Studies on length-weight relationship, condition factors and length-length relationship of Anguilla bengalensis bengalensis, Gray, 1831 (Actinopterygii, Anguillidae) collected from River Mayurakshi, Siuri, Birbhum, West-Bengal, India

Length-weight, length-length relationships and condition factors are the most important aspects to assess the growth, maturity and well-being of fish population. These are also helpful for scientific management of fisheries and stock assessment. To assess the above mentioned criteria, length-weight relationship was studied in size groups of Anguilla bengalensis bengalensis, a freshwater catadromous mottled eel of Indian subcontinent. The results show highly significant relationship in all the size groups. The ‘b’ value of the exponential equation shows positive allometric growth in all the three juvenile size groups while negative allometric growth is observed in the largest size group. Results of regression analysis of total length vs. anodorsal length and total length vs. head length show highly positive significant correlation. Multivariate regression analysis of body weight on anodorsal and total length shows a perfect significant linear relationship. Condition factor, relative condition factor and modified condition factor of all the size groups shows that the earlier stages of A.bengalensis bengalensis are in good condition in respect to growth but in the largest size group, weight gain is minimum relative to growth. From the entire study it is to be concluded that like all non-migratory fishes the results of juvenile stages of A. bengalensis bengalensis show normal allometric growth and hence the fishes are in good condition. But due to unavailability of spawning ground, far reaches from sea, this catadromous fish lacks gonadal differentiation and development and hence negative allometric growth is observed in the largest size group.