Evaluating trends in abundance of immature green turtles, Chelonia mydas, in the Greater Caribbean

Bjorndal, Karen A., Bolten, Alan B. and Chaloupka, Milani Y. (2005) Evaluating trends in abundance of immature green turtles, Chelonia mydas, in the Greater Caribbean. Ecological Applications, 15 1: 304-314. doi:10.1890/04-0059

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Author Bjorndal, Karen A.
Bolten, Alan B.
Chaloupka, Milani Y.
Title Evaluating trends in abundance of immature green turtles, Chelonia mydas, in the Greater Caribbean
Journal name Ecological Applications   Check publisher's open access policy
ISSN 1051-0761
Publication date 2005-02-01
Sub-type Article (original research)
DOI 10.1890/04-0059
Open Access Status File (Publisher version)
Volume 15
Issue 1
Start page 304
End page 314
Total pages 11
Editor L. F. Pitelka
Place of publication Washington, DC, United States
Publisher Ecological Society of America
Language eng
Abstract Many long-lived marine species exhibit life history traits. that make them more vulnerable to overexploitation. Accurate population trend analysis is essential for development and assessment of management plans for these species. However, because many of these species disperse over large geographic areas, have life stages inaccessible to human surveyors, and/or undergo complex developmental migrations, data on trends in abundance are often available for only one stage of the population, usually breeding adults. The green turtle (Chelonia mydas) is one of these long-lived species for which population trends are based almost exclusively on either numbers of females that emerge to nest or numbers of nests deposited each year on geographically restricted beaches. In this study, we generated estimates of annual abundance for juvenile green turtles at two foraging grounds in the Bahamas based on long-term capture-mark-recapture (CMR) studies at Union Creek (24 years) and Conception Creek (13 years), using a two-stage approach. First, we estimated recapture probabilities from CMR data using the Cormack-Jolly-Seber models in the software program MARK; second, we estimated annual abundance of green turtles. at both study sites using the recapture probabilities in a Horvitz-Thompson type estimation procedure. Green turtle abundance did not change significantly in Conception Creek, but, in Union Creek, green turtle abundance had successive phases of significant increase, significant decrease, and stability. These changes in abundance resulted from changes in immigration, not survival or emigration. The trends in abundance on the foraging grounds did not conform to the significantly increasing trend for the major nesting population at Tortuguero, Costa Rica. This disparity highlights the challenges of assessing population-wide trends of green turtles and other long-lived species. The best approach for monitoring population trends may be a combination of (1) extensive surveys to provide data for large-scale trends in relative population abundance, and (2) intensive surveys, using CMR techniques, to estimate absolute abundance and evaluate the demographic processes' driving the trends.
Keyword Abundance
Chelonia Mydas
Costa Rica
Greater Caribbean
Green Turtle
Long-lived Species
Population Trends
Sea Turtles
Capture-recapture Data
Nesting Numbers
Model Selection
Marked Animals
Marine Turtles
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2006 Higher Education Research Data Collection
School of Economics Publications
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Citation counts: TR Web of Science Citation Count  Cited 39 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 42 times in Scopus Article | Citations
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Created: Wed, 15 Aug 2007, 16:24:16 EST