Non-indigenous freshwater fish research in Greece: Current status and future prospects

Many studies around the globe have documented that the introduction of non-indigenous fish species (NIFS) may pose severe impacts on native biota, ecosystem functioning, and ecosystem services. In Greece, publications on NIFS have increased in recent decades, however, review studies of past and current scientific research on freshwater NIFS in the country are currently lacking. Τhe aim of the present study was to: (a) assess the current state of knowledge of freshwater NIFS in Greece based on the existing scientific literature, (b) evaluate well-studied areas of NIFS research, and (c) identify important gaps that may direct national authorities to implement appropriate research, management and conservation actions reversing the negative impacts of NIFS. A systematic literature review on NIFS research within Greek inland waters was performed by applying the PRISMA methodology (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Overall, our initial search resulted in 2,794 published articles, 87 of which met our selection criteria and were thus included for full analysis. Evidently, NIFS failed to attract the interest of ecologists in Greece until the turn of the century, at which point, publications increased at a rapid rate. However, the majorityof the studies were mainly monothematic concerning NIFS distribution within freshwater ecosystems of Greece (37%), followed by studies on ecological and biological aspects of NIFS (28%). Studies based on fieldwork and laboratory experiments were by far the most common type of research, followed by studies based on bibliographic data. Despite the fact that almost half of the publications were field observational studies, most of them used only qualitative data (plain presence/absence data). Critical aspects of impact assessment were missing; 84% of the reviewed studies did not provide any concrete evidence of NIFS impacts to native biota. Overall, the focus of the studies was uneven, with important gaps in areas of theoretical and practical importance for policy-relevant detection, control, and management of NIFS. Findings may assist researchers in filling scientific gaps identified by our review and guide authorities to define national priorities to prevent and control the spread of NIFS within the country

ELNAIS: A collaborative network on Aquatic Alien Species in Hellas (Greece)

ELNAIS is a dynamic online information platform aiming to collect and report spatial information on Aquatic Alien Species in Greek waters. It covers freshwater, marine and estuarine waters, including not only established aliens but also casual records and cryptogenic species. The ELNAIS system includes: News, List of Greek experts, Literature of findings in Greece, List of species with information on their first introduction date and source as well as photos and distribution maps. Data providers are the scientific community (publications, grey literature, and databases) as well as citizen scientists. ELNAIS provides a useful tool towards national obligations and commitments under both the European and global frameworks in respect to Non Indigenous Species (CBD, WFD, MSFD).JRC.H.1-Water Resource

Distribution patterns of fish assemblages in an Eastern Mediterranean intermittent river

The distribution patterns of fish assemblages within streams can provide insights for river type classifications and may warrant specific conservation actions. However, there is limited knowledge of how fish assemblages assort along a longitudinal axis in Mediterranean intermittent streams. Patterns in spatial and temporal distribution of fish communities were analysed in a Mediterranean intermittent river (Evrotas River) located in Southern Greece, hosting three endemic range restricted species of high conservation concern, during the period 2007−2009, with 80% of the river’s total length desiccating in the 2007 and 2008 droughts. The general trend was an increase in fish density and species richness along an upstream-downstream gradient. Fish assemblages from upstream to downstream were characterized by a decrease of the most rheophilic species (Squalius keadicus) and an increase of the most stagnophilic species (Tropidophoxinellus spartiaticus). Three river segments, characterized by a high degree of homogeneity were delineated. Habitat and environmental preferences for the studied fish species were identified, with elevation and low flowing habitats being the most important environmental factors affecting fish distribution patterns. The current study provides evidence that even in an intermittent river an assemblage pattern following a longitudinal gradient can be identified, mainly due to the lack of instream barriers that allows recolonization after flow resumption

Impacts of the alien mosquitofish on the abundance and condition of two Mediterranean native fish

The rapid decline of the Greek native Valencia letourneuxi, and its recently described sister species Valencia robertae, has been often attributed to habitat degradation, as well as aggression from or resource competition with the alien mosquitofish Gambusia holbrooki. The mosquitofish is extremely wide-spread in Mediterranean freshwater ecosystems, however, documentation on its presumed negative impacts on native freshwater fishes is limited. In this study, we compared abundance, condition and gonad weight of Valencia spp. in no co-occurrence versus co-occurrence to the mosquitofish, using data collected from eight aquatic systems of Greece, over a five year period (2005 to 2009). Our results show that Valencia abundance is significantly lower in co-occurrence to the Eastern mosquitofish. Furthermore, female Valencia spp. individuals in co-occurrence to the mosquitofish were smaller in length and had poorer somatic condition compared to females in habitats not invaded by the mosquitofish. The mechanisms responsible for these effects of the alien mosquitofish as well as the conservation implications for native Valencia populations are discussed

Tackling invasive alien species in Europe II: Threats and opportunities until 2020

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.</p

Τhe fish fauna in lentic ecosystems of Greece

This study provides an annotated checklist of the freshwater fish species recorded in lentic ecosystems of Greece. Species distributional data were derived from an extensive review of published and unpublished sources and were evaluated for their consistency, adequacy and reliability. Overall, 650 freshwater lentic ecosystems (149 natural and 501 artificial) were investigated from which, 480 were fishless or fish data were unavailable. In the remaining 170 ecosystems, 122 taxa were recorded (belonging to 22 families and 57 genera). Some of the records concerned species with extirpated populations, species of doubtful occurrences and taxa of uncertain taxonomic status. The highest species richness (52 species) was recorded in the Ionian ecoregion while endemicity was highest in the Macedonia-Thessaly ecoregion (43.75%). The Eastern Aegean ecoregion presented the highest level of introduced species (75%). Only eight ecosystems hosted 20 or more species, while 92 ecosystems had over 50% of introduced species. The most widespread native species (Anguilla anguilla and Luciobarbus albanicus) were two highly migratory species, highlighting the importance of connectivity of aquatic ecosystems. The most widespread translocated species was Cyprinus carpio due its high commercial and recreational value, whereas Gambusia holbrooki confirmed its high dispersal ability being the most widespread alien species. More than one third of the species recorded (37.23 %) are threatened based on the IUCN Red List. The ultimate contribution of this study is to support the coordination and dissemination of baseline information on the freshwater fishes of Greek lentic ecosystems, required by a range of users. This knowledge will enable further understanding of the regional assemblage structure and other biogeographical patterns of the ichthyofauna of Greece and will contribute to species conservation by prioritising areas hosting species in need of protection. Finally, this study reveals the high knowledge gap regarding species composition in many Greek lentic ecosystems and highlights the need for relevant primary research including more systematic and standardised samplings

Nationwide tracing of two top freshwater fish invaders in Greece using environmental DNA sampling

Alien fish invasions are causing devastating impacts on native freshwater fauna; thus, rigorous, non-invasive and cost-effective biomonitoring of lotic and lentic freshwaters to design and implement appropriate prevention and control measures is now a priority. In this study, we used a species-specific qPCR eDNA assay to monitor two of the most invasive fish species (Gambusia holbrooki and Pseudorasbora parva) in 15 river basins of Greece and validated these results with conventional fish sampling as well as existing field sampling data. Our monitoring provided new records of invasive species indicating basins for rigorous future monitoring and possible eradication attempts. The eDNA proved more sensitive as a detection tool (56% detection rate) compared to conventional electrofishing (50% detection rate) for G. holbrooki. In contrast, it proved less sensitive for detecting P. parva (38% accuracy) compared to electrofishing (44% accuracy), as evident by the two locations where the eDNA failed to detect the target species. Our study illustrates the potential of the eDNA method for regular, standardised monitoring of riverine habitats for invasive fish species by local managers for early detection. Finally, we discuss the application of eDNA in management interventions for identifying invasive species’ hotspots for management prioritisation, for early detection of invaders and for the monitoring of eradication/control actions

To be, or not to be, a non-native species in non-English languages: gauging terminological consensus amongst invasion biologists

In invasion biology, terminological frameworks contribute to the improvement of effective communication among scientists, stakeholders, and policy-makers. This is important not only for informing policy decisions but also for engaging the broader public in understanding the risks associated with biological invasions. Meanwhile, the role of non-English languages in advancing knowledge in invasion biology has gained momentum in recent years. Building on the seminal contributions in this scientific discipline by Professor Gordon H. Copp, this paper examines the provision of three key terms defining species invasiveness in 28 non-English languages. We first define the three non-redundant terms “non-native species”, “established species”, and “invasive species”. Through a comparative analysis of the equivalent of these terms in the 28 non-English languages, as contributed by our panel of invasion biologists and native speakers, with those in a reference review paper, and following the diffusion-of-English versus ecology-of-language paradigms, we identify discrepancies and nuances reflecting the dynamic nature of terminology in invasion biology. While some languages showed consensus in terminology, others differed due to either the avoidance of a culturally or politically laden term for “non-native” or the achievement of greater precision in meaning. Our findings highlight the requirement for clear and precise terminology in invasion biology and suggest the adoption of multidisciplinary approaches to reach consensus and facilitate communication amongst scientists, policy-makers, and the general public in a globally interconnected and rapidly changing world. This will enhance international collaboration and accelerate knowledge exchange, leading to more effective management of biological invasions