Impact of river salinity on fish diversity in the south-west coastal region of Bangladesh

Saline water intrusion is a major problem and conflicting issue in south-west coastal region of Bangladesh. The present study provides an assessment of changes of fish diversity with the changes of salinity level in the nearby river over the last thirty years. This study is carried out through semi-structured questionnaire survey in selected villages of different salinity prone areas such as high saline zone and moderate saline zone, namely Paikgacha and Rampal, respectively. The increased salinity has negative impact on fish diversity in this region. Local people's perception, experts' judgment was used in detecting decreasing of fish diversity with increasing in river salinity. The study has revealed that in Paikgacha, the salinity varies approximately within the range from 20,000 to 45,000 micromhos and in Rampal it is from 10,000 to 30,000 micro-mhos. Due to increased salinity, the fish species in Paikgacha and Rampal have been reduced from 29 to 12 and 24 to 19 species respectively during the period 1975-2005. Dominancy of very few salinity tolerant species is increasing in both areas but it is more visible in Paikgacha than Rampal. © National Institute of Ecology, New Delhi