Florida’s sea turtle nesting and stranding trends; 2002 a mixed year

Issue 1, 2003 Articles:

* Proposed TED Rule Would Better Protect Sea Turtles
* Florida’s sea turtle nesting and stranding trends; 2002 a mixed year
* CCC Playing Major Role in Protecting Caribbean Leatherbacks

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Florida’s sea turtle nesting and stranding trends;
2002 a mixed year

Over 90% of all sea turtle nesting in the continental United States takes place on Florida beaches. Consequently, the issues affecting turtles in Florida, as well as the trends in Florida turtle nesting, tell us a great deal about overall sea turtle trends in the U.S. The results from 2002 are a real mixed bag. Biologists with the Florida Fish and Wildlife Conservation Commission (FWCC), the agency responsible for tracking statewide sea turtle trends, report that 2002 produced the lowest number of loggerhead sea turtle nests in more than a decade. In stark contrast, nesting numbers for both green turtles and leatherbacks, both endangered species, reached record and near record levels, respectively.

Florida Sea Turtle Nesting Numbers

Sea turtle nests in Florida are counted each year by a well-coordinated network of volunteers who monitor nesting beaches around the state and report their findings to the FWCC. During 2002, the total number of loggerhead turtle nests documented was 62,905 — the lowest number of nests since 1993. Green turtles deposited 9,201 nests in Florida (the highest number ever recorded in this state) and leatherbacks produced 596 nests (the second highest on record for this species in Florida).

Researchers at CCC and elsewhere have learned over the years that you can not predict sea turtle population trends by looking at nesting numbers for a single year. A lot of factors influence turtle nesting patterns in any given year (weather, temperature, ocean currents, etc.), so nesting numbers must be monitored over long periods of time in order to estimate population trends. This is one reason why CCC’s long-term monitoring program in Tortuguero, Costa Rica, is so important.

In Florida, nesting trends are monitored by systematically counting nests on the state’s “index nesting beaches” utilizing a standard methodology that allows for accurate comparisons from year to year. The Florida Index Nesting Beach Survey (INBS) is administered by the FWCC.

As part of the INBS program, 396 km of nesting beach, divided into zones averaging 0.8 km in length, are monitored every day during the 109-day-long nesting season. The program has been in operation since 1989. Surveyors record information such as the number of nests, nesting attempts (false crawls), location and date nests are deposited. In addition, by looking at the tracks left by turtles in the sand, experienced surveyors can determine the species.

Between 1989 and 2002 the annual number of loggerhead nests deposited on index nesting beaches ranged from 39,091 to 59,918 nests. Nesting on index beaches represents approximately 67% of all the loggerhead nesting in the state of Florida. While the total annual number of loggerhead nests has varied widely, the overall trend for the period has been stable.

“Loggerhead nesting has had ups and downs between 1989 and 2002, but what had appeared to be an increase in nesting only a few years ago has now leveled off,” said Dr. Blair Witherington, a marine biologist with the FWCC’s Florida Marine Research Institute. “The recent low level of loggerhead nesting is a concern because Florida beaches are perhaps the most important in the world for this threatened species,” Witherington said.

Nesting in Florida by green turtles and leatherbacks has increased during the period of 1989-2002, and the trend is continuing in that direction. During the 14-year period of the INBS program, the annual number of green turtle nests deposited on index beaches ranged from 267 to 6,981. Nesting on these beaches represents approximately 74% of green turtle nesting in the state of Florida. The dramatic rise in green turtle nesting has caught the attention of CCC and others in Florida working to recover this species. Most sea turtle conservationists are now “cautiously optimistic” that green turtles are showing signs of a recovery in Florida. Leatherback nesting on index beaches represents about 34% of total leatherback nesting in Florida. The annual number of leatherback nests on index beaches has ranged from 27 to 357 between 1989 and 2002.

Florida Sea Turtle Stranding Numbers

An ever increasing number of sea turtles, such as this green sea turtle, are stranding on Florida’s coast with injuries and scars from collisions with boats and other watercraft. Photo Courtesy of Dean Bagley

For sea turtle conservationists, a “stranded” turtle is a sea turtle that has washed ashore dead or injured. Just as there is a network of volunteers monitoring turtle nesting around Florida, these same volunteers participate in a complex Sea Turtle Stranding Network, which responds whenever someone reports a stranded turtle on the beach or in the nearshore waters. The STSN also allows researchers to track the rate and causes of sea turtle mortality in Florida. More than 1,270 dead or debilitated sea turtles have been found in Florida during each of the last two years, the greatest numbers since monitoring began in 1980. Over half (54%) of all stranded turtles are loggerheads. Collisions with watercraft, disease, and drowning in fishing nets are among the most likely causes of death for loggerheads in Florida. Turtle Excluder Devices (TEDs), which are supposed to allow turtles to escape without drowning in shrimp trawls, are only partially effective. In fact, the TEDs currently required by law simply are not large enough to allow large loggerheads and leatherbacks to escape. Fortunately, a new TED rule recently published by the National Marine Fisheries Service seeks to remedy this problem and reduce the number of turtles being drowned (see New Turtle Excluder Device Rules Approved by NMFS to Protect Sea Turtles).

Through the first quarter of 2003, sea turtle strandings have been unusually high, with disturbing new records being set in some parts of the state. Researchers don’t yet know what may be causing the increase in turtle mortality. As CCC learns more, we will report it in future issues of the Velador.