Investigation of growth phases for bottlenose dolphins using a Bayesian modeling approach

Authors

  • Wayne E. McFee,

    1. Center for Coastal Environmental Health and Biomolecular Research, National Ocean Service, NOAA, 219 Ft. Johnson Road, Charleston, South Carolina 29412, U.S.A.
      E-mail: wayne.mcfee@noaa.gov
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  • John H. Schwacke,

    1. Department of Biostatistics, Bioinformatics and Epidemiology, Medical University of South Carolina, 135 Cannon Street, Suite 303, P. O. Box 250835, Charleston, South Carolina 29425, U.S.A.
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  • Megan K. Stolen,

    1. Hubbs-Sea World Research Institute, 6295 Sea Harbor Drive, Orlando, Florida 32821-8043, U.S.A.
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  • Keith D. Mullin,

    1. Southeast Fisheries Science Center, National Marine Fisheries Service, NOAA, 3209 Frederic Street, Pascagoula, Mississippi 39567, U.S.A.
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  • Lori H. Schwacke

    1. Hollings Marine Laboratory, National Centers for Coastal Ocean Science, National Ocean Service, NOAA, 331 Ft. Johnson Road, Charleston, South Carolina 29412, U.S.A.
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Abstract

The Gompertz function is the most commonly used growth function for cetacean studies. However, this function cannot represent multiple phases of growth. In this study, we present a Bayesian framework fitting parameters of a triple-logistic growth function to describe multiple phases of growth for bottlenose dolphins (Tursiops truncatus), simultaneously fitting and comparing all growth parameters between South Carolina (SC), Mississippi Sound (MSS), and Indian River Lagoon (IRL) cohorts. The fitted functions indicated a preliminary early, rapid growth phase, followed by a second phase of slower growth, and then a moderate growth spurt later in life. Growth parameters between geographic cohorts did not show obvious differences, although asymptotic length for SC dolphins was lower than MSS and IRL dolphins and significantly lower between females from SC and the IRL. Growth rate velocities between the sexes showed females exceed males initially (<1 yr), followed by males gaining an advantage around the ages of 3–4 yr until the age of around 15 yr when growth rates for both sexes approached zero (asymptotic length). This study demonstrates age-related changes in growth rates between bottlenose dolphin sexes and evidence of at least some differences (i.e., asymptotic length) across geographic cohorts.

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