Age, growth, mortality and stock assessment of Epinephelus diacanthus (Valenciennes) from Bombay waters

Abstract

The age, growth, mortality, yield and stock estimates of Epinephelus diacanthus is reported in this communication. Using the length frequency data 1989 to 1992, the Loo was estimated as 502 mm and K as 0.16 on annual basis. This species grows to 229, 354, 421, 458, 478 mm at the end of I - V years of its life span. The total, natural and fishing mortality coefficients were estimated as 1.94,1.15 and 0.79 respectively. The exploitation rate and ratio was found to be 0.3486 and 0.4072 respectively. The total and standing stocks were estimated as 1815.54 and 801.13 t and MSY 368.5 t as compared to the present yield of 632.9 t. The age at first recruitment (t^) and the age at first capture worked out to be 0.4054 and 0.67 years respectively. The Woo was estimated as 1870 gm. The yield per recruit was estimated as 84.25 gm at the present level of F = 0.79. The yield per recruit study indicate that the 'F' can almost be doubled to 1.46 to get an Yw /R of 91.906 gm. But as the gain in Yw /R would be only 7.45 gm increasing the fishing efforts to that level is not advisable.