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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.

Freshwater mussels (Bivalvia, Unionida) play essential roles in the well-functioning of ecosystems, even providing essential services to humans. However, these bivalves face numerous threats (e.g. habitat loss and fragmentation, pollution, introduction of invasive species, and climate change) which have already led to the extinction of many populations. This underscores the need to fully characterize the biology of these species, particularly those, such as Potomida acarnanica , that are still poorly studied. This study presents the first mitogenome of P. acarnanica (Kobelt, 1879), an endemic species of Greece with a distribution limited to only two river basins. The mitochondrial genome of a P. acarnanica specimen, collected at Pamisos River (Peloponnese, Greece), was sequenced by Illumina high-throughput sequencing. This mitogenome (16,101 bp) is characterized by 13 protein-coding genes, 22 transfer RNA and 2 ribosomal RNA genes. The size of this mitogenome is within the range of another Potomida mitogenome already published for the species Potomida littoralis . In the phylogenetic inference, P. acarnanica was recovered as monophyletic with P. littoralis mitogenome in the Lamprotulini tribe, as expected. This genomic resource will assist in genetically characterizing the species, potentially benefiting future evolutionary studies and conservation efforts., Competing Interests: No potential conflict of interest was reported by the author(s)., (© 2024 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.)

Despite significant population declines and targeted European Union regulations aimed at Anguilla anguilla conservation, little attention has been given to their status at their easternmost range. This study applies wide-scale integrated monitoring to uncover the present-day eel distribution in Cyprus' inland freshwaters. These are subject to increasing pressures from water supply requirements and dam construction, as seen throughout the Mediterranean. We applied environmental DNA metabarcoding of water samples to determine A. anguilla distribution in key freshwater catchments. In addition, we present this alongside 10 years of electrofishing/netting data. Refuge traps were also deployed to establish the timing of glass eel recruitment. These outputs are used together, alongside knowledge of the overall fish community and barriers to connectivity, to provide eel conservation and policy insights. This study confirm the presence of A. anguilla in Cyprus' inland freshwaters, with recruitment occurring in March. Eel distribution is restricted to lower elevation areas, and is negatively associated with distance from coast and barriers to connectivity. Many barriers to connectivity are identified, though eels were detected in two reservoirs upstream of dams. The overall fish community varies between freshwater habitat types. Eels are much more widespread in Cyprus than previously thought, yet mostly restricted to lowland intermittent systems. These findings make a case to reconsider the requirement for eel management plans. Environmental DNA-based data collected in 2020 indicate that "present-day" eel distribution is representative of 10-year survey trends. Suggesting that inland freshwaters may act as an unrealized refuge at A. anguilla's easternmost range. Conservation efforts in Mediterranean freshwaters should focus on improving connectivity, therefore enabling eels to access inland perennial refugia. Thus, mitigating the impact of climate change and the growing number of fragmented artificially intermittent river systems., Competing Interests: The authors declare no conflicts of interest., (© 2023 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.)

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., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The Balkans are one of the European biodiversity hotspots, hosting outstandingly rich, yet threatened, flora and fauna. This region hosts one of the richest endemic freshwater ichthyofauna in Europe, including several genera occurring exclusively here. One of these is the genus of the primary freshwater minnows Pelasgus, which was designated only in 2007. The genus is one of the most ancient genera of the family Leuciscidae and comprises seven small-bodied species, inhabiting slower, well-vegetated courses of rivers. This work is the first molecular multilocus phylogeny of the genus, based on one mitochondrial and three nuclear markers. In total, 305 individuals across almost entire distribution range of the genus were analysed. We inferred the evolutionary history of the species by comparing the results of our calibrated multilocus coalescent species-tree to palaeogeological events. The diversification of the genus started in the early Miocene and continued through to the beginning of Pleistocene. We identified the regions of the oldest colonization by Pelasgus, the drainages of the ancient lakes Ohrid and Prespa, and the southernmost part of the Peloponnese, hosting Pelasgus minutus, P. prespensis and P. laconicus, respectively. We showed that P. prespensis is not endemic to Lake Prespa, as previously thought; it occurs also in the Albanian River Devoll. This corroborates the emerging opinion that the endemic taxa of ancient lakes evolved within larger-scale historic drainages and not only within the lakes. Our results showed that the species with the most recent common ancestor of the early Pliocene origin, P. thesproticus, P. epiroticus, P. stymphalicus and P. marathonicus, have neighbouring distribution ranges. Pelasgus epiroticus is especially interesting, not only for its pronounced genetic diversity with a geographic pattern, but also for being found at three localities within the native distribution range of P. stymphalicus as a result of a translocation. At two of these localities, we identified hybrids between the two species, and at one of them, the genetically pure native species was not found at all. This points to a threat of the loss of the native ichthyofauna due to unintentional translocations., (Copyright © 2021 Elsevier Inc. All rights reserved.)

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., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Increasing anthropogenic pressures often jeopardize ecosystem integrity and policy-relevant conservation management in protected areas. To harmonize nature conservation with human well-being, EU Biodiversity Strategy to 2020 suggests Mapping and Assessment of Ecosystems and their Services (MAES) as the key concept for environmental planning and management in EU Member States. Applying this procedure is challenging due to its data-demanding and multidisciplinary nature, resulting in the ecoystem services (ES) approach being scarcely used in protected areas management. Increased data availability under EU biodiversity-related inventories and monitoring projects, as well as theoretical and empirical research advances developed during the last decade, should be put into practice to guide Member States towards local management frameworks and scenario building under the ongoing changes in the EU socio-economic environment. This study aims at filling this gap by embodying into the MAES operational framework a scenario-based approach and demonstrates this in a challenging case study of a Natura 2000 site, Lake Stymfalia, in Greece. The present management strategy, an ecological-friendly management practice, a water-efficient management practice and a non-environmentally friendly option (e.g. ecosystem destruction) are examined for current and future water demand under current and future climatic scenarios. The proposed methodological framework for ES operationalization is based on the available data (derived by EU Directives and/or modelling), expert judgment and stakeholder involvement. Therefore, this work applies and tests the importance of the MAES approach as a management and coordination platform., (Copyright © 2019 Elsevier B.V. All rights reserved.)

We report a hitherto unknown radiation within the clingfishes (Gobiesocidae), discovered in one of the best-studied marine biomes, the Mediterranean Sea. The monotypic genus Gouania is a Mediterranean endemic inhabiting the interstices of gravel beaches. Using geometric morphometric analyses, we identified two distinct morphotypes (characterized by a slender and a stout body shape, respectively) among Gouania willdenowi sampled from the three major Mediterranean basins (Eastern, Western and Adriatic). Slender and stout G. willdenowi occurred sympatrically in the Adriatic and the Eastern Mediterranean basins. Only the stout morphotype was found in the Western Mediterranean. Morphotypes were further distinguished by relative eye size and number of vertebrae. Based on mitochondrial and nuclear gene sequences, five highly divergent clades (COI-based K2P distances of 8 to 15%) were identified. The clades represented, respectively, stout Adriatic, slender Adriatic, stout Eastern, slender Eastern and stout Western Mediterranean Gouania. This suggests that the genus Gouania comprises at least five different species. Phylogenetic relationships among clades furthermore imply repeated evolution of convergent morphotypes. The onset of the Gouania radiation was dated to 3.23 (95% HPD 2.08-5.90) mya, and may therefore have overlapped with or followed the Messinian salinity crisis., (Copyright © 2019 Elsevier Inc. All rights reserved.)