Life‐history traits of three Ambassid fishes (Chanda nama, Parambassis lala and Parambassis ranga) from the Mathabhanga River, southwestern Bangladesh

The present study provides the first indication of the life‐history traits, including, population structure, growth pattern, condition factor, form factor (a₃.₀), size at first sexual maturity (Lₘ), natural mortality (MW) and optimum catchable length (Lₒₚₜ), of three Ambassid (Chanda nama, Parambassis lala and Parambassis ranga) fishes from the Mathabhanga River in southwest Bangladesh. A total of 370 individuals were occasionally collected from August 2017 to July 2018 with cast nets, gill nets, square lift nets, and conical‐ and box‐traps. The total length (TL) ranged from 2.4 to 7.5 cm for C. nama, 1.9–3.8 cm for P. lala and 1.8–6.5 cm for P. ranga. The length‐frequency distributions (LFDs) showed the 4.0–5.0 cm TL size group for C. nama and the 3.0–4.0 cm TL size group were numerically dominant for P. lala and P. ranga. The length–weight relationships (LWRs) indicated isometric growth for C. nama, and positive allometric growth for P. lala and P. ranga. All the LWR values were very significant (p < .001), with all r² values > .950. Based on the Spearman rank correlation test, body weight (BW) versus Fulton's‐condition factor (KF) was extremely correlated (p < .001), indicating a better wellbeing for these species. The a₃.₀ value was 0.0082, 0.0138 and 0.0104 for C. nama, P. lala and P. ranga, respectively. Based on the maximum length (Lₘₐₓ), the Lₘ was 4.4 cm TL for C. nama, 2.5 cm TL for P. lala, and 4.0 cm TL for P. ranga. Based on the asymptotic length (L∞), the Lₘ was 4.88 cm TL for C. nama, 2.63 cm TL for P. lala, and 4.28 cm TL for P. ranga. The MW value was 2.2, 3.3 and 2.7/year for C. nama, P. lala and P. ranga, respectively. The optimum catchable length (Lₒₚₜ) was 5.36 cm TL for C. nama, 2.75 cm TL for P. lala and 4.65 cm TL for P. ranga. The findings of the present study should be very useful for effective and sustainable management of these fishes in the Mathabhanga River and the connecting ecosystems.