Biometric evaluation of the freshwater snail Pila globosa (Swainson, 1822) from the river Ganga in Bihar, India

Length-frequency distribution, morphometry, length-weight relationship, relative condition factor and sex ratio of the apple snail Pila globosa (Swainson, 1822) were studied from the river Ganga. A total of 922 specimens were collected during July 2020 to June 2021, ranging from 3.53 to 62.99 g and from 16.49 to 59.78 mm (shell length). Length-frequency distribution revealed that more than 50% of male and female specimens were within 35 to 45 mm in length and only a few (1.58%) female specimens were observed in the higher length (>55 mm). Females have significantly longer shells and are heavier than males. Shell length has the strongest correlation with shell width (r=0.974) and the least with penultimate whorl length (r=0.855). Length-weight relationship, indicated that the species has negative allometric growth (b<3). The relative condition factor was 1.07 for males, 1.00 for females and 1.01 for pooled data. Sex ratio (M:F) statistically deviated from the hypothetical ratio of 1:1, indicating a heterogeneous snail population (1:1.9, p<0.05).