Morphometric correlations and meristic characters in eight species of family Bagridae from the Beki River, Assam, India

Abstract

The present study investigates morphometric and meristic variations among 473 samples of eight catfish species of family Bagridae viz. Mystus tengara, Mystus bleekeri, Mystus cavasius, Mystus carcio, Mystus vittatus, Sperata aor, Sperata seenghala and Rita rita in the Beki River, Assam, India. Using traditional morphometrics, linear regression and Pearson’s correlation, the study explored growth patterns and trait relationships. Weight ranges varied from the small Mystus carcio (2-4.9 g) to the significantly larger Sperata seenghala (395-944 g), with other species such as Mystus tengara (7-16 g), Mystus bleekeri (5-24 g), Mystus cavasius (5-69 g), Mystus vittatus (8-24 g), Sperata aor (29-368 g) and Rita rita (49-387 g) falling in between. Statistical results revealed strong positive correlations between total length (TL) and various body parameters, indicating proportional growth. High correlations (r) were found between total length (TL) and standard length in M. cavasius (0.991), M. vittatus (0.973), M. bleekeri (0.996), and S. aor (0.993). Other high correlations included total length with adipose fin base in M. tengara (0.971), inter-orbital distance in M. carcio (0.997), pre-dorsal length in R. rita (0.988), and pre-pelvic length in S. seenghala (1.000). Lowest correlations were notably found with the adipose-dorsal fin distance in M. vittatus (0.004) and maxillary barbel length in S. seenghala (0.042). Meristic analysis showed four pairs of barbels in all Mystus and Sperata species, while Rita rita possessed only three due to the absence of outer mandibular barbels. These findings suggest that environmental factors such as water flow, substrate type and resource availability may influence morphometric traits in Beki River populations. The study contributes valuable baseline data for regional biodiversity monitoring and supports future taxonomic and ecological research on freshwater catfishes in Northeastern India.