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Marine Biology

, Volume 153, Issue 1, pp 35–46 | Cite as

Population ecology of the green/black turtle (Chelonia mydas) in Bahía Magdalena, Mexico

  • Volker Koch
  • Louise B. Brooks
  • Wallace J. Nichols
Research Article

Abstract

The mangrove channels of Bahía Magdalena, Mexico, are important developmental areas for juvenile green, or black turtles (Chelonia mydas), but incidental bycatch and illegal hunting threaten population persistence. We studied size distribution, condition index (CI), growth rates, and mortality of black turtles in Estero Banderitas, the largest mangrove channel in Bahía Magdalena, to supply information for the development of effective conservation strategies. A total of 213 black turtles (including 88 recaptures) were caught in entanglement nets between July 2000 and July 2003. Average yearly catch per unit of effort (CPUE, 1 unit: 100 m of net fishing for 12 h) dropped during the study from 2.19 to 0.76. About 97% of all turtles were considered juveniles, average size was 54.6 ± 9.5 cm. Turtles were significantly smaller at the head of Estero Banderitas than in the central part of the Estero and in the open bay, indicating size-based habitat segregation. Average growth rate was 1.62 cm/year and declined with increasing size. Growth was seasonal and three times higher in summer (0.28 cm/month) than in winter (0.09 cm/month), body CI was also significantly higher during the summer months. A seasonalized von Bertalanffy growth function (VBGF) was used to model growth for the size range studied (43–73 cm SCL), with the parameters: L = 101 cm SCL; K = 0.04 year−1; t0 = 0; C = 0.4 and ts = 0.75. Growth data indicate that black turtles may spend up to 20 years in Bahía Magdalena before they reach maturity at about 77 cm SCL. The total mortality estimate (Z) from the length converted catch curve was 0.16, corresponding to a yearly survival probability of 0.85.

Keywords

Condition Index Coastal Lagoon Green Turtle Nest Size Body Condition Index 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

The authors gratefully acknowledge the financial and logistical support provided by the School for Field Studies, Center for Coastal Studies, Puerto San Carlos, and for the support provided by SEMARNAT and the National Institute of Ecology with the research permits for the current study. We are grateful for the help provided by the students and interns of the SFS Center for Coastal Studies, especially those who worked in the Sea Turtle Directed Research project, and numerous volunteers and graduate students. Members of the communities helped collect data, especially Rodrigo Rangel, Julio Solis, Juan Rodriguez and Joel Talamanca. The authors wish to acknowledge use of the Maptool program from www.seaturtle.org.

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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Volker Koch
    • 1
    • 2
  • Louise B. Brooks
    • 3
  • Wallace J. Nichols
    • 4
    • 5
  1. 1.The School for Field StudiesCenter for Coastal StudiesPuerto San CarlosMexico
  2. 2.Departamento de Biología MarinaUniversidad Autónoma de Baja California SurLa PazMéxico
  3. 3.Moss Landing Marine LaboratoriesMoss LandingMontereyUSA
  4. 4.PropeninsulaDavenportUSA
  5. 5.Department of HerpetologyCalifornia Academy of SciencesSan FranciscoUSA

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