Age Distribution and Growth of Two Bottlenose Dolphin (Tursiops truncatus) Populations from Capture-Release Studies in the Southeastern United States

Abstract: Information regarding the growth parameters of wild bottlenose dolphins (Tursiops truncatus) is sparse despite increased captures of wild bottlenose dolphins for research over the last two decades. The present study investigated age distribution and growth parameters (e.g., length, age, body-mass index [BMI], mass, and girth) of dolphins examined during health assessment studies performed from 2003 to 2007 in the Indian River Lagoon (IRL), Florida, and Charleston Estuary (CHS), South Carolina. Age distributions of 94 dolphins from the IRL and 71 dolphins from CHS showed that significantly younger dolphins were caught in the IRL than in the CHS, though this may be a sampling issue. CHS female dolphins reached a higher girth asymptote than IRL females, whereas both IRL sexes attained higher mass asymptotes than their CHS counterparts. No significant differences in BMI, mass, or girth were detected between IRL and CHS dolphins when accounting for age. Male growth rates obtained from longitudinal data showed IRL dolphins exceeded growth rates of CHS dolphins throughout life. IRL dolphins captured in the northern region of the IRL showed significantly lower mean BMI, mass, and girth than their counterparts captured in the central and southern IRL. While this study demonstrated the varied growth patterns of wild bottlenose dolphins between two geographically separate populations, continued use of longitudinal data on growth parameters may provide for more subtle variations in growth between populations.

Key Words: asymptotic growth, age distribution, capture-release study, bottlenose dolphins, Tursiops truncatus

Document Type: Research article

DOI: 10.1578/AM.38.1.2012.17

Page Numbers: 17-30

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