| The agricultural sector is major water user and is responsible for 70% of global water footprint. Climate change exacerbate the crisis of water scarcity. Dietary change, attracting more and more attention, becomes a research hotspot in quantitatively environmental decision-making to reduce water uses. Replacing territorial animal-product by captured fish is regarded as an effective way to reduce water uses because captured fish is usually assumed as no water consumption. However, this assumption is unsuitable for China, where the tons of farmed fish close to 70% of the world, leading to huge feed-associated water footprint. Thus, an urgent research is needed on water footprint and associated optimal aquaculture policy.This study calculated the both direct and indirect water footprint of 22 typical farmed fish in China, by using von Bertalanffy growth model to quantify the feed consumption. Monte Carlo simulation was used to quantify multiple sourced uncertainties. Then policy scenarios for the aquaculture development in 2020 were developed based on the calculated water footprint and growing trend of China's future aquaculture structure in 2020, on which we conducted the uncertainty optimization to investigate the optimal aquaculture policy minimizing water footprint and maximizing economic and protein outputs. Thesis conclusions are as follows:(1) Water footprint of farmed fish in China is 1.59 times as much as that of the global level. Indirect production-weighted water footprint of feed consumption is 3.11 L g-1, with footprint of 1.49 L g-1 for marine farmed fish and 3.16 L g-1 for freshwater farmed fish. Water footprint varies greatly among fish species. Sturgeon and Bream generates the highest of 13.42 L g-1 and 10.55 L g-1, respectively; while Flounder and Grouper the least of 0.18 L g-1 and 0.36 L g-1, respectively.(2) Water footprint per gram of protein and per kilocalorie is 17.72 L g-1 and 2.74 L kcal"1, respectively. Aquaculture in China consume huge feed along with large quantities of water footprint, thus replacing land-sourced animal protein by farmed fish in China is not necessarily beneficial to water resource conservation because large variations in footprint and uncertainties among various fish are observed.(3) The total water footprint of the 24 farmed fish species accounting for 91% of China's production is 189.60×109 m3 yr-1 in 2014, along with 4.60×109 kg yr-1 of protein and 163.30× 109 RMB yr-1 of economic output. Scenario analysis shows that the optimal aquaculture policy in China in 2020 will reduce the annual water footprint to 127.61 ×109 m3 yr-1 with protein and economic outputs increasing to 5.34×109 kg yr-1 and 181.48×109 RMB yr-1. Accordingly, policy promoting feeding Silver carp, Black carp, Grass carp, Pirapatinga, River eel, Grouper, and so on should be executed in the future.This study quantifies both direct and indirect water footprints of major typical farmed fish in China, on which the optimal aquaculture policy is generated in a purpose to lower water consumption, and maximize both protein and economic outputs. We believe our results contributes to the improvement of climate change adaptation for fishermen who are very vulnerable when facing challenge from climate change. |
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