Dermal denticle assemblages in coral reef sediments correlate with conventional shark surveys

TitleDermal denticle assemblages in coral reef sediments correlate with conventional shark surveys
Publication TypeJournal Article
Year of Publication2020
AuthorsDillon EM, Lafferty KD, McCauley DJ, Bradley D, Norris RD, Caselle JE, DiRenzo GV, Gardner JPA, O'Dea A
JournalMethods in Ecology and Evolution
Keywordsabundance estimation, dermal denticle assemblages, fossil record, N-mixture model, palaeoecology, Palmyra Atoll, shark, taphonomy

Abstract 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 palaeoecological 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 time-scales in other contexts.

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