SPATIAL AND TEMPORAL TRENDS IN SEA TURTLE STRANDINGS IN NORTH CAROLINA, 1980-2003

Abstract

Natural and anthropogenic activities cause injured or dead sea turtles to wash ashore or strand along coastlines. In North Carolina, the NC Wildlife Resources Commission collects stranding information on sea turtles as part of the Sea Turtle Stranding and Salvage Network, which was formed in 1980. In this study, I characterized temporal and spatial trends in sea turtle strandings in North Carolina. I described temporal trends in sea turtle strandings by year, season, sex, cause of death (if known), and mean body size, overall and by species. I also looked at spatial trends in stranding locations to determine if they were uniformly or aggregately distributed, overall and seasonally, by dividing the shoreline into 10 km bins and creating histograms. Stranding numbers have increased over the past 23 years, but seem consistent since 1995 when effort is believed to have been standardized. Strandings generally increased from May through July as well as from November to December. For turtles whose sex was reliably classified by observers, all species except leatherbacks exhibited a heavy female bias; leatherbacks showed a male bias. Mean size of strandings per species appears roughly constant. With the exception of leatherbacks whose mean stranding size corresponded with adults, the mean size of all species corresponded with juvenile size classes. Spatially, strandings are not uniformly distributed, but appear clumped around several areas along the North Carolina coast including the east ends of Raleigh, Onslow, and Long Bays, and just north of Cape Hatteras. These strandings correspond seasonally with alongshore currents modeled by Hart et al. (submitted). I was unable to find any correlation between frequency of surveys and numbers of stranding reports normalized for shoreline distance, suggesting that the distribution of the stranding data are not biased by sampling effort.