Bangladesh hosts most of what is left of Indian Skimmer (Rhynchops albicollis) populations a globally endangered species. Each October-March from 2015-2020, 21 surveys of nonbreeding birds were made in Nijhum Dweep National Park, Bangladesh. High tide or evening roosts were counted from vantage points whenever a build-up or breakdown of skimmer concentration was noticed, and site use noted by marking all observations of presence and activity on maps. The largest single count was 3,108 skimmers on 18 February 2020, constituting 30-50% of the known global population. Indian Skimmers mostly occurred in Damar Char West and at the tip of the Majher Char. Throughout the day with incoming tide, skimmers moved between preferred roosting areas to forage in the shallows. We describe a unique group-foraging strategy in which skimmers chase fish from deep water to shallow water along the shoreline.Circling high over the tidal channel, the flock of skimmers dives down in unison to just above the water surface, then spreading like a net towards the shore. Raptors caused disturbances to roosting skimmers, and we observed one instance of predation of a skimmer by White-bellied Sea Eagle (Haliaeetus leucogaster). Human fishing activities disturbed nearshore foraging and shoreline roosting skimmers. We suggest protecting Damar Char West side by regulating human activities to minimize disturbance from December to March.

Nijhum Dweep National Park lacks a detailed inventory of aquatic fauna including fish. This study reported the diversity and abundance of fish along with their conservation status from the surrounding waters of the national park to fill the knowledge gap. Fish samples were collected randomly from 16 spots of surrounding water of the park between October 2017 and March 2018. There were 47 fish species recorded belonging to 10 orders, 27 families and 44 genera. Odontamblyopus rubicundus was the dominant fish species that comprised 20.24% of the total catch, followed by Rhinomugil corsula (15.54%), Mystus gulio (12.03%) and Eleutheronema tetradactylum (9.92%). One nationally Endangered fish species (Clupisoma garua) and three Vulnerable fish species (Gudusia chapra, Sicamugil cascasia and Wallago attu) were recorded. Fish diversity of the park was rich but exceeding extraction rate, huge disposal of by catch, and presence of exotic omnivorous fish species was disconcerting that require monitoring and further studies.