Growth, Condition, Maturity and Mortality of the Dwarf Gourami, Trichogaster lalius (Hamilton, 1822) in a Wetland Ecosystem (Beel Dakatia), Southwestern Bangladesh

The dwarf gourami, Trichogaster lalius, is a low-cost freshwater edible fish for the people of South Asian countries containing a variety of essential nutrients. The first wide-ranging explanation on the population parameters specifically; length-frequency distribution (LFD), length-weight relationships (LWRs), length-length relationship (LLR), form factor (a_3.0), condition factors (allometric, K_A; Fulton’s, K_F; relative, K_R; relative weight, W_R), size at first sexual maturity (L_m) and natural mortality (M_w) of T. lalius were estimated. 768 specimens were collected over one calendar year (March 2019 to February 2020) from a wetland ecosystem named Beel Dakatia, Khulna, southwestern Bangladesh through various traditional fishing gears. Lengths (in cm) and weight (in g) were assessed through a wooden fitted measuring scale and digital balance with accuracy 0.1 cm and 0.01g, respectively. In the current study, the total length ranged from 2.6-9.9 cm while the bodyweight ranged from 0.63-23.80 g for T. lalius. The TL size for classes of 7.00 to 7.99 and 8.00 to 8.99 cm indicated numerically prominent groups. Moreover, the calculated allometric coefficient (b) of LWRs represented a negative allometric growth pattern (b<3.00) for T. lalius in the Beel Dakatia. Noticeably, the a_3.0 was 0.015 signifying that the fish is fusiform in shape. K_F is the best-suited tool to assess the well-being of T. lalius among the four types of condition factors. According to Wilcoxson signed-rank test, the W_R revealed significantly dissimilarities from 100 (P<0.0001), signifying the unbalanced territory for T. lalius. Moreover, the estimated L_m was 5.91 (~6.0) cm TL and M_w was 1.28 year^-1 in the Beel Dakatia, southwestern Bangladesh. Finally, the knowledge about the biological aspects of T. lalius may be used for improved management tools in the future.