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

Key-words:invasion, signal crayfish, decline of native species, Astacus astacus, Austropotamobius torrentium, threats Crayfish plague and introductions of non-indigenous freshwater crayfish species (NICS) have had major consequences for the survival of autochthonous crayfish populations in Europe. Beside habitat loss, the invasive signal crayfish Pacifastacus leniusculus is currently responsible for the decline of indigenous crayfish species (ICS) in Carinthia (Austria). Here, we studied the distribution of P. leniusculus and native Astacus astacus and Austropotamobius torrentium in selected catchments to assess the ongoing colonisation with signal crayfish and to monitor the existence of ICS localities. Our results showed that P. leniusculus is widespread in Carinthia and many areas with native crayfish have disappeared within nine years. However, whereas populations of A. astacus became extinct in running waters, those of A. torrentium seemed to be more protected by occupying headwaters. In contrast to the ICS, P. leniusculus was found in a broad range of freshwater habitats and water quality conditions. We hypothesise that the fast expansion of P. leniusculus and the decline of ICS was caused by human-mediated stockings of NICS, followed by active signal crayfish invasions from established populations into new watercourses. RÉSUMÉ

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Human mediated introductions of nonindigenous crayfish species (NICS) are responsible for their rapid colonisation of European freshwaters. The introduction of North American crayfish is furthermore linked to the spread of crayfish plague and the decline of indigenous crayfish species (ICS). As the management of ICS and NICS have become necessary, a detailed knowledge on their distribution and ecological requirements is needed. We studied the current range of native noble crayfish Astacus astacus and stone crayfish Austropotamobius torrentium, as well as alien signal crayfish Pacifastacus leniusculus in Carinthia (Austria) and evaluated environmental and physical habitat features in streams with and without crayfish. Meanwhile, the loss of many ICS populations was recorded and alien P. leniusculus was found to be widespread in this region. Most of the habitat features of streams having crayfish differed significantly from sites lacking crayfish for at least one investigated native or alien species. Furthermore, multivariate and regression analyses showed specific differences in the habitat use of the investigated crayfish. Our results showed that the presence of alien P. leniusculus was associated with larger and smoother sloped lowland rivers, while the occurrence of the two native species was confined to smaller streams either at higher altitudes and with distinct physical habitat conditions (A. torrentium) or with moderate water temperatures (A. astacus). This study helps to identify potential refuge areas for the endangered native species and to predict the further spread of the most common non-native crayfish species in European streams.

Crayfish are among the largest and most threatened invertebrates in freshwater habitats. Due to their size, behaviour and feeding activity they may affect structure and function of aquatic ecosystems and their organisms. Despite their importance in many freshwaters and available information on their ecology for several species little is known about the European crayfish Austropotamobius torrentium. In order to evaluate the potential effects of indigenous crayfish presence on the structural and functional composition of the zoobenthic community, we measured population size and densities of three A. torrentium populations and compared macroinvertebrate assemblages and physicochemical parameters in three streams with and three without crayfish. The experimental setup considered crayfish effects at a large scale in defined reaches of pristine headwaters in association with the whole benthic fauna under natural conditions. Presence of A. torrentium significantly affected zoobenthic abundance, diversity and the relative proportions of functional feeding groups. In crayfish streams, especially Trichoptera and collector gatherers were more abundant and diverse, while sites without crayfish had significantly higher abundances and diversities of shredders and wood feeders. Our study provided strong evidence that the presence of the indigenous crayfish A. torrentium had important effects on the trophic cascades of headwater stream communities. Les écrevisses sont parmi les invertébrés les plus menacés dans les habitats aquatiques. En raison de leur taille, de leur comportement et de leur nourriture, elles peuvent modifier la structure et le fonctionnement des écosystèmes aquatiques. Malgré leur importance dans beaucoup de milieux d'eau douce et les connaissances disponibles pour plusieurs espèces, peu de chose est connu sur l'écrevisse européenne Austropotamobius torrentium. Pour évaluer les effets potentiels de la présence de l'écrevisse indigène sur la structure spécifique et fonctionnelle de la communauté du zoobenthos, nous avons évalué les taille et densité de population de trois populations d'A. torrentium et comparé les assemblages de macroinvertébrés et les paramètres physico-chimiques dans trois ruisseaux avec écrevisses et trois sans écrevisses. Le dispositif expérimental considère les effets de l'écrevisse à une large échelle dans des tronçons de tête de bassin vierges de Article published by EDP Sciences M. Weinländer and L. Füreder: Knowl. Managt. Aquatic Ecosyst. (2011) 401, 22 tout impact en association avec l'ensemble de la faune benthique dans ces conditions naturelles. La présence d'A. torrentium affecte significativement l'abondance du zoobenthos, sa diversité et les proportions relatives des groupes fonctionnels du réseau trophique. Dans les ruisseaux avec écrevisses, les trichoptères en particulier et les filtreurs sont plus abondants et variés, alors que dans les sites sans écrevisses l'abondance des brouteurs et décomposeurs de bois est significativement plus élevée. Notre étude montre clairement ...