Aquaculture production is a large, spatially concentrated source of nutrients in Chinese freshwater and coastal seas

Aquaculture production in China has been increasing by 50% from 30 to 47 million tonnes per year between 2006 and 2017, and this makes up more than 50% of the global aquaculture production. There is growing concern about eutrophication caused by aquaculture, since nutrients excreted by fish farms are directly released to surface water bodies.

This paper presents a model-based estimate of nutrient flows in China’s aquaculture system using provincial scale data, to spatially distribute nutrient loads with a 0.5-degree resolution. Between 2006 and 2017 the nitrogen (N) release increased from 1.0 to 1.6 Mt yr-1 and that of phosphorus (P) from 0.1 to 0.2 Mt yr-1.

Nutrient release from freshwater aquaculture was concentrated in three provinces (Guangdong, Jiangsu, and Hubei), and that from mariculture in Shandong, Fujian, and Guangdong. Its nutrient release is >20% of total nutrient inputs to freshwater environments in some provinces, and nutrients from mariculture are comparable to river nutrient export to Chinese coastal seas.