Scenario analysis on optimal farmed-fish-species composition in China: A theoretical methodology to benefit wild-fishery stock, water conservation, economic and protein outputs under the context of climate change.

Fish production from aquaculture and wild captures suffers from the rising risk of climate change. This impacts the livelihoods of fishers and fish farmers by shrinking wild fishery stocks, inland water scarcity, and consequent declines in economic and protein productions. China, feeding the most fish of the world with water-intensive crops, faces challenges of water scarcity but still be premature in developing strategies to adapt to climate change. Here, focusing on methodology development, we quantified the water footprint of fish-farming and economic and protein productions in the baseline year 2014. Then, 29 scenarios of farmed-fish-species composition (FFSC, i.e., tons of each farmed fish species) were developed for the target year 2020. The baseline 2014 shows that fish farming generates an average of 150 billion m of water footprint, 4.70 million tons of protein, and 263 billion RMB of economic output (~39 billion USD). Uncertainty optimizations were conducted to generate the optimal FFSC solutions that show a potential to increase fish production by 22%, economic and protein output by 18% and 29%, respectively and simultaneously lower water footprint by 22% to the maximum extent. Nine scenarios that lower wild fishery captures were further examined, with optimal FFSC solution that encourages aquaculture of Grass carp, Bighead Carp, and Silver Carp, and discourages Black carp, Tilapia, Crucian carp, Sea bass, and Wuchang bream. From a methodology aspect, this study pulls back policymakers from only focusing on the short-term economic interest of fish-farming and persuades them to rethink long-term adaptive strategies to climate change from multiple sustainable dimensions.