Development of a new tool for fish-based river ecological status assessment in Poland (EFI+IBI_PL)

Abstract

Background. Fish-based indices for evaluation of river ecosystem quality have been used since the 1980s, when the Index of Biotic Integrity (IBI) was first introduced.  Assessment of the ecological status of rivers, based on fish assemblages is required by the Water Framework Directive. During last 15 years a number of national assessment methods based on fish fauna were developed. The recently designed tool for fish-based assessment of ecological status (EFI+IBI_PL) applied in river monitoring in Poland is presented in this paper. Materials and methods. The new European Fish Index EFI+ is a multimetric tool consisting of two specific indices, each with two metrics developed separately for salmonid- and cyprinid-river zones. Those metrics were used in the European intercalibration process to validate national methods. However, the original EFI+ method is not adequate to some lowland river types (physical-factor classification), so it was complemented by a type-specific modification of the Index of Biotic Integrity (IBI_PL). The method was tested on fish data from 493 sites located in 431 surface water bodies sampled in 2011–2012 according to the CEN standard 14011. Results. The EFI+ index was adapted to the specificity of Polish rivers by eliminating some inconsistences of the ecoregion division and problems related to the lack of the Dniester River in the EFI+ software and presented in this paper as EFI+PL. The index of diadromous fish occurrence (D) was also adapted from an original EFI+ method and used as a supplementary assessment tool. Specific IBI metrics were developed for large lowland rivers (with sandy or gravel bottom substrate), organic rivers (flowing through peat areas), and rivers connecting lakes (with the presence or lack of salmonid fish species). A software tool for indices calculation was also developed. The method combination (EFI+IBI_PL) was than tested on a set of 493 monitoring sites sampled in 2011–2012. Both indices classified the highest percentage of sites into moderate ecological state/potential class, but for IBI_PL this percentage was much higher than for EFI+.  Percentage of sites classified to good ecological status or high ecological potential by IBI_PL index were lower than for EFI+. The analysis indicates the consistence of classification for 77% of sites to high/good and below good ecological status by the EFI+PL/IBI_PL method and pressure index. Conclusion. The results of a two-years monitoring program show that the combination of modified  EFI+ and IBI methods can be applied as a tool for river ecological status assessment in Poland, however some further method modifications are needed.

Keywords

• ecological status
• new European Fish Index
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