Estimates of mortality and yield per recruit of 'ghol' Pseudosciaena diacanthus (Lacepede)

Abstract

The mortality rate and yield per recruit of 'ghol, Pseudosciaena diacanthus, are estimated from the age composition of catches of the bull-trawlers of the New India Fisheries Ltd., Bombay, for the years 1958 to 1961. The annual mortality rate estimated from (1) catch per unit effort data and (2) the average catch curve of 1958-'61 lies roughly between 0.55 and 0.60 and the instantaneous mortality rate between 0.83 and 0.87. Since the fishery for 'ghol' was at the beginning stage with only two pairs of bull-trawlers operating commercially, the estimated total mortality rate (Z=0.83) is regarded as practically equal to natural mortality rate (M). The yield per recruit Yw/R for various lex els of fishing mortality (F) were calculated with M=0.83 and the maximum value of Yw/R was found at a value of F=0.6, which shows that the catch from the stock can be stepped up considerably over the present level. Before deciding to step up the catches of 'ghol' by expanding the trawl fishery, it is necessary to have estimates of fishing mortality generated by the.'dol' nets and gill nets on this fish.