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January 24, 2008

DNR monitors sea turtles on the beach, in the water

Monitoring all stages of the life cycle of loggerhead sea turtles, both in the water and on the beaches, provides an important and comprehensive indication of their population status.

Because of the important role that South Carolina beaches and coastal waters play in sustaining loggerhead populations in the Southeast, the S.C. Department of Natural Resources (DNR) has been engaged in sea turtle research since the 1970s and along with other collaborators continues to stand out as a leader in protecting, conserving and managing this marine natural resource. 
           
Currently, several aspects of sea turtle life history are studied, including the management and monitoring of adult nesting females and hatching success on South Carolina beaches, as well as the relative abundance and health of juvenile and adult sea turtles inhabiting our coastal waters. Data is also collected on stranded sea turtles, such as those that wash ashore, because this also provides important life history information about sea turtles that utilize near shore waters. Lastly, data collected remotely using satellite transmitters to monitor sea turtles where they spend the majority of their lives has demonstrated year-round occurrence of juvenile loggerheads off the South Carolina coast as well as long-distance post-nesting migrations from South Carolina beaches to waters off the Mid Atlantic states.

To date, DNR biologists have tagged numerous sea turtles with these satellite transmitters: 36 juveniles, 31 adult males (including two male turtles tagged in cooperation with the South Carolina Aquarium), and 15 nesting females.

Additional information about DNR’s loggerhead telemetry work.

Because of the slow-growing nature of loggerheads and other sea turtles, both positive and negative changes to population structure do not reveal themselves instantly, but rather, may take several decades to become apparent. As such, for an extended period of time following implementation of protective measures for sea turtles, one should expect to observe a continued and gradual decline in nest numbers, concurrent with a steady improvement in the relative abundance of juvenile sea turtles and a decline in the number of these sea turtles washing ashore. Thus, observations of declining loggerhead nesting and strandings can occur at the same time as documentation of increasing juvenile abundance, reflecting the long-term trend of the recovery process for a species that can take nearly 30 years to mature and reproduce.
           
Regional nesting data are consistent with the observations by biologists. Standardized ground surveys of nests on 11 beaches in North Carolina, South Carolina and Georgia show a significant declining trend of 1.9 percent annually in loggerhead nesting from 1983 to 2005, with slightly lower rates of decline observed from aerial surveys (Pdf) in South Carolina during 1980 to 2007.

Loggerhead stranding events on South Carolina beaches also continue to decline, with stranding events in 2007 being among the lowest since reporting began in 1980. Given stable catch rates of loggerhead sea turtles in coastal waters off South Carolina, Georgia and northern Florida during 2000 to 2003, with these catch rates being more than five times greater than catch rates observed in the 1970s where comparisons are possible (Pdf file), it is likely that reduced stranding events with time represent the effectiveness of management, both on the beaches and in the water, rather than a reduced in-water sea turtle population.
           
Although DNR cannot predict precisely when loggerhead nesting on Southeastern beaches will improve, it appears that a combination of nest management in the late 1970s and recent effective fishery management are having at least some benefits and that nesting is possibly on the very slow path to recovery. Only time, continued management, careful monitoring and conservation-based research on both nesting beaches and in important marine foraging and developmental habitats as revealed by telemetry will enable us to properly gauge progress, as well as to evaluate and mitigate new threats that may emerge. As such, DNR remains steadfast in an effort to provide the most comprehensive information available for the management and stewardship of this treasured marine resource. 

DNR protects and manages South Carolina’s natural resources by making wise and balanced decisions for the benefit of the state’s natural resources and its people.


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