Grant: 22-016R
Project Title: Seasonal Movements of Immature Kemp's Ridley Turtles in a Warming Gulf of Mexico
Project Manager: Richard Herren
Organization: Sea Turtle Conservancy (Non-Profit Organization)
Grant Amount: $21,625.00
Completion Date: 2025-10-06
Summary: The Big Bend appears to play a significant role as a developmental habitat for immature and mature Kemp's ridleys. In 2018, Sea Turtle Conservancy (STC), in collaboration with the USGS Florida Cooperative Fish and Wildlife Research Unit at the University of Florida, began conducting sea turtle research in this region and has encountered dozens of sites containing Kemp's ridleys. Until recently there was strong evidence that Kemp's ridleys were recovering based on nesting numbers, but recent counts have been erratic and it is unclear if the nesting population has stabilized or is in decline. In the northeastern Gulf of Mexico, Kemp's ridleys have previously shown site fidelity to near shore areas during the warmer months, but display southerly migrations in the winter as sea surface temperatures decrease to between 18 and 22 C. However, this research was conducted several decades ago and recent warming trends in the Gulf of Mexico may be altering these migratory patterns. Understanding the distribution and habitat requirements of endangered species is one of the keys to managing their recovery. Endangered immature Kemp's ridley turtles recruit to shallow bays and estuaries in Florida's Big Bend region, yet very little research has been conducted to look at the possible impacts of climate change on the movements and habitat use of these turtles. The purpose of this study is to identify potential seasonal shifts in movement and diet of immature Kemp's ridley turtles in response to changes in sea surface temperatures over the past two decades.
Results: The goal of this study was to track overwintering Kemp's ridleys and compare movement with previously published tracking data several decades ago. We satellite tracked six Kemp's ridleys using Lotek Argos K2G 276A transmitters, four in November 2023 and two in November 2024. Three of these transmitters had the Dive sensor and three had the Depth-Temperature sensor. All six of the Kemp's ridleys were successfully tracked from the fall, through the winter, and into the following spring. We compared the Kemp's ridley overwintering tracks in the current study with those tracked in 2000 near Cedar Key, approximately 38 km north of Crystal River (Schmid and Witzell, 2006). In both studies, turtles traveled south of their original capture site in late fall-winter. However, two Kemp's ridleys in this study migrated northwest towards the Florida Panhandle. Additionally, two other turtles from the current study migrated south to Florida Bay, traveling significantly further than any of the turtles satellite tracked two decades ago. It is unclear at this time if these differences are related to changing patterns in water temperatures, currents, prey availability, or a combination of factors.
The lack of Kemp's ridleys in Crystal River prevented us from deploying all the transmitters. Kemp's ridley encounter rates near Crystal River were far less than anticipated. Fewer smaller turtles have been observed compared to data collected 10 years ago. It is unclear at this time what has caused a decline in Kemp's ridleys near Crystal River, but we think this trend warrants further investigation.