Taxonomic Notes
Three subspecies are known (Crandall & De Grave 2017, WoRMS Editorial Board 2024): Austropotamobius torrentium torrentium von Paula Schrank 1803, A. t. danubicus Starobogatov 1996, and A. t. macedonicus Karaman 1929.
Justification
Austropotamobius torrentium has been assessed as Least Concern given its large range.
Based on patchy available literature, the species does not currently meet the criteria for a threatened status. However, ongoing significant declines suggest it may qualify for a threatened category in the near future pending further studies.
Geographic Range Information
This species is primarily found in south-eastern and central Europe, and centres around the Danube system, extending from the Jiu River basin in Romania upstream to Germany and Switzerland, and into parts of the Rhine and Elbe basins. Germany, Czechia, and Slovakia are at the north-western periphery of its natural range, while Croatia, Montenegro, Albania, Greece, and the European part of Türkiye lie at the south-eastern margin of its distribution. In the light of the latest molecular investigations (Pârvulescu et al. 2019, Lovrenčić et al. 2020), some of the populations probably belong to new species yet to be described, which are endemic populations in northern Dinarides, Croatia.
Population Information
Albania: There is no information on the population status of this species in this country. The only confirmed recent specimen was collected from the Fan river in the north of the country (Subchev 2011, Mrugala et al. 2017).
Austria: The Signal Crayfish is driving rapid declines in the population numbers of this species (Holdich et al. 2009). This species is most abundant in Austria and Germany. There are many recorded localities in Austria, mainly along the Danube (including significant tributaries like Inn, Enns, Mur, and Drau), with a few also in the Upper Rhine (Pöckl 1999, Ion et al. 2024).
Bosnia-Herzegovina: There have been mass mortalities of this species (Holdich et al. 2009). It is found in the tributaries of the Una, Vrbas, and Bosna rivers (all part of the Sava basin) (Trožić-Borovac 2011, Roljić et al. 2022, Ion et al. 2024). Although larger populations were first reported in the creeks of the Bosna basin (Trožić-Borovac 2011), populations in good condition were also found throughout the rest of the area (Roljić et al. 2022).
Bulgaria: Native in Balkan Sredna Gora and Rhodopes surrounding river network. There are 49 hydrobasins (level 8) where the species is present (Ion et al. 2024) covering the superior part of the rivers Struma, Mesta, Maritsa and Tundzha in the Aegean Sea catchment basin as well as Nishava, Iskar, Vit, Osam and Yantra (Danube tributaries). The most abundant populations of A. torrentium were found in some protected areas like Rodopi Zapadni, Reka Belitsa, Sredna Gora, Tsentralen Balkan-Bufer, and Tsentralen Balkan, making up 74.2% of all recorded individuals found in protected areas. The highest densities were recorded in the first three (Todorov 2014). Co-existance with Astacus astacus and A. leptodactylus were also found (Todorov et al. 2014).
Croatia: This species is thought to be reasonably well preserved in this country; however, anthropogenic pressure on its habitat is increasing and is likely to be driving some declines in its abundance. Some parts of the population have also been significantly impacted by drought which has caused 95% mortality in some streams (I. Maguire pers. comm. 2010). Austropotamobius torrentium is a native species and occurs in springs and streams at higher elevations. It primarily inhabits water bodies within the Black Sea drainage (in Kupa, Una and Sava basins), with a limited presence in the Adriatic Sea basin (Maguire et al. 2018). Even a co-existance of this species with Astacus astacus and Austropotamobius pallipes is recorded (Maguire 2009). There are 60 populations in Croatia, with 80% of them being inside Natura 2000 sites, thus most of the phylogroup diversity being covered by legal protection (Lovrencic et al. 2020).
Czechia: It is unclear whether this species is native or introduced to this country. It has been found at varying densities in streams, but a study by Kozak et al. (2002) reveals it at a density of 12 individuals/km2 in Klabava Brook. Most populations are within Berounka drainage basin, with fewer in lower Vltava and Elbe (Kozak et al. 2002). Outbreaks of crayfish plague pathogen Aphanomyces astaci caused several mass mortalities in the stone crayfish population since the 19th century (Mojžišová et al. 2020, Ungureanu et al. 2020). One population in eastern Bohemia (Luční brook; Giant Mountains) is spatially isolated and is considered that it was introduced by men, probably from Slovenia (Petrusek et al. 2017).
France: This species is considered to be close to extinction within this country (Collas, Julien and Monnier 2007). The populations are distributed in Alsace and Lorraine within the Rhine basin (Machino and Füreder 2005, Ion et al. 2024). The newest known location is in the eastern part of France, in Haute-Savoie, on a tributary of the Rhône basin, where it is suspected to have been introduced (Collas et al. 2015).
Germany: This species is undergoing a decline; however there is no trend information available (H. Schulz pers. comm. 2009). The populations are located in the southern part of the country, in the rivers and brooks from Rhine and Danube basins (Chucholl et al. 2017, Waldmann 2019, Ion et al. 2024). A new population in good condition was recently discovered in Saxony on a small brook within Elbe basin (Martin et al. 2008).
Greece: This species only occurs in the northern part of the country, in Eastern Macedonia and Thrace, Central and Western Macedonia, and close to the northern border of Thessaly. These populations are located in the Aliakmon, Axios, Struma, and Nestos river basins. Most populations are now found in isolated areas, with many historical populations declining or lost due to the crayfish plague (Perdikaris et al. 2017).
Hungary: This species is threatened by organic pollution and the spread of non-native crayfish species. This has resulted in a population decline. (P. Miklós pers. comm. 2009). Populations are limited to small streams in the Northern (Ipoly river basin) and Western (Gyöngyös, a tributary of the Rába) parts of the country(Ludanyi et al. 2016, Ion et al. 2024).
Italy: The species is restricted in its distribution (Ion et al. 2024). Currently residing in the Province of Udine, 2 of the 3 populations recorded in 1995 went extinct in 2005 (Machino and Füreder 2005), and this trend seemingly continues. There has been a strong decline in the species in Northern Italy (Füreder 2009). More recently, eDNA data analysis were positive for the species only in the Slizza basin (six sites out of which four new, while two sites already knew for the species were negative), while the nearest basin Tagliamento was positive only for A. pallipes. The population trend is considered negative, with possible local extinctions (Manfrin et al. 2022).
North Macedonia: Museum collections indicate that this species is widely distributed across the country, particularly in high-altitude wooded areas within the Axios River basin (crossing Macedonia and Greece) and the Strumica River basin (a tributary of the Struma River in Bulgaria). Few populations are also found in creeks and rivers of the Crn Drim basin, which flows towards the Aegean Sea (Slavevska-Stamenković et al. 2016). However, there is no current information about the distribution and status of these populations.
Montenegro: Austropotamobius torrentium is already thought to have gone extinct in a tributary of Lake Ohrid (Koselska Brook) below Rečica due to pollution (Y. Machino pers. comm. 2009). This species exists in the north and north-eastern parts of the country, in river basins draining into the Danube. A relatively isolated population is found in Crnojevica, a river flowing into Skadar lake situated in the south of the country on the border with Albania (Simić et al. 2008, 2015).
Romania: The species is present in the mountainous and submountainous areas of South-western Romania, in the Jiu, Cerna, Nera, Caraș, Timiș, and Strei basins, as well as in the small tributaries of the Danube in Portile de Fier and the Mehedinti Plateau area. Populations are stable, and there is a low risk of impact from invasive species currently active in the region (Satmari et al. 2023).
Serbia: The species can be found in watercourses across the Danube, Drina, Kolubara, West Morava, South Morava, Timok, facing habitat degradation, pollution, and invasive species threats. It is present at higher altitudes in the Western, Southern, and Eastern parts of the country, but also an isolated population was confirmed in the Northern part of the country in Rakovački River from Fruška Gora Mountains (Simić et al. 2008, 2015; Markovic et al. 2017, Zorick et al. 2018, Ion et al. 2024).
Slovakia: The species is rare in this country, but population numbers are currently considered stable (P. Manko pers. comm. 2009). Here, the species is only present in the Western part of the country (Ion et al. 2024), with relatively isolated populations on the left bank of the Danube River, in streams and brooks from the Western Carpathian Mountains. Major threats are population fragmentation and habitat deterioration (Stloukal et al. 2004, Stloukal and Harváneková 2005).
Slovenia: The species is distributed in the tributaries of the Sava and Drava rivers and, very locally, in the tributaries of the Mura River. Its presence in the Adriatic catchment is confirmed only for a few tributaries of the Idrijca river (Bedjanič 2004, Govedič 2006, Govedič et al. 2006). Among the monitored population in protected sites, around 30% of the individuals have disappeared between 2020-2023, some being absent for extended periods, while only in a few sites was the species rediscovered, the negative trend being more accentuated in the Eastern part of the country (Govedič et al. 2023).
Switzerland: This species is found only in the northeast of Switzerland in the Rhine (and Aar sub-basin), where it is known to be severely declining (Hefti and Stucki 2006, Krieg et al. 2021). The Swiss National Legislation on Fisheries considers it's highly endangered' (D. Hefti pers. comm. 2009).
Türkiye: This species is only known from the European part of Türkiye in Madara Brook and Velika River, the latter with a stronger population (Harlioglu and Güner 2007). There is no information on the population status of this species in this country.
Habitat and Ecology Information
This species is most commonly found in streams with plenty of riparian and instream cover, however it has occasionally been found in lowland rivers (Souty-Grosset et al. 2006). Key ecological elements relevant to population stability are the pristine water quality (Pârvulescu and Zaharia 2013) and riverbank integrity (Pârvulescu et al. 2016, Neculae et al. 2024).
Female size at maturity has been observed at 4.61 cm (total length) (I. Maguire pers. comm. 2010). Recorded sizes for A. torrentium ranged from 6 to 9 cm (females) and from 8 to 10.5 cm (males) (Laurent 1988).
The ovigerous females carried external eggs from early November until mid-June the following year (Maguire et al. 2002). In Germany, stone crayfish females may incubate 40 to 70 eggs (Laurent 1988). The maximal number of eggs per female (in Croatia) we found was 104 (an average value was 53.56) (Maguire et al. 2002).
In populations studied in Austria, a maximum of 86 eggs per female was found, while in Croatian populations the number of eggs per female was maximally 117 (Maguire et al. 2010).
Declines in this keystone species are said to negatively impact both ecosystem structure and function within freshwater environments through loss of: a) provisioning services – food production from fisheries, recreational fishing, b) regulatory and support services – trophic cascades, water purification, nutrient cycling, primary productivity, c) cultural value – recreational fishing, education, heritage. Crayfish are also an important food source to a range of species including otters, salmonids, and birds such as kingfishers (Kettunen and ten Brink 2006).
Threats Information
This species is most threatened by the presence of non-native species such as the Signal Crayfish (Pacifastacus leniusculus) and the Spiny-cheek Crayfish (Faxonius limosus), crayfish plague (Aphanomyces astaci), and habitat loss and degradation (Füreder et al. 2006). This species is not tolerant to environmental change, so threats such as domestic and industrial pollution, agriculture, sedimentation, eutrophication, damming, water abstraction, and channelisation have all negatively impacted this species (Füreder et al. 2006). Even though protected areas offer good local conditions, one of the most serious problems remains the fragmentation of populations (Pârvulescu et al. 2020). This species is reported to be undergoing population declines in most of the countries in which it is known to exist, however no quantitative data on the rate of decline is available.
Use and Trade Information
This species is not used or traded.
Conservation Actions Information
The species is listed under Annex II of the EU Habitats Directive as requiring special conservation measures (Souty-Grosset et al. 2006). It is also listed on the German Red List (RL3, Appendix 1) and as threatened in several other countries (Souty-Grosset et al. 2006). The species is also listed under Appendix III of the Bern Convention. It occurs in some protected areas within its range.
Long-term monitoring is necessary to measure population decline rates.
