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Satellite tracking: an example

Project Paola -Status of the Sea Turtles in the Gulf of Naples and preliminary study of Migration.
Dr. Flegra Bentivegna

The first sea turtle Caretta caretta, released from Greece, to be tracked via satellite in the Mediterranean through an electronic transmitter fitted on her back. Project directed by the Curator, Dr. Flegra Bentivegna of the Stazione Zoologica "Anton Dohrn" in Naples (Italy) in collaboration with MEDASSET (Mediterranean Association to Save the Sea Turtles).

Sea Turtle Symposium

4-5 March 1997 Orlando, U.S.A. Dr. Flegra Bentivegna*
Angela PagHalonga*

* STAZIONE ZOOLOGICA ”Anton Dohrn•

Villa Comunale 1, 80121 Napoli ITALY

STATUS OF THE SEA TURTLES IN THE GULF OF NAPLES AND PRELIMINARY STUDY OF MIGRATION.

ABSTRACT
The present study was performed under the auspices of the Sea Turtle Conservation Pro~am that has been conducted in the Gulf of Naples (Italy) by the Zoological Station since 1983.
All information, collected from 1993 to 1996, on marine turtles is studied and evaluated. Data on the number and size of captured sea turtles, method of capture and type of damage suffered is recorded. The feeding habits of sea turtles and the impact of anthropic pollution was explored using fecal and stomach content analysis.This gives a measure of the status of the Mediterranean sea turtle population and, in general, defines the degree of danger present in the Gulf of Naples to this species . The dispersal and migratory movements of Mediterranean marine turtles are completely unknown. F or that in October 1995 we began to track a loggerhead using satellite telemetry.
The results seems to show that most loggerheads found in the mid-southern to southern regions of the Tyrrenian Sea come from the eastern basin of the Mediterranean Sea.

© 1997 MEDASSET/H.C.U.A.R./photo: Costas Papaconstantinou
INTRODUCTION
The present study was performed under the auspices of the Sea Turtle Conservation Program that has been conducted in the Gulf of Naples (Italy) since 1983 (Bentivegna et al, 1986;1992;1994).
The Gulf of Naples, located on the western coast of Italy and opening directly to the Mediterranean Sea, is frequented by the loggerhead sea turtle (Caretta caretta). The data collected over the last four years includes the number and size of specimens recovered, the time and method of recovery, and the probable cause of injury. These data were used to evaluate the loggerhead turtle situation in the Gulf of Naples, an area of the Mediterranean Sea which has never before been considered in studies of this species.Loggerhead feeding habits in offshore waters and the impact of anthropic pollution were also studied in order to define the level of danger that the Gulf of Naples presents to the this species.
It was known from previous studies that loggerheads do not come into the Gulf to reproduce, but rather, to feed (Bentivegna et al, 1994). In all probability, they originate from the eastern Mediterranean basin where there are numerous egg deposition sites (Venizelos, 1991). In order to verify this hypothesis, we began to track a loggerhead sea turtle in the Mediterranean using satellite telemetry. The tracking study helped to better understand the life history of the loggerhead in the Mediterranean Sea.

METHODS
Data regarding the loggerhead turtle population in the Gulf of Naples have been collected from specimens recovered over a period of four consecutive years ( 1993-1996). Information pertaining to their number and size, and the type of injury suffered was based entirely on records of turtles found dead either on beaches or floating in coastal waters, or caught incidentally by fishermen.The feedings habits of the loggerhead turtle and the impact of anthropic pollution were investigated by analyzing the fecal content of live specimens and the stomach content of dead ones. Fecal content was divided into natural and anthropic material.
The tracking program began on October 1, 1995 and continued to the end of May 1996. The turtle tracked was originally found by a group of fishermen using a trawl net. The turtle, a female in good health, had a curved carapace 73 cm long and 63 cm wide, and weighed 43.7 kg. A Telonics model ST-6 platform transmitter terminal (PTT) with a salt water switch was fitted on her carapace.

© 1997 MEDASSET
The map also shows the satellite tracking of "Gaeta", a female loggerhead turtle released by Statione Zoologica in July 1995.

Paola

Island of Kefalonia - Paola release point (13/04/97)

Cape Tenaro - Paola loss in transmission (25/05/97)

Island of Kea - Paola resumes transmission (06/97)

PTT transmissions were monitored by the ARGOS tracking system which uses NOAA satellites that guarantee complete coverage over the earth‘s surface. Each satellite was equipped with a data collection and location system (DCLS) that received and recorded signals from the PTT during an overpass.

RESULTS and DISCUSSION
Most animal recoveries occurred from late spring to autumn , the period when boat-traffic and fishing activity in the Gulf of Naples increase. The largest number of recoveries occurred in May, the month when human aquatic activities begin, and in November, which is the beginning of the winter season. Winter is hazardous for turtles because of the quick drops in water temperature, sometimes up to 5°C in a month, which tend to reduce their activity, and hence, render them vulnerable to the dangers of maritime traffic and fishing nets.
The high level of danger that the Gulf of Naples represents to the loggerhead turtle has been described in a previous study (Bentivegna et al, 1994). Most of the animals recovered are affected by stress caused by maritime traffic or by pollution, or they have been wounded by hooks or nets. Overall, 70 % of the injuries were due to fishing gear, 28% to maritime traffic, and 3% to pollution. All specimens recovered in the Gulf of Naples have been defined as either juvenile or as sub-adult because their CCLs have been less than or equal to 70cm. The majority of the specimens recovered have fallen within the CCL range from 50 to 70 cm. (Margaritoulis , 1988).
Most of the recovered specimens had swallowed either non- biodegradable material, such as plastic and tar, or little pieces of wood, or feathers. This indicates that there is a high level of anthropic pollution in the Gulf and that, as the loggerhead turtle approaches the coast to feed, it searches through the floating garbage for food. In addition, the presence of algae, sea-weed, squid parts, crustaceans (Parthenope angulifrons, Squilla mantis), Gastropods and fish parts in the feces or stomachs of the recovered specimens indicates that the loggerhead feeds at all depths in the Gulf of Naples, from the surface to the bottom.
During the eight months that the tracking study lasted, the loggerhead travelled a route 2600 km long. Immediately after its release of Sicily, in October, the turtle turned southeast and swam continuously for two months (Oct-Nov) and maintained an average speed of one kilometer per hour. The animal crossed the straits of Messina and headed southeast to the Isle of Crete, and then turned southeast to Crete, and then to Lybia. It then returned to Crete and went southeast Turkey. It is likely that during the winter season the loggerhead searches for warm water. The average surface temperatures (16°-18°C) on its route were higher than in other areas of the Mediterranean where an isolated yearly isotherm averaging 20°C (Tortonese, 1951). The stopping points on the turtle‘s route may be explained in terms of a search for a nesting site. In fact the turtle approached known nesting sites, e.g., she stopped in Lybia where a very large nesting site has recently been discovered (Venizelos, 1996).
It is also likely that the loggerhead turtles which visit the Gulf of Naples come from the warmer eastern Mediterranean waters. Tagged female loggerheads nesting in Greece (Margaritoulis, 1988) have been shown to disperse over a very wide area of the central Mediterranean extending west to Sardinia. By taking advantage of the favourable currents off the coast of Naples from the southwest to the northeast (Ovchinnikov, 1966), the loggerhead comes into the Gulf of Naples in order to search for feeding grounds.
The results of the studies of the loggerhead in the Gulf of Naples has contributed to our understanding of the function that the Gulf serves in the life history of the Mediterranean loggerhead turtle. The identification of the Gulf of Naples as one of its preferred habitats in the Mediterranean Sea should persuade the competent authorities to aid the development of, and to adopt, suitable programs and laws which eliminate, or at least reduce, the dangers that threaten the survival of the loggerhead.

ACKNOWLEDGMENTS
We would like to express our thanks and gratitude to Dr. Karen Eckert for the travel grant provided;to Dr. Scott Eckert for his generous aid and advice; and to the World Wildlife Fund for financial support.

LITERATURE CITED
Bentvegna F., P. Cirino, 1986. Reintegration de Caretta caretta (Linneo) dans la Medterranee. Vie Madne 8 : 126-128.
Bentvegna F., P. Cirino & A. Toscano, 1992. Sea turtles in the Naples Aquarium: conservation policy. E.U A.C., Naples 10-16 October 1992. Memories de l‘Institut Oceaographique Paul Ricard, 1993 . 39-42.
Bentvegna F., 1994. Naples Aquarium and Conservation. E.U A.C., Leipzig Memories de l‘Institut Oceanographique Paul Ricard, 1994 . 105-106.
Bentvegna F., P. Cirino, and A. Toscano, 1994. Threasts to Caretta caretta in the Gulf of Naples. Proceedigs of the 14th Annual Symposium on Sea Turtle Biology and Conservation. 1-5 March 1994, Hilton Head, South Carolina U.S.A., NOAA Technical Memorandum NMFS 35l:l88-189.
Venizelos L. E., 1991. Pressure on the endangered Mediterranean Marine turtles is increasing. The role of MEDASSET Marine Pollution Bulletin, 23 : 613-616.
Venizelos L. E., 1996. Mediterranean loggerheads are thriving in Libya! Marine Turtle Newsletterter, 1996, No76.
Margaritoulis D., 1988. Nesting of Loggerhead Sea Turtle Caretta caretta on the shores of Kiparissia Bay, Greece, in 1987. Mesogee, 48 : 59-65.
Margaritoulis D.,1988. Post nesting movements of Loggerhead Sea Turtles in Greece. Rapport et Proces-Verbaux des Reunion. Condenses des travaux presentes lors du XXXI Congres-Assemblee Pleniere Athens (Grece). Volume 31 (2) : 284, V-III3. C.I.E.S.M. Monaco.
Tortonese E., 1951. I caratteri biologici del Mediterraneo orientale e i problemi. Attual. Zool., 7 . 207-251.
Ovchinnikov I. M., 1966. Circulation in the surface and intermediate layers of the Mediterranean. Oceanology, 6 :48-59.
Further resources:
Status of the Sea Turtles in the Gulf of Naples and preliminary study of Migration.
Press Release No.2 16/04/97
Brief notes on migration in Sea Turtles.
Brief notes on satellite tracking methods.
The "Paola" project.