Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Mollusca Bivalvia Unionoida Unionidae

Scientific Name: Pseudanodonta complanata
Species Authority: Rossmõssler, 1835
Regional Assessments:
Common Name(s):
English Depressed River Mussel

Assessment Information [top]

Red List Category & Criteria: Vulnerable A2ace+4ace ver 3.1
Year Published: 2011
Date Assessed: 2011-07-22
Assessor(s): Van Damme, D.
Reviewer(s): Böhm, M. & Collen, B.
Contributor(s): Dyer, E., Soulsby, A.-M., Whitton, F., McGuinness, S., Kasthala, G., Milligan, H.T., De Silva, R., Thorley, J., Herdson, R., McMillan, K. & Collins, A.
Pseudanodonta complanata has been assessed as Vulnerable. Recent data clearly indicate the population decrease and the fragmentation of the range of this species in the major part of its distribution except in the region of the Baltic Basin, where the species seems to be still relatively widespread, yet nowhere in high densities. Except for the northwestern part of Russia (Baltic basin), it appears to be quite rare in this country with a strongly disjunct distribution. The species does not occur east of the Caucasus as was formerly surmised and hence is an European endemic. From the data cited above it can be concluded  that in western, central and southeastern Europe the population decline is significantly more than >30 % over a period of three generations (ca. 45 years). Whilst the northern and northeastern populations do seem to be still relatively unaffected, the projected effects of climate change are also likely to be highly detrimental to these populations, because of increasing seasonal stratification and hypoxyia in the deeper layers and turn-overs with algal blooms (Solheim et al. 2010). Threats in Europe, existing ones (in particular eutrophication and river management) as well as projected ones (hypoxic conditions and stratification in lakes due to climate change) can be expected to increase in the near future.
Previously published Red List assessments:
1996 Lower Risk/near threatened (LR/nt)
1994 Insufficiently Known (K)

Geographic Range [top]

Range Description: This species is widely distributed throughout Europe, with the U.K. and Finland hosting the largest populations (Mcivor and Aldridge 2005). It is also recorded in the European part of the Russian Federation (D. Van Damme pers. comm. 2011). Despite being a widespread species, populations are unstable and occur patchily where found.

The following gives more specific distribution information for this species in parts of its range (this is not an exhaustive list):

Slovakia: The species has been recorded from the River Danube at two localities (Elexová and Némethová 2003).

Norway: This species is restricted to the southeast of the country (Dolmen and Kleiven 2000).

France: It is thought to be widespread, as far south as the Garonne (Graf and Cummings 2009); the species has been recorded live from only one locality in the Upper Helpe River (Cucherat 2003), while in Picardie, it was recorded from the Oise (Prié et al. 2007) and from the Seine (bij de Vaate et al. 2007). Since 1970, the species has only been recorded in one of the five departments of the Loire (Maine et Loire; Boulord et al. 2007, Blond et al. 2009). It is now extinct or rare in parts of France, such as the Garonne, Saone-Rhône and the Doubs (Mouthon 2007, Bertrand 2008).

Russian Federation: Older records suggest that the species is found in the northern part of European Russia in the rivers and lakes of the Baltic Basin from Kaliningrad to the St. Petersburg region and more to the East in the Northern Dvina basin (Zhadin 1952). In the south, it occurs in the rivers of the Black Sea basin (Dnieper, Dniester, Southern Bug, Don and Kuban rivers) and also in the Caspian basin (Volga and Ural rivers; Zhadin 1952). More recent data (e.g., Kantor et al. 2010) suggests that the distribution is more restricted and strongly disjunct, with the species found in the northwest (rivers and lakes of the basin of the Baltic Sea) in  e.g., Lake Peipsi or Pihkva (Timm et al. 1996) and in Lake Ilmen (Andreeva 2010), and in the southwest (Don basin, Voronezh oblast) as well as in the delta of the Volga (Kantor et al. 2010). Its presence further east, i.e., in the Ural River (Russian Federation, Kazakhstan) has not been confirmed and the Northern Dvina is not mentioned any more by Kantor et al. (2010). The records from the Asian parts of Russia and the former Soviet Union (e.g., Kazakhstan) are all considered erroneous (Kantor et al. 2010).

Belarus: The species has been recorded from Lake Lepelskoe, Lake Naroch, Lake Dolzha and Lake Malye Shvaksht in the northwest of the country (Balthic basin) (Burlakovai et al. 2000).
Countries occurrence:
Andorra; Austria; Belarus; Belgium; Bosnia and Herzegovina; Bulgaria; Croatia; Czech Republic; Denmark; Estonia; Finland; France (France (mainland)); Georgia; Germany; Greece; Hungary; Italy; Kazakhstan; Latvia; Macedonia, the former Yugoslav Republic of; Netherlands; Norway; Poland; Portugal; Russian Federation (West Siberia); Serbia (Serbia); Slovakia; Slovenia; Spain; Sweden; Switzerland; Turkey; Ukraine (Ukraine (main part)); United Kingdom (Great Britain)
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: This species never occurs in high densities and is often considered rare. Despite being a widespread species, populations are unstable and occur patchily where found. Localised declines have been recorded in response to habitat loss, degradation and due to the effects of pollution.

Yanovich and Pampura (2010) recorded a maximal density of 4 ind/m² for the Dnieper River in the Ukraine. Here, the species was only found in eleven out of 100 sampling stations compared with 23 stations in previous surveys (Yanovich and Pampura 2010, Yanovich et al. 2010). This suggests that the species here is rare and decreasing (>50%). A 30% loss of suitable habitat has occurred in the U.K. and populations in many parts of Germany have been extirpated. Populations in Poland are small, isolated and in decline (Mcivor and Aldridge 2005). In the Netherlands, the population decrease since 1990 exceeds 50% and it has disappeared from the north and southeast of the country (D. Van Damme pers. comm. 2011). In the Rhine-Meuse Delta Region however, where the species was extirpated in the 1960-70s due to pollution, the populations have recovered (bij de Vaate et al. 2007). Based on the information given in the 'Distribution' section, it is clear the species is severely decreasing in France. While populations are significantly declining across central, western and southeastern Europe, populations in the Baltic basin seem to be healthy (D. Van Damme pers. comm. 2011). According to McIvor and Aldridge (2005), the U.K. and Finland host the largest populations. There are no available population data for the species in Russia.
Current Population Trend: Unknown
Additional data:
Population severely fragmented: No

Habitat and Ecology [top]

Habitat and Ecology: This species is found in lotic freshwater ecosystems including lakes and rivers, and prefers a silt-sandy substrate (D. Van Damme pers. comm. 2011). It is usually found in deep parts of rivers below 1 m depth and up to a depth of 11 m (D. Van Damme pers. comm. 2011). Although not found in lakes in the U.K., Swedish lakes with riverine through-flows do support the species, which shows a preference for deeper waters, and buries deeper than other unionids due to a stronger anchoring foot (McIvor and Aldridge 2005). This is also the case for populations in Finland, the Baltic states and Russia (D. Van Damme pers. comm. 2011).
Systems: Freshwater
Generation Length (years): 15

Threats [top]

Major Threat(s): The full extent of threats to this species are unclear, with a particular lack of information regarding Russian populations. Threats are likely to include water pollution (organic and inorganic), siltation, channelization, habitat disturbance and loss through water abstraction, drought and poaching for private collections and aquaria (McIvor and Aldridge 2005). One of the effects of global warming on standing waters is increasing seasonal stratification and hypoxyia in the deeper layers and turn-overs with algal blooms (Solheim et al. 2010). If the projected trend continues, then even the currently safe populations in the Baltics could become gravely affected. All of these threats are likely to have caused significant population declines across the entire distribution range of  this species (D. Van Damme pers. comm. 2011).

Conservation Actions [top]

Conservation Actions: This species is listed as threatened in a number of countries, as part of national Red Lists. It is listed as Critically Endangered in Germany and Poland (Zajac 2009, D. Van Damme pers. comm. 2011); Endangered in the Czech Republic, Belarus, Hungary and Slovakia (Bódis 2008, Anonymous 2010, D.Van Damme pers. comm. 2011); in the Ukraine, it was assessed as Vulnerable (Korniushin 2002); it is considered Near Threatened in France, Moldova, Sweden and Estonia (von Proschwitz 2008, Timm 2011, D. Van Damme pers. comm. 2011); it is 'rare' in Lithuania (Zettler et al. 2005) and Least Concern in Finland (Rassi et al. 2001). In the Netherlands, it is considered to be 'Threatened' (Anonymous 2004), while it is a priority for conservation under the U.K. biodiversity action plan (BAP 1995). Conservation recommendations include restricting management operations in areas with large populations and leaving sufficient recovery periods at particular seasons, temporarily translocating mussels where necessary  The species is protected by law in Germany and Poland (McIvor and Aldridge 2005).

Data for population trends are insufficient, particularly in Russia. A greater knowledge of population distribution, trends and threats is required to accurately assess the species. Furthermore, molecular investigation, as was recently carried out  in the U.K. (Skidmore et al. 2010) is necessary to establish the degree of genetic differentiation between the geographic groups of P. complanata in Europe. It is likely that two (or three) distinct species or geographical races exist, e.g., Pseudanodonta complanata (Rossmässler, 1835) and P. nordenskioldi (Bourguignat, 1880). This will have a bearing on the conservation assessment for these potentially distinct species.

Citation: Van Damme, D. 2011. Pseudanodonta complanata. The IUCN Red List of Threatened Species 2011: e.T18446A8279278. . Downloaded on 13 October 2015.
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