Ecological Indicators for Surface Water Quality - Methodological Approaches to Fish Community Assessments in China and Germany

Assessments of aquatic ecosystem health rely increasingly on biological indicators such as fish community structure, but national approaches differ. To use bioindicators efficiently and to allow cross-country comparisons, standardized tools and methods are required. Within this study, currently applied procedures for stream ecosystem assessment in China and Germany are summarized and active and passive fish sampling methodologies used in both countries are investigated. The methodological comparison was based on the results of a joint Chinese German workshops within the SINOWATER project in 2016. A joint sampling campaign was then conducted in 2017 at 6 representative sites within 70 km of the Fan River, a tributary to the Liao River System in Liaoning province, China. Active methods comprised single-pass electrofishing methods as typically applied in Germany and China as well as seining. As passive methods, common minnow traps, gill-netting and longline-fishing were used. To allow the comparability between methods, a standardized sampling design comprising several replicates at each site was chosen, covering a range of different ecological stream conditions. By comparison of the different fishing methodologies, electrofishing yielded the best overall results to assess fish biodiversity in terms of species abundance, richness and catch per unit effort. Differences in the effectiveness of the different electrofishing approaches mostly depended on the power source used. To cover the full spectrum of the fish community and to detect very rare species, a combination of different active and passive methods was most useful. If electrofishing is the method of choice, it is very important to adjust the gear power to river specific conditions such as flow, size and depth. The results of this joint Chinese-German study may aid in the selection of suitable sampling methods for fish community assessments in the future.