Status of fish and shellfish diversity and their decline factors in the Rupsa River of Khulna in Bangladesh

The study was aimed to find out the present status and causes of fish and shellfish diversity reduction in the Rupsa River of Bangladesh. Studies were conducted for a period of 6 months from July to December 2016. Focus group discussions (FGD), questionnaire interviews (QI) and key informant interviews (KII) were done to collect appropriate data from the local fishers and resource persons. A total of 62 species of fish and shellfish from 23 families were found in the river and 9 species disappeared in last 10 years. The species availability status was remarked in three categories and obtained as 14 species were commonly available, 28 species were moderately available and 20 species were rarely available. The highest percentage of fishes was catfishes (24.19%). There was a gradual reduction in the species diversity from previous 71 species to present 62 species with 12.68% declined by last 10 years. Average fish catch per fishermen per day reduced from 8.35 kg to 2.95 kg in last 10 years. Combined effects of some manmade and environmental factors are responsible for the loss of biodiversity. Majority of the respondents (90%) agreed that two manmade factors namely overfishing and navigation are mainly responsible for the loss of fish and shellfish diversity in the river followed by use of illegal fishing gears (86%), pollution (72.5%) and urbanization (64%). During the survey, 93.25% respondents reported water depth reduction as the main environmental factor followed by siltation and sedimentation (91%), temperature (61.75%) and turbidity (56%). The present work recommends preventing water pollution, maintaining fishing gears, increasing fishers’ awareness, implementing fisheries laws and establishing fish sanctuary to conserve finfish and shellfish diversity in the river. Moreover, counter and random surveys are also recommended to crosscheck the fishes’ status and decline causes for ensuring their proper management and conservation