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

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Koch, V., Brooks, L. B., & Nichols, W. J. (2007). Population ecology of the green/black turtle (Chelonia mydas) in Bahía Magdalena, Mexico. Marine Biology, 153(1), 35-46. doi:10.1007/s00227-007-0782-1
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TitlePopulation ecology of the green/black turtle (Chelonia mydas) in Bahía Magdalena, Mexico
AuthorsV. Koch, B. Brooks, J. Nichols
AbstractThe 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; t 0 = 0; C = 0.4 and t s = 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. © 2007 Springer-Verlag.
JournalMarine Biology
Date2007
Volume153
Issue1
Start page35
End page46
ISSN00253162
Subjectsgrowth rate, mortality, population ecology, size distribution, species conservation, survival, turtle, Baja California Sur, Magdalena Bay, Mexico [North America], North America, Chelonia mydas, Testudines
NoteCited By (since 1996):22, CODEN: MBIOA

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