Carp are the world's most farmed freshwater fish species by volume, but welfare standards in carp aquaculture vary enormously between production systems and regions.
Carp welfare science is less developed than for salmon and trout, partly because carp are more physiologically tolerant of poor conditions and partly because their lower market value reduces economic incentive for welfare investment. However tolerance of poor conditions does not mean those conditions are welfare-neutral. Carp show stress responses to crowding, handling and poor water quality, and evidence of pain sensitivity suggests welfare consideration is warranted. The enormous scale of global carp production means that even small per-fish welfare improvements represent significant aggregate benefit.