Evaluating the size at sexual maturity for 20 fish species (Actinopterygii) in wetland (Gajner Beel) ecosystem, north-western Bangladesh through multi-model approach: A key for sound management

Effective fisheries management depend on having an exact assessment of biological parameters, including growth parameters, reproduction, size at sexual maturity (Lm), and stock assessment. The purpose of this research was to estimate the size at sexual maturity (Lm) for 20 fish species belongs to 14 families from a wetland (Gajner Beel) ecosystem in the north-western (NW) Bangladesh through multi-models such as length (Lmax) based empirical model, gonadosomatic index (GSI)-based model, and logistic model using commercial catches from January to December 2018. Also, we assessed the Lm in other water-bodies worldwide. Specimens’ total length (TL) was noted up to 0.1 cm using measuring board body weight (BW) and gonad weight (GW) weighed by digital electronic balance with 0.01 g accuracy. To assess the Lm, maximum body length (Lmax) based empirical model; the relation between TL (total length in cm) vs. GSI (gonadosomatic index in %); and a logistic model were considered. The minimum Lm was 4.64, 3.90, and 4.15 cm for Chanda nama Hamilton, 1822 and the maximum was 25.33, 24.50, and 24.70 cm for Channa striata (Bloch, 1793) through Lmax, GSI, and logistic-based models, respectively. From these three models, the minimum mean Lm was 4.23 cm for C. nama and the maximum was 24.84 cm for C. striata. The Lm with 50.0% species was in 8.80 cm TL. We also calculated the Lm from different bodies of water based on Lmax. This study was generated data of 17 new Lm among 20 species, which are globally absent. Therefore, the study will help develop sustainable management strategies, conservation through the implementation of mesh size based on the size at sexual maturity (Lm).