Invasive alien species (IAS) are a significant and growing problem worldwide. In Europe, some aspects of IAS have been addressed through existing legal instruments, but these are far from sufficient to tackle the problem comprehensively. The FINS II Conference considered the relevance of Top 20 IAS issues (Top 10 threats and opportunities) for Europe determined at the 1st Freshwater Invasiveness – Networking for Strategy (FINS I) conference held in Ireland in 2013. Using a similar format of sequential group voting, threats from FINS I (lack of funding, of awareness and education; poor communication) and several new threats (lack of lead agencies, of standardized management and of common approach; insufficient monitoring and management on private property) were identified by 80 academics, applied scientists, policy makers and stakeholders from 14 EU and three non-EU countries (including 10 invited speakers) during four workshop break-out sessions (legislation remit in both EU/non-EU countries; best management and biosecurity practice for control; data management and early warning; pathways of introductions and citizen science). Identified opportunities include improved cooperation and communication, education and leadership to enhance public awareness and stakeholder participation, systems establishment for early detection, rapid response, monitoring and management of IAS using standardised methods of data collection, storage and usage. The sets of threats and opportunities identified underline the importance of international cooperation on IAS issues in communication, education and funding as priorities, as well as in standardization of legislation, control methods and best practise of research

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We investigated somatic condition, growth rate, diet and food resources of the native (lower Danube) and non-native (upper Danube) populations of invasive bighead goby Neogobius kessleri and round goby N. melanostomus within the Danube River to answer the question whether prey availability and type may have facilitated successful goby invasion to the upper Danube. The non-native populations of both species were in better somatic condition and grew faster. The biomass of nonmollusc macrozoobenthos, dominated by Amphipoda, was markedly higher in the non-native range while molluscs were recorded frequently in both the native and non-native ranges. Amphipods were far the most consumed prey by nonnative fish, whereas native fish combined two main prey types -amphipods and fish (bighead goby) and amphipods and bivalves (round goby). A laboratory experiment was conducted to reveal whether the low consumption of bivalves by the round goby in the non-native range reflects prey encounter rates or alternatively prey selectivity. When bivalves and amphipods were offered simultaneously in excess to the experimental fish, round goby showed strong preference towards amphipods. Molluscs are hypothesised to be an alternative rather than the most preferred prey for the round goby. Rich food resources utilised by the non-native bighead and round goby contribute to their invasive success in the upper Danube.

The Czech Republic has experienced a number of inter-and intra-continental introductions (42 introduced species total), with 29 species historically confirmed and 20 species still present in the wild. Fourteen species have become established, representing 27% of the current fish fauna. Pond aquaculture and recreational fisheries are the two major pathways of introduction and spread, and they are responsible for 80% and 36% of all introduced fish, respectively. Over the last decade, there has been a significant increase in the management practice of stocking recreational fisheries with non-native fish, particularly alarming in salmonid waters. Pond aquaculture is associated with high risk in terms of the numbers of unintentional fish introductions; all species introduced as contaminants of carp stocks have become established (Lepomis gibbosus, Ameiurus melas) and then widespread (Pseudorasbora parva, Carassius gibelio) and have been evaluated as invasive.Here, the historical chronology and facts regarding fish introductions in the Czech Republic are given, in addition to the current distribution of established populations. Present issues and future perspectives concerning the control of nonnative fish and are briefly discussed.

Since 1997, three new Neogobius species (Neogobius kessleri, N. fluviatilis and N. melanostomus) have been regularly recorded in the Slovak part of the Danube River, formerly inhabited only by one native gobiid species (Proterorhinus marmoratus). The study of their food habits proved that the amphipod Corophium curvispinum, chironomid larvae and pupae, caddis fly larvae (Hydropsyche sp.) and mayfly nymphs (Ephoron virgo, Potamanthus luteus) were the most important food items contributing to the similarity of the diets of the gobiid species. Fish (0+ Zingel zingel and Sander lucioperca) appeared in the diet of N. kessleri only.