ESR 15:151-158 (2011)  -  DOI: https://doi.org/10.3354/esr00379

Sea turtle population estimates incorporating uncertainty: a new approach applied to western North Atlantic loggerheads Caretta caretta

Paul M. Richards1,*, Sheryan P. Epperly1, Selina S. Heppell2, Rachel T. King3, Christopher R. Sasso1, Felix Moncada4, Gonzalo Nodarse4, Donna J. Shaver5, Yosvani Medina4, Julio Zurita6

1National Marine Fisheries Service, Southeast Fisheries Science Center, 75 Virginia Beach Drive, Miami, Florida 33149, USA
2Department of Fisheries and Wildlife, 104 Nash Hall, Oregon State University, Corvallis, Oregon 97331, USA
3Southeast Environmental Research Center, Florida International University, 11200 SW 8th Street, OE-148, Miami, Florida 33199, USA
4Centro de Investigaciones Pesqueras, 5ta Ave y 248, Barlovento, Ciudad Habana, Cuba
5National Park Service, Padre Island National Seashore, PO Box 181300, Corpus Christi, TX 78480, USA
6Comité de Protección de Tortugas Marinas en Quintana Roo, Hermosillo 26−104. Col. Roma Sur, O6760 México, D.F.

ABSTRACT: Loggerhead sea turtles Caretta caretta have been listed as threatened under the US Endangered Species Act since 1978, and a change in their listing status to endangered was recently under consideration. Estimates of adult population size are needed to evaluate population status, but include a number of uncertainties. A point estimate of loggerhead population size based on a nest count fails to convey the range of our uncertainty in the estimated number of individuals in a population. We developed distributions of adult female loggerhead subpopulation sizes for 5 subpopulations of the western North Atlantic, and for the western North Atlantic population as a whole. Distributions were derived by re-sampling from available nest counts (2001−2010) and data on breeding interval, survival and clutch frequency, each affecting the extrapolation of nest numbers to adult females. Our best estimate for the western North Atlantic adult female loggerhead population was 38334 (SD = 2287) adult females. Confidence limits on estimates for the individual subpopulations ranged from a high of 45058 adult females for Peninsular Florida to a low of 258 adult females in the Dry Tortugas. To reduce uncertainty in population estimates, research needs to focus on quantifying breeding interval and clutch frequency, especially in the less-studied subpopulations.


KEY WORDS: Sea turtle · Population size · Bootstrap · Extrapolation · Conservation · Caretta caretta · Loggerhead


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Cite this article as: Richards PM, Epperly SP, Heppell SS, King RT and others (2011) Sea turtle population estimates incorporating uncertainty: a new approach applied to western North Atlantic loggerheads Caretta caretta. Endang Species Res 15:151-158. https://doi.org/10.3354/esr00379

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