Length–Weight Relationships, Condition Factors, and Form Factors of 10 Freshwater Small Indigenous Fish Species in a Wetland Ecosystem of Northwestern Bangladesh

Abstract

A total of ten species of freshwater small indigenous fish species (SIFS) were examined in order to study their length–weight relations (LWRs), condition factors (K_R), and form factors (a_3.0) caught by a small-scale fishery from the Babu Mondoler beel, a wetland ecosystem in northwestern Bangladesh. In addition, the form factor (a_3.0) was calculated for ten freshwater fish species in worldwide habitats. The samples were collected between June 2021 and May 2022 with various fishing equipment and traps, including box traps, cast nets, and gill nets. The study focused on the following species: Ailia coila (Hamilton, 1822), Amblypharyngodon mola (Bleeker, 1854), Channa punctata (Bloch, 1793), Channa straita (Bloch, 1793), Esomus danricus (Hamilton, 1822), Eutropiichthys vacha (Hamilton, 1822), Gagata cenia (Hamilton, 1822), Labeo catla (Hamilton, 1822), Lepidocephalichthys guntea (Hamilton, 1822), and Macrognathus aculeatus (Bloch, 1786). Total length (TL) was strongly correlated with body weight (BW) (p < 0.001). The slope b was between 2.55 and 3.38, with 7 species experiencing negative allometric growth, 1 species experiencing positive allometric growth, and 2 species experiencing isometric growth. The mean relative condition factor (K_R) ranged from 0.9746 ± 0.0870 (Channa punctata) to a maximum of 1.0344 ± 0.2101 (Ailia coila) as a benchmark of the well-being of individuals of the various species in the same ecosystem. In our studied ecosystem, we observed a form factor (a_3.0) ranging from 0.0025 to 0.0151. The results on LWRs, condition factors, and form factors are important baseline data for monitoring the status of fish populations, detecting environmental stress, and sustainable management. Therefore, habitat action is required to reduce the growth-affecting stressors on these SIFS.