Length-Weight Relationship and Condition Factor of Three Species of Freshwater Spiny Eels (Mastacembelidae) Collected from Indo-Gangetic Plain, India

The present study investigates the length-weight relationship (LWR) and Fulton’s condition factor (K) for three species of freshwater spiny eels (Family: Mastacembelidae) inhabiting the Indo-Gangetic Plain. A total of 242 specimens, comprising Mastacembelus armatus (Lacepède, 1800), Macrognathus pancalus (Hamilton, 1822), and Macrognathus aculeatus (Bloch, 1786), were collected between August 2023 and July 2024 from the River Ganga (Patna) and its two major tributaries, the River Ghaghara (Bahraich) and the River Gomti (Lucknow). The regression analysis revealed a strong correlation between length and weight across all the species, with coefficients of determination (r²) ranging from 0.72-0.98. The estimated growth coefficient (b) ranged from 2.85-4.13, while the condition factor (K) remained below 1.0 (ranging from 0.262-0.588) across all the species-river systems. A t-test comparison against the hypothetical isometric value (b = 3) of an ideal fish showed that M. armatus and M. aculeatus exhibited isometric growth across all three rivers, suggesting a growth physiology relatively resilient to inter-riverine habitat variations. Conversely, M. pancalus demonstrated significant inter-riverine adaptability, exhibiting positive allometric growth in the Rivers Gomti and Ghaghara while isometric growth in the River Ganga. One-way ANCOVA further revealed distinct patterns of inter-specific and inter-riverine variation in LWRs, which indicates that both growth trajectories and body conditions in these species are population-specific and fluctuate in response to local hydrological, trophic, and ecological conditions. The study provides updated and comparative data on the growth dynamics of commercially important spiny eels, offering essential information for the sustainable management of fish under culture and capture fisheries.