Morphometry, length-weight relationship and relative condition factor of red-toothed trigger fish, Odonus niger

Aim: The study aimed to investigate the morphometric and meristic measurements, length-weight relationship and relative condition factor of Odonus niger landed along coastal Karnataka. Methodology: The morphometric and meristic measurements, length-weight relationship and relative condition factor (Kn) of O. niger was studied for a period of eight months from August 2019 to March 2020. The different morphometric characters were subjected to statistical analysis. The length-weight relationship was analyzed for both the sexes (female and male) and combined data. Monthly relative condition factor was analyzed for both the sexes and for different size group. Results: A comparison of different morphometric measurements exhibited good extent of correlation indicating good extent of interdependence of these characters. Four out of eight morphometric characters are environmentally controlled and suggested wide range of zoogeographical distribution of O. niger. The length-weight relationship is indicated as W = 0.046 L2.565, W = 0.044 L2.589 and W = 0.047 L2.561 with coefficient of determination (r2) of 0.910, 0.913 and 0.910 for male, female and combined sexes, respectively. The 'b' values of both the sexes (male and female) exhibited negative allometric growth (p<0.05) and appeared to be leaner. There was no significant (p<0.05) variation for relative condition factor (Kn) among the months and size groups. However, little higher values were observed during November and February. Interpretation: The study fills the knowledge gap and support for developing a suitable management system for this fish species.