Age and growth parameters of Siganus sutor in Kenyan marine inshore water, derived from numbers of otolith microbands and fish lengths

Siganus sutor (Valenciennes, 1835) is, together with the Lethrinidae, commercially the most important fish of Kenyan waters. Age and growth parameters of this fish have been estimated for stock assessment purposes, using the von Bertalanffy growth model while taking into account the initial small but finite length of fish, L _o. Microbands on the otoliths were used as a measure of age in days. Data of fish length against numbers of microbands were fitted to the growth formula by a least squares procedure applied to a non-linear fit. This gave an L _∞ of 36.2 cm s.l. and a K of 0.87 on an annual basis. Independently, a curve was fitted by eye to the same data, and values were read off the curve and used in a standard Ford–Walford plot. This gave an L_x of 35 cm and a K of 0.9. The close agreement of the values obtained by the two methods, and of these with values in the literature, demonstrates the value of using microbands for determining growth parameters in a tropical fish.