Morphometrics are important in fish taxonomy and fishery biology studies. Nine standard morphometric lengths, viz; total length, fork length, standard length, body depth, eye diameter, snout length, post orbital length, head length and caudal peduncle height of the Indian mackerel Rastrelliger kanagurta were measured by the conventional morphometric method and also using an image analysis technique.Algorithm for the same is described.The image analysis showed good validation with corresponding conventional measurements. Nearly 50 per cent of the measurements representing the nine morphometric lengths showed no difference and 31 to 34 per cent showed a difference of < 3 per cent. Another 11 to 19 per cent showed a difference < 5 per cent. The results proved that digital image processing and morphometric measurements using image analysis are dependable.

Morphometry, image analysis, mackerel, digital imaging