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Salinity intrusion due to climate changes in the coastal area is substantially jeopardized for sustainable aquaculture. This study was focused on behavioral and histo-pathological changes (gills, liver and kidney) of striped catfish (Pangasionodon hypopththalmas) exposed to four salinities (0, 4, 8 and 12 ppt), each with three replications for 56 days. Both behavioral and histological analyses were carried out for durations of 7, 14, 28 and 56 days of exposure. Mild to moderate behavioral abnormalities such as rate of swimming, food intake, gill motion and convulsions were observed in 8 ppt, but pronounced alterations were detected at higher salinity (12 ppt), increasing with longer exposures. Similarly, mild to moderate histological anomalies in gills (hypertrophy of the chloride cell, telangiectasia at the tips of secondary lamellae, epithelial necrosis, fusion of some secondary lamellae and lifting of the lamellar epithelium), liver (vacuolation, blood congestion, melanomacrophage centers, patchy degeneration, necrosis and hypertrophy nucleus) and kidney (degeneration of renal tubule, enlarged Bowman's capsule, increased space in between glomerulus center, melanomacrophage centers, vacuolation and necrotic cell in the hematopoetic tissue) were detected in 8 ppt but pronounced alterations were detected at higher salinity (12 ppt) with increasing the days of exposure. This preliminary study revealed more profound responses to higher salinity exposure in the striped catfish, and this species could serve as a model bio-indicator in costal aquaculture.

Grass carp (Ctenopharyngodon idella) was cultured in the inundated low-lying coastal wetlands using Asian watergrass (Hygroryza aristata) as feed for 6 months. The study was carried out with three treatments, each with three replications. The grass was planted during plot preparation in treatment one (Grass Planted; GP); the grass was collected those grown in an adjacent land and supplied to the fish in treatment two (Grass Supplied; GS); and the fish were fed with commercial feed in treatment three (Commercial Feed; CF). Similar sized juveniles of grass carp (51 ± 6 g) were stocked at the rate of 12,500 fish ha−1 in each treatment. Important water quality parameters were measured at a monthly interval and found within the suitable range for growth of grass carp. The survival was significantly higher in GP (92.7 ± 1.0 %), followed by GS (90.0 ± 1.7 %) and CF (90.0 ± 2.9 %). The growth parameters (weight gain and specific growth rate; SGR) of fish were found significantly higher in GP, followed by CF and GS. The highest total production was found in GP (6770 ± 424 kg ha−1), followed by CF (6733 ± 536 kg ha−1) and GS (5519 ± 483 kg ha−1). The highest net economic benefit and benefit-cost ratio were found in GP (US$ 13375.50 ha−1 and 3.32) and the lowest in CF (US$ 4958.25 ha−1 and 0.42). The results of the present study indicate that Asian watergrass can successfully be used in commercial culture of grass carp and it may significantly reduce the production cost.