Demography of a large exploited grouper, Plectropomus laevis: implications for fisheries management

Abstract

Species in the coral trout complex Plectropomus spp. are some of the most desired and exploited in the Indo- Pacific, although data are limited for most species. Demographic parameters of blue-spot coral trout, Plectropomus laevis, were estimated on the basis of specimens collected from five regions of the Great Barrier Reef and Torres Strait, Australia, between 1995 and 2005 to define demography and population status over a broad range. In total, 1249 individuals were collected to estimate growth, mortality and reproductive parameters. Growth parameters based on the von Bertalanffy model were K=0.096 year−1, L∞ =1159mm fork length (FL) and the best-fit model suggested non-asymptotic growth over the size and age ranges represented in the sample. Maximum age was 16 years, total mortality was estimated at 0.39 (±0.031), and estimated size and age at first maturity were 299mm FL (range: 299–872) and at 1 year (range: 1–6.5), respectively, with the size range over which sex change occurred at 460–872mm FL. Population parameters and available relative abundance estimates indicated that long-term sustainable harvest rates of P. laevis will be lower than those for P. leopardus and species-specific size-based management measures are necessary to ensure the species is not overfished.