Age and Growth of Spotted Snakehead, Channa punctata from the Ganga River

Abstract

The present study was undertaken to estimate age and growth of the spotted snakehead Channa punctata (Bloch, 1793) from the Ganga River, based on 390 fish samples collected during August 2016 to July 2017. Each of the 3 otoliths (lapillus, asteriscus and sagitta) were dissected out, cleaned and observed to identify the annual rings. Based on clarity of annuli and ease of reading, sagittae (whole as well as sectioned) were selected for age estimation. Standard procedures were followed to prepare and study the age structures viz., the otoliths and scales. The alternating opaque and translucent bands present on the ageing structures were interpreted as annuli. Amongst the 3 methods used for age estimation, the sectioned otolith exhibited highest percentage of agreement (92.4) between readers, and least values of average percent of error (2.68) and coefficient of variation (2.36). Age estimates from sectioned otoliths were taken to develop the von Bertalanffy growth equation [L_t = 31.5(1 – e^{–0.29(t+ 1.06)})] for the target fish species. The observed and calculated lengths in the fish did not vary significantly. Thus, the sectioned otoliths may be used for precise age estimation as well as calculation of various age-based population parameters of C. punctata inhabiting the river Ganga.