Growth Parameters and Total Mortality of the Sardine Sardinella aurita (Valenciennes, 1810) in Northeastern Venezuela in the Period 1990-2008

摘要

Sardinella aurita is the main species exploited by small-scale fisheries in northeastern Venezuela and represents an important source of low cost protein in the Venezuelan market. Due to natural variability its economic, social and ecological relevance this resource is under a regular monitoring program to obtain biological information and fishery. In this context, in this study growth parameters (L and K) of the von Bertalanffy growth equation and total mortality (Z) were estimated from length frequency data. We used modal decomposition of length frequencies and then monthly growth increments to estimate L and K by the method of Fabens (1965). Parameter estimates were obtained for the total study period (L = 326 mm and K= 0,66 year-1) and for three subperiods: 1) 1990-1995 (L = 375 mm and K= 0,45 year-1); 2) 1996-2001 (L = 348 mm and K= 0,62 year-1) and 3) 2002-2008 (L = 266 mm and K= 1,30). Confidence intervals were estimated from joint likelihood profiles. Total mortality (Z) was determined by the method proposed by Ehrhardt and Ault (1992), with an average Z of 5,41 year-1 (range 2,01 9,26 year-1) with an increasing trend during the study period. The variability of the growth and mortality rate of the Sardinella aurita in the northeastern region, they are due to a combination of environmental factors and of fishing exploitation.