Study of the dynamics of the exploited stock of Metapenaeus dobsoni indicates that for an age at first capture ( t c) of 1.5 years the fishery generates a steadily increasing yield up to about 17 000 tons for an annual effort ( f) of 2500 trawlers per day (tpd), equivalent to 537.5 × 10 3 boat-days (bd), at which the annual fishing mortality coefficient ( F) is 2.50 and the annual exploitation ratio ( E) is 0.52. Beyond this level of exploitation, the rate of increase in yield is negligible. The potential yield per recruit ( Y′) is estimated to be 1.12 g (for the natural mortality coefficient M = 2.303, E = 1, F ∞ = 4772 tpd or 1026 × 10 3 bd and the optimum age of exploitation t y = 1.06 years). The biologically optimum yield (i.e. the MSY) is 18 000 tons (Kerala = 15.2 × 10 3 tons, Karnataka = 2.1 × 10 3 tons and Goa = 1.1 × 10 3 tons) for an effort ( f MSY) of 2702 tpd, equivalent to 580.9 × 10 3 bd (Kerala = 1535 tpd = 330.0 × 10 3 bd, Karnataka = 676 tpd = 145.3 × 10 3 bd and Goa = 491 tpd = 105.6 × 10 3 bd) for an average 215 fishing days a year, at which E is 0.54 and F is 2.70. The average yield of 17.4 × 10 3 tons from 1976 to 1984 is marginally less than the MSY, whereas the average annual effort for this period (f = 2760 tpd or 59.3 × 10 3 bd, F = 2.76 and E = 0.53) is marginally higher than the f MSY. Although the current (1983–1985) yield (17.7 × 10 3 tons) remained much the same as the average annual yield for 1976–1984, the current effort has increased substantially to 3500 tpd, equivalent to 752.5 × 10 3 bd ( F = 3.5, E = 0.61) much beyond the f MSY.
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