Kemp's Ridley Sea Turtle

Kemp's ridley (Lepidochelys kempii)

The Kemp's ridley turtle is considered the most endangered sea turtle species in the world and also happens to be the most common sea turtle residing in the nearshore waters of southwest Florida. Our estuaries provide the resources that young Kemp's ridleys need to grow to adulthood and females will one day emerge on the primary nesting beaches along the gulf coast of Mexico. Conservation efforts have brought the Kemp's ridley back from the brink of extinction but understanding how turtles live in estuaries and protecting these vital feeding areas will ensure the viability of this endangered species.

Scientists at the Conservancy and Mote Marine Laboratory have been collaborating on in-water studies to characterize sea turtle aggregations and have found that immature Kemp's ridleys are the most abundant species inhabiting the Charlotte Harbor estuarine complex. A specially designed research vessel was constructed with funds generated from the sale of boats donated to the Conservancy. A large mesh net is rapidly deployed from the vessel to encircle and capture sea turtles.

Kemp's ridleys are placed temporarily in a holding tank at Mote's Charlotte Harbor field station for diet studies and tissue samples are collected for stable isotope analysis. Kemp's ridleys are primarily feeding on spider crabs in the Pine Island Sound region of the estuary.

The concept behind dietary stable isotope analysis is "you are what you eat", whereby the chemical composition of a turtle's body is related to its diet. The isotope composition of Kemp's ridleys is being compared to those of their prey and various habitat components (seagrass, drift algae, and sessile invertebrates) to characterize a food web in the Charlotte Harbor estuary. This is one of the first and most comprehensive investigations into the trophic ecology of Kemp's ridleys in their estuarine feeding grounds.

Kemp's ridleys have also been instrumented with satellite transmitters to provide a better understanding of how this species uses the Charlotte Harbor estuary and surrounding waters. During the exceptionally cold winter of 2010-11, a Kemp's ridley exhibited seasonal migrations by leaving the estuary in late fall, heading south and wintering off the Florida Keys, and returning to within a few miles of her capture site in early spring.

In comparison, the winter of 2011-12 was unseasonably warm and most turtles remained within the estuarine system. This was fortunate because a major red tide event occurred offshore and alongshore the southwest Florida coast.

The winter of 2012-13 was also unusually warm and another red tide bloom occurred, but this time the harmful algae moved in to Charlotte Harbor. Kemp’s ridleys responded by leaving inshore waters and moving around off the coast in what could be interpreted as red tide avoidance behavior. Adult-size Kemp's ridleys have also been captured in these nearshore waters and appear to be more transitory, moving to deeper Gulf waters offshore or traveling up the coast.

The movements of Kemp's ridleys in Charlotte Harbor can be followed by visiting www.seaturtle.org.

These studies are supported in part by grants awarded to the Conservancy from the Sea Turtle Grants Program. The Sea Turtle Grants Program is funded from proceeds from the sale of the Florida Sea Turtle License Plate. Learn more at www.helpingseaturtles.org. Satellite transmitters were also funded by Mote Marine Laboratory, National Marine Fisheries Service, and private donations to the Conservancy. Research activities are conducted under NMFS permit #13544 and FFWCC permit #136.


Read more:

Tucker, T. and J. Schmid. 2012. Ridley riddles unravel in Florida. Florida Environmental Outreach, Volume 3, Number 4

Tucker, T. and J. Schmid. 2013. Charlotte Harbor in-water studies answer new ridley riddles. Florida Environmental Outreach, Volume 4, Number 3