Integration of grass carp pen culture along with IMCs for habitat management and production enhancement pen culture of grass carp Ctenopharyngodon idella as a biocontrol for macrophytes along with Indian major carps was implemented in a co-management mode in Beledanga. Indian major carps Labeo catla (6.28±0.23g), Labeo rohita (5.1±0.12g), Cirrhinus mrigala (3.5±0.08g) were stocked in the ratio 4:3:3 at the rate of 20 Nos.m⁻² in pens (0.1ha each) in triplicate. Grass carp (7.1±0.42g) was stocked in pen at the rate of 20Nos.m⁻² in duplicate.

The fishes were fed with pelleted feed twice a day at the rate of 2–3% of body weight. The seed was overwintered in pens for a period of 90 days. Average weight recorded at the end of culture period was 25.13±1.70g, 18.11±0.63g, 14.53±0.87g, and 39.20±1.90g in L. catla, L. rohita, C. mrigala, and C. idella, respectively. The survival of fish ranged from 70 to 81%. Growth performance and feed utilization efficiency of grass carp were significantly higher (p<0.05) compared to other carp species. The pen culture was found to be economically viable with a benefit cost ratio of 1.53. The fishes produced were released back into the open wetland as an additional input for culture-based fisheries.

The intervention along with niche-based enhanced stocking led to 24% increase in the fish production from the wetland with grass carp contributing 20–22% of the total catch with 32% increase in revenue generated by the sale of fish within a short span of 1 year. The study successfully demonstrated technological suitability and economic feasibility of pen culture in this wetland and role of grass carp as a potential biocontrol species for macrophyte management. Integration and optimization of grass carp will not only aid in habitat management of macrophyte-choked wetlands but will also boost their small-scale fisheries by converting standing macrophyte biomass into protein-rich fish biomass. The enhanced production will also cater to nutritional and livelihood security of the dependent fishers.