Biometric indices of eight fish species from the catchment area of Kaptai lake, Bangladesh

Abstract

Biometric indices viz. i) Length-weight relationships (LWRs), ii) form factor (a0.3) and iii) condition factors (relative KR and Fulton's KF) were presented for 8 fish species collected from Kaptai lake at five sampling points including Rangamati Sadar, Barkal, Naniarchar, Langadu and Kaptai upazila. A total of 3204 individuals belonging to 3 families were measured and weighed between August 2020 to April 2021 by the catch assessment survey with different types of fishing gear (seine net, current net, gill net and lift net). Calculations were made for the parameters a and b of the eq. W = aTLb. The analysis of covariance (ANCOVA) revealed significant differences between stations in LWRs for all species (P < 0.01). The parameter b of the LWRs ranged from 2.34 (Parambassis lala) to 3.34 (Ailia coila) with a mean value of 2.98 (SE: 0.11) and 50% of its fall within the interval 2.9–3.2. Results showed that 3 species showed positive allometric growth (Gonialosa manminna, Ailia coila, and Eutropiichthys vacha), 3 showed negative allometric growth (Gudusia chapra, Chanda baculis, and Parambassis lala), and 2 exhibited isometric growth (Corica soborna, Chanda nama). The findings further indicated that the LWRs of 8 species were highly correlated (r2 > 0.90, P < 0.001). The a3.0 value estimated for eight species varied from 0.0043 to 0.0114. The KR value ranged from 0.26 to 4.97 and KF value ranged from 0.17 to 2.89; showed significant differences of KR and KF between stations for eight species. As per FishBase, a new record for the maximum size of C. soborna and C. baculis was documented as 7.1 cm and 8.1 cm, respectively. This research is the first to provide information on biometric indices for six species (C. soborna, C. nama, C. baculis, P. lala, A. coila and E. vacha) in Kaptai Lake, which may aid in management and conservation throughout the country, including their geographical distribution.