Mohammad Afzal Khan

Assessment of growth zones on whole and thin-sectioned otoliths in Sperata aor (Bagridae) inhabiting the River Ganga, India

The present study was undertaken with the objective to assess the clarity of growth zones on whole and thin-sectioned otoliths in Sperata aor. A total of 125 sagittal otoliths of S. aor were collected monthly from the river Ganga during the period, April to December 2013 at Narora, Uttar Pradesh, India. Thin sections (approximately 0.5 mm) of one of the sagittal otoliths of each fish were cut using IsoMet® Low Speed Saw. Both whole otoliths and thin-sectioned otoliths were then examined under stereozoom microscope. Parameters of agreement on growth zones were calculated by comparing the number of growth zones obtained independentlyby the two readers (R1 and R2) from the two methods (whole otolith and thin-sectioned otolith method). Thin-sectioned otolith method exhibited higher agreement than whole otolith method based on linear regression analysis and growth zones bias plot. Between readers, higher agreement was noted for reader 1 than reader 2, plausibly due to his relatively more experience in examining the growth zones on the otoliths. However, both readers reported independently that the growth zones were clearer on thin sections than on whole otoliths especially those from older individuals. Thus, it may be concluded that the thin-sectioned otolith method should be utilized for assessment of growth zones in S. aor populations from the river Ganga.

Precise age estimation and growth of three Schizothoracinae fishes from Kashmir valley

Studies on the precision of age estimates from different structures/readers and growth assessment were undertaken in selected Schizothoracinae fishes. Ageing structures were prepared and read following standard protocols. The maximum ages of the observed Schizopyge curvifrons and Schizopyge niger specimens were 6 years and 5 years of Schizothorax esocinus specimens. Based on the highest percentage of agreement (PA) and the lowest average percentage of error as well as on the values of coefficient of variation between readers, otoliths provided a precise age estimate of S. curvifrons and S. niger individuals, while vertebrae showed a precise age estimate of those of S. esocinus. Among structures, the highest PA was found between otoliths and opercular bones in S. curvifrons, between otoliths and scales in S. niger, and between vertebrae and opercular bones in S. esocinus. Comparable values of mean age estimates were obtained from different structures in specimens of the following species: from otoliths, op...

Length-weight and length-length relationships of Cirrhinus mrigala (Cyprinidae) and Xenentodon cancila (Belonidae) from the river Ganga

Length-weight and length-length relationships are presented for two fish species collected during May 2015 to August 2016 from Narora site of the river Ganga. The parameters a and b of the length-weight relationships were estimated after the logarithmic transformation of the equation: W = aLb. The lengthlength relationships were also estimated using linear regressions. The coefficients of determination (R2) values were >0.9 for both target fish species and linear regressions were highly significant (p < 0.001). Length-weight relationship indicated positive allometric growth pattern for Cirrhinus mrigala and negative allometric growth pattern for Xenentodon cancila. Length-length relationships for the selected fish species were also highly significant (R2 > 0.9, p < 0.001).