SUFB 085: Sea Turtle Abundance and Density in and out of the Florida Current

Speak Up For Blue Podcast

Happy Thursday SUFB crew! On today’s episode, we discuss an article recently published in the open access journal PLOS One that examines population distribution of sea turtles in the Florida current.

Sea turtles are commonly found throughout the Atlantic coast of Florida, specifically around the Southeast Florida current (located just east of Miami and West Palm Beach). Researchers believe that they use this fast-moving body of water, which can reach speeds of up to two meters per second, to migrate between nesting areas and offshore waters. They’re also thought to use the surrounding area outside of the current as foraging grounds, based on its productivity and proximity to the Gulf Stream. However, energy companies are also interested in harnessing the power of the Florida current, and their future presence in the area could disrupt sea turtles’ migratory routes or nesting areas. Therefore, it’s important that we gather any information we can about the specific disitrbution and abundance of sea turtle species in the Florida current prior to establishing an industrial presence in the area.

A research team out of Florida Atlantic University, consisting of Caitlin Bovery and Dr. Jeanette Wyneken, designed a study that would collect this information. Their article, entitled “Seasonal Variation in Sea Turtle Density and Abundance in the Southeast Florida Current and Surrounding Waters,” was published this past December in the journal PLOS One. The team used monthly aerial surveys from 2011-2012 of the area to determine the species composition, abundance, and seasonal variability in sea turtle populations observed around the Florida Current. They sought to understand not only how sea turtle abundances change throughout the year but also which habitats surrounding the Florida current they utilize most frequently.

It turns out that the loggerhead turtle (Caretta caretta) and the green turtle (Chelonia mydas) are the most common sea turtle species observed in the study site. During the spring and summer, sea turtles were observed in greater numbers than in the fall and winter. This suggests these individuals are using this region at least partially for breeding, nesting, and early-life history feeding. The warmer months are when the majority of green, leatherback, and loggerhead sea turtles come ashore to nest on Florida beaches. Therefore, it’s probable that most of the individuals observed during the spring and summer were either adults ready to breed or juveniles foraging before moving further offshore. Additionally, 72.8% of all observations were within 20 km of the shoreline, emphasizing the notion that these individuals were primarily using this area as breeding and nursery habitat.

The major drawback of aerial studies is the resolution of collected data. The researchers note that it was difficult to identify potential hawksbill sea turtles in this study because they appear very similar to green sea turtles, and it was impossible to distinguish between them in the air. However, for larger marine species that need to surface to breathe (like sea turtles), aerial surveys can be an effective method of estimating abundance. Because the authors were able to conduct these surveys monthly, they were also able to estimate seasonal variations and potential activities of present individuals. While it would be nice to have additional data collected from dives (to truly estimate the abundance of sea turtles), these surveys should go a long way towards providing necessary ecological information on the Florida Current.

Enjoy the Podcast!

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