Fish assemblage structure and functional guild composition of Matla Estuary, Indian Sundarbans

The fish assemblage and functional guild composition of Matla estuary (ME), Indian Sundarbans, was studied across different estuarine reaches and seasons for the first time based on spatial and temporal data. A total of 57 finfish species belonging to 15 orders and 34 families were recorded during the study period from August 2022 to July 2023 along ME. The number of species recorded (n) exhibited a declining trend from the lower to upper reaches and was highest during the monsoon season (n = 53) and lowest during pre-monsoon (n = 40). The classification of fishes into guild resulted in seven estuarine use guilds and six feeding guilds. The composition of fish guilds exhibited variation based on site and season. Among estuarine use guilds, marine migrants (n = 28) and marine stragglers (n = 15) were the most prominent categories throughout the sample sites and seasons, while piscivores (n = 30) were the dominant feeding guild throughout the sites and seasons. This study indicates low record of fish diversity, particularly true estuarine and freshwater species. Assessing patterns in the spatial and temporal distribution of estuarine species, as well as variations in their fish diversity and trophic guilds, improves our understanding of the species’ ecological functioning and contributes to our understanding of the effects of anthropogenic stressors on the species for the conservation and management of fishes of Matla estuary.