Desert Star Helps Tag Loggerheads in the Gulf with SeaTag

Marina, CA, July 10, 2010 --(PR.com)-- Evelyn came ashore in the wee hours of Tuesday morning in Casey Key, Florida. After making her nest and depositing her eggs, she headed back toward the warm Gulf waters. Little did she know she would be stopped en-route by researchers from Mote Marine Lab.

Evelyn is an adult female loggerhead turtle measuring 94.6cm curved carapace length who was originally seen in 2006 at Casey Key. She is also the first loggerhead to be tagged with Desert Star’s solar powered, geo-magnetic tag (SeaTag-GEO). The tagging project is managed by Dr. Tony Tucker of Mote Marine Lab. The main goal of the project is to test the accuracy and suitability of using these inexpensive data loggers to either augment satellite tagged turtles or to allow researchers to tag turtles that they otherwise wouldn’t due to the high cost of satellite tags. Because SeaTag-GEO uses a 3-axis magnetometer to measure the Earth’s magnetic field, the data from the tag may be used to answer additional questions such as if and how the female loggerheads are using Earth’s magnetic field to navigate and choose specific nesting sites.

The daily magnetic values the tag acquires are related to a well established Earth magnetic field reference map which shows the accuracy of magnetic latitude estimates at around 35nm. It is powered via stored solar power, through a solar cell and capacitor, which allows the tag to be used repeatedly without any associated battery replacement costs. The solar cell also senses light from the sun to determine “noon time” which gives the tag its longitude. The tag has a temperature sensor which records the temperature throughout the day. SeaTag-GEO can store daily positions (up to 544 days) or customer-programmable sampling rates.

While Evelyn was in the temporary wooden box, Dr. Tony Tucker cleaned the carapace. Once cleaned an epoxy covered the area where the satellite tag and the geo-magnetic tag would go. The satellite tag was placed on the carapace followed by the SeaTag-GEO. The GEO was placed behind the satellite tag to both reduce drag on the turtle and allow the biologist to easily remove one or both of the tags independently. The satellite tag is used alongside the geo-magnetic tag as a known standard in precision and accuracy. The geo-magnetic data will be compared to the satellite tags’ data once the tags are recovered to compare the accuracy of the two methods. Satellite tags have been used on loggerhead turtles for many years as they are accurate methods to locate a turtle throughout their migration. However, the cost per tag and the cost for satellite time can add up; whereas, a data logger simply records and logs data. The advantage is that the cost per tag is significantly less expensive and the researchers can tag significantly more turtles. However, the researcher must get the tag back to get any data. Using data loggers on commercial fisheries is pretty common and on species that are known to return to the same areas, like sea turtles.

Desert Star Systems’ Thomas Gray was on-site for the tagging of Evelyn as well as Salty and June Bug, who we’re also tagged using the SeaTag-GEO, offering logistical support in placement and procedure for the tag’s attachment. Desert Star also learned a great deal during these tagging expeditions in regards to the methods used to deploy tags, what other data the biologists are collecting, and the amount of steps that biologists have to take, as well as developing a greater understanding of the process(es).

The first geo-magnetic data from loggerheads is expected in July-August 2010 when turtles return back to Casey Key to nest. Full sets of data will not be available for 1-3 years with an average of 2-3 years for turtles returning to the Casey Key area for nesting after they have migrated to and from Mexican Gulf waters.

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