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All issues No 423 (2022) Knowl. Manag. Aquat. Ecosyst., 423 (2022) 21 Full HTML
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Knowl. Manag. Aquat. Ecosyst.
Number 423, 2022
Biological conservation, ecosystems restoration and ecological engineering
Article Number 21
Number of page(s) 10
DOI https://doi.org/10.1051/kmae/2022016
Published online 29 July 2022

© M. Danilović et al., Published by EDP Sciences 2022

Licence Creative CommonsThis is an Open Access article distributed under the terms of the Creative Commons Attribution License CC-BY-ND (https://creativecommons.org/licenses/by-nd/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. If you remix, transform, or build upon the material, you may not distribute the modified material.

1 Introduction

In most parts of the world, human activities have altered the landscape and disrupted fluvial processes to the extent that fluvial and riparian ecosystems are among the world’s most threatened (Tockner and Stanford, 2002; Helfield et al., 2012). These disturbed river dynamics have massive negative consequences for riverine communities (Palmer et al., 2010), especially aquatic keystone species and their ecosystem services (Malmqvist and Rundle, 2002; Richter et al., 2003).

In order to regain ecological integrity of riverine systems and mitigate the threats of biodiversity loss, national governments under the European Union have implemented diverse laws and directives. The most important are the Water Framework Directive (WFD) 2000/60/EC (EC, 2000), the Floods Directive 2007/60/EC (EC, 2007) and the Conservation-directive of Natural Habitats and of Wild Fauna and Flora, also known as Habitats Directive 92/43/EEC (EC, 1992; European Union, 2020). Considering conservation issues in the European Union, a network of nature protection areas called Natura 2000 was established. In spite of the “umbrella effect” of the EU Natura 2000 protected areas network, 60% of freshwater habitats are failing to have a good ecological status (EEA, 2018) while 46% are still threatened (critically endangered, endangered, or vulnerable), and therefore far from having a favourable conservation status (Grzybowski and Glińska-Lewczuk, 2019).

Here, we aimed to highlight the main threats to fluvial ecosystems in the SEE region through presenting an overall summary of the status of freshwater crayfish in the region. In order to do so, we have included existing studies originating from different countries in SEE. Finally, we suggest measures that can be additionally applied for successful conservation programs and emphasize obstacles that should be overcome.

2 Study area & Sources of information

In this study we put a focus on SEE countries bordering the Danube River basin and Adriatic drainages according to the Freshwater Ecoregions of the World (FEOW) map (FEOW, 2008). The main area of SEE includes the Mediterranean, Alpine, Continental and Pannonian biogeographical regions (Eionet, 2021).

Literature included relevant publications, not restricted to any journals, and was searched by using the ISI Web of Science. For the chapters we discuss in this paper, we searched literature by crossing the following keywords: [Revitalization OR Rehabilitation OR Restoration] AND/OR [Macroinvertebrates OR Macrozoobenthos OR Crayfish] AND/OR [SIA OR Stable AND Isotope] AND [Southeast Europe OR Southeastern Europe OR Balkan OR Slovenia OR Croatia OR Serbia OR Bosnia and Herzegovina OR Montenegro OR Albania OR Macedonia OR Bulgaria OR Romania]. Number of ISI-publications found by crossed keywords search are listed in Table S1. Cited literature of every relevant paper was also consulted.

For the assessment of river restoration projects within the LIFE program the advanced search was used in the online tool of the LIFE Public Database (EC, 2021). Search criteria sorted by each country, included all projects with themes classified as “habitat – freshwater” or “water – river basin management” to get the wider possible spectrum.

For comparison within EU member states, Natura 2000 sites designated to each crayfish species listed in Annex II of the Habitats Directive were taken from the Natura 2000 Public Database (EEA, 2021).

3 Status of SEE rivers with a focus on the Danube River basin

In contrast to situation in the rest of Europe, an assessment of a total of 34,468 km of rivers in 2012 showed that around 30% of rivers on the Balkan Peninsula still have a near-natural (referred as pristine) status, and therefore a very high conservation value (Schwarz, 2012). Additionally, SEE is considered a unique hotspot for freshwater fauna (Griffiths et al., 2004). Of all European threatened species, 52% of molluscs (151 species) and 28% of freshwater fishes (52 species) occur in the Balkan region (Huđek et al., 2020; Schwarz, 2012). The river network of SEE with its protected areas (National parks, World heritage, Biosphere reserves, Ramsar sites) as well as the watershed of the Danube River basin are shown in Figure 1. However, the amount of natural river stretches is drastically declining due to anthropogenic impacts. Beside designation of conservation sites, active river restoration is also implemented in order to mitigate anthropogenic impacts, restore previous natural states and create conditions for the return of natural processes, native species and watercourse functions (Palmer et al., 2010; Blagus and Tadić, 2018). As described in the WFD, member states should aim to achieve at least a good status for freshwater systems by defining and implementing necessary measures within integrated programs. Yet, not every country in SEE is a member of the European Union and the WFD is not applied there. All SEE countries are however members of the Energy Community, which obligates them under the legal framework to implement several EU directives. These include directives to prevent or remedy environmental damage on the environment (Energy Community, 2018).

One of the biggest recent conservation projects within SEE is the nomination for a Transboundary UNESCO Biosphere Reserve “Mura-Drava-Danube” (TBR MDD) which stretches over five countries (SEE sections shown in Fig. 1), where, according to the WWF Europe, most of the ecologically important riverine habitats can be found. However, anthropogenic impacts already led to a loss of up to 80 % of the former floodplain areas and altered about 1100 km of natural river banks and stretches (WWF Austria, 2013). River sections within Croatia and Hungary have been designated as a Biosphere Reserve by UNESCO since July 2012 (UNESCO, 2012) and the whole area in its present dimension was established in September 2021 (WWF Adria, 2021). In the mentioned area several sites were already assigned as Natura 2000 sites and a few restoration measures were executed (e.g. LIFE Programme, 2014, 2015). Within the framework of these restorations, some preliminary ecological baseline studies were carried out, e.g. on Avi-, Entomo-, Ichthyo- and Herpetofauna in the Old-Drava oxbows (BioRes Bt., 2015).

The planning and construction of Hydropower plants (HPPs) in SEE is currently booming, due to greenhouse gas reduction goals (Schwarz, 2012; EC, 2018; Huđek et al., 2020). Unfortunately, in most SEE countries EU Natura 2000 sites or regional parks are not an obstacle for the construction of HPPs that are known to have negative impacts on river ecosystems (Schwarz, 2012; Neubarth, 2018). Beside the existing ca. 1500 HPPs, 108 are in construction and 3431 more are planned over the whole SEE region (Schwarz, 2020). Taking the high number of planned HPPs into account, it is not surprising that 45% of them are planned or built in protected areas (Schwarz, 2020). Weiss et al. (2018) predicted that eleven of the 69 endemic fish species inhabiting the region will potentially suffer extinction, if most or all planned hydropower projects are carried out. Additionally, a review by Huđek et al. (2020) showed that the monitoring stations at HPP in the Balkans, insufficiently assess the impact on macroinvertebrates communities, if at all. These mentioned studies show that strategies for the development of renewable energy are still often in contrast with fluvial habitat preservation as previously addressed by Schwaiger et al. (2013).

thumbnail Fig. 1

Freshwaters in SEE with watershed of the Danube River basin marked with red line, produced in QGIS v. 3.16.10. Protected SEE areas (without Romania) with high category (National parks, World heritage, Biosphere reserves, Ramsar sites), highlighted in green, were taken from the Eco-masterplan for Balkan Rivers (Riverwatch and EuroNatur 2018) provided by Fluvius Vienna (https://riverwatch.eu/en/balkanrivers/map).

4 Freshwater crayfish - diversity and threats

European freshwater crayfish play a significant role for freshwater ecosystems. Considered as keystone species (Nystrom et al., 1999; Dorn and Wojdak, 2004; Kouba et al., 2014), crayfish provide top-down and bottom-up control through their omnivorous diet. From grazing macrophytes to active predation on macroinvertebrates and even small vertebrates, crayfish are known to control freshwater community composition (Usio, 2000; Füreder et al., 2006; Mathers et al., 2020). Through burrowing activities for food search and dwelling for shelter they also contribute to sedimentation processes in the benthic zone and are therefore considered as ecosystem engineers (Creed Jr., 1994; Statzner et al., 2000; Weinländer and Füreder, 2016). Aside from being active predators, they also form an important part of food webs as prey species (Reynolds et al., 2013). Since crayfish cover a specific ecological niche, their decline may thus substantially impair local biodiversity and ecosystem services.

European freshwaters are inhabited by indigenous crayfish species (ICS) belonging to the genera Pontastacus, Astacus and Austropotamobius (Souty-Grosset et al., 2006; Crandall and De Grave, 2017). Due to their historical usage as a food source and frequent translocation by humans, distribution patterns of some species have changed throughout history (Maguire et al., 2018). The ICS appearing in SEE freshwaters are as follows:

  • 1

    Astacus astacus (Linnaeus, 1758) (Noble crayfish) is mainly distributed in the tributaries of the Danube River and other water bodies belonging to the Black Sea basin (Pârvulescu and Zaharia, 2013). There are also few recorded populations in the Adriatic Sea drainage, e.g. Croatia and Albania, where they were probably introduced (Maguire and Gottstein, 2004, Mrugała et al., 2017) and the Prespa Lake and its adjacent tributaries, shared by North Macedonia, Albania and Greece (Krstić, 2012). Outside the Black Sea basin, the widest distribution can be found in the northern and central Greece (Perdikaris et al., 2017).

  • 2

    Pontastacus leptodactylus (Eschscholtz, 1823) (Narrow-clawed crayfish or Turkish crayfish) is a widely distributed taxon across Europe, including the Danube River basin in SEE (Trichkova et al., 2013). Mainly introduced in western Europe by anthropogenic translocation, its native range is restricted to the Ponto-Caspian and Asia Minor basins (Kouba et al., 2014). However, this species is not distributed in all of the southwestern Balkans (Trožić-Borovac, 2011) but is spreading into new areas previously inhabited by A. astacus (Maguire et al., 2011; 2018).

  • 3

    Austropotamobius torrentium (Schrank, 1803) (Stone crayfish) has a wide distribution in SEE (Kouba et al., 2014). However, results showed that this species is the most sensible to anthropogenic pressure on their habitats (e.g., canalization, influx of pesticides from surrounding cultivated fields) (Machino and Füreder, 2005; Füreder et al., 2006) and prefers intact natural water courses with high habitat heterogeneity (Weinländer and Füreder, 2010; Trichkova et al., 2013).

  • 4

    Austropotamobius pallipes (Lereboullet, 1858) (White-clawed crayfish), in SEE countries mainly lives in freshwaters of the Adriatic basin (Kouba et al., 2014) with a few recorded exceptions like the Una River (Trožić-Borovac, 2011), which belongs to the Black Sea drainage.

The first molecular phylogenetic study of the genus Austropotamobius by Trontelj et al., (2005) indicated that the centre of genetic diversity for A. torrentium lies in the southern Balkan peninsula, while the primary centre of radiation of A. pallipes was probably in Istra, both regions in SEE. High genetic diversity within this genus was also confirmed for A. pallipes by Jelić et al. (2016), and studies on A. torrentium by Klobučar et al. (2013) and Lovrenčić et al. (2020a) showed that the hotspot of this species diversity is located in the Dinaric karst of Croatia. High genetic diversity in the Black Sea basin for A. astacus was shown by Schrimpf et al. (2014), especially in the western Balkans. Lovrenčić et al. (2022) confirmed these findings by showing, that Croatian populations harbour an important part of species genetic diversity and represent significant genetic reservoir at the European level. For P. leptodactylus Maguire et al. (2014) found two distinct evolutionary lineages, one Asian and one European.

The distribution of crayfish has been assessed at the continental scale in the very detailed publication “Atlas of Crayfish in Europe” by Souty-Grosset et al. (2006). However, there are still gaps that need to be filled for the Balkan Peninsula and SEE in general.

Native crayfish species, face simultaneously multiple threats such as:

  • 1

    water pollution. Even if some crayfish species can withstand moderate water pollution (Simić et al., 2008), it is an important factor causing the disappearance of freshwater crayfish in the whole of Europe (Füreder et al., 2002; Schulz and Schulz, 2004). Various toxicants such as fertilizers, insecticides, polychlorinated biphenyls (PCBs) or heavy metals can negatively affect crayfish distributed in contaminated waterbodies (Füreder et al., 2006). Related to the latter, inundated areas of the Drava River have shown to accumulate excessive amounts of heavy metals (e.g. As, Cu, Cd and Hg) originating from developing industry, agriculture as well as urbanization (Tošić et al. 2019). These substances accumulate in crayfish through the food chain and may cause toxic or teratogenic effects (Kouba, et al., 2010).

  • 2

    habitat loss. Hydro-morphological degradation and fragmentation (Holdich et al., 2009) of the habitat by dams or other watercourse changes, decreases local populations gene flow, resulting in genetic diversity reduction. The following bottleneck may eventually end up in population extinction (Keller and Waller, 2002; Fitzpatrick et al., 2012). Furthermore, due to habitats reductions, intraspecific competition occurs more often. This may results in age and sex ratio changes as the number of sexually mature females decreases because of direct competition with males over food and space (Abrahamson, 1966).

    Reduction in water levels, due to excessive water abstraction for agriculture or to climatic droughts have also major negative effects (Füreder et al., 2006; Simić et al., 2008; Holdich et al., 2009). Maguire et al. (2011), for example, established that 68% of the disappearance of A. pallipes populations from the Adriatic Sea waterbodies can be linked to habitat loss through water abstraction and water body engineering.

  • 3

    competition with non-indigenous crayfish species (NICS) for habitat and food sources (Schulz and Schulz, 2004; Souty-Grosset et al., 2006; Simić et al., 2008; Weinländer and Füreder, 2009; Twardochleb et al., 2013). In SEE, as in Europe in general, the most abundant and widespread invasive species are Pacifastacus leniusculus (Dana, 1852) (Signal crayfish), Faxonius limosus (Rafinesque, 1817) (Spiny-cheek crayfish), both introduced before the 1980s in Europe (Spitzy, 1973; Holdich et al., 2009), and the parthenogenetic Procambarus virginalis Lyko, 2017 (Marbled crayfish). These NICS are widely distributed in water bodies of SEE and are continuously invading new freshwaters (Twardochleb et al., 2013; Maguire et al., 2018; Dragičević et al., 2020; Weiperth et al., 2020). With a more aggressive behaviour and higher female fecundity, NICS are often superior competitors and long-term coexistence results not only in displacing habitat (Füreder et al., 2006; Hudina et al., 2016) and creating trophic endpoints for native crayfish (Nystrom et al., 1999; Vander Zanden et al., 1999; Weinländer and Füreder, 2016; Pacioglu et al., 2020), but also in changes in their morphology, growth rate and physiology (Hudina et al., 2012; Pârvulescu et al., 2015). A common ground for the implementation of legislation between the EU and its neighbouring countries has been proposed but has not yet been applied (Piria et al., 2017). Only Montenegro aligned its legislative framework with the EU Alien Regulation 1143/2014 on non-native species (Piria et al., 2021).

    Pacifastacus leniusculus appears in the Mura River as well as in the Drava River, from where it spread naturally over Austria and Slovenia further down the Danube River basin. This invasive species was also illegally introduced into the Korana River, a tributary of the Sava River, in Croatia and into the Una River in Bosnia and Herzegovina (Simić et al., 2008; Maguire et al., 2011). Faxonius limosus spread as well into south through the Danube River from Hungary (Maguire and Klobučar, 2003; Maguire and Gottstein, 2004) and further downstream into Serbian (Pavlović et al., 2006; Zorić et al., 2020), Bulgarian (Todorov et al., 2020) and Romanian (Pârvulescu et al., 2009) freshwaters. This species has also been recorded in the Slovenian part of the Drava River (Govedič, 2017).

    Procambarus virginalis was found in the waterbodies of the Balaton region in Hungary (Ludányi et al., 2016) as well as in a lake near the Drava River in Croatia (Dobrović et al., 2021; Samardžić et al., 2014). Given the fact, that this invasive species is known to reproduce by parthenogenesis, this makes the marbled crayfish even a bigger concern, because only one female might be enough to establish a new population (Scholtz et al., 2003).

    Procambarus clarkii (Girard, 1852) (Red swamp crayfish), which is considered as a high-risk species for European freshwaters (Kouba et al., 2014), has not yet been found in countries of SEE. However, as this species is already established in 16 European territories, P. clarkii is still a species of future concern (Souty-Grosset et al., 2016).

  • 4

    the crayfish plague caused by the pathogen Aphanomyces astaci Schikora, 1906. All of the introduced NICS in Europe are potential vectors of this pathogenic oomycete that causes the crayfish plague (Souty-Grosset et al., 2006; Weinländer and Füreder, 2009), a disease which is known since the 19th century (Edgerton et al., 2004). While NICS are mostly immune or less susceptible, this disease is able to lead to a quick death of native crayfish (Oidtmann et al., 2002). With this advantage NICS can replace native species even faster. However, recent studies showed that native crayfish, which managed to survive over decades in habitats infested with the crayfish plague, can gain a partial resistance to this disease (Kušar et al., 2013; Maguire et al., 2016; Pacioglu et al., 2020).

  • 5

    climate change. As most other native organisms, indigenous crayfish currently suffer from this major pressure (Edsman, et al. 2010; Pecl, et al. 2017). Changes in precipitation patterns and the frequency of extreme weather conditions, which result in water temperature increase and changes in the water flow regimes, negatively impact ICS (Moss et al., 2009). Additionally, climate change may increase future spread of NICS and their pathogens (Hulme, 2017). Future climate change will probably have further negative impacts onto ICS population, through contracting number of suitable habitats for their survival as shown in a recent study by Lovrenčić et al. (2022).

Considering all these threats, indigenous crayfish are listed in the IUCN Red List of endangered species (IUCN, 2011) with a “Vulnerable” (VU) or higher status, except for A. torrentium, and are protected by national and European laws (Weinländer and Füreder, 2010). In some of the SEE countries in which evaluation according to IUCN Red List criteria were used, certain ICS have a higher threatened status than at the global scale; e.g. A. torrentium has a VU status in Croatia, whereas on international level its status dada is deficient (DD), or A. astacus is evaluated as “Endangered” (EN) in Serbia in contrast to VU at the global level (Simić et al., 2008; Maguire et al., 2018).

However, only a few studies put a focus on crayfish populations within the frame of broad-scale conservation projects, like Natura 2000 and compare the effectiveness of designated sites to the actual species distribution (Lovrenčić et al., 2020b). Additionally, only Slovenia, Croatia, Bulgaria and Romania contribute to the Natura 2000 network and asses the local crayfish status in protected areas as members of the European Union (Trichkova et al., 2013; Todorov et al., 2014).

We investigated Natura 2000 sites for each protected crayfish species listed in Annex II of the Habitats Directive ( Fig. 2). Except Romania no other SEE member state designated Natura 2000 sites for A. astacus (AstAst). In total 135 Natura 2000 sites have A. astacus listed in Annex II (Fig. 2A), with the most designated sites per country located in Germany (42) and Latvia (22). In contrast, 389 of all Natura 2000 sites were designated for A. torrentium (AusTor), among them 224 in SEE countries (Fig. 2B). Compared to the country size, Slovenia has almost five times more sites (120) than Croatia (25). Germany and Bulgaria designated 119 and 67 sites for A. torrentium, respectively. The highest number of all Natura 2000 sites concerned A. pallipes (AusPal), with 812 sites, Slovenia and Croatia contributing with only 11 and 26 sites for this species, respectively (Fig. 2C). In comparison countries outside SEE like Italy (312), France (251) and Spain (186) contributing most Natura 2000 sites. List of Natura 2000 sites designated for A. astacus, A. pallipes and A. torrentium can be found in Tables S2, S3 and S4, respectively.

Concerning conservation projects including river restoration or rehabilitation efforts, crayfish are rarely listed in the policies. Analysing the database of LIFE programmes for crayfish species as target species, we found 477 LIFE projects from 1992 - 2020 classified as “habitat – freshwater” or “river basin management” in EU and non-EU countries. Among these, 33 LIFE projects were performed in SEE countries (48 LIFE projects, if Greece is included) ( Fig. 3), none of them mentioning crayfish in their project description. In contrast, 48 LIFE projects in other European countries had crayfish species in their agenda or at least mentioned them in some way in their project description. Out of these projects around half of them were conducted in Italy (Fig. 3). In total 20 LIFE projects with crayfish in their agenda executed restoration measures, most of them in Italy (12) and Austria (3) ( Fig. 4). Detailed projects description can be found in Table S5 for LIFE projects including crayfish and Table S6 for all LIFE projects in SEE countries.

thumbnail Fig. 2

Designated numbers of Natura 2000 sites per member states which have (A) Astacus astacus (AstAst), (B) Austropotamobius torrentium (AusTor) and (C) Austropotamobius pallipes (AusPal) listed in Annex II of the Habitats Directive. EU-member states are shown in two-letter country codes according to the EU (Eurostat, 2021) (https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Country_codes). Member states from SEE were put together on the right side for easier comparison.
thumbnail Fig. 3

Number of LIFE projects in each EU and non-EU member state from 1992 – 2020 classified as “habitat – freshwater” or “river basin management”. Black fractions of the columns show the number of projects containing crayfish in the agenda (No. LIFE proj. w/ CF). INT = International transboundary programs including non-EU SEE countries.
thumbnail Fig. 4

Total number of LIFE projects in each EU member state from 1992 - 2020 classified as “habitat – freshwater” or “river basin management” containing crayfish in the agenda. Blue fractions of the columns show the number of projects with restoration measures.

5 Obstacles and need for action

As highlighted in this review, native crayfish face various threats that jeopardize their conservation (Weinländer et al., 2014; Pacioglu et al., 2020). It is therefore essential to provide protected recovery zones and refugia for freshwater crayfish as well as to include crayfish in restoration measures of SEE freshwaters.

However, previous studies have reported that success rates of stocking and reintroduction of once present freshwater invertebrates remain quite low, even after restoration activities (Palmer et al., 2010; Geist and Hawkins, 2016; Leps et al., 2016; dos Reis Oliveira et al., 2020). We assume that in the latter cases, habitat is still not suitable for reintroduced species after river restoration. However, it is difficult to support or refute this assumption as no studies describing restoration effects on crayfish populations are available to date for SEE.

Hence, habitat suitability modelling may be a helpful tool to indicate which restoration measures are helpful for ICS recovery zones in future projects (Ghia et al., 2013; Weinländer et al., 2014). In addition to keep the population status of native and invasive species in protected areas further updated, long term monitoring is essential (Trožić-Borovac, 2011; Kouba et al., 2014).

Furthermore, the roles played by freshwater crayfish in SEE freshwater ecosystems, is not sufficiently known. Various studies performed food web analyses through gut content or food choice analyses (Nyström et al., 1999; Correia, 2002; Weinländer and Füreder, 2016). Complementary to this classical method, trophic position and trophic niche width of crayfish in Europe was also assessed using stable isotope analyses (SIA). Most of SIAs focused on the differences between ICS and NICS (Olsson et al., 2009; Ercoli and Ruokonen, 2014; Veselý et al., 2021), whereas scarce researches compared the dietary change of those species during different stages of invasion (Pacioglu et al., 2020). The latter study showed a gradual contraction of the trophic niche of native crayfish and a decrease in trophic overlap with invasive species over time and was the only study we found to date, focusing on SEE countries. Assessing the food web structure and trophic position of various crayfish communities in their habitats by trophic niche modelling should be thus a priority in SEE countries.

Supplementary Material

Access here

Table S1: Number of ISI-publications found by crossed keywords search in the ISI Web of Science.

Table S2: Natura 2000 Sites with Astacus astacus listed in Annex II of the Habitats Directive.

Table S3: Natura 2000 Sites with Austropotamobius pallipes listed in Annex II Habitats Directive.

Table S4: Natura 2000 Sites with Austropotamobius torrentium listed in Annex II Habitats Directive.

Table S5: LIFE projects in European countries from 1992 - 2020 including crayfish in their agenda and classified as ?habitat ? freshwater? or ?river basin management?. Grey labelled projects carried out restoration measures.

Table S6: LIFE projects in SEE countries from 1994 - 2017 classified as ?habitat ? freshwater? or ?river basin management?. None of them have crayfish in their agenda. Grey labelled projects carried out restoration measures.

Acknowledgements

This work was supported by the doctoral grant from the office of the vice rector for research by the University of Innsbruck Austria. Thanks to Dr. Ulrich Schwarz for correspondence and providing the dataset of protected areas on the Balkan peninsula. We also thank an anonymous reviewer for helpful comments.

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Cite this article as: Danilović M, Maguire I, Füreder L. 2022. Overlooked keystone species in conservation plans of fluvial ecosystems in Southeast Europe: a review of native freshwater crayfish species. Knowl. Manag. Aquat. Ecosyst., 423, 21.

All Figures

thumbnail Fig. 1

Freshwaters in SEE with watershed of the Danube River basin marked with red line, produced in QGIS v. 3.16.10. Protected SEE areas (without Romania) with high category (National parks, World heritage, Biosphere reserves, Ramsar sites), highlighted in green, were taken from the Eco-masterplan for Balkan Rivers (Riverwatch and EuroNatur 2018) provided by Fluvius Vienna (https://riverwatch.eu/en/balkanrivers/map).
In the text
thumbnail Fig. 2

Designated numbers of Natura 2000 sites per member states which have (A) Astacus astacus (AstAst), (B) Austropotamobius torrentium (AusTor) and (C) Austropotamobius pallipes (AusPal) listed in Annex II of the Habitats Directive. EU-member states are shown in two-letter country codes according to the EU (Eurostat, 2021) (https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Country_codes). Member states from SEE were put together on the right side for easier comparison.
In the text
thumbnail Fig. 3

Number of LIFE projects in each EU and non-EU member state from 1992 – 2020 classified as “habitat – freshwater” or “river basin management”. Black fractions of the columns show the number of projects containing crayfish in the agenda (No. LIFE proj. w/ CF). INT = International transboundary programs including non-EU SEE countries.
In the text
thumbnail Fig. 4

Total number of LIFE projects in each EU member state from 1992 - 2020 classified as “habitat – freshwater” or “river basin management” containing crayfish in the agenda. Blue fractions of the columns show the number of projects with restoration measures.
In the text

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