Using the example of sturgeons in the Yangtze River and impacts on the critically endangered Chinese sturgeon, work by Rui-Ting Ju et al. looks into policies around escaping non-native species from aquaculture. The corresponding cover image for issue 57:01 was taken by Ping Zhuang.
Sturgeon farming is expanding worldwide due to the overexploitation of wild stocks. In China, the main farmed species are non-native species or their hybrids. These non-native species can invade and establish in natural ecosystems if they escape from farming facilities. In July 2016, when floods hit the middle reaches of the Yangtze River, a total of 9800 tonnes of non-native sturgeon escaped. They have since spread into almost all of the lower streams (> 1000 km) in the Yangtze River. The escapees are greatly threatening the Chinese sturgeon Acipenser sinensis.
The Chinese sturgeon is extinct in Korea and throughout the rest of its pre-Anthropocene range, and all individuals of this species are in China. The species has an independent history of >1 billion years and is therefore regarded as an ideal species for studies of climate change and fish evolution. China’s government has assigned the Chinese sturgeon the highest priority for conservation, and all commercial captures have been prohibited since 1983. Because of human disturbances in the Yangtze River basin, however, the Chinese sturgeon population has now declined to < 100 individuals, and therefore is considered critically endangered by IUCN and is listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).
The Yangtze River currently contains a large number of escaping non-native sturgeon than Chinese sturgeon. Because the non-native and Chinese sturgeons have similar ecological niches, asymmetric competition can reduce the availability of spawning grounds and other resources for the Chinese sturgeon. In addition, most escaping non-native sturgeons are congeneric species with the Chinese sturgeon, and hybridization can lead to genetic pollution and destruction of the genetic integrity of the Chinese sturgeon. In addition to the Chinese sturgeon, about 370 native fish species inhabit the Yangtze River, among which >30 species are rare and endemic to China. Because sturgeons are carnivorous, the non-native escapees also threaten these native species. The fishery sector is still seeking effective approaches to dealing with this serious problem.
The full Policy Direction, Emerging risks of non‐native species escapes from aquaculture: Call for policy improvements in China and other developing countries is free to read in issue 57:1 of Journal of Applied Ecology.
One thought on “Cover stories: escapes from aquaculture”
Interesting. Is there any danger of hybridization, or is it competition only?