UTTAR PRADESH JOURNAL OF ZOOLOGY

The population structure of Rita rita was delineated using conventional (body morphometrics and meristic) and image-based (truss network analysis) methods. The study was done with three stocks, Tezpur stocks from the Brahmaputra River, and Nagaon stocks from Kolong River and Jamuna stocks from the Jamuna River, the latter two rivers are tributaries of River Brahmaputra.  A total of 30 truss measurements constructed by inter-connecting 14 landmarks based on 300 samples were used to delineate the population structure. The Factor Analysis (FA) and Principal Component Analysis (PCA) and Discriminant Function Analysis (DFA) were employed to determine the populations' variations. The factor analysis (FA) based on truss morphometry indicated body depth-related traits loading heavily on the first factor and shape-relatedcharacteristics belonging to the caudal portion on the second factor.Principal components explained 85.70% variation among morphometric characters, while the first two, the principal component 1 (PC1) and PC2 explained82.14% and 3.56% respectively. The discriminant function analysis (DFA) correctly classified74% of the original grouped classes of Tezpur, Nagaon and Jamuna Stocks.Bilinear data models based on PCA were generated using SPSS software (SPSS 22) for predicting each stock. Two clusters were identified, the Nagaon and Jamuna stocks were similar compared to Tezpur stocks. Geographic isolation, riverine ecology, temperature variation and biology can be attributed to the discrimination of the stock. The stock structure analysis of this species may help frame management and conservation measures incorporating marker-based studies.

The findings suggested the possible existence of two stocks of Rita rita, a single stock in the Brahmaputra River while Jamuna River and Kopili River contained the same stock.