Studies on the scales of Pseudosciaena diacanthus (Lacepede) for estimating growth parameters

Abstract

The nature of the different types of growth checks on the scales of Pseudosciaena diacanthus (ghol) has been described for faciUtating an easy identification of the annular margins. The time of ring formation (transparent bands) was fouiid to be annual, taking place during Fisbruary-April. It has been suggested that the ring formation on the scales may not be due to growth-inhibiting factors. Back-calculatiotis were made on the basis of total length — scale size relationship, which was found to bi; a straight line after logarithmic transformation of the two variables. The weighted mean length of all the fish examined was estimated to be 46.39, 64.13, 80.52, 93.44, 101.21 and 105.85 cm, at I + to VI + ages. The maximum age was observed to be VII + years, of a fish measuring 127.0 cm. The results of the backcalculations were checked with the mean lengths at different ages obtained by the length frequency analysis. Ttie length composition was dominated by fish belonging to the IV + age group, with the mean length ranging from 90.25 cm to 93.50 cm. The logistic curve was found to describe the growth of 'ghol' most adequately. The estimated L^^ was 118.01 cm for the logistic equation while it was 144.72 cm for the von BertalanfFy growth eqiation.