Freshwater ecosystem degradation in the Turag River basin is increasing due to rising human settlement, reduced water flow during the dry season, new large land development projects, and toxic emissions caused by brick kilns. The population of river dolphins was estimated through surveys carried out from December 2012 to November 2013. Surveys were conducted on a fortnightly basis. The dolphins were counted within an 18.4 km stretch (known to be the most polluted stretch) of the 75 km long river. A total of 62 dolphin sightings were recorded, both as individual sightings and as groups. The highest monthly count was in August. The besthigh-low estimates of 9-11-7 individuals were recorded in August 2013 in river ecology. Seasonal changes in spatial distribution were observed. The survey revealed that rising floodwater stimulated an increase in the dolphin population in the study area from July to October. The maximum encounter rate was also 0.49 sightings km −1 for the month of August. The sightings and encounter rates of dolphins were lower from December to July (dry and premonsoon period) likely due to reduced water flow and adverse water quality of this river.

Fish species, fishing gear and crafts in the most polluted river Buriganga were inventorial. During December, 2012 to November, 2013, a total of 56 fish species belonging to 20 families and 9 orders were recorded. Cypriniformes observed to be the most dominant order with 18 species (32%). The highest fish diversity was recorded during monsoon season, and lowest during winter. Maximum diversity variance (7.616 ± 2.76 Sd) observed in the monsoon season for 56 species (220 individuals). Also 12 different types of gears of two categories (active and passive) and two types of crafts were observed to be used for fishing in the study area. The highest number of species of fishes (n = 56) recorded in August and lowest (n = 3) in April and May 2013. Strong correlation between water depth and number of fish species (r = 0.74) and fishing activities (r = 0.96) was observed.

Biodiversity of many Bangladesh Rivers is seriously threatened by industrial and municipal pollution. The study was conducted in the Turag River starting from Amin Bazar bridge (23°47' N 90°20'E) to Kamarpara bridge (23°53' N 90°23'E). This inventory survey was sampled at a fortnightly interval usually between 7.00 am to 5.00 pm by a team using a boat from December 2012 to November 2013. Detailed information on catch by species, fish length and weight, different types of gear and craft were collected through direct observation. A total of 71 (65 indigenous and 6 exotic) fish species (under 25 families of 9 orders) have been identified. 17 different types of gears of two categories (active and passive gear) and 8 different types of crafts were observed to harvest fish in the study area. The survey revealed that rising floodwater stimulated an increase in fishing activities in the study area from July to October. Fish numbers were recorded lower from November to July (dry and pre-monsoon period) likely due to reduced water flow and adverse water quality of this river. A paired t-test indicate that fish species numbers were significantly difference between Dry and pre-monsoon (P=0.02), Dry and monsoon (P=0.02) and Dry and post-monsoon season (P=0.03) respectively. However, fisheries resources contribution is very limited for livelihood of the surrounding people.

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Population abundance and density of the Ganges River Dolphin Platanista gangetica gangetica (Roxburgh, 1801) was studied in the Buriganga River from December 2012 to November 2013.The survey was conducted twice a month. The dolphins were counted directly and applied in transect length of 10.5 km within 15 km stretches of the river. A total of 34 sightings of dolphins were recorded both in individuals and groups. We encountered the dolphins at the rate of 0.48 dolphins per km in the Buriganga River. Highest best-high-low estimate of 12-14-10 individuals were recorded in November 2013. The mean density was 0.38 (SD ±0.37) dolphins/km² with the highest density of dolphin observed also in the month of November, which was 1.14 dolphin/km². Pollution and water traffic were observed to be the major threats to the dolphins.