ISTS: Research and management of loggerhead sea turtles, Caretta caretta, at the CRIP sea turtle research station, Bahia de los Angeles, Baja California, Mexico

INTRODUCTION

The origin of loggerhead sea turtles (Caretta caretta) along the coast of Baja California has until recently been a mystery. Various authors have cited the abundance of subadult and adult individuals in this area (Shaw, 1947, Marquez,1969, Ramirez Cruz et al., 1991, Bartlett, 1989), but no nesting areas along the eastern Pacific are known.

Sternberg (1981) speculated that C. caretta nested in Panama and Cornelius (1982) in Nicaragua, but these re- ports are unsubstantiated. Bartlett (1989) was the first to sug- gest that these animals originate in the western Pacific (Aus- tralia).

In 1993 a group of geneticists from the United States and Mexico investigated the genetic affinities between indi- viduals captured as bycatch in the Pacific high-seas fishery and individuals along the Baja California peninsula (Bowen et al.,1995). They demonstrated that loggerheads found in the eastern Pacific had affinities with nesting populations in Japan (95%) and Australia (5%). Following this, two adult loggerhead sea turtles raised in the CRIP-Sea Turtle Research Station (STRS) and included in the Bowen et al., survey were released along the Pacific coast of the Baja Peninsula in the summer of 1994. One of these two adults was later captured along the southeastern coast of Japan near Kyushu (Resendiz et al., 1998). In the summer of 1996 an additional adult fe- male raised at the CRIP-STRS was released with a satellite tag along the Pacific Coast of the Baja Peninsula. The trans-Pacific migration of this turtle, "Adelita", has been followed by thousands of people over the Internet (Nichols, et al., 1997) and she has recently completed the journey (Nichols et al., in prep).

CRIP SEA TURTLE RESEARCH STATION

The CRIP Sea Turtle Research Station in Bahia de Los Angeles, Baja California, Mexico was founded in 1979. Dur- ing times of a legal sea turtle fishery in Bahia de Los Ange- les, the monitoring of this fishery was carried out by the lo- cal Canal de Las Ballenas fishing cooperative. Originally, all harvested turtles were inventoried at the Coronado Island lagoon north of town. In 1980 monitoring efforts were up- graded and a holding facility (later to become CRIP STRS) was constructed on the northern edge of Bahia de Los Ange- les. The first studies of captive sea turtles at this facility occurred in 1981 when several juvenile loggerheads and black sea turtles were donated from the Canal de Las Ballenas fish- ing cooperative. The original goal was to house and reha- bilitate turtles injured in fishing nets and keep undersized animals (< 75 cm) for studies and eventual release. In 1982, economic hardship in Mexico and declining sea turtle popu- lations brought about the collapse of the fishing cooperative in Bahia de Los Angeles and marked the independence of the CRIP Sea Turtle Research Station.

METHODS

Loggerhead sea turtles (Caretta caretta) captured in the central province of the Gulf of California near Bahia de los Angeles, Baja California, Mexico (28 58 N,113 33 W) were held in outdoor circular concrete tanks (5 x I.5 m). Turtles were fed a variable diet consisting of fish, shark, and ray in addition to seasonally available items such as the Cali- fornia sea hare (Aplysia californica), giant squid (Dosidicus gigas), mussels (Modiolus capax), blue swimming crabs (Gallinectes arcuatus), princely fiddler crabs (Uca princeps) and pelagic red crabs (Pleuroncodes planipes). Weight and straight carapace length were taken every month. Cleaning occurred every day. Tanks were shaded with plastic mesh. Turtles were identified with plastic tags placed on the front flippers. All loggerheads were released offshore from Santa Rosaliita, Baja California, Mexico (28o40' N, 114o12' W).

RESULTS

Loggerhead #1 ID# 309 and 39;

Origin: Donated from local Fish Coop. "Canal de Ballenas" BLA;

In Captivity: 1981-1994;
Released: July 19, 1994;
Growth: From 42.0 cm / 12.7 kg. to 79.8 cm /80.8 kg. (Female);
Comments: This loggerhead had the longest stay (13 yrs) at the STRS and was released with "Rosita" in 1994 (see Resendiz et al., 1998).

Loggerhead #2 ID# 27 and 310;

Origin: Donated from a sport fisherman;
In Captivity: 1986-1994;
Released: July 19, 1994;
Growth: From 32.9 cm / 6 kg. to 85.6 cm / 97 kg. (Female); Comments: 478 days after her release from Baja California waters, this turtle ("Rosita") was caught by a fisher- man off-shore from Kyushu, Japan (Resendiz et al.,1998).

Loggerhead #3 ID# 38;

Origin: Donated by Canal de Las Ballenas Fish Coop.,BLA; In Captivity: 1981-1991;
Released: Oct. 18,1991;
Growth: From: 46.7 cm. / 11.4 kg to 74.6 cm. / 69.9 kg.(Male);
Comments: Released with Loggerhead #4 (Resendiz et al.,1992).

Loggerhead #4 ID# 40;

Origin: Donated by Canal de Las Ballenas Fish Coop., BLA; In Captivity: 1981-1991; Released: Oct. 18,1991; Growth: From 36. 2 cm / 7.2 kg to 77.9 cm / 78.0 kg. (Female);
Comments: Released with loggerhead #3 (Resendiz et al.,1992).

Loggerhead #5 ID# 37 and 333;

Origin: Donated by Canal de Las Ballenas Fish Coop., BLA; In Captivity: 1982-1993;
Released: Donated to Museo*;
Growth: From 40.0 cm / 10.4 kg. to 65.4 cm / 48.12 kg.

(Female);
Comments: This individual was donated to the Museo de La Tortuga, Mazunte, Oaxaca, Mexico for Pacific loggerhead exhibit (Nov. 1993).

Loggerhead #6 ID# 302;

Origin: Donated by local fishermen;
In Cap-tivity: 1986-1996;
Released: Aug. 10,1996;
Growth: From 29.9 cm / 4 kg. to 83 cm / 95.3 kg. (Female); Comments: This turtle ("Adelita") was released with a

Telonics ST-3 satellite transmitter supplied by the United States Fish and Wildlife Service. It has recently completed an east-west transpacific migration that was followed by many via the Internet (Nichols et al., 1997).

Each of these six turtles was used in the initial genetic analysis of the Pacific loggerhead assemblage (Bowen et al., 1995) and have been confirmed to have haplotypes consistent with those found on Japanese nesting beaches.

DISCUSSION

The migratory and genetic research that has been fa- cilitated by this station has been important to our understand- ing of Pacific loggerhead ecology. The genetic analyses (Bowen et al., 1995), the flipper tag recovery (Resendiz et al., 1998), and the migratory route as demonstrated through satellite tagging efforts (Nichols, this symposium) all sup- port the transpacific migratory nature of this endangered spe- cies. Movements that encompasses the entire North Pacific emphasize the importance of increasing the geographical scale of investigations and modifying our approach to sea turtle conservation to incorporate such vast migrations.

We suggest that efforts must continue to perform simi- lar flipper-tagging and satellite tracking efforts with wild- caught individuals so that our findings may be supported. Regardless, the research efforts carried out at the CRIP-STRS illustrate the importance of an interdisciplinary approach to sea migratory studies and the benefit of cooperative multi- national investigations of sea turtle biology.

ACKNOWLEDGEMENTS

We would like to thank the local community of Bahia de los Angeles (Ejido) and the hundreds of volunteers and fishermen who have been involved with this project. In ad- dition, Dr. Grant Bartlett, One World WorkForce, Coastal Conservation Foundation were critical to the success of these projects. We would especially like to thank CRIP-PESCA, the Bartlett Lab, Foundation For Field Research, Sea Turtle Center, and University of Arizona for their generous finan- cial assistance.

LITERATURE CITED

Bartlett, G. 1989. Juvenile Caretta off Pacific coast of Baja California. Noticia Caguamas 2:2-10.

Bowen, B.W., F.A. Abreu-Grobois, G.H. Balazs, N. Kamezaki, C.J. Limpus and R.J. Ferl. 1995. Trans- Pacific migrations of the Loggerhead sea turtle demonstrated withmitochondrial DNA markers. Proc. Natl. Acad. Sci. U.S.A. Vol. 92, pp. 3731-3734.

Cornelius, S.E. 1982. Status of sea turtles along the Pacific coast of Middle America. Pages 211-219 in K. Bjorndal (Ed). Biology and conservation of sea turtles.Smithsonian Institution Press, Washington, D.C.

International Union for Conservation of Nature and Natural Resources. 1995. By UCN/SSC Marine Turtle Specialist Group.

Marquez, M.R. 1969. Additional records of the Pacific Loggerhead turtle, Caretta caretta gigas, from the North Mexican Pacific Coast. J. Herp. 2:108-110.

Nichols, W.J., J.A. Seminoff, and L. Jimenez. (In Press.) Sea turtles, Science, and surfing: Riding the Internet from the classroom to the field. Proceedings of theSeventeenth Annual Sea Turtle Symposium. Sharon Epperly (Comp.).

Ramirez Cruz, J.C., I. Pena Ramirez and D. Villanueva Flores. 1991. Distribucion y abundancia de la tortuga perica Caretta caretta Linnaeus (1758) en la costa occidental de Baja California Sur, Mexico. Archelon 1:1-4.

Resendiz, A., B. Resendiz. 1992. Loggerhead turtles released after ten years in captivity. Marine Turtle Newsletter 57: 7-9.

Resendiz, A., B. Resendiz, W.J. Nichols, J.A. Seminoff, and N. Kamezaki. 1998. First confirmed east-west transPacific movement of a loggerhead sea turtle, Caretta caretta, released in Baja California, Mexico. Pacific Science, Vol. 52, no. 2: pp. 151-153.

Shaw, C.E. 1947. First record of the red brown loggerhead turtle from the eastern Pacific. Herpetologica 4:55-56. Sternberg, J. 1981. The worldwide distribution of sea turtle nesting beaches. Center for Environmental Education, Washington DC.

Uchida, S., and H. Teruya. 1988. Transpacific migration of a tagged loggerhead Caretta caretta. International Symposium on Sea Turtles, Hiwasa, Japan. Poster presentation.