Growth of Namibian silver kob Argyrosomus inodorus based on otoliths and mark-recapture data

Abstract

The growth of silver kob Argyrosomus inodorus sampled from two regions (northern and southern) along the Namibian coast was determined using longitudinally sectioned otoliths. The special Von Bertalanffy growth model adequately described the growth of kob in both regions. Growth rate for kob in the south was validated using mark-recapture data, and similar growth rates were obtained using both methods. Growth of kob sampled in the south (maximum age 19 years) was significantly different from those in the north (maximum age 28 years). Kob from the two regions appeared to be from the same stock, and consequently length-at-age data from the regions can be pooled for management purposes. Growth of Namibian silver kob was markedly different from the South African silver kob, for which growth was best described by logistic (South-Western Cape) and Richards (Southern and South-Eastern Cape) models. The special Von Bertalanffy growth parameters were determined by the equations: L(t) = 116 (1-e(0.120 (t+1.47))) mm for the southern region, L(t) = 112 (1-e(-0.094 (t+2.29))) mm for the northern regions, L(t) = 103 (1-e(-0.136 (1+1.58))) mm for both regions combined.