Study of External Morphometric Variants and Length-Weight Relationship of Labeo rohita (Hamilton-1822) Fed with Varying Protein Levels

External morphometric studies along with Length-weight relationships (LWRs) were carried outfor five groups of juvenile Labeo rohita fed with various protein: Energy ratios; fish meal (T0), 25%CP (Crudeproteins) (T1), 30%CP (T2), 35%CP (T3) and 40%CP (T4). Experiment was designed to replace enriched fishmeal diets with cheaper plant origin crude protein diets in fish culture. A total of 15 aquaria having 20 sampleseach were arranged in triplicate for 90 days to study the effect of five feeding groups on Length-weightrelation and external morphometric variants of Labeo rohita. A total of 75 fish samples @ 5 fish samples peraquaria were analyzed in present study. T1 showed the highest values for mean wet weight 11.32±1.78, Totallength 10.54±0.51, Fork length 8.94±0.46, Standard length 8.27±0.44, Body depth 2.64±0.16 and Body girth5.28±0.33. Pectoral fin length, pelvic fin length, dorsal fin length and caudal fin length also showed highestvalues; 1.56±0.09, 1.36±0.09, 1.72±0.15 and 2.27±0.13 respectively in T1. Length-weight increment order invarious treatment groups was T1 T2 T3 T4 T0. Highly significant correlations (p 0.01) were noted whenlog total length and log wet weight were plotted against each other and with log values of all external morphometricvariants except condition factor (K). “b” (regression coefficient) value for LWRs of Labeo rohita invarious groups was calculated as 3.37, 3.11, 3.20 in T1, T2 and T3 respectively and showed positive allometricgrowth pattern while negative allometric pattern was observed in T4 and T0. The coefficient of determination(r^2) was ranged from 0.888 to 0.989 in LWRs, expressing highly significant correlation (p 0.01). The varianceinflation factor (VIF) was observed as: 17.86 (T1), 12.50 (T2), 01.79 (T3), 10.75 (T4) and 10.20 (T0); expressingmulti-collinearity among morphometric variants and LWRs with change in diet compositions. Diets withdecreased fish meal percentage and maximum plant origin sources showed an increment in length-weightvariants. Present findings indicate that fish dislike the fish meal diet and preferred the plant origin sources.