Comparative Morphometrics, Condition Factor and Gonadosomatic Index of Oreochromis mossambicus and Oreochromis niloticus from Reservoirs of Akola District, India

Tilapias are prominent components of tropical reservoir fisheries, yet meaningful stock comparisons require joint interpretation of body dimensions, meristic characters, condition and reproductive investment. This study evaluated 588 specimens collected from freshwater reservoirs of Akola District, Maharashtra: 271 Oreochromis mossambicus (131 males and 140 females) and 317 O. niloticus (164 males and 153 females). Body weight, total and standard length, selected morphometric and meristic characters, relative condition factor (Kn) and gonadosomatic index (GSI) were examined. O. niloticus showed greater mean total and standard length and larger absolute values for most linear measurements; because this species also had a wider size distribution, these measurements are interpreted as absolute biometric differences rather than size-independent shape divergence. Meristic contrast was clearest in first-gill-arch rakers (27-33 in O. niloticus versus 20-22 in O. mossambicus) and in lateral-line and caudal-peduncle scale counts. Mean Kn was close to unity in all species-sex groups (1.001-1.007), and Welch's ANOVA detected no significant difference among groups, F(3, 308.16) = 0.122, p = 0.947. Kn variability was lowest in male O. mossambicus (CV = 3.27%) and highest in female O. niloticus (CV = 11.84%). GSI showed stronger descriptive contrasts: males averaged 0.283% in O. mossambicus and 0.923% in O. niloticus, whereas females averaged 2.474% and 1.435%, respectively. These findings provide a district-level biometric baseline and show that morphometrics, condition and gonadal investment should be interpreted together with body size, sex and sampling structure.