Fish Diversity in Relation to Salinity Gradient in the Meghna River Estuary, Bangladesh

Variation in salinity is one of the major environmental factors influencing the species diversity of fish in an estuary. Therefore, evaluating the relationship between salinity and species diversity is important. In this study, fish diversity was assessed by fish sampling and visiting local fish markets from February to November 2021. Mean salinity was 10.59 psu (Practical Salinity Unit) and 0.46 psu during the dry and wet seasons, respectively. Harpadon nehereus, Odontamblyopus rubicundus and Pseudapocryptes elongatus species were found as polyhaline (0.06~18.1 psu) species. Anguilla japonica and Arius gagora were abundant in brackish water conditions (0.35~14.2 psu). However, Acanthopagrus latus and Setipinna phasa were found in freshwater conditions (0.06~0.11 psu). The suitability index indicates that commercially important fish species such as Liza parsia, Macrobrachium rosenbergii, Mugil cephalus, Penaeus monodon and Scylla serrata can be used for mariculture during the dry season, and Acanthopagrus latus, Pethia canius and Setipinna phasa during the wet season. Overall, these findings suggest that salinity, water temperature, and chlorophyll-a had a significant (p < 0.05) effect on the fish distribution and assemblage composition in the study area. This finding will be helpful in developing policies for the conservation and management of the aquatic resources in the coastal zone to enrich the blue economy.