Developing a biotic river typology and defining reference conditions in the rivers of Greece: a spatially- based approach A.N. Economou, S. Zogaris, S. Giakoumi, R. Barbieri & D. Petridis Abstract Developing a biotic river typology and reference conditions are vital components of ecological assessment using fish. In Greece, due to the absence of systematic monitoring data, fish sampling data from previous ichthyological surveys conducted primarily in the southern and western parts of the Hellenic Western Balkan ecoregion (Illies' ecoregion 6) were utilised. These surveys were undertaken for the purpose of fish conservation and were not designed with the prospect of ecological assessments. As a consequence, the sampling methodologies, the site selection criteria, the analytical procedures and the recorded parameters were not in line with the requirements of the WFD. A brief synopsis of the main environmental features of the Greek rivers which indicate a remarkable environmental heterogeneity is presented. Greece is a geographically fragmented mountainous country with a large number of medium and small sized rivers. Most rivers run through narrow mountain valleys that descend abruptly to the coast. Usually a mountain river becomes a lowland river very near its estuary. As a result many small and medium sized rivers have a flashy and erosive behavior and suffer from the lack of lowland riverine habitat. Lowland rivers are usually small; large floodplain rivers are very few, almost wholly restricted to northern Greece. Precipitation is irregularly distributed and hydrology varies remarkably among basins. Semi-arid regions and areas with seasonally arid conditions exist in parts of the south and southeast where localized karstic springs play an important role in enabling perennial water flows. Hence, hydrology, river geomorphology, biogeography and climatic conditions vary remarkably among basins and longitudinally along river courses. The major degradation types and their impacts on fish communities are reviewed. Throughout most of Greece, major impacts have resulted from water abstraction, which most often takes place mainly during the summer, and therefore coincides with the summer drought. The impacts of hydroelectric dams and other water exploitation practices and the operation of dams as reservoirs are ranked as next in importance, followed by reclamation and river management works, pollution, river bed substrate exploitation and the drainage of lakes and wetlands associated with rivers. Generally, streams and small rivers have been affected more adversely due to severe water abstraction (tapping of springs for domestic use and irrigation use) and their inability to buffer the harmful effects of pollutants in the way that large rivers can. The distributional patterns of 59 native freshwater species were used to investigate biogeographical relationships among river basins in the Hellenic part of ecoregion 6. For the purpose of this analysis the results of previous ichthyological investigations conducted by the NCMR were primarily utilised, however unpublished information on fish distribution was also used here to investigate biogeographical relationships. This analysis corroborates recent biogeographical proposals, but goes further in hypothesizing new biogeographical divisions in western and southern Greece. Paucity of data from some areas, taxonomic problems still evident in some taxa and a confusing pattern of faunal affinities and divergences make the use of the overall similarity of ichthyofaunas among drainage basins difficult to complete over the entire ecoregion. The results of statistical analysis on current fish distribution and fish community structure, supported by geological data and phylogenetic evidence, propose that the Greek part of Ecoregion 6 may be preliminarily divided into 5 freshwater fish subecoregions: (a) Macedonia- Thessalia, (b) Adriatic, (c) Ionian, (d) Evrotas and (e) Attiki-Beotia. Despite broad similarities, the rivers within the subecoregions Attiki-Beotia and Ionian show distinctive regions, which necessitate a further subdivision into “fish districts” for the interpretive purposes of this regionalization exercise. Linking ichthyological communities in reference sites with abiotic variables was proved to be a task beyond the abilities of the available dataset. Of the problems encountered, the most important concern the calibrated reference sites, some of which are poorly selected and not representative, others have sampling effect problems, and other sites proved to be more impacted than the screening process may have shown. Further complexities arise from the high degree of endemism and disjunct geographical distributions, which generate the need for a high level of typological discrimination. The extensive hydrological 1 fragmentation and a great diversity of factors affecting the fish communities in Greek rivers, requires us to set reference conditions in a large number of strata. It is postulated that specifically designed research is necessary to arrive at a biologically meaningful typology scheme. Despite these difficulties, using available data and statistical analysis we identified some abiotic variables as potentially important for predicting community types; of which the most important in a nationwide scale seem to be basin size, altitude (a surrogate of temperature) and discharge (some other variables appear to be locally important also). Scarcity of appropriate data has prevented us to statistically justify the specific prominence of these variables and the significance of other abiotic variables, or to set biologically defensible boundaries among abiotic types. A preliminary top-down river biotic typology for the Peloponnesian part of the Ionian subecoregion, using combinations of these three variables only, is presented. During the work of WP3 candidate metrics were selected on the basis of knowledge of the fish fauna and of the aquatic systems of Greece, and the theoretical expectations for each metric were delineated. A general difficulty for establishing metrics for the development of a biologically-based multimetric index for ecological assessment in small rivers is that species richness is low and the fish communities in these rivers are dominated by tolerant species with wide ecological requirements. Multimetric approaches such as the IBI, using lots of metrics may not provide reliable assessment of ecological quality, because by adding a metric that is not biologically relevant or sensitive to the prevailing pressures less weight is given to more relevant metrics. We suggest that appropriate methods for the Greek low speciesrich rivers should rely on a limited number of metrics. For the case of flow regime disturbances the methods could include metrics for total fish abundance and biomass, abundance or proportion of sensitive species to flow reduction, and longevity or proportion of large age (size) groups, which seem to be intolerant to reduced flow. A short discussion is presented of the problems associated with the setting of reference conditions and building a multimetric index for ecological assessment using spatial methods in Greece. 2 1. Introduction An analysis of the available ichthyological data was made with the objective to define a fish-based river typology and to identify reference conditions for FAME. The analysis was based on the following: (a) the results of previous ichthyological investigations conducted by the NCMR - Institute of Inland Waters – and (b) on published and unpublished fish data and biogeographical research. The NCMR’s field investigations concentrated on the southern and western portion of the Hellenic Western Balkan ecoregion (Illies' ecoregion 6), however sporadic data from the eastern portion are also available (Appendix 1, Map 1). The investigations were undertaken mainly for the purposes of endemic fish surveys and conservation assessments and they were not designed with the prospect of river ecological status assessments. As a consequence, the sampling methodologies, the site selection criteria, the analytical procedures and the recorded environmental and abiotic parameters were not in line with the requirements of the WFD, or adequate for the development of a multimetric index. The aims of this report are the following: 1. A synopsis of the characteristics of Greek rivers and a brief description of degradation types in the scope of developing a spatially-based approach using a multimetric index for ecological assessment, 2. Initial development of a fish-based typology which centers on: The definition of biogeographically-relevant subecoregions (regionalization) Linking ichthyological communities in reference (plus calibrated reference) sites with important abiotic variables Provisional establishment of an abiotic typology for a portion of Peloponnese based on system B using the top-down approach. The data available were not adequate (a) to develop a biotic typology and to link biotic river types with abiotic variables, nor to perform comparisons with typologies based on systems A and B, (b) to set reference conditions and develop a rating system. Scarcity of data from other Balkan counties also prevented an expansion of our analyses to the whole ecoregion 6. 2. Methods 2.1. Data utilised The NCMR dataset contains site-specific data from about 600 samples taken from 48 rivers of western Greece, the Peloponnese and the Island of Rhodes (most of these data have been stored in a PARADOX database). The usefulness of these data