new habitat range information Neocyttus helgae and Lepidion sp.

Freshwater marshes are a harsh wetland ecosystem classified by seasonal water level fluctuation. Dry down periods are common in some marshes, making life difficult for fish and other aquatic organisms. The goal of this study was to compile an updated species list of fishes inhabiting the freshwater marsh system within Savannas Preserve State Park. Twenty-three fish species were collected between August 2005 and May 2007. This survey, along with past collections, and the current species list in the park's management plan were used to make a new proposed species list. Three species of nonnative fishes were observed during the study, the first report of exotic fishes in the park. It is believed that abnormally high water levels for an extended period may have allowed the water in neighboring canals to connect to the marsh system and, as a result, new species were able become introduced in the park.

Coral reefs harbor ~1-9 million species, including 30% of all marine fish species. Reef health worldwide is declining due to many factors: e.g. pollution, sedimentation, dynamite fishing, and global warming. Working with the Planetary Coral Reef Foundation and the crew aboard the R/V Heraclitus, I examined coral health and fish diversity in the Solomon Islands, Melanesia. In 2006, I surveyed coral and fish on Sagharughombe reef, Solomon Islands using SCUBA and compared the results with surveys done in 2000 and 2002. Coral surveys indicated a significant decline in health over the six-year period. Fish surveys found no clear trend in species abundances and species richness, but a significant decline in species diversity over the years. The decline in coral health we observed may have contributed to diminished fish diversity. To protect marine biodiversity, coral reefs must be better protected and declines in coral health must be halted.