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Alien fish species in the Ob River basin

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Abstract

To date, 22 alien fish species are known in the Ob River basin. Of them, nine species—Pike-perch Sander lucioperca, Freshwater bream Abramis brama, common carp Cyprinus carpio, belica Leucaspius delineatus, bleak Alburnus alburnus, Stone moroko Pseudorasbora parva, Amur sleeper Perccottus glenii, Nikolsky’s loach Misgurnus nikolskyi, and southern ninespine stickleback Pungitius platygaster—formed self-reproducing populations and started self-spreading in natural waterbodies. This paper summarizes the data on invasion of alien fish species in the Ob River basin. The data on history, rate of spread, modern distribution, and relative abundance are given. It is shown that water temperature is the main environmental factor which limits the expansion of introduced species in the Ob basin.

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References

  • Amstislavskii, A.Z., Role of the pike perch in ichthyogenesis of left-bank and Ural tributaries of the Ob River, in Vodoemy Sibiri i perspektivy ikh rybokhozyaistvennogo ispol’zovaniya (Siberian Reservoirs and Their Prospective Use for Fishery), Tomsk: Tosmk. Gos. Univ., 1973, pp. 46–75.

    Google Scholar 

  • Anchutin, V.M., About find of the pike perch in the Tazovskaya Inlet basin, Vopr. Ikhtiol., 1976, vol. 16, no. 3, pp. 556–557.

    Google Scholar 

  • Atlas presnovodnykh ryb Rossii (Atlas of Freshwater Fishes of Russia), Reshetnikov, Yu.S., Ed., Moscow: Nauka, 2002.

    Google Scholar 

  • Babkina, I.B., Petlina, A.P., and Shestakova, A.S., Morphological and ecological features of the bleak (Alburnus alburnus (L.)) in the Lower Tom’ River, Vestn. Tomsk. Gos. Pedagog. Univ., 2013, vol. 8 (136), pp. 61–69.

    Google Scholar 

  • Babueva, R.V., Modern ichthyofauna of the Upper Ob River, Pervyi kongr. ikhtiologov Rossii (First Congr. of Russian Ichthyologists), Moscow, 1997, p. 140.

    Google Scholar 

  • Berg, L.S., Ryby presnykh vod SSSR i sopredel’nykh stran (Freshwater Fishes of Soviet Union and Adjacent Countries), in 2 vols., Leningrad: Akad. Nauk SSSR, 1933, pp. 545–903.

    Google Scholar 

  • Bezmaternykh, D.M., Zoobentos kak indicator ekologicheskogo sostoyaniya vodnykh ekosistem Zapadnoi sibiri: Analiticheskii obzor (Zoobenthos as an Indicator of Ecological Status of Aquatic Ecosystems of Western Siberia: Analytical Review), Novosibirsk: Inst. Vodn. Ekol. Probl., 2007.

    Google Scholar 

  • Biologicheskie resursy vodoemov basseina reki Chulyma (Biological Resources of the Reservoirs of the Chulym River Basin), Tomsk: Tosmk. Gos. Univ., 1980.

  • Bogdanov, V.D., Fish resources of eastern slope of Polar and Cispolar Ural, Ekon. Reg., 2007, no. 2, pp. 90–98.

    Google Scholar 

  • Bykov, G.M. and Mukhachev, I.S., Fishery in the Andreevskoe Lake during change of ecological regime, in Ekologicheskie problemy rekul’tivatsii ozer zamornogo tipa (Ecological Problems of Recultivation of the Lakes with Low Water Oxygen), Tyumen: Tyumensk. Gos. Univ., 1994, pp. 176–188.

    Google Scholar 

  • Doklad ob ekologicheskoi situatsii v Tomskoi oblasti v 2010 (A Report on Ecological Situation in Tomsk Oblast in 2010), Tomsk: Admin. Tomsk. Obl., 2011, no. 2/2 (67), pp. 249–304.

    Google Scholar 

  • Ekologiya ryb Ob’-Irtyshskogo basseina (Ecology of Fishes of Ob-Irtysh Basin), Moscow: KMK, 2006.

  • Feoktistov, M.I., Naturalization of the pike perch in Novosibirsk Reservoir, Extended Abstract of Cand. Sci. (Biol.) Dissertation, Novosibirsk, 1970.

    Google Scholar 

  • Golubtsov, A.S. and Malkov, N.P., Ocherk ikhtiofauny Respubliki Altai: sistematicheskoe raznoobrazie, rasprostranenie i okhrana (Description of Ichthyofauna of Altai Republic: Systematic Diversity, Distribution, and Protection), Moscow: KMK, 2007.

    Google Scholar 

  • Gundrizer, A.N., Zaloznyi, N.A., Golubykh, O.S., et al., Available data on hydrobionts in the channel of Central Ob River, Sib. Ekol. Zh., 2000, no. 3, pp. 315–322.

    Google Scholar 

  • Interesova, E.A., Belica Leucaspius delineatus (Cyprinidae) in waterbodies of southwest Siberia, J. Ichthyol., 2012, vol. 52, no. 5, pp. 356–361.

    Article  Google Scholar 

  • Interesova, E.A. and Chakimov, R.M., Bleak Alburnus alburnus (Cyprinidae) in the Inya River (southwestern Siberia), J. Ichthyol., 2015, vol. 55, no. 2, pp. 282–284.

    Article  Google Scholar 

  • Interesova, E.A., Yadrenkina, E.N., and Vasil’eva, E.D., The first record of Misgurnus nikolskyi (Cobitidae) in the South of Western Siberia, J. Ichthyol., 2010, vol. 50, no. 3, pp. 281–284.

    Article  Google Scholar 

  • Ioganzen, B.G., Essays on geography and genesis of Siberian ichthyofauna. Message II.Ecological-geographic description of fishes of the Ob River basin, Uch. Zap. Tomsk. Gos. Univ., 1947, no. 3, pp. 43–60.

    Google Scholar 

  • Ioganzen, B.G. and Petkevich, A.N., Naturalization of fishes in the Western Siberia, Tr. Barabinsk. Otd., Vses. Nauchno-Issled. Inst. Ozern. Rechn. Rybn. Khoz., 1951, vol. 5, pp. 3–204.

    Google Scholar 

  • Ioganzen, B.G. and Petkevich, A.N., Novye ryby Zapadnoi Sibiri (New Fishes in Western Siberia), Novosibirsk: Vses. O-vo Okhrany Prirod., 1961.

    Google Scholar 

  • Ioganzen, B.G., Petkevich, A.N., Votinov, N.P., Nesterenko, N.V., Podlesnyi, A.V., and Tironov, M.D., Akklimatizatsiya i razvedenie tsennykh ryb v estestvennykh vodoemakh i vodokhranilishchakh Sibiri i Urala (Naturalization and Reproduction of Valuable Fishes in Natural Reservoirs of Siberia and Ural), Sverdlovsk: Sredne-Ural. Knizh. Izd., 1972.

    Google Scholar 

  • Karasev, G.L., Zoogeographical zoning of the West-Siberian region by fish fauna, in Ekologiya ryb Ob’-Irtyshskogo basseina (Ecology of Fishes of Ob-Irtysh Basin), Moscow: KMK, 2006, pp. 37–70.

    Google Scholar 

  • Karasev, G.L., Ecology and morphological features of the Lower Tobol River basin, Extended Abstract of Cand. Sci. (Biol.) Dissertation, Surgut, 2003.

    Google Scholar 

  • Kizhevatov, Ya.A., Dynamics of fish resources in the Sob’ River, Extended Abstract of Cand. Sci. (Biol.) Dissertation, Yekaterinburg, 2010.

    Google Scholar 

  • Kolomin, Yu.M., The find of two species of Cyprinidae fishes: bleak Alburnus alburnus and verkhovka Leucaspius delineatus in reservoirs of North Kazakhstan region, in Rybokhozyaistvennye issledovaniya v Respublike Kazakhstan (Fishery Studies in Kazakhstan Reoublic), Almaty: Bastau, 2006, pp. 203–206.

    Google Scholar 

  • Kolomin, Yu.M., Ichthyofauna of reservoirs of North Kazakhstan region, Mater. Vseross. konf. “Vodnye ekosistemy Sibiri i perspektivy ikh ispol’zovaniya” (Proc. All-Russ. Conf. “Aquatic Ecosystems of Siberia and Their Prospective Use”), Tomsk, 2011, pp. 78–82.

    Google Scholar 

  • Kolosov, M.Yu. and Skalon, N.V., Ichthyofauna of Belovskii and Yashkinskii regions of Kemerovo oblast, Tr. Kuzbas. Kompleksn. Eksped., 2004, vol. 1, pp. 290–297.

    Google Scholar 

  • Korlyakov, K.A. and Korlyakova, E.M., Naturalization of the channel catfish Ictalurus punctatus in Ob-Irtysh basin (cooling reservoir of Troitskaya Hydropower Plant), Vestn. Chelyab. Gos. Univ., 2013, vol. 7 (298), no. 2, pp. 173–174.

    Google Scholar 

  • Korlyakov, K.A. and Mukhachev, I.S., On the European smelt Osmerus eperlanus introduced to Bolshoi Kisegach Lake in the South Urals, J. Ichthyol., 2009, vol. 49, no. 5, p. 668.

    Article  Google Scholar 

  • Korlyakov, K.A. and Nokhrin, D.Yu., The possible appearance of invasive channel Volga-Ob, Vestn. Soveta Molodykh Uchenykh Spetsialistov Chelyab. Obl., 2014, no. 2, pp. 19–28.

    Google Scholar 

  • Korzun, A.S. and Kassal, B.Yu., Distribution of alien fish species in water bodies of Omsk oblast, Russ. J. Biol. Invasions, 2013, vol. 4, no. 1, pp. 39–44.

    Article  Google Scholar 

  • Kotov, V.D. and Vizer, A.M., The status of ichthyofauna in Novosibirsk Reservoir in Siberia, Vodn. Khoz. Ross., 2007 vol. 2, no. 5, pp. 439–443.

    Google Scholar 

  • Kottelat, M. and Freyhof, J., Handbook of European Freshwater Fishes, Berlin: Kottelat, Cornol, and Freyhof, 2007.

    Google Scholar 

  • Krivoshchekov, G.M., The verkhovka in Western Siberia, in Vodoemy Sibiri i perspektivy ikh rybokhozyaistvennogo ispol’zovaniya (Siberian Reservoirs and Their Use for Fishery), Tomsk: Tosmk. Gos. Univ., 1973, pp. 86–87.

    Google Scholar 

  • Kuchin, A.P., Flora i fauna Altaya (Flora and Fauna of Altai), Gorno-Altaisk: Vsemirn. Fond Dikoi Prirod., 2001.

    Google Scholar 

  • Kuchin, A.P. and Kuchina, A.S., Aquatic fauna of Altai and its impact on a man over last half of century, in Voprosy okhrany prirody Gornogo Altaya (Nature Protection in Altai Mountains), Gorno-Altaisk: Gorno-Altaisk. Otd., Altaisk. Knizhn. Izd., 1976, pp. 12–15.

    Google Scholar 

  • Kuderskii, L.A., Naturalization of fishes in Russian reservoirs: status and prospective development, Vopr. Rybolov., 2001, vol. 2, no. 1 (5), pp. 6–85.

    Google Scholar 

  • Kulikov, E.V., Possible consequences for fishery in Irtysh River caused by water uptake in the People’s Republic of China, Izv. Chelyab. Nauch. Tsentra, 2007, no. 4, pp. 55–58.

    Google Scholar 

  • Litvinenko, A.I., Herbivorous fishes in Tyumen oblast, Rybovod. Rybolov., 1995, no. 3, pp. 26–27.

    Google Scholar 

  • Lobovikova, A.A., Naturalization of bream in Krasnoyarsk krai, in Akklimatizatsiya ryb i bespozvonochnykh v vodoemakh SSSR (Naturalization of Fishes and Invertebrates in Reservoirs of Soviet Union), Moscow: Nauka, 1968, pp. 219–222.

    Google Scholar 

  • Lugas’kov, A.V., Distribution, biology, and morphology of rotan in Ural reservoirs, Mater. mezhd. konf. “Sovremennoe sostoyanie vodnykh bioresursov” (Proc. Int. Conf. “Modern Status of Aquatic Biological Resources”), Novosibirsk, 2008, pp. 149–154.

    Google Scholar 

  • Magazov, O.A. and Rechkalov, V.V., Ichthyofauna of reservoirs in Chelyabinsk oblast, Vestn. Chelyab. Gos. Univ., Ekol., 2007, no. 6, pp. 85–87.

    Google Scholar 

  • Mikhailov, T.V., Ecology of Amur sleeper (Perccottus glenii) in Kurgan oblast, Mater. II Vseross. konf. “Problemy biologicheskoi nauki i obrazovaniya v pedagogicheskikh vuzakh” (Proc. II All-Russ. Conf. “The Problems of Biological Science and Education in Pedagogical Higher Education Institutions”), Novosibirsk: Novosib. Gos. Pedagog. Univ., 2002, pp. 123–126.

    Google Scholar 

  • Mukhachev, I.S., Fishery and naturalization measures in reservoirs of Chelyabinsk oblast, in Akklimatizatsiya ryb i bespozvonochnykh v vodoemakh SSSR (Naturalization of Fishes and Invertebrates in Reservoirs of Soviet Union), Leningrad, 1968, pp. 197–207.

    Google Scholar 

  • Mukhachev, I.S., Extension of biological diversity of fish fauna in Ob River basin, Konf. “Novye tekhnologii v zashchite bioraznoobraziya v vodnykh ekosistemakh,” Tezisy dokladov (Conf. “New Technologies Applied in Protection of Biological Diversity in Aquatic Ecosystems,” Abstracts of Papers), Moscow, 2002, p. 149.

    Google Scholar 

  • Pavlov, D.S., Lupandin, A.I., and Kostin, V.V., Pokatnaya migratsiya ryb cherez plotiny GES (Downstream Migration of Fishes through the Dams of Hydroelectric Power Plants), Moscow: Nauka, 1999.

    Google Scholar 

  • Pereskokov, A.V., Ichthyofauna of the Bol’shoe Miassovo Lake, Sibirskaya Zoologicheskaya konf., Tezisy dokladov (Siberian Zoological Conf., Abstracts of Papers), Novosibirsk, 2004, pp. 166–167.

    Google Scholar 

  • Petlina, A.P. and Ryabova, T.S., Ecology of Amur sleeper in suburb reservoirs of Tomsk city, Sibirskaya Zoologicheskaya konf., Tezisy dokladov (Siberian Zoological Conf., Abstracts of Papers), Novosibirsk, 2004, pp. 303–304.

    Google Scholar 

  • Petrachuk, E.S., Ecological variability of biological parameters and morphological type of bream in Ob-Irtysh basin related to areal extension, Extended Abstract of Cand. Sci. (Biol.) Dissertation, Tyumen, 2013.

    Google Scholar 

  • Petrachuk, E.S., Yankova, N.V., and Islamgalieva, K.R., The data on the biology of bream in the Irtysh River, X Sezd Gidrobiologicheskogo obshchestva Rossiiskoi Akademii Nauk, Tezisy dokladov (X Congr. of Hydrobiological Society, Russian Academy of Sciences, Abstracts of Papers), Vladivostok, 2009, pp. 309–310.

    Google Scholar 

  • Podlesnyi, A.V., Naturalization of fishes in Ural region and its results, Tr. Ural. Vseross. Nauchno-Issled. Inst. Ozern. Rechn. Khoz., 1939, vol. 1, pp. 86–141.

    Google Scholar 

  • Popov, P.A., Ryby Sibiri (Fishes of Siberia), Novosibirsk: Novosib. Gos. Univ., 2007.

    Google Scholar 

  • Popov, P.A., Vizer, A.M., and Upadyshev, E.E., Fishes of Novosibirsk Reservoir, Sib. Ekol. Zh., 2000, no. 2, pp. 177–186.

    Google Scholar 

  • Promotorova, E.Yu., Ecology of bream in the Lower Irtysh basin, Extended Abstract of Cand. Sci. (Biol.) Dissertation, Tyumen, 2000.

    Google Scholar 

  • Reshetnikov, A.N. and Petlina, A.P., Distribution of Amur sleeper (Perccottus glenii Dybowski, 1877) in the Ob River, Sib. Ekol. Zh., 2007, no. 4, pp. 551–555.

    Google Scholar 

  • Rostovtsev, A.A., Morphobiological characteristics of the rainbow trout naturalized in Altai krai, in Rybovodstvo v Sibiri i na Dal’nem Vostoke (Fish Farming in Siberia and Far East), Novosibirsk: Sib. Otd., Vses. Akad. S-kh. Nauk im. V.I. Lenina, 1982, pp. 59–65.

    Google Scholar 

  • Ryby Kazakhstana (Fishes of Kazakhstan), Almaty: Nauka, 1988, vol. 3.

  • Ryby Kazakhstana (Fishes of Kazakhstan), Almaty: Nauka, 1989, vol. 4.

  • Ryby Kazakhstana (Fishes of Kazakhstan), Almaty: Gylym, 1992, vol. 5.

  • Selezneva, M.V. and Trifonova, O.V., The effect of operation regime of Novosibirsk reservoir on fishery resources, Mater. Vseross. nauchno-prakt. konf. “Nauchnye osnovy ekologicheskogo monitoringa vodokhranilishch” (Proc. All-Russ. Sci.-Pract. Conf. “Scientific Basis of Ecological Monitoring of Reservoirs”), Khabarovsk: Dal’nevost. Otd., Ross. Akad. Nauk, 2005, pp. 147–150.

    Google Scholar 

  • Sheffer, F.F., Naturalization of fishes in southern reservoirs of Western Siberia, in Biologicheskie osnovy rybnogo khozyistva Sibiri (Biological Principles of Fish Farming in Siberia), Novosibirsk: Nauka, 1983, pp. 17–20.

    Google Scholar 

  • Skopintseva, V.T., First experience of trout farming in Altai krai, in Voprosy sel’skokhozyaistvennogo rybovodstva i gidrobiologii Zapadnoi Sibiri (Fish Farming and Hydrobiology in Western Siberia), Barnaul: Altai. Knizhn. Izd., 1967, pp. 106–110.

    Google Scholar 

  • Sobanskii, G.G., First results of introduction of trout to the Ezhelyukol Lake in Altai, in Biologicheskie resursy Altaiskogo kraya i puti ikh ratsional’nogo ispol’zovaniya (Biological Resources of Altai Krai and Their Rational Use), Barnaul, 1979, pp. 179–180.

    Google Scholar 

  • Solovov, V.P., The pike perch in the Upper Ob River, Vopr. Ikhtiol., 1971, vol. 11, no. 1 (66), pp. 145–147.

    Google Scholar 

  • Terent’eva, N.N. and Mukhachev, I.S., Ecological and fishery role of new species in the Ob River basin, IXSezd Gidrobiologicheskogo obshchestva Rossiiskoi Akademii Nauk, Tezisy dokladov (IX Congr. of Hydrobiological Society, Russian Academy of Sciences, Abstracts of Papers), Tolyatti, 2006, vol. 2, pp. 188.

    Google Scholar 

  • Tereshchenko, V.G., Trifonova, O.V., and Tereshchenko, L.I., Development of the fish community in a reservoir when new species are introduced from the first years of its existence, Vopr. Ikhtiol., 2004, vol. 44, no. 5, pp. 619–631.

    Google Scholar 

  • Toropov, A.V., Naturalized fishes in the Biya River and their influence on local ichthyofauna, Mater. Vseross. konf. “Regional’nye problemy ekologii i prirodopol’zovaniya” (Proc. All-Russ. Conf. “Regional Problems of Ecology and Nature Management”), Tomsk: Tomsk. Gos. Univ. Sist. Uprav. Radioelektron., 2000, pp. 35–36.

    Google Scholar 

  • Ubas’kin, A.V., Ichthyofauna of reservoirs in Pavlodar oblast, Mater. Vseross. konf. “Biologicheskie aspekty ratsional’nogo ispol’zovaniya i okhrany vodoemov Sibiri” (Proc. All-Russ. Conf. “Biological Aspects of Rational Use and Protection of Siberian Reservoirs”), Tomsk: Tosmk. Gos. Univ., 2007, pp. 274–278.

    Google Scholar 

  • Vodoemy Altaiskogo kraya: biologicheskaya produktivnost’ i perspektivy ispol’zovaniya (Reservoirs of Altai Krai: Biological Productivity and Prospective Use), Novosibirsk: Nauka, 1999.

  • Yakovlev, V.N., Distribution of freshwater fishes in Neogene of Holarctic and zoogeographical zoning, Vopr. Ikhtiol., 1961, vol. 1, no. 2, pp. 209–220.

    Google Scholar 

  • Yurakova, T.V. and Petlina, A.P., Structure of ichthyocenes of the Lower Tom River tributaries, in Sovremennye problemy gidrobiologii Sibiri (Modern Problems in Hydrobiology of Siberia), Tomsk: Tosmk. Gos. Univ., 2001, pp. 105–106.

    Google Scholar 

  • Zhdanov, V.D. and Sobanskii, G.G., Rare and new fish species in the Teletskoe Lake, Mater. konf. “Biologicheskie resursy Zapadnoi Sibiri i ikh okhrana” (Proc. Conf. “Biological Resources of Western Siberia and Their Protection”), Novosibirsk: Nauka, 1975a, pp. 19–21.

    Google Scholar 

  • Zhdanov, V.D. and Sobanskii, G.G., Required and possible fish introduction of some lakes and rivers in the northeastern Altai, in Okhrana, ratsional’noe ispol’zovanie i vosproizvodstvo prirodnykh resursov Altaiskogo kraya (Protection, Rational Use, and Reproduction of Natural Resources of Altai Krai), Barnaul: Altai. Knizhn. Izd., 1975b, pp. 364–366.

    Google Scholar 

  • Zhuravlev, V.B., Ryby basseina Verkhnei Obi (Fishes of the Upper Ob’ River Basin), Barnaul: Altai. Gos. Univ., 2003.

    Google Scholar 

  • Zhuravlev, V.B., Lomodurov, E.I., and Luk’yanov, D.P., Introduction of Amur sleeper in floodplain reservoirs of the Upper Ob River basin, IXSezd Gidrobiologicheskogo obshchestva Rossiiskoi Akademii Nauk, Tezisy dokladov (IX Congr. of Hydrobiological Society, Russian Academy of Sciences, Abstracts of Papers), Tolyatti, 2006, vol. 1, p. 163.

    Google Scholar 

  • Zinov’ev, E.A. and Baklanov, M.A., Unusual elements in fish fauna in reservoirs of Chelyabinsk and Kurgan oblasts, Vestn. Permsk. Univ., Ser. Biol., 2007, no. 5 (10), pp. 53–56.

    Google Scholar 

  • Zlotnik, D.V., Modern revision of species composition of fishes in the Chulym River basin (basin of Central ob River), Mater. II Vseross. shkoly-konf. “Ekosistemy malykh rek: bioraznoobrazie, ekologiya, okhrana” (Proc. II All-Russ. School-Conf. “Ecosystems of Small Rivers: Biodiversity, Ecology, and Protection”), Borok, 2014, pp. 154–157.

    Google Scholar 

  • Zlotnik, D.V. and Romanov, V.I., Modern status of population of European cisco introduced to the Ingol Lake, Rybovod. Rybn. Khoz., 2011, no. 4, pp. 23–26.

    Google Scholar 

  • Zyuganov, V.V., Invasion of the Aral stickleback to the Ob River basin, Vopr. Ikhtiol., 1984, vol. 24, no. 4, pp. 671–672.

    Google Scholar 

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Correspondence to E. A. Interesova.

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Original Russian Text © E.A. Interesova, 2016, published in Rossiiskii Zhurnal Biologicheskikh Invazii, 2016, No. 1, pp. 83–100.

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Interesova, E.A. Alien fish species in the Ob River basin. Russ J Biol Invasions 7, 156–167 (2016). https://doi.org/10.1134/S2075111716020089

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