Alien invertebrates in Ukrainian inland waters in the context of basin approach to river management and monitoring

The Dnieper River basin is an important part of the European network of inland waterways and the European inland water “central invasion corridor”, linking basins of the Black and Baltic Seas. Five exotic invertebrates are established in the natural ecosystems of this area Physa acuta (Draparnaud, 1805), Ferrissia californica (Rowell, 1863), Eriocheir sinensis H. Milne Edwards, 1853, Rhithropanopeus harrisi (Gould, 1841), and Craspedacusta sowerbii Lankester, 1880 (Semenchenko et al., 2015, 2016; Protasov, 1978). The New Zealand mud snail Potamopyrgus antipodarum (J.E. Gray, 1843), which is widespread mostly along the Black Sea coast, was once reported from Sluch River (Afanasyev, 2005).

A lot of exotic species were recorded mostly in artificial waterbodies.

Only in warm-water techno-ecosystems were pointed Melanoides tuberculata (Mьller, 1774), Tarebria granifera (Lamarck, 1822), Planorbella sp., Branchiura sowerbyi Beddard, 1892 (Silaeva et al., 2010; Protasov et al., 2013; Marenkov et al., 2018).

Several localities of Urnatella gracilis Leidy, 1851 were known in natural habitats (Tseeb, 1964), but the recent distribution of this species is also related to warm-water techno-ecosystems (Protasov, 1995; Protasov et al., 2013)

Two alien crustaceans were found in artificial waterbodies isolated from riverine channels: the ornamental cryfish Procambarus virginalis Lyko, 2017 in an old flooded quarry (Novitsky & Son, 2016) and the clam shrimp Eocyzicus orientalis Daday, 1915 in fishing ponds (Dobrynina, 2004).

More than 40 Ponto-Caspian species expand their range in the Dnieper Basin (Semenchenko et al., 2015, 2016).

The Dniester RBD

Ukrainian freshwater part of the Dniester Basin includes two isolated districts: Lower Dniester with freshwater zone of the Dniester Estuary and Kuchurgan Estuary and Middle-upper Dniester stretch in Western Ukraine.

In the lower part, four exotic invertebrates are established: F. californica, Ph. acuta, Rh. harrissii, and P antipodarum (Son, 2007a, 2007c, 2008; Son et al., 2013). An established population of the tropical prawn Macrobrachium nipponense (De Haan, 1849) is present in Kuchurgan Estuary, which is a waterbody with warm-water influence from the Moldavian Hydro-power Station; this species also migrate to Dniester Delta in the warm season of the year (Son et al., 2013).

Among Ponto-Caspian species, only the invader Dreissena bugensis (Andrusov, 1897) is non-native for this region (Son, 2007b).

Only one exotic species Ph. acuta is present in the Western Ukrainian part of the Dniester Basin (Shevtsova et al., 1998). Significantly expand their ranges and penetrate to Western Ukraine such Ponto-Caspian species as Obesogammarus crassus (Sars G.O., 1894) (Shevtsova et al., 1998), D. bugensis, (Son, 2007b), Dreissena polymorpha Pallas, 1771, Theodoxus donasteri (Lindholm, 1908) (collections of ZMLNU and NMNH), and isopod Jaera istri Veuille, 1979 (new data).

The Danube RBD

The Danube basin is an important part of the European network of inland waterways and the European inland water “southern invasion corridor”, linking basins of the Black and North Seas (Panov et al., 2009).

The basin consists of two isolated parts: Lower Danube with associated lakes and small rivers and sub-basins of the Prut and Tisa.

In the “lower” sub-basin, established are Sinanodonta woodiana (Lea, 1834), Corbicula fluminea (Mьller, 1774) and Ph. acuta, Rh. harrissii, B. sowerbyi, P antipodarum, F. californica, Lophopodella carteri (Hyatt, 1866), Pectinatella magnifica (Leidy, 1851) (Polischuk, 1974; Son, 2007 a; Aleksandrov et al., 2011; Sanzhak et al., 2011; Son et al., 2013, new data).

The state of two species that were noted for the Danube Delta are unclear. The cryptic line of Corbicula clam, which is called “Danubian fluminalis” (Son, 2007a) or “morph II” (Bodis et al., 2011), was massive in many locations in the early 2000s, but was notrecorded later. U. gracilis was a common species in the 1960s, but has not been recorded during recent years.

The Chinese mitten crab E. sinensis was repeatedly recorded in the estuarine part of the Lower Danube and surrounding marine waters (Son et al., 2013). E. sinensis was not reported from the main channel of the Danube, but this waterway must be a corridor of its migrations to upper courses. Also, on a local internet-resource information was published about the record of this species in the Yalpuh-Kuhurluy lake system. This resource also indicates the appearance of American crayfish Orconectes limosus (Rafinesque, 1815) into the Lower Danube, which requires further confirmation.

Only one Ponto-Caspian species is alien for this region D. bugensis (Lyashenko et al., 2010).

Carpathian sub-basins are not directly connected with other Ukrainian waterways. In the Ukrainian part of the Prut River, no alien invertebrates were recorded. In the Tisa sub-basin S. woodiana is established (Pampura & Yanovich, 2011). The state of three species: F. californica, Ph. acuta (present in collections of ZMLNU and NMNH) and Ponto-Caspian Hypania invalida (Grube, 1860) (Afanasyev, 2015) is unclear.

In a lot of local news resources and online forums observations of freshwater medusa in Zakarpattia Region by amateur divers were discussed. Usually, such cases refer to C. sowerbii, but we have not found scientific publications confirming it.

The Southern Bug RBD

Only two exotic species, Ph. acuta and P antipodarum, are relatively widespread in the basin (new data). Two species (M. tuberculata and U. gracilis) were reported from cooling ponds (Protasov, 1995; Grigorovitch et al., 2002).

Several relic species are probably expanded to the basin, but data about their original distribution might be incomplete: Cryptorchestia cavimana (Heller, 1865), D. bugensis, J. istri (new data).

Two exotic species of Atlantic origin (Mytilopsis leucophaeata (Conrad, 1831) and Rh. harrissii) occur in the Lower Southern Bug and Ingul (Son et. al., 2013; Zhulidov et al., 2018), but, probably, they are limited by transitional zone.

The Don RBD

Only one exotic species (Ph. acuta) is widespread in this basin (Zatravkin, 1980). Another species, the ornamental snail Planorbella duryi (Wetherby, 1879) was found only once Timoshenko, E. G. N. N.Yaroshenko, 1991. Freshwater mollusks of Donetsk Oblast'. Donetsk: Donetsk State University, 9 pp. (In Russian). Manuscript deposited in UkrNIINTI. 11.07.1029-UK91..

A lot of Ponto-Caspian species penetrate this basin through systems of canals: Pontogammarus ro- bustoides (Sars, 1894), Obesogammarus obesus (Sars, 1894), Gmelina pusilla G.O. Sars, 1896, Chelicor- ophium curvispinum (G.O. Sars, 1895), Chelicorophium maeoticum (Sowinsky, 1898), Psammoryctides deserticola (Grimm, 1877), D. polymorpha, D. bugensis, (Dedyu, 1980; Zatravkin, 1980; Grigorovitch et al., 2002; Sidorovsky, 2014).

The Vistula RBD

Only one alien species of Ponto-Caspian origin (D. polymorpha) was reported (Tsaryk et al., 2014).

The Crimean RBD

Only two exotic species, Ph. acuta and F. californica, are established in Crimean rivers (Son, 2007c; Son et al., 2010; Prokopov, 2011). Several freshwater plankton species, such as medusa C. sowerbii and cyclopids Eucyclops roseus Ishida, 1997, Mesocyclopspehpeiensis (Hu, 1943), and Mesocyclops isabellae Dussart et Fernando, 1988, are known only by a few records from isolated lakes and artificial ponds (Prokopov, 2011; Anufriieva & Shadrin, 2016).

In the lower course of the Chornaya River having very specific salinity conditions we also found an exotic polychaete Merceriella enigmatica Fauvel, 1923 (unpublishied data). Probably, this river section can be considered as transitional waters.

The expansion of freshwater species native for the Black Sea region is difficult to assess. A lot of Ponto-Caspian and common European species were introduced to artificial waterbodies or expanded through the systems of canals. However, the fact of their intentional introductions does not guarantee that these species were historically absent in the Crimea before, because the Crimean aquatic fauna was not well studied before their introduction, except for molluscs.

Most of such “nearby” aliens did not spread beyond the system of canals and water bodies filled with the Dnieper's water, and such case must by analysed as part of the Dnieper River Basin District. The fate of many species noted as introduced is little known (especially in connection with the modern change in the operating regime of the North Crimean canal).

Among “nearby” aliens reported from the Crimean Peninsula only a small part are really present and established in natural habitats of Crimean rivers: D. polymorpha, D. bugensis, Theodoxus fluvia- tilis (Linnaeus, 1758), Esperiana esperi (Fйrussac, 1823), Dikerogammarus villosus (Sowinsky, 1894) (Prokopov, 2011).

The Black Sea RBD

Only two exotic species, P antipodarum and Ph. acuta, are widespread and established in this district (Son, 2007a, 2008). A separate situation is observed in the original estuarine Sasyk Lake, which turned into a freshwater reservoir connected to the Danube Delta. In the lake and Danube- Sasyk Canal, several species common for the Danube Delta are present, including C. fluminea (SIZK collections), S. woodiana, Rh. harrissii (Son, 2007a; Son et al., 2013), but absent in other small Black Sea river basins. In the Kogylnik River that flows into the Sasyk Lake B. sowerbyi was recorded too (unpublished data).

Unidentified freshwater prawns were sampled in waterbodies near Sarata, Odesa Region. According to the photographs on local internet sources (especially, bessarabiainform.com) they can be preidentified as M. nipponense.

The expansion of Ponto-Caspian species in this district is contradictory. Originally, all small rivers and estuaries of the Black Sea coast could be occupied by relic Ponto-Caspian fauna, but the degradation of such ecosystems in the last centuries led to a significant reduction in the range of relic species. Modern anthropogenic processes caused resettlement of Ponto-Caspian species in this region. Massive expansion of Ponto-Caspian species from the Lower Danube occurred as a result of changes in the hydrological regime of the Sasyk Lake (Khalaim et al., 2017). A similar process of a smaller scale is observed in the Baraboy River as a result of the transfer of water from the Dniester (Son, 2007a). In many other cases of finds of Ponto-Caspian species in small rivers, it is difficult to determine whether they have an anthropogenic source.

The Azov Sea RBD

Several species, including Ph. acuta (Degtyarenko & Anistratenko, 2011), T. granifera (Khaliman & Anistratenko, 2006), Rh. harrissii (Son et al., 2013), Eu. roseus and M. pehpeiensis (Anufriieva & Shadrin, 2016) are known by a few records. Only one Ponto-Caspian invader, D. bugensis, is established (Sidorovsky et al., 2013). In many other cases of finds of Ponto-Caspian species in small rivers, it is difficult to determine whether they have an anthropogenic source.

Problems of basic concepts and definitions