A biomass dynamics assessment of the southeastern Caribbean snapper–grouper fishery

Abstract

Southern red snapper, Lutjanus purpureus, and yellowedge grouper, Epinephelus flavolimbatus, are the main species exploited by handliners and longliners of the Venezuelan medium range snapper–grouper fleet in the southeastern Caribbean. Catch and effort data for the period 1981–2000 are used to assess both species by means of a Schaefer biomass dynamic model. Due to lack of contrast in both time series empirical estimates of the intrinsic rate of population increase ( r) were used as auxiliary information for fitting the model to the data. Model parameters and derived variables uncertainty was estimated using a conditioned non-parametric bootstrap with fixed r values and normally distributed r values with estimated coefficients of variation of 55% for yellowedge grouper and 42% for red snapper. Also, 10-year biomass projections under different catch scenarios for both species were used to assess the impact of fishing on future population levels. Results indicate that L. purpureus is more intensely exploited than E. flavolimbatus and biomass levels in the year 2000, depending on the initial biomass B i hypothesis, were on average between 22% ( B i=0.5 K) and 39% ( B i=K) and 13% ( B i=0.5 K) and 25% ( B i= K) of virgin biomass ( K) for E. flavolimbatus and L. purpureus, respectively. Significant population recoveries are possible if catches are maintained at relatively low levels for both species, but biomass recovery to MSY levels depending on species and scenarios may require a longer time frame than the 10-year period used for projections.