SPATIAL AND TEMPORAL VARIATIONS OF FISH ASSEMBLAGE IN RELATION TO ECOLOGICAL PARAMETERS AT TWO RIVERS OF DINAJPUR DISTRICT IN BANGLADESH

Abstract

The present study was conducted to assess the spatial and temporal variations of fish assembles in relation to ecological parameters in the Atrai and Dhepa Rivers, Dinajpur, Bangladesh from November 2016 to October 2017. The water quality parameters and fishes were collected total four sampling sites namely, Khansama area and Mohonpur area were in the Atrai River and another two sites were Birgonj and Karnai area in the Dhepa River. A total of 15532 individuals, comprising 44 genera and 59 species was dominated (>4.95%) by Pethia ticto, Chanda nama, Cirrhinus reba, Pethia sophore, Salmophasia bacaila, both in space and time. The highest number of fish species were found at Mohonpur (MP) in autumn at the Atrai River, but lowest at Karnai Bazar in Monsoon at the Dhepa River. No statistical differences on water temperature (WT) (F = 0.03, P > 0.05), dissolve oxygen (DO) (F = 0.09, P > 0.05), pH (F = 1.26,P > 0.05), transparency (F = 0.65, P > 0.05), air temperature (AT) (F = 0.03, P > 0.05) and rainfall (RF) (F = 0.01, P > 0.05)were observed among stations while significant differences were found in water depth (WD) (F = 3.76, P< 0.05) and water flow (F = 3.92, P < 0.05).Conversely, highly significant variations were observed among seasons based on all factors such as WT (F = 48.80, P > 0.01), DO (F = 17.19, P > 0.01), WD (F = 10.33, P > 0.01), pH (F = 4.88, P > 0.05), TR (F = 19.61, P > 0.01), AT (F = 20.65, P > 0.01), RF (F = 9.43, P > 0.01)and water flow (F = 19.85, P > 0.01). The significant differences were spatially observed in dominance (F = 11.82, P< 0.01), Margalef (F = 11.75, P< 0.01), Shannon (F = 18.48, P< 0.01) and evenness (F = 2.88, P< 0.05) diversity indices. Similarly, significant differences were also determined in the values of dominance (F = 3.91, P < 0.01), Margalef (F = 5.77, P < 0.01) and Shannon (F = 4.07, P < 0.05) except for evenness (F = 0.70, P > 0.05) diversity indices among seasons. This study may be effective for conservation study in future after establishing and managing in restricted areas like fish sanctuary in the both rivers.