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

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.