Shahista Khan

Precision of aging structures for Indian major carp, Cirrhinus mrigala, from the River Ganga

Scales, opercular bones, otoliths, vertebrae, and dorsal fin rays were compared to ascertain the best aging structure of Cirrhinus mrigala. All structures showed alternating opaque and translucent bands that were interpreted as annuli; however, structures differed greatly in the clarity of their presumed annual marks. Age estimates were compared by calculating the percentage of agreement (PA), average percentage of error (APE), and coefficient of variation (CV) and by constructing age bias plots. Age estimates were evaluated between readers and between the pairs of aging structures. Among all structures, scales showed the clearest annual rings and had highest (94.6%) PA between readers, followed by opercular bones (88.6%), otoliths (83.9%), vertebrae (79.9%), and dorsal fin rays (62.4%). Due to highest PA and lower minimal aging error, the scales were considered the most reliable bony structure for aging C. mrigala. When scale ages were compared with those of the other structures, the highest PA and lowest APE and CV values were found between scale and opercular bone estimates. Mean values of age estimate from scales were comparable (p > 0.05) to the values obtained from opercular bones, otoliths, and vertebrae and were significantly (p < 0.05) different with the dorsal fin ray age estimates. Scales were the most suitable structures for age estimation in C. mrigala.

Evaluation of ageing precision from different structures of three threatened freshwater fish species, Clarias batrachus, Heteropneustes fossilis and Wallago attu

Abstract. Ageing precision from otoliths, vertebrae and pectoral spines was studied in Clarias batrachus, Heteropneustes fossilis and Wallago attu. In C. batrachus, otoliths showed the highest (92.9 %) agreement between readers followed by vertebrae (87 %) and pectoral spines (83.8 %). The highest percentage of agreement (87 %) and lowest average percentage of error (1.89 %) and coefficient of variation (3.81 %) values were observed between otoliths and vertebrae age estimates. In H. fossilis, vertebrae showed the clearest annual rings and had highest (90.8 %) PA values between readers, followed by otoliths (80.3 %) and pectoral spines (73.7 %). The highest PA and lowest APE and CV values were found between vertebrae and otoliths estimates. In W. attu, otoliths showed the highest PA (86.7 %) values between readers followed by pectoral spines (70.3 %) and vertebrae (67.9 %). The highest PA and lowest APE and CV values were found between otoliths and pectoral spines. On account of the highest PA, lowest APE and CV values, the most suitable ageing structure was otolith in C. batrachus and W. attu, while vertebrae in H. fossilis. If mean age estimates are considered then in the absence of the most suitable ageing structure, alternatively, vertebrae can be used in C. batrachus, otoliths in H. fossilis and pectoral spines in W. attu.