Abstract:
The damming of rivers and canal has been a major contributor to the decline of fish migration and population in Bangladesh. Fish are confronted to a challenging hydrodynamic environment when they swim upstream. Nevertheless, the knowledge of fish behaviour in these conditions is limited, particularly for coarse species such as cyprinids. The principle focus of the study is to evaluate fish swimming behaviour in different hydrological condition, onset of migration, fish migratory behavior, swimming speed and survival in different of water velocity condition. In situ experiment in Sariakandi shows fish fry, hatching, juvenile and adult movement from Jamuna to Bangaliriver. After construction of the fish pass, the diversity of fish species of the Bengali River is increased. Ex situ experiments have been conducted in an indoor full scale vertical slot fish pass model with different sizes (fry, fingerling, juvenile and sub-adult) of cyprinid species Rui (Labeorohita), Catla (Catlacatla) and Mrigal (Cirrhinusreba) as well as some other test fishes. Different water velocity used to study fish cruising, sustained and burst swimming activity, indicating some degree of anaerobiosis occurs during crossing passage. Energy used by individual fish to pass the fish friendly structure varied greatly due to different migration behavior, passage routes, and the time it takes to pass related to water current. Mortality risk to the migrant is estimated. Results identified areas of difficulties in a fish passage that may be modified to help decrease energy use of upstream migrating fishes. The results emphasize the value of achieving a deeper understanding of fish requirements in these devices and show the potential of the methodology developed to fulfil this objective. Results can contribute to develop robust guidelines for future fishway designs in Bangladesh.
