Studies on the major characteristics of the Karatoa river and its fisheries at Shahjadpur upazilla of Sirajganj district, was carried out during a period from October 1999 to September 2000. Physical, chemical and biological parameters were observed. Fishing methods, marketing system and socio-economic condition of the people those who depends upon the resources of the river were studied.
Soil analysis revealed that sandy-silty soil of the study area endowed with organic materials. Maximum and minimum air temperature were recorded as 29.25°C (June) and 18.80°C (January), water temperature were found to vary from 1 to 3°C less than air temperature. Maximum rainfall was 150.7 mm (May) and in the months of November, December and March there were trace rainfall. Relative humidity varied from 88.5% (September) and 66% (March). Maximum and minimum values of water depth were 6.75 m (October) and 1.95 m (March), water area were 93.91 m2 (October) and 10.05 m2 (February), turbidity were 397.98 mg/l (June) and 250.83 mg/l (September), water velocity were 0.533 m/sec (October) and 0.071 m/sec (February), pH were 7.89 (October) and 6.81 (December), range of DO was 4.0 to 9.0 mg/l, CO2 were 8.57 mg/l (August) and 5.0 mg/l (January). The families Chlorophyceae, Bacillariophyceae and Myxophyceae were dominant among the phytoplanktons throughout the year. Moreover, some common aquatic plants were also found. Among the zooplanktons copepods, cladocerans, ostracods, rotifers, aquatic insect and crustacean larvae were common with copepods as dominant group.
A total of 104 different species of fishes of 55 genera, 24 families and 10 orders were found of which 17 species are rare. Six different types of crafts, 5 nets and a number of traps and other fishing gears were found to be used. Marketing system at the fish markets were found to be traditional one. Socio-economic condition of the fishers and fish traders were found as of very poor standard. The fishers only get 55.50 to 58.30% and 55.57 to 65.50% of the consumer’s price for the larger and smaller fish species respectively.
Key word: Socio-economic condition, Sandy-silty soil, Relative humidity, Turbidity, Phytoplankton, Zooplanktons, Dominant group, Consumer’s price.