| Species |
Recipient region |
Date of the first record |
|
| Obelia dichotoma | Australia / Bass strait | 1966 |  |
| Obelia dichotoma | Portugal / Madeira | 1980 |  |
| Obesogammarus crassus | Germany / Baltic Sea | 1990 - 2015 |  |
| Obesogammarus crassus | Germany / North Sea | 2016 |  |
| Obesogammarus crassus | Lithuania | 1962 |  |
| Obesogammarus crassus | Poland | 1999 |  |
| Obesogammarus crassus | Russia / Baltic Sea / Kaliningrad area | 1962 |  |
| Ocenebra erinaceus | Netherlands | To 2007 |  |
| Ocinebrellus inornata | France / Biscay Gulf | 1995 |  |
| Ocinebrellus inornata | France / Celtic seas | 1995 |  |
| Ocinebrellus inornata | Netherlands | 2007 |  |
| Ocinebrellus inornata | Portugal / Iberian Coastal | 1999 |  |
| Ocinebrellus inornatus | Denmark / Baltic Sea | 2006 |  |
| Ocinebrellus inornatus | Denmark / North Sea | 2006 |  |
| Ocinebrellus inornatus | France / Biscay Gulf | 1993 |  |
| Ocinebrellus inornatus | France / English Channel | 1994 |  |
| Ocinebrellus inornatus | Netherlands | To 2007 |  |
| Ocinebrellus inornatus | Portugal / Iberian Coastal | To 1999 |  |
| Octactis octonaria | Bulgaria | 1948 |  |
| Octactis octonaria | Romania | 1948 |  |
| Octactis octonaria | Ukraine / Black Sea | From 1948 |  |
| Octopus cyanea | Israel | 1998 |  |
| Oculina patagonica | France / Western Mediterranean | 1972 |  |
| Oculina patagonica | Greece / Eastern Mediterranean | 2005 |  |
| Oculina patagonica | Italy / Western Mediterranean | 1966 |  |
| Odessia maeotica | Russia / Caspian Sea | 1960 |  |
| Odetta zekiergeni | Italy / Western Mediterranean | 2019 |  |
| Odontella sinensis | Belgium | 1904 |  |
| Odontella sinensis | Denmark / Baltic Sea | 1903 |  |
| Odontella sinensis | Denmark / North Sea | 1903 |  |
| Odontella sinensis | France / Biscay Gulf | To 1934 |  |
| Odontella sinensis | France / Celtic seas | 1930 |  |
| Odontella sinensis | France / English Channel | To 1930 |  |
| Odontella sinensis | France / North Sea | To 1930 |  |
| Odontella sinensis | Germany / Baltic Sea | 1904 |  |
| Odontella sinensis | Germany / North Sea | 1903 |  |
| Odontella sinensis | Ireland | 1995 |  |
| Odontella sinensis | Netherlands | 1905 |  |
| Odontella sinensis | Norway / North Sea | 1903 |  |
| Odontella sinensis | Norway / Norwegian Sea | 1903 |  |
| Odontella sinensis | Sweden / North Sea | 1903 |  |
| Odontella sinensis | United Kingdom (Britain) / Celtic seas / Channel Islands | |  |
| Odontodactylus scyllarus | France / Biscay Gulf | 2009 |  |
| Odontodactylus scyllarus | France / English Channel | To 2009 |  |
| Odostomia lorioli | Israel | 1974 |  |
| Ogyrides mjoebergi | Israel | 1947 |  |
| Oithona brevicornis brevicornis | Ukraine / Black Sea | From 2001 |  |
| Oithona davisae | Bulgaria | 2009 |  |
| Oithona davisae | Denmark / Baltic Sea | 2023 |  |
| Oithona davisae | Denmark / North Sea | 2023 |  |
| Oithona davisae | Georgia | 2007 |  |
| Oithona davisae | Germany / North Sea | 2008 |  |
| Oithona davisae | Greece / Eastern Mediterranean | 2018 |  |
| Oithona davisae | Italy / Adriatic Sea | 2014 |  |
| Oithona davisae | Italy / Central Mediterranean | 2014 |  |
| Oithona davisae | Italy / Western Mediterranean | 2014 |  |
| Oithona davisae | Romania | 2010 |  |
| Oithona davisae | Russia / Black Sea | 2003 |  |
| Oithona davisae | Ukraine / Black Sea | 2001 |  |
| Oithona plumifera | Ukraine / Black Sea | From 2001 |  |
| Oithona setigera | Ukraine / Black Sea | From 2001 |  |
| Oithona similis | Russia / Caspian Sea | 2004 |  |
| Okenia pellucida | Israel | 2021 |  |
| Okenia picoensis | Italy / Central Mediterranean | 2021 |  |
| Okenia picoensis | Italy / Western Mediterranean | 2021 |  |
| Omobranchus punctatus | Israel | 2003 |  |
| Onchocleidus dispar | Norway / North Sea | 2004 |  |
| Oncorhynchus clarkii | Sweden / North Sea | |  |
| Oncorhynchus gorbuscha | Denmark / Baltic Sea | 1958 |  |
| Oncorhynchus gorbuscha | Denmark / North Sea | 1973 |  |
| Oncorhynchus gorbuscha | Faroe Islands | 2019 |  |
| Oncorhynchus gorbuscha | Finland | 1970 - 1979 |  |
| Oncorhynchus gorbuscha | France / English Channel | 2017 |  |
| Oncorhynchus gorbuscha | Iceland | 1960 |  |
| Oncorhynchus gorbuscha | Ireland | 1973 |  |
| Oncorhynchus gorbuscha | Latvia | 1973 |  |
| Oncorhynchus gorbuscha | Norway / Barents Sea | 1960 |  |
| Oncorhynchus gorbuscha | Norway / Norwegian Sea | 1960 |  |
| Oncorhynchus gorbuscha | Russia / Baltic Sea / St. Petersburg area | 1973 - 1980 |  |
| Oncorhynchus gorbuscha | Sweden / Baltic Sea | 1974 |  |
| Oncorhynchus gorbuscha | Ukraine / Azov Sea | From 1961 |  |
| Oncorhynchus gorbuscha | Ukraine / Black Sea | From 1961 |  |
| Oncorhynchus gorbuscha | United Kingdom (Britain) / North Sea | 1960 |  |
| Oncorhynchus keta | Finland | 1971 |  |
| Oncorhynchus keta | Latvia | 1970 |  |
| Oncorhynchus keta | Norway / Barents Sea | 1960 |  |
| Oncorhynchus keta | Norway / Norwegian Sea | 1960 |  |
| Oncorhynchus kisutch | Belgium | To 1996 |  |
| Oncorhynchus kisutch | Denmark / Baltic Sea | 2017 |  |
| Oncorhynchus kisutch | Denmark / North Sea | 2017 |  |
| Oncorhynchus kisutch | Latvia | 1980 |  |
| Oncorhynchus kisutch | Netherlands | 1982 |  |
| Oncorhynchus kisutch | Sweden / Baltic Sea | 1984 |  |
| Oncorhynchus kisutch | United Kingdom (Britain) / English Channel | 1975 |  |
| Oncorhynchus mykiss | Belgium | 1884 |  |
| Oncorhynchus mykiss | Denmark / Baltic Sea | 1899 |  |
| Oncorhynchus mykiss | Denmark / North Sea | 1899 |  |
| Oncorhynchus mykiss | Estonia | 1896 |  |
| Oncorhynchus mykiss | Faroe Islands | To 1990 |  |
| Oncorhynchus mykiss | Finland | 1898 |  |
| Oncorhynchus mykiss | France / Biscay Gulf | 1984 |  |
| Oncorhynchus mykiss | France / English Channel | To 1984 |  |
| Oncorhynchus mykiss | Germany / Baltic Sea | 1882 |  |
| Oncorhynchus mykiss | Iceland | 1951 |  |
| Oncorhynchus mykiss | Ireland | 1895 |  |
| Oncorhynchus mykiss | Latvia | 1899 |  |
| Oncorhynchus mykiss | Lithuania | 1890 |  |
| Oncorhynchus mykiss | Netherlands | 1898 |  |
| Oncorhynchus mykiss | Norway / Barents Sea | To 2012 |  |
| Oncorhynchus mykiss | Norway / North Sea | To 2012 |  |
| Oncorhynchus mykiss | Norway / Norwegian Sea | 1902 |  |
| Oncorhynchus mykiss | Poland | 1881 - 1889 |  |
| Oncorhynchus mykiss | Portugal / Azores | To 1990 |  |
| Oncorhynchus mykiss | Portugal / Madeira | To 2002 |  |
| Oncorhynchus mykiss | Russia / Baltic Sea / Kaliningrad area | 1882 |  |
| Oncorhynchus mykiss | Russia / Baltic Sea / St. Petersburg area | 1881 - 1896 |  |
| Oncorhynchus mykiss | Sweden / Baltic Sea | 1892 |  |
| Oncorhynchus mykiss | Sweden / North Sea | 1894 - 1900 |  |
| Oncorhynchus mykiss | Ukraine / Black Sea | 1938 - 1965 |  |
| Oncorhynchus mykiss | United Kingdom (Britain) / Celtic seas | 1884 |  |
| Oncorhynchus nerka | Finland | 1967 |  |
| Oncorhynchus tshawytscha | Finland | 1930 |  |
| Onisimus sextoni | Canada / Hudson Bay Complex | To 2012 |  |
| Ophiactis macrolepidota | Israel | 1968 |  |
| Ophiactis savignyi | France / Western Mediterranean | To 1969 |  |
| Ophiactis savignyi | Greece / Eastern Mediterranean | 1993 |  |
| Ophiactis savignyi | Israel | 1948 |  |
| Ophioblennius atlanticus | Italy / Central Mediterranean | 2017 |  |
| Ophryotrocha diadema | Italy / Central Mediterranean | 2006 |  |
| Ophryotrocha japonica | Italy / Adriatic Sea | 1999 - 2001 |  |
| Ophryotrocha japonica | Italy / Central Mediterranean | 1999 - 2001 |  |
| Ophryotrocha japonica | Italy / Western Mediterranean | 1999 - 2001 |  |
| Oplegnathus fasciatus | Italy / Adriatic Sea | 2015 |  |
| Orchestia cavimana | Belgium | To 1927 |  |
| Orchestia cavimana | Estonia | 1999 |  |
| Orchestia cavimana | Germany / Baltic Sea | 1920 |  |
| Orchestia cavimana | Germany / North Sea | 1920 |  |
| Orchestia cavimana | Netherlands | To 1878 |  |
| Orchestia cavimana | Poland | 1899 |  |
| Orchestia cavimana | Russia / Baltic Sea / Kaliningrad area | 1957 - 1959 |  |
| Orchestia gammarellus | Iceland | 1968 |  |
| Oreochromis niloticus | Belgium | To 2000 |  |
| Oscilla galilae | Greece / Eastern Mediterranean | 2016 |  |
| Oscilla galilae | Israel | 2009 |  |
| Oscilla jocosa | Israel | 1984 |  |
| Oscilla virginiae | Israel | 2018 |  |
| Osmundea oederi | Italy / Central Mediterranean | 2007 |  |
| Ostorhinchus fasciatus | Israel | 2008 |  |
| Ostracion cubicum | Israel | 2017 |  |
| Ostracoblabe implexa | Ireland | 1949 - 1963 |  |
| Ostracoblabe implexa | United Kingdom (Britain) / North Sea | 1950 |  |
| Ostrea angasi | France / Biscay Gulf | 1985 |  |
| Ostrea angasi | France / Celtic seas | 1985 |  |
| Ostrea denselamellosa | France / Biscay Gulf | 1982 |  |
| Ostrea denselamellosa | France / Celtic seas | 1982 |  |
| Ostrea equestris | Ireland | 1995 |  |
| Ostrea puelchana | France / Biscay Gulf | 1989 |  |
| Ostrea puelchana | France / Celtic seas | 1989 |  |
| Ostrea stentina | Spain / Iberian Coastal | To 2015 |  |
| Ostreid herpesvirus 1 | Netherlands | To 2010 |  |
| Ostreopsis ovata | France / Biscay Gulf | 2021 |  |
| Ostreopsis ovata | France / Western Mediterranean | 1972 |  |
| Ostreopsis ovata | Greece / Eastern Mediterranean | 2003 |  |
| Ostreopsis ovata | Portugal / Iberian Coastal | To 2011 |  |
| Ostreopsis siamensis | Portugal / Iberian Coastal | To 2008 |  |
| Owenia borealis | Canada / Canadian Eastern Arctic | To 2011 |  |
| Oxydromus humesi | Spain / Iberian Coastal | To 2017 |  |
| Oxyphysis oxytoxoides | Bulgaria | 1987 |  |
| Oxyphysis oxytoxoides | Turkey / Black Sea | 2007 - 2008 |  |
| Oxytoxum criophilum | Sweden / North Sea | 2003 |  |
| Oxytoxum gladiolus | Ukraine / Black Sea | 1989 |  |
| Oxytoxum variabile | Russia / Black Sea | 2008 |  |
| Oxyurichthys papuensis | Greece / Eastern Mediterranean | 2010 |  |
| Oxyurichthys petersii | Israel | 1982 |  |