Primary Growth Rings in Otoliths of Some Clupeids from Sri Lanka

Abstract

This paper describes the otolith structure and the pattern. of ring deposition of four species belonging to the family Clupeidae from the coastal waters of Sri Lanka. The otoliths of all these species were found to contain primary growth rings which could be used in age determination. The structure of the otolith and the ring deposition pattern of the clupeids studied were similar to each other and to Sardinella spp. Age estimates were made by assuming that these rings are formed daily. Dussumieria acuta and Ilisha melanostoma seem to grow similar to Sardinella, attaining a length of about 14 cm and 11 cm, respectively, in one year, while Eseualosa thoracata reach a size of about 9 cm in one year. Opisthopterus tardoore grow relatively fast to a size of about 8 cm in 4 months. Calculated birthdates were in agreement with known spawning seasons except for 0. tardoore. This could be the result of bias due to poor ring visibility.