Development and application of a second-generation multilingual tool for invasion risk screening of non-native terrestrial plants

Under the increasing threat to native ecosystems posed by non-native species invasions, there is an urgent need for decision support tools that can more effectively identify non-native species likely to become invasive. As part of the screening (first step) component in non-native species risk analysis, decision support tools have been developed for aquatic and terrestrial organisms. Amongst these tools is the Weed Risk Assessment (WRA) for screening non-native plants. The WRA has provided the foundations for developing the first-generation WRA-type Invasiveness Screening Kit (ISK) tools applicable to a range of aquatic species, and more recently for the second-generation ISK tools applicable to all aquatic organisms (including plants) and terrestrial animals. Given the most extensive usage of the latter toolkits, this study describes the development and application of the Terrestrial Plant Species Invasiveness Screening Kit (TPS-ISK). As a second-generation ISK tool, the TPS-ISK is a multilingual turnkey application that provides several advantages relative to the WRA: (i) compliance with the minimum standards against which a protocol should be evaluated for invasion process and management approaches; (ii) enhanced questionnaire comprehensiveness including a climate change component; (iii) provision of a level of confidence; (iv) error-free computation of risk scores; (v) multilingual support; (vi) possibility for across-study comparisons of screening outcomes; (vii) a powerful graphical user interface; (viii) seamless software deployment and accessibility with improved data exchange. The TPS-ISK successfully risk-ranked five representative sample species for the main taxonomic groups supported by the tool and ten angiosperms previously screened with the WRA for Turkey. The almost 20-year continuous development and evolution of the ISK tools, as opposed to the WRA, closely meet the increasing demand by scientists and decision-makers for a reliable, comprehensive, updatable and easily deployable decision support tool. For terrestrial plant screening, these requirements are therefore met by the newly developed TPS-ISK.

Exploring microplastic pollution in a Mediterranean river: The role of introduced species as bioindicators

Studies of plastic contamination in freshwater ecosystems and their biota remain scarce, despite the fact that the vast majority of plastic waste initially passes through lotic ecosystems. Biomonitoring provides valuable information regarding plastic pollution and microplastic threats to biota and human health. The aim of this study was to explore the potential use of a non-indigenous fish species as a bioindicator of microplastic pollution in an Eastern Mediterranean River. Our study area is located in a heavily modified and vastly impacted urban river which flows through the largest part of the Metropolitan area of Athens, Greece. We used an introduced chub species (Squalius vardarensis) to assess microplastic ingestion in the river. The results indicated moderate occurrence and abundance of microplastics in the fish gastrointestinal tracts; one-third of specimens (35%) contained microplastics, although the average number of microplastics per specimen was relatively low (1.7 ± 0.2). Overall, the abundance of microplastics in the water confirmed the moderate level of microplastics contamination in our study area. The major polymer types of microplastics identified by FT-IR analysis were: polyethylene (PE), polyvinyl alcohol (PVA) and polypropylene (PP); reflecting the fragmentation of larger litter from industrial packaging and/or household goods. Surface runoff of the urban environment, via motorways and major road networks, could be the contributing factor to the reported microplastics. Our results suggest that generalist's non-indigenous species such as chubs could be used as bioindicators of microplastics in inland waters. Introduced fishes can be a feasible, nondestructive, and cost-effective option for the assessment of microplastics in freshwater ecosystems, while freshwater chubs' high abundance and omnipresence in European rivers further serve this scope. However, it is worth noting that the suitability of any particular species as a bioindicator of microplastics may depend on a variety of factors, including their feeding behavior, habitat, and exposure to microplastics in their environment.

REVIVE: A feasibility assessment tool for freshwater fish conservation translocations in Mediterranean rivers

Conservation translocation is a management action applied for population recovery of threatened freshwater fishes, often however with partially successful outcome, mainly due to inadequate feasibility assessment prior to the translocation. Up to date, feasibility assessments have been mainly focused on economically important species (e.g., salmonids) inhabiting perennial rivers, while little attention has been given to fish translocations in rivers in Mediterranean climate areas. In this study, we developed a robust feasibility assessment tool for freshwater fish translocations in Mediterranean-type riverine ecosystems within an interdisciplinary, multispecies approach. The REVIVE tool integrates quantitative and semi-quantitative data, incorporates uncertainty and consists of two main components. The first component is the evaluation of the potential release water bodies (R-WBs) for their suitability for the planned translocation, incorporating a number of essential criteria for Mediterranean rivers, with emphasis on flow regime and habitat quantity. Additional criteria include the current and historical presence of the target species, water and biological quality, habitat suitability in terms of the ecological requirements of the target species, alien invasive species' pressure, and hydromorphological pressures, including their mitigation potential. The second component is the evaluation of the potential source water bodies (S-WBs) in terms of genetic compatibility and provision of a sufficient number of propagules. A trial application in a Mediterranean basin (Vassilopotamos River, Southern Greece) for the potential translocation of two threatened cyprinids in five R-WBs indicated the robustness of the tool. This integrative, flexible tool combines several elements identified as essential in reintroduction biology and can have wider applications, for a multitude of freshwater fish taxa and riverine systems, maximizing the success of planned translocation actions by natural resources' managers. Modifications to enable its transferability to other river types or fish taxa are also discussed.

Stakeholders Perceptions of Non-indigenous Freshwater Fish Species: A Case Study from a Mediterranean Biodiversity Hotspot

Even though the ecological impacts of invasive alien species (IAS) have been well studied, social aspects of IAS in freshwater ecosystems are still poorly explored. This study aimed to assess the perceptions associated with non-indigenous freshwater fish species (NIFS) among environmental-related professional and non-professional stakeholders in a Mediterranean country that displays high levels of fish species endemism, by using a questionnaire survey approach. Overall, 203 individuals participated, from which, the majority (n = 144) were related to environmental sciences. Most of the respondents perceived NIFS to be a threat of national importance, possibly attributed to the emotional effect of the term non-indigenous (conceived as intruder). However, NIFS were indicated as the least important threat affecting aquatic ecosystems when compared with other pressures. This contrasting perception could be explained by the fact that broad-scale impacts (i.e., climate change) exert stronger reactions compared to NIFS. Interestingly, non-professionals were more successful in identifying NIFS and native species compared to professionals, however both indicated low overall identification success. The majority of the respondents, both professionals and non-professionals, considered that: (a) the official authorities do not implement actions for NIFS management, (b) government spending should be increased to manage NIFS even if it should be reduced for other needs, and (c) early detection is the best way to manage NIFS. The establishment of a nationwide network consisting of all related stakeholders on NIFS issues, aiming to public awareness and preventive management actions to limit the spread and impacts of NIFS should be set as a priority.

A global-scale screening of non-native aquatic organisms to identify potentially invasive species under current and future climate conditions

The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium- and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a 'very high risk' of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate 'rapid' management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be restricted or banned with regard to importation and/or sale as ornamental or aquarium/fishery enhancement.

Defining non-indigenous fish assemblage types in Mediterranean rivers: Network analysis and management implications

The design and implementation of appropriate management actions to tackle the spread and negative impacts of non-indigenous fish species (NIFS) in freshwater ecosystems still remains a complex task. In an effort to address the limitations of current managerial approaches, our study develops and applies a classification framework to define non-indigenous fish assemblage types (FATs) in Mediterranean riverine ecosystems and identifies the linkage with various regional, local, biotic and abiotic environmental factors. This framework contributes to a pre-invasion stage screening and to the design of effective type-specific post-invasion management actions dealing with specific NIFS assemblages. A network analysis was applied in order to extract NIFS community level information from 393 samples obtained from 51 river basins of Greece, while a multivariate ordination analysis was conducted to detect the factors best explaining the structure and distribution of FATs. The association patterns of the study's inputs and outcomes are illustrated through an alluvial diagram, providing insights across different spatial scales. In total, five FATs were generated where the major NIFS contributors of average similarity within each modularity class revealed the key indicator species (Gambusia-FAT; Carassius/Lepomis-FAT; Pseudorasbora-FAT; Salmonids-FAT and Carp-FAT). Overall, the identified FATs varied spatially, indicating different community structure, mainly based on the diverse habitat preferences and life-history traits of indicator species. Alien FATs were mainly distributed within large and transboundary rivers, while Translocated and Salmonids FATs mostly occupied ecoregions with relatively depauperate faunas and often in biodiversity hotspots. The results of this study can identify conservation priorities within FATs, inform specific-type post-invasion management actions tackling NIFS, while in addition may provide valuable information for protecting high-priority water bodies before invasion.

Tracking non-indigenous fishes in lotic ecosystems: Invasive patterns at different spatial scales in Greece

Mediterranean lotic waters such as rivers, streams and springs are poorly monitored for non-indigenous fish species (NIFS). Since these systems are stressed by multiple anthropogenic pressures, it is important to build robust procedures to track NIFS distribution and spread. This study applies a multi-faceted assessment of NIFS in the lotic ecosystems of Greece at different spatial scales by providing: a) a historical review of temporal patterns and arrival pathways of fish introductions in river basins of Greece (140 basins) across 100years; b) an analysis of occurrence and abundance data of NIFS assemblages at the lotic site scale (644 electrofished sites); c) the mapping of NIFS distributional patterns at river basin (75 basins) and regional scales (7 freshwater ecoregions); and, d) a vector analysis of fish translocations using an ecoregional framework. In total, 55 NIFS were recorded (25 alien and 30 translocated); however, there is a low incidence of NIFS in lotic waters at the site scale (30 NIFS recorded in the field samples; 10 alien and 20 translocated). NIFS introductions in Greece appear to be influenced by specific socio-historical periods, indicating a gradual increase since late 1970s. Despite this increase, our study provides evidence that only four alien species are currently widespread and common in the rivers and streams of Greece: Gambusia holbrooki, Carassius gibelio, Pseudorasbora parva, and Lepomis gibbosus (in order of recorded abundance). NIFS tend to be absent or distributed in very low numbers in upland streams and in smaller river basins. However, the issue of translocated fish species is shown to be a sorely neglected problem that is difficult to track. This review tests a readily transferable screening procedure, contributes to the application of the European Union Regulation on Invasive Alien Species; it suggests gaps and uncertainties, and proposes conservation and management actions.

A model-based fish bioassessment index for Eastern Mediterranean rivers: Application in a biogeographically diverse area

In ecosystems with high fish species endemicity, such as Mediterranean-type rivers, biogeographical differences among ecoregions present serious obstacles to developing broadly-applicable river bioassessment indices. This impediment has contributed to a serious time-lag in developing EU policy-relevant fish-based indices in the Eastern Mediterranean countries. Here we present the first model-based fish index for the Eastern Mediterranean (the Hellenic Fish Index, HeFI) in an effort to overcome biogeographic differences among the area's biotically heterogeneous rivers. The index is based on modelled reference conditions and employs site-specific electrofished fish samples from an extensive dataset from Greece that covers six freshwater ecoregions, including five transboundary river basins flowing through six countries. Environmental and anthropogenic pressure data were procured from 403 sampled river sites and ecologically-relevant traits were defined for 103 collected fish species. For the development of the index, we first diagnosed least degraded sites forming a calibrated reference site dataset and secondly quantified differences of fish metrics between the reference and impaired sites. Four trait-based fish metrics showed the best ability to discriminate between impaired and reference sites. The index performed well in discriminating anthropogenic pressure classes, giving a significant negative linear response to a gradient of anthropogenic degradation. HeFI successfully assessed both small and large rivers in different freshwater ecoregions. This geographically broad-scale index development shows that key trait-based reference conditions can be produced by a predictive model in remarkably heterogeneous rivers where range-restricted fishes dominate. This index promotes a screening-level bioassessment application that may be further developed and refined with relevant monitoring.