Bionomics, length-weight relationship and condition factor of Chocolate mahseer, Neolissochilus hexagonolepis from Dikhu River, Nagaland

Abstract

Aim: Chocolate mahseer (Neolissochilus hexagonolepis) is widely distributed in the North-eastern region of India. The study aimed to evaluate the bionomic aspects of chocolate mahseer of Nagaland to validate its status. Methodology: Fish Neolissochilus hexagonolepis were collected from March 2019 to February 2020 from Dikhu River, Nagaland. Regression analysis for morphometric study was conducted using the least square method. Logarithmically transformed total length and weight data were utilized to determine the correlation coefficient 'r', coefficient of determination 'r²', and condition factor for male, female, and pooled groups. Results: The highest correlation was seen in standard length ('r' = 0.9968), and the least correlation was observed in eye diameter ('r' = 0.7769). The length-weight relationship exhibited two growth patterns, namely negative allometric growth, which were represented by females (b = 2.807) and pooled (b = 2.868) population, whereas the population of males displayed positive allometric growth (b = 3.015). The correlation coefficient and coefficient of determination of males, females and the pooled sexes showed a positive correlation with relation to its length and weight ranging from 'r' = 0.970 - 0.981 and 'r²' = 0.941 - 0.961, respectively. The condition factor for all the groups ranged from 1.10 - 1.14. Interpretation: Morphometric traits like standard length, snout length, head length etc. (dependent variable) were analyzed on total length (independent variable), signifying a positive correlation among variables. Length-weight relationship displayed high significance between length and weight parameters. The condition factor for all the groups indicated general well-being of fish condition in their environment. Key words: Chocolate mahseer, Condition factor, Length-weight relationship, Morphometric studies