STUDY ON LIMNOLOGICAL ASPECTS OF DHEPA RIVER IN DINAJPUR DISTRICT

Abstract

An experiment was conducted on limnological aspects of Dhepa river in Dinajpur district. In this experiment six sampling sites were selected. The name of six sites was Rajaparaghat, Bangibechar bridge, Gosaipur, Dumurtoli, Chandandoho and Kornai ghat. The research was carried out at the field level and Laboratory of Fisheries Faculty, HSTU, Dinajpur from September 2011 to April 2012. Water temperature, alkalinity and nitrate was not varied significantly (P<0.05) among the sites. Highest transparency (48.70 cm) was observed in February in St.2 and lowest value (8.10 cm) was also observed in St.2 in the month of September. The maximum water depth was observed in September and lowest in April. Dissolved oxygen was found in higher concentration (11.60 mg/l) in St.4 in December and lower concentration (3.80 mg/l) in St.2 in April. The pH value of Dhepa river ranged from 6.50 to 7.90. The highest (0.30 mg/l) and lowest (0.01 mg/l) PO,-P concentration was observed in November and April in St.2 and St.5, respectively. The NO3-N concentration of Dhepa river was very high (13.20 mg/l). The water quality conditions and variations reflected seasonal changes and pollution by anthropogenic activities. The phytoplankton recorded 31 genera. For the phytoplankton dominant group was Bacillariophyceae followed by Chlorophyceae, Cyanophyceae and Euglenophyceae. In zooplankton, 10 genera were identified. A significant direct relationship was observed between dissolved oxygen and phytoplankton both in terms of biodiversity and cell density. Similar negative relationship was observed between water temperature and phytoplankton. On the basis of physical, chemical, biological and environmental conditions Gosaipur (St.3) and Chandandoho (St.5) site may be in better condition for sanctuary establishment and for further fisheries management.