Theoretical yield studies on the large-scaled tongue sole, Cynoglossus macrolepidotus (Bleeker), from the Arabian sea
Abstract
Theoretical yield values of Cynoglossus macrolepidotus were computed from a simple Beverton and Holt type model using informations on growth and mortality rates The effects of various fishing mortality rates (F) and ages of exploitation (Tp) on yield were considered at three different natural mortality rates, M=0.4, 0.5 and 0.6, since the calculated natural mortality was found to range from 0.4 to 0.575 The conclusion drawn from the simple model is that the population is at present underfished and considerable increase in the yield is possible by increasing the fishing intensity The yield values clearly indicate that when M=0.4, fish of 2 years and older may be fished at F greater than 0.5; when M=0.5, fish older than 1 year may be fished at F less than 1.15 and when M=0.6 fish of 1 year and older may be fished up to F=1.8 A precise estimate, however, of a Tp' required to give the maximum yield for a given F can be determined from the eumetric fishing curve The yield of Cynoglossus macrolepidotus has been found to be low in relation to the fishing intensity This may be because of high M and low W infinity The optimum age of exploitation is also low in this fish probably because the growth is largely confined to the first few years and M is high
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