Evaluating biometric indices for Indian Gagata, Gagata cenia (Hamilton, 1822) through multi-model inferences

Biometric indices provide crucial information on fish population growth and aquatic habitat well-being. This study offers the first comprehensive elucidation on biometric indices of Gagata cenia (Hamilton, 1822) specifically; population structure, growth pattern and parameters, form factor (a3.0), conditions factors, prey-predator status, reproduction, optimum catchable length (Lopt), mortality and exploitation rate in the Jamuna River, northern Bangladesh. The aim of this study is to estimate stock status of G. cenia in order to protect the declining wild stock. Total of 725 fishes were randomly collected (ranges between 2.7 and 8.5 cm total length (TL), while 0.30–8.24 g body weight (BW)) occasionally using conventional fishing gears during June 2020 to May 2021. The b value of length-weight relationship (TL vs. BW) was 3.33 which indicated positive allometric growth pattern with r2 value 0.942. Growth parameters were supposed as asymptotic length (L∞) = 9.09 cm, (K) = 0.94 year−1, growth performance index (Ø′) = 1.89 and longevity (tmax) = 3.2 year−1 for this population. The calculated a3.0 was 0.0172 and Fulton’s condition (KF) is the best suited tool for assessing the well-being of this population. Additionally, relative weight (WR) specifies an imbalanced territory with regard to the occurrence of predators. The size at sexual maturity (Lm) and Lopt for combined sexes of G. cenia were 5.4 cm and 6.0 cm, respectively henceforth fish sizes 6.0–6.5 cm TL are recommended for exploitation. The current study verified fishing mortality was significantly lower than natural mortality and the exploitation rate (E) was 0.32 which indicated the stock was under fishing. Our findings would be very beneficial in planning the sustainable and appropriate management of this fish in Bangladesh and nearby ecosystems.