Morphometrics, growth allometry, and condition status of the dark mahseer (Naziritor chelynoides) in a Nepalese hill stream

Abstract

This study assessed morphometric and meristic variation, length–weight relationship, and condition indices of Naziritor chelynoides from the Chidiyar River, Nepal. A total of 128 individuals were collected from September to December 2025, including 43 specimens examined for detailed morphometric and meristic variation. The length-weight relationship showed significant negative allometry (b = 2.519; 95% CI = 2.33–2.71; R² = 0.841). Mean Fulton’s condition factor (K) and relative condition factor (Kn) were both 1.01 ± 0.26. Principal Component Analysis showed that the first two components explained 34.377% of the total variance, with higher loadings associated with fin-base, head, and body-proportion variables. Meristic characters exhibited limited variation, while morphometric variation was continuous without visually apparent discrete groups. These results provide baseline biometric information for the sampled N. chelynoides population in the Chidiyar River and a reference for future spatial and temporal comparisons. Further studies across populations and seasons are needed to assess the consistency of these patterns.