Estimates of the stocks of oil sardine and mackerel in the present fishing grounds off the West coast of India

Abstract

The annual exploitation rate (U) in a fish population is given by the well- F (1-e"^''^^^) known expression p -r- ' where M is the annual instantaneous natural mortality coefficient and F the annual instantaneous fishing mortality coefficient. An estimate of the annual total stock may be obtained by dividing the total catch (Y) by U, and the annual average standing stock by dividing the annual catch by F. In the oil sardine fishery of the west coast, M has been estimated as 1.12, F as 0.54 and U as 0.26. The annual average catch for 1960-71 was 210,000 tonnes. Then the annual total stock in the fishing grounds during this period may be estimated as 810,010 tonnes on the average, and the annual average standing stock as 390,000 tonnes. In the mackerel stock, M is estimated as 0.9 and F as 1.15. The annual average catch on the west coast for the period 1960-71 was 65,000 tonnes. The total annual stock in the fishing grounds may then be estimated as 130,000 tonnes on the average and the average standing stock as 57,000 tonnes. Stock estimates based on slightly different values of F and M are also given.