Download or read book Demographic Characteristics of Selected Epinepheline Groupers (family Serranidae, Subfamily Epinephelinae) from Aldabra Atoll, Seychelles written by E. M. Grandcourt and published by . This book was released on 2005 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sagittal otoliths were extracted from samples of six species of groupers (Serranidae: Epinephelinae) caught with hand lines around the periphery of Aldabra atoll (southwest Indian Ocean) in December 2000: Epinephelus fuscoguttatus (n=26), Epinephelus multinotatus (n=33), Epinephelus polyphekadion (n=77), Epinephelus tukula (n=62), Plectropomus laevis (n=22) and Variola louti (n=101). Growth increments consisting of alternating translucent and opaque bands were observed in transverse sections of sagittae. The von Bertalanffy growth function was fit to size and increment number data, values of the growth coefficient (k) ranged from 0.13 for E. tukula to 0.48 for V. louti, with a mean value of 0.24 for all species. Estimates of the annual instantaneous rate of natural mortality ranged from 0.13 yr−1 for E. polyphekadion to 0.28 yr−1 for V. louti. The maximum number of putative annuli observed in transverse sections of sagittae ranged from 15 for V. louti to 31 for E. polyphekadion. While the study demonstrates the utility of structural increments in sagittal otoliths for establishing key demographic characteristics, parameters derived from age estimates are preliminary given the need to validate the periodicity of increment formation. Nevertheless, the results suggest that groupers in general are long-lived, slow-growing species that have low rates of natural mortality. The findings are important to fisheries management and conservation authorities as they support the contention that these species have a low resilience to exploitation and their populations may be particularly vulnerable to overfishing.