Project Title: Identifying Migratory Pathways and Offshore Foraging Habitat Use Patterns of Florida's Declining Loggerhead Turtle Population
Project Manager: Daniel Evans
Organization: Caribbean Conservation Corporation (Non-Profit Organization)
Grant Amount: $34,000.00
Completion Date: 2011-11-29
Summary: Florida beaches account for 90 percent of loggerhead nesting in the southeastern United States. The beaches in and around the Archie Carr National Wildlife Refuge (Carr Refuge) on the central east coast of Florida represent a significant loggerhead rookery in the state of Florida. Florida’s loggerhead sea turtle populations have declined approximately 41 percent from 1998 to 2008. There is a high likelihood that this decline is associated with fisheries bycatch, including drowning in various trawl fisheries (such as shrimp and scallop trawls) and incidental capture by longline fisheries, especially in habitats off the Gulf Coast of Florida. Learning about migration pathways of loggerheads from Atlantic coast nesting beaches to foraging grounds would help confirm fisheries interactions and identify other possible sources attributing to the nesting population decline. In addition, this information could identify critical Florida coastal habitats being utilized by Florida loggerheads during the non-nesting season.
This project will deploy satellite transmitters on five post-nesting adult loggerhead sea turtles from in and around the Carr Refuge to help identify principle foraging habitats for post-nesting Florida loggerheads, with an emphasis on the population nesting between Southern Brevard and Northern Indian River Counties in the Carr Refuge. Being able to identify offshore habitats utilized by these Atlantic coast nesting loggerheads could also help protection and management efforts for the fragile and important habitats the turtles utilize. This information will be of importance to the U.S. Fish and Wildlife Service, the National Marine Fisheries Service, and the FWC in establishing regulations to reduce bycatch in US fisheries and in evaluating long-term threats and protection efforts.
Results: All of the transmitters have been deployed and none from the 2010 season are still transmitting. A total of six loggerheads were released from the Archie Carr Refuge, five under this project and one funded by sponsorships obtained by the Sea Turtle Conservancy (formerly Caribbean Conservation Corporation). Three of the turtles were released early in the nesting season by UCF, while the remaining three were released by STC/UCF at the end of the nesting season.
Initial analysis of the thirteen loggerheads from the Archie Carr National Wildlife Refuge that were fitted with satellite tags between 2008 and 2010, identified three major migratory pathways and foraging areas: (1) a seasonal North-South migratory pattern between Virginia and North Carolina; (2) a residency in southern foraging areas; and (3) a residency in an area adjacent to the nesting beach. Half of the individuals migrated north, revealing for the first time that the coast of the United States constitutes an extremely important feeding area for nesting loggerheads from Florida. Turtles that migrated north from Florida over the course of the year showed a seasonal movement between Virginia/Delaware (warmer months) and North Carolina (cooler months). Loggerheads moving south showed a year-round residency two feeding areas: Bahamas (n=2) and Florida Bay/Florida West Coast (n=2). The remaining loggerheads (n=3) did not make long post-nesting migrations. Instead they remained in the shallow waters off the east central Florida coast with no evidence of nesting activity.
When looking at the tracks, only two turtles, from previous deployments, went into the Gulf of Mexico. Of those only one went into the area that overlaps with bottom long-line fishing areas. The other southern moving turtles went into the territorial waters of the Bahamas, which only recently made turtle fishing illegal. These turtles still face illegal sea turtle fishing in and around the Bahamas. Turtles moving north were exposed to shrimp fisheries along the southeast Atlantic coast of United States, as well as scallop fisheries off the mid-Atlantic states. All turtles were subject to possible impacts from pelagic longlines. Almost all migration and foraging areas had the potential exposure to an estimated fishing effort of less than 750,000 hooks in a year. Individuals spending time off the coast of Delaware were exposed to an estimated fishing effort of 750,000 to nearly 2 million fish hooks in a year (Lewston et al. 2004).
During the 2011 season, an additional eight transmitters were deployed, including one unit that was deployed on a turtle that was previously satellite tagged in 2009. Preliminary results show four moving south to the Bahamas (n=3) and Cuba (n=1), a known foraging area for loggerheads, but a new site for our tracking research. Three loggerheads moved north towards Virginia/Delaware, while the last loggerhead moved to the east of the Bahamas into deep ocean before head south and then back west into the waters of the southern Bahamas.
The 2008 – 2010 data (see image) was included in two abstracts submitted to the 31st International Sea Turtle Symposium, one by the principle investigator (included with the report), and one by the researcher at UCF.