Spatial distribution and introduction pathways of non-native freshwater fish species in China

Non-native freshwater fish species are regarded as a key factor responsible for the degradation of freshwater ecosystems.Although research on China's non-native freshwater fish species has been conducted at the national scale,the spatial distribution and introduction pathways of these species in China remain unclear.To address this knowledge gap,this study compiled a dataset of non-native freshwater fish species across administrative regions in China.We first assessed the number of non-native freshwater fish species by taxonomy,geographical origin,introduction pathway,and province.There were 177 non-native freshwater fish species,belonging to 17 orders,48 families,and 118 genera.The orders Cypriniformes(33.3%),Perciformes(28.2%),Siluriformes(10.2%),and Salmoniformes(6.2%)accounted for the largest proportion of non-native freshwater fish species.Eighty-nine nonnative species were introduced from other countries or regions,mostly from North America(31 species;34.8%),Asia(20 species;22.5%),Africa(13 species;14.6%),Europe(11 species;12.4%),and South America(10 species;11.2%).Aquaculture was the most common introduction pathway.Non-native freshwater fish species were more widely distributed in southwest China.Our study showed that there were obvious differences in the number and composition of non-native freshwater fish species across various provinces in China.The variation in the number of non-native freshwater fish species across provinces in China was attributed to distinct geographical features,development of the aquaculture industry,and efforts to study non-native freshwater fish species.Therefore,comprehensive surveys and studies of non-native freshwater fish species are needed,which are of great importance for the management and control of non-native species invasions.

Current status of greenhouse gas emissions from aquaculture in China

Aquaculture and mariculture are becoming an increasingly important source of food supply in many countries and regions.However,with the expansion of aquaculture and mariculture comes increasing emissions of greenhouse gases(GHG)which contribute to global warming and climate change.China leads the world in aquaculture and mariculture production,but there are no studies that systematically assess China's overall carbon footprint from these industries.This study quantified GHG emissions from aquaculture and mariculture by four source phases(feed,energy use,nitrous oxide and fertilizers),and then analyzed the carbon footprint of each of these phases for GHG production of nine major species groups over the past ten years to show the spatial distribution of GHG emissions from aquaculture and mariculture in China.Our results showed that the production of feed materials contributed most to the GHG emissions and found that crop energy use,crop land use changes(LUC),fertilizer production,crop nitrous oxide production and rice methane production were the main sources of feed emissions.The total GHG emissions of the nine species groups were 112 Mt(10^(9) kg)CO_(2)e,the nine species accounting for approximately 86%of aquaculture and mariculture production.GHG emissions of cyprinids had the highest contribution at 47%.Spatial analysis based on our study showed Guangdong,Hubei,Jiangsu and Shandong had the highest GHG emissions of all the provinces in this study,and they accounted for approximately 46%of all emissions.The regional Gross Domestic Product(GDP)was significantly positively correlated with GHG emissions in every province,with a correlation coefficient higher than 0.6.Our results showed for the first time the relationship between the relative production by species composition and spatial distribution of GHG emissions from aquaculture and mariculture in China.Our findings provide the scientific basis for reduction of GHG emissions within a broader context of expanding aquaculture in the future.