Abstract
Elasmobranchs are known to be present off the urban shores of Miami but there is no clear data on elasmobranch abundance or diversity in the shallow nearshore marine environments most impacted by human activity, including areas close to commercial shipping channels or point sources of pollution. Heavy human recreational and commercial use of Biscayne Bay has, over decades, altered habitats in ways elasmobranchs are forced to navigate. Noise pollution from coastal construction, the Port of Miami, and recreational boating is changing the soundscape of South Pointe Park. Human activity has also polluted parts of the Bay such as Miami Marine Stadium through agricultural runoff and sewage spills from the Central District Wastewater Treatment Plant. Through the use of drone surveys, this study observed and compared the abundance and diversity of elasmobranch species at two sites facing different anthropogenic impacts. A variety of species were found at each site, with blacktip sharks found to be most commonly seen at South Pointe Park while southern stingrays and spotted eagle rays were abundant at Miami Marine Stadium. These results demonstrate that even areas in which human impacts are likely to be constant, severe, and to have led to significant changes in ecosystems, these habitats may still be valuable to elasmobranch species. Changes in natural patterns may also be short-lived and future surveys taking a more experimental approach may be able to assess the extent to which these habitats are rendered less usable for wildlife by polluting events. This study highlights the effectiveness of drone surveys in identifying elasmobranch species in the shallow sandflats and seagrass beds of Biscayne Bay and may serve as a starting point for other researchers looking for an affordable, noninvasive way to study local marine life.