It is challenging to assess long-term trends in mobile, long-lived, and relatively rare species such as sharks. Despite ongoing declines in many coastal shark populations, conventional surveys might be too fleeting and too recent to describe population trends over decades to millennia. Placing recent shark declines into historical context should improve management efforts as well as our understanding of past ecosystem dynamics. A new paleoecological approach for surveying shark abundance on coral reefs is to quantify dermal denticle assemblages preserved in sediments. This approach assumes that denticle accumulation rates correlate with shark abundances. Here, we test this assumption by comparing the denticle record in surface sediments to three conventional shark survey methods at Palmyra Atoll, Line Islands, central Pacific Ocean, where shark density is high and spatially heterogeneous. We generally found a significant positive correlation between denticle accumulation rates and shark abundances derived from underwater visual census, baited remote underwater video, and hook and line surveys. Denticle accumulation rates reflected shark abundances, suggesting that denticle assemblages can preserve a signal of time-averaged shark abundance in low-energy coral reef environments. We offer suggestions for applying this tool to measure shark abundance over long timescales in other contexts.

DillonMEE_SupData_Palmyra_Sharks This dataset includes relative shark abundance data from Palmyra Atoll, Line Islands, central Pacific collected using three conventional shark survey methods - underwater visual census, hook and line, and baited remote underwater video - as well as one new method - the shark dermal denticle record. Data were collected at low-energy sites in the lagoon and backreef between 2006 and 2016. Data were collected to compare shark dermal denticle assemblages preserved in surface sediments with conventional shark survey data to assess the ecological fidelity of the denticle record. Data provide an indication of relative shark abundance for the species observed at each site. This dataset contains six csv files: "denticle_accum", "sedimentation", "weathering", "uvc", "bruv", and "hook_line". Field attributes for each csv file are described in the accompanying Metadata ReadMe file.