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Marine Ecology Progress Series

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MEPS 202:265-272 (2000)  -  doi:10.3354/meps202265

Somatic growth model of juvenile loggerhead sea turtles Caretta caretta: duration of pelagic stage

Karen A. Bjorndal1,*, Alan B. Bolten1, Helen R. Martins2

1Archie Carr Center for Sea Turtle Research and Department of Zoology, University of Florida, PO Box 118525, Gainesville, Florida 32611, USA
2Department of Oceanography and Fisheries, University of the Azores, 9901-862 Horta, Azores, Portugal

ABSTRACT: The pelagic juvenile stage of sea turtles is poorly studied. We present a growth model and estimates for duration of the pelagic juvenile stage for loggerhead sea turtles Caretta caretta in the North Atlantic based on length-frequency analyses and sizes of young-of-the-year stranded in the Azores. The size-specific growth model is a monotonic, nonlinear, declining function. The growth model is consistent with growth rates calculated from recaptures of tagged loggerheads. Loggerheads leave the pelagic habitat and recruit to neritic habitats over a range of sizes from 46 to 64 cm curved carapace length (CCL). From this size range and the growth model, we estimate the duration of the pelagic stage varies from 6.5 to 11.5 yr. Nonparametric smooths of the size frequency distributions of loggerheads in pelagic (n = 1692) and neritic (n = 1803) habitats intersect at 53 cm CCL, which is equivalent to an 8.2 yr duration for the pelagic stage. More growth data from loggerheads <2 yr old would strengthen the database for our growth model and perhaps lengthen our estimates of the duration of the pelagic stage. Incorporating our estimates for duration of the pelagic juvenile stage into the stage-based population model developed for North Atlantic loggerheads would have a major effect on estimates of population growth.

KEY WORDS: Azores · Length-frequency analysis · Loggerhead sea turtles · Pelagic stage · Somatic growth

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