Hermes Heads West
-Yonat Swimmer, NOAA PIFSC
In 2008, a collaborative, multiyear project was started in the southwest Mediterranean Sea to investigate methods to reduce incidental capture of sea turtles with longline fishing gear and to better understand the impact of these interactions on the physiology and movements of turtles incidentally captured. Part of the study was to compare blood biochemistries and movements of turtles that had been caught and released from fishing gear, while a control group would be from turtles that were free-swimming prior to capture. This collaboration has been ongoing and includes scientists from NOAA Pacific Islands Fisheries Science Center, Kai Marine Services, Submon, and University of North Carolina Wilmington. Much of the work was accomplished on board the Toftevag, a Norwegian fishing vessel retrofitted for sea turtle and marine mammal research and skippered by Dr. Ricardo Sagarminaga van Buiten.
On July 19, 2012, a loggerhead turtle was spotted on the surface of the water and brought on board the Toftevag by Ricardo and crew. A satellite transmitter (Wildlife Computers ™ #96204) was affixed to the carapace using epoxy and body measurements were taken. The turtle, named “Hermes”, measured 74 cm curved carapace length (CCL) and was released at the same day at location ~ 37.506 N, -0.300 W.Based upon satellite data communication from CLS America, and relayed through the Sea Turtle Analysis Tracking Tool (STAT), we confirmed location data for Hermes for 89 days after its initial release (Figure1). The last transmission received was on October 16, 2012.
Five hundred and sixty five days later, on April 29, 2014, Hermes (Figures 2) was entrained into the Florida Power & Light St. Lucie Nuclear Power Plant intake canal in St. Lucie County, Florida (27.345074, -80.237565). Biologists with Inwater Research Group retrieved Hermes after it had made the journey across the Atlantic and into the power plant’s intake canal (Figure 3).
The St. Lucie power plant commonly entrains sea turtles that frequent the nearby reefs and nesting beaches adjacent to the plant’s intake canal. Biologists working for Inwater Research Group are responsible for removing turtles from the canal, assessing their health, taking morphometrics, and tagging these animals before safely releasing them. Since 1976, the project has captured nearly 16,000 sea turtles.
Upon capture at the intake canal, Hermes appeared healthy and measured 78.6 CCL, suggesting a growth of ~ 2.6 cm in a 21 month period. New flippers tags and a PIT were applied and the turtle was released back into the ocean.
Loggerheads in the same size class as Hermes are commonly captured at the power plant throughout the year. They are frequently sighted by divers and fisherman in the coastal waters of Florida and are the most common species in the region. Many of these loggerheads will migrate seasonally along the Atlantic seaboard of the U.S. from as far north as Massachusetts, south to the Florida Keys and northern Caribbean. As hatchlings loggerheads leave the beaches of Florida and enter the North Atlantic gyre following the Gulf Stream up the Atlantic coast of the U.S., across the Labador current and then south along the coast of Europe. They’ll spend many years and cross many miles of ocean in this pelagic environment until eventually migrating to shallower coastal waters that provide benthic developmental habitat where most will stay until they reach maturity. Hermes is unique because this is only the second record of a turtle coming from the Mediterranean Sea and making the transatlantic crossing before being captured in Florida. This represents the longest migration of a sea turtle captured at the power plant’s intake canal.
Inwater Research Group has several in-water sea turtle studies ongoing in Florida and Louisiana and has captured, tagged and released thousands of sea turtles. Of all the turtles captured by IRG, Hermes’s migration from the Mediterranean to Florida is remarkable because only four other sea turtle encountered by IRG have been documented as making a transatlantic migration.
Hermes, if a female, with a straight carapace length (SCL) of 72.5 cm might be a bit small to be nesting on a Florida beach because loggerheads of this size class are rarely reproductively active. However, according to University of Central Florida (UCF) assistant professor Dr. Kate Mansfield there are records of females as small as 69.0 cm SCL nesting on beaches in this region. Kate and her team at UCF’s Marine Turtle Research Group will look for Hermes as they monitor nesting activity at the Archie Carr National Wildlife Refuge this summer.
As for Hermes’s transatlantic crossing, at a minimum, the distance represents a track of 7130 km (Figure 4) over the course of 18 months. It will be interesting to further explore Hermes’ movements in the context of Atlantic Ocean current patterns and assumed turtle migratory routes. (Figure 5) This will help generate hypotheses on the likely route and timing on Hermes’ voyage.
This July, Kai Marine Scientists, Ricardo and Ana Tejedor, and a group of Spanish fishermen, will join USFWS scientist Earl Possardt and other US federal biologists on a trip to Florida to see hatchling loggerhead turtles emerge from nests on a beach not far from where Hermes was captured The trip is an effort to thank fishermen for their efforts to reduce sea turtle bycatch in longline fishing gear by switching to deep sets and using mackerel bait. This will also provide an opportunity to link resources, such as sea turtles, between the US East Coast and the Mediterranean, as Hermes has already done.