Recent years have seen a global and rapid resurgence of fungal diseases with direct impact on biodiversity and local extinctions of amphibian, coral, or bat populations. Despite similar evidence of population extinction in European fish populations and the associated risk of food aquaculture due to the emerging rosette agent Sphaerothecum destruens, an emerging infectious eukaryotic intracellular pathogen on the fungal–animal boundary, our understanding of current threats remained limited. Long-term monitoring of population decline for the 8-year post-introduction of the fungal pathogen was coupled with seasonal molecular analyses of the 18S rDNA and histological work of native fish species organs. A phylogenetic relationship between the existing EU and US strains using the ribosomal internal transcribed spacer sequences was also carried out. Here, we provide evidence that this emerging parasite has now been introduced via Pseudorasbora parva to sea bass farms, an industry that represents over 400 M€ annually in a Mediterranean region that is already economically vulnerable. We also provide for the first time evidence linking S. destruens to disease and severe declines in International Union for Conservation of Nature threatened European endemic freshwater fishes (i.e. 80% to 90 % mortalities). Our findings are thus of major economic and conservation importance.

Invasion risk assessments are reliant on ecological data that assist the predictions of whether an introduced species will adapt to novel conditions. Data from the native range of potential invaders can thus assist these assessments. Here, the growth and reproductive characteristics of the Western tubenose goby Proterorhinus semilunaris, a Ponto-Caspian gobiid, were assessed in three natural lakes in their native range, as there are few extant data on these traits. Across the three lakes, the gobies were found in varying abundances. Sex ratios varied, with females significantly outnumbering males in only one lake, with equal sex ratios in the other lakes. The fish always showed a positive allometric growth, but had high variability in their somatic growth rates and relative body conditions between the lakes. Scale ageing revealed all populations comprised of individuals to four years old, with one lake having individuals to 5 years old. Reproductive characteristics, including size at maturity, gonado-somatic index and fecundity, did not differ significantly between the lakes. These data suggest that plasticity in aspects of their life history traits provides P. semilunaris with considerable adaptive capacity following their introduction into novel conditions.

-The pumpkinseed Lepomis gibbosus was introduced to Europe and parts of the Mediterranean Region more than 100 years ago. However, relatively little is known of its potential ecological impacts on the native species and freshwater ecosystems of Anatolia (Turkey), where the species is currently established in ponds and rivers. In this study, interactions between L. gibbosus and native and non-native stream fishes were investigated between June 2009 and May 2010 in Sarıçay Stream, a Mediterranean-type water course. Microhabitat preferences for depth, substratum composition, distance from bank and from vegetation, plant cover, velocity, turbidity and light intensity were studied by Constrained Quadratic Ordination. The species sampled in larger frequency of occurrence (and for which microhabitat relationships could be investigated) comprised endemic Smyrna chub Petroleuciscus smyrnaeus and Aegean chub Squalius fellowesii, and nonnative L. gibbosus (both juveniles and adults) and topmouth gudgeon Pseudorasbora parva. Adult L. gibbosus were found to prefer locations closer to the bank with less turbid water, plant cover, light intensity, woody structure and with sandy substratum whilst avoiding riffle habitats with coarser debris, deeper water, dense submersed aquatic vegetation and higher velocities. These preferences overlapped with those for the other nonnative species P. parva, but not with those for the endemic species and for L. gibbosus juveniles. The results of this study suggest that the potential for adverse impacts through competition for habitat of adult L. gibbosus with the native fish fauna is not apparent in Sarıçay Stream.Keywords: endemic / invasion / lotic system / Constrained Quadratic Ordination (CQO) Résumé -Les interactions du microhabitat de la perche soleil Lepomis gibbosus dans une rivière de type méditerranéen ne suggèrent aucune preuve de l'impact sur les poissons endémiques. La perche soleil Lepomis gibbosus a été introduite en Europe et certaines parties de la région méditerranéenne, il y a plus de 100 ans. Cependant, on sait relativement peu sur ses impacts écologiques potentiels sur les espèces indigènes et les écosystèmes d'eau douce de l'Anatolie (Turquie), où l'espèce est actuellement implantée dans les étangs et les rivières. Dans cette étude, les interactions entre L. gibbosus et les poissons indigènes et non indigènes des cours d'eau ont été étudiées entre juin 2009 et mai 2010 dans la rivière Sariçay, un cours d'eau de type méditerranéen. Les préférences de microhabitat pour la profondeur, la composition du substrat, la distance de la rive et de la végétation, la ripisylve, la couverture végétale, la vitesse, la turbidité et les conditions de lumière ont été étudiées par ordination quadratique sous contraintes. Les espèces échantillonnées en plus grande abondance (et pour lesquelles les relations de microhabitat pouvaient être étudiées) étaient le chevesne Smyrna Petroleuciscus smyrnaeus et le chevesne Aegean Squalius fellowesii endémiques, et L. gibbosus non indigène (j...

The aim of this study was to provide baseline data and fill an outstanding knowledge gap in our understanding of factors affecting the invasiveness of the Ponto-Caspian gobiid Neogobius fluviatilis. To this end, the life history traits (as somatic growth and reproduction) of N. fluviatilis were studied in three natural freshwater lakes in its native range. These populations were characterised by slow somatic growth rates, being the slowest reported across all the native and non-native ranges of N. fluviatilis. Ages were recorded to 7 years. Across the three lakes, there was considerable variability in sex ratios and reproductive traits (including length at maturity and fecundity at length and age), revealing considerable interpopulation variability. These data suggest that N. fluviatilis has considerable plasticity in the expression of its life history traits, with this plasticity argued as a key factor in facilitating the ability of N. fluviatilis to establish and invade new waters following introductions.

Several Ponto-Caspian gobiids have expanded from their native distribution ranges to Europe and North America. As knowledge on their bio-ecological features in their native range is still limited, the trophic ecology of monkey goby Neogobius fluviatilis and Western tubenose goby Proterorhinus semilunaris was studied in three natural lakes in the Marmara Region of NW Turkey using the stable isotopes of δ 13 C and δ 15 N. In two of the lakes, the trophic niches (as the isotopic niche) of the gobies were highly divergent with co-existing native fishes, with no overlap. Moreover, mixing models suggests considerable inter-specific dietary differences. In all lakes, the trophic niches of gobies were never significantly larger than those of coexisting fishes. These results suggest that when introduced outside of their natural range, the gobies might integrate into new fish communities via exploiting resources that are underexploited by native fishes or will initially share resources with these species before their niches diverge, perhaps through competitive displacement.