Dynamics of the Bombay duck (Harpodon nehereus) stock along the northwest coast of India

Fernandez, Irene and Devaraj, M (1996) Dynamics of the Bombay duck (Harpodon nehereus) stock along the northwest coast of India. Indian Journal of Fisheries, 43 (1). pp. 1-11.

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Abstract

The fishery for the Bombay duck, (Harpodon nehereus) along the northwest coast of India was studied from the data for the annual catch, effort and length- at-age composition for the period 1947 to 1986. Three models, viz., the Beverton and Holt analytical model, Cushing’s stock-recruitment relation, the surplus production models of Schaefer and of Fox and the prediction model of Roff were applied to dEscribe the state of the stock. The length growth parameters; L0 ranged from 37.45 cm (1985) to 60.97 cm (1958), annual k ranged from 0.29 (1958) t0 0.77 (1948) and t, ranged from —0.12 year (1948) to 0.06 year (1985), while the weight growth parameters; W0 ranged from 319.14 g (1948) to 1,910.65 g (1950-51), annual k ranged from 0.26 (1984 and 1985) to 0.85 (1948) and t, ranged from —0.08 year (1948) to 0.03 (1950-51). The length at first capture, l, was 3.00 cm (t0 = 0.13 year) while the length at recruitment, lr was 2.00 cm (tr = 0.08 year). Total annual mortality, Z, ranged from 2.32 (1985) to 8.29 (1948), natural mortality, M, ranged from 0.93 (1950-51) to 1.20 (1948- ‘49) while fishing mortality, F, ranged from 1.32 (1985) to 2.70(1983). Cohort analysis indicated maximum F at 4+age group in 1983 (=2.70) and at 3+ age group in 1984 (=1.77). The stock-recruitment data indicated a linear relation with density dependence (b) ranging from 0.32 to 1.03 with an average of 0.68. The MSY estimated according to the analytical model was found to be 189,844 t which according to the Schaefer and Fox models was 101,158 t and 103,483 t respectively. The prediction model indicated an estimated catch of 92,189 t in the year 2000 if the effort remained a constant.

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