Sustainable management of non-native grass carp as a protein source, weed-control agent and sport fish

Grass carp, a native Chinese freshwater fish species, has been widely introduced and established worldwide for different purposes (protein source, weed control agent, and sport fish). This species can be very effective in controlling aquatic plants. A few countries, such as Afghanistan, Myanmar, Laos and Vietnam, have cultured grass carp as human food for decades. In contrast, other countries, such as Bangladesh, India, and Iran, initially cultured grass carp as weed control agents and later transitioned to using them as food fish. The uncontrolled population of grass carp and the adverse ecological effects cause concern. Grass carp are a source of nutrients, including essential omega-3 fatty acids, eicosapentaenoicacid (EPA) and docosahexaenoic acid (DHA), which greatly benefit human health. Farming and consuming low trophic-level fish is more sustainable than relying on high trophic-level fish. A sustainable Polyculture system yields positive social, economic, ecological and aquaculture outcomes. It involves culturing grass carp together with filter-feeding fish of different ecological requirements, feeding habits and behaviours in the same pond. The application of sustainable feeding materials (e.g., food processing waste and food waste-based fish feed pellets) may significantly improve sustainable aquaculture. It might mitigate the adverse ecological impacts experienced by some countries.