Scientists from the Institute of Biodiversity and Ecosystem Research (BAS) and from the Institute of Vertebrate Biology (ASCR), Czech Republic, participated in a field trip in June 2015. The field trip was organised in the framework of the ESENIAS-TOOLS project WG3: Data collection, analysis, standardisation and harmonisation on alien freshwater species; and within collaboration between the Bulgarian Academy of Sciences (BAS) and the Academy of Sciences of the Czech Republic (ASCR).

During the ten-day field trip, a total of 27 sites in three types of water bodies were sampled:

• 15 sites in the shoreline zone of the Danube River, north-western Bulgaria (from Vrav, 840 rkm, to Archar, 770 rkm);
• Four sites in the lower reaches of the Danube tributaries, north-western Bulgaria
• Eight sites in standing water basins (reservoirs and the Danube wetlands).

About 50 samples of benthic macroinvertebrates (mollusks and crayfish) and fish were collected.

The shoreline ichthyofauna and benthic fauna (distribution, abundance, habitat preferences) in the north-western Bulgarian stretch of the Danube River were studied in order to compare these data with data from previous studies and to assess any short-term changes in species composition.

During the sampling in the Danube tributaries and adjacent wetlands, the spiny-cheek crayfish Orconectes limosus (Rafinesque, 1817) was found for the first time in Bulgaria. Fourteen specimens were caught with a hand-net for 1.5 hours in the Topolovets River, near the town of Vidin (N 43.941306; E 22.838611), on 17.06.2015. More information can be found in the Species alerts section >>>

Four sites in standing waters were sampled to study the metazoan parasites of the non-native fish species, Lepomis gibbosus (Centrarchidae), introduced from North America over hundred years ago to Europe. The results will be compared with other populations in four river drainages in Europe: Black Sea, Aegean Sea, Mediterranean and North Sea drainages.