Growth, mortality and yield per recruit of Polynemus heptadactylus (Cuvier) (Teleostei: Polynemidae) from Mumbai waters, India

The growth, mortality and yield parameters of seven fingered threadfin Polynemus heptadactylus (Cuvier) based on 2 years length frequency data collected from shrimp trawlers in Mumbai, India are reported. The catches as well as the catch rates have shown wide fluctuations. The von Bertalanffy's parameters in length were estimated as L∞ = 384 mm, K = 0.82 year−1 and to = −0.00065 year. The rates of total, natural and fishing mortalities were calculated as 5.61, 1.47 and 4.14, respectively, on annual basis. The Z/K was estimated as 6.81. The relative yield per recruit study shows that the maximum yield can be obtained at E of 0.56, whereas, the present E is around 0.74. This shows that there is high fishing pressure on the stock. Yield isopleth diagram indicates that with an Lc/L∞ of 0.359 eumetric fishing can be achieved at E of 0.60. All these factors point out a reduction in the efforts to prevent depletion of stock.