Fishing gear efficiency and their effects on fish biodiversity in the Old Brahmaputra River, Mymensingh, Bangladesh

FISHING GEAR EFFECTS ON FISH BIODIVERSITY IN THE RIVER BRAHMAPUTRA

Abstract

The old Brahmaputra River is one of the most important river systems of Bangladesh. With its rich biodiversity, it is an important source of open water capture fisheries resources. To ensure sustainable yield and rational use of this water resource, efforts were made to estimate fishing gear efficiency and their effects on fish biodiversity in this river over a period of 1 year from April 2011 to March 2012. A total of 19 types of fishing gears were recorded during this period. Seine net showed the highest catch per unit effort (CPUE) of 5.56 kg/gear/day with fishing effort 0.0224 gear/haul/day followed by push net and lift net. Among traps, CPUE and fishing effort were 3.74 and 0.0034, respectively while hook and line had 1.38 and 0.0048, respectively. Among all types of nets, highest CPUE of 2.44 kg/gear was found immediately before pre-monsoon during June and lowest of 1.49 kg/gear in dry season during January while in case of traps, highest CPUE of 3.0 kg/gear and lowest of 0.5 kg/gear were recorded during the same period. The highest biomass and number of fish species were also recorded during pre-monsoon (June) and lowest in January and February which showed a gradual rise during March through April, identified as pre-monsoon season. These results suggest that monsoon and occasional flood reduce fishing gear efficiency although the number of fishers increased during that period.