Studies on the age and growth of the oil-sardine Sardinella longiceps Val. by means of scales

Abstract

A sound knowledge of age and growth of fishes is of prime importance in the management and forecast of their fisheries. Conflicting views have been expressed regarding the age and the life span of the oil-sardine based on the studies of the growth-checks of its scales, otoliths and the length-frequency. Hornell and Nayudu (1923) concluded that the fish attains sexual maturity and adult size of 15 cm. at the end of one year and that the life span of the oil sardine is limited to 2\ years, based on the growth-rings .of the scales. Devanesan (1943) detected the, first growth ring on the scales of fish of 6.5 cm. in length and six of them in fish of 8.7 cm., and. suggested that nine and fourteen "rings" may be expected in the fish of 15 and 18 cm. group respectively and that the fish might live for fourteen years, ^air (1949), working on the oil-sardine otoliths, stated that the fish live for three years; and later (1952) stated that it is probable that the growth-checks detected on the otoliths of the oil-sardine, especially the first two, are formed during the summer when the phytoplankton is scarce and that the third ring formed in some is either due to the same cause or due to the suspension of their feeding activity during spawning. Nair (1960), in a review, suggested that the average life span of the fish is "about 3 to 4 years." Chidambaram (1950) studied the length-frequency of the fish and concluded that its life span is four years. For resolving the' above-said divergences of views on age and growth it was felt desirable to undertake a detailed study of its scales; and, therefore, the scale data and the length-frequency data were simultaneously collected at Calicut and Cochin. Balan (1959) in a preliminary note based on scale-studies and length frequency data indicated that the biggest fish have, without doubt, completed three years of their life.