DIVERSITY AND HABITAT ECOLOGY OF INDIGENOUS FISH SPECIES IN RATARGUL SWAMP FOREST SYLHET BANGLADESH

Abstract

Ratargul swamp forest is only the freshwater swamp forest of Bangladesh which supports diverse fisheries communities compared to others. The present study was conducted from April to October 2015 to assess the status of indigenous fish species of Ratargul swamp forest along with relevant hydrological and ecological aspects. A total 62 fish species comprising 28 threatened species were recorded from the study area. Cypriniformes (37.46%) was the most dominant order followed by Siluriformes (35.123%), Perciformes (19.456%), Synbranchiformes (3.298%), Clupeiformes (2.282%), Beloniformes (1.161%), Osteoglossiformes (0.725%), Tetraodontiformes (0.462%) and Anguiliformes (0.026%). Among the identified fish species 19.98% was recorded as threatened according to IUCN (International Union for Conservation of Nature). The Mean Shannon-Wiener diversity index, Margalef richness index, Pielou’s evenness index and Simpson dominance index were found to be 3.690±0.191, 9.497± 1.314, 0.971±0.003 and 0.982±0.003, respectively. In case of SIMPER (Similarity Percentages) analysis the highest number of similar species was found during July to August and the lowest during April to October. At the similarity of 76.9%, four groups were attained where June, July, August and September showed in a cluster while April, October and May showed separate clusters. Non-metric Multidimensional scaling shows 60% similarity for all months. On the other hand, 70% similarity observed among all the months except April. Environmental parameters such as photoperiod, rainfall, relative humidity, temperature, transparency, dissolved oxygen, p , ammonia and nitrite were determined and found in acceptable limit for fisheries communities. Diversity of plankton assemblage were assessed and a total of 34 planktons belonging to Chlorophyceae (10 taxa), Bacillariophyceae (4 taxa), Cyanophyaceae (6 taxa), Euglenophyceae (2 taxa), Rotifer (4 taxa), Cladocera (5 taxa), Copepods (2 taxa) and Protozoans (2 taxa). A total of 8 major groups of benthos were identified including Oligichaetes, Polychaetes, Gastropods, Bivalvia, Copepods, Isopods, Crab and Prawn larvae. A total of 20 different species were identified which belongs to Emergent (15 taxa), Floating (3 taxa) and Submerged (2 taxa). It may be concluded that Ratargul swamp forest is enriched with fish biodiversity having 28 threatened fish species of Bangladesh. H