Diversity of Fish Species in relation to Climatological Fluctuations in a Coastal River of Bangladesh

In the Sandha river of Bangladesh, we investigated the temporal and geographical fluctuation in species of fish composition and diversity. The extent of our understanding of the fish variety in this river varies greatly on both a temporal and a geographical scale. From July 2021 to June 2022, fish specimens were gathered from five stations using various conventional fishing methods. During the study period, 5118 individuals from 67 species were collected which include 8 orders, 24 families, and 54 genera. Cypriniformes made up the majority of the order (32.84%), whereas Beloniformes and Tetraodontiformes made up the least number of species (1.49% each). Six species were listed as endangered (8.96%), seven as vulnerable (10.45%), nine as near threatened (13.43%), forty-three as least concern (64.18%), one with data deficient (1.49%), and one as not evaluated (1.49%) in Bangladesh. In order to quantify the temporal and geographical changes in community composition, diversity indices were calculated and put to use. Three (temperature, humidity, and rainfall) out of the four environmental factors (temperature, humidity, rainfall, and photoperiod) had a big impact on how species were distributed. At a similarity level of 79% and 75.5% separation, 2 substantial clusters were seen in the case of stations and 2 large clusters were detected in the case of months, respectively. However, at a similarity threshold of 20% separation, three different groups of fish species were found. Our research offers the most recent status data on fish distribution in the Sandha river. The knowledge acquired from this research is crucial for creating protection and management plans that will promote the long-term viability of fishery resources in the Sandha river and its nearby coastal tributaries.