| Species |
Recipient region |
Date of the first record |
|
| Sabella spallanzanii | Australia / Bass strait | 1984 |  |
| Sabella spallanzanii | New Zealand / New Zealand Shelf / North Island | 2009 | |
| Sabella spallanzanii | New Zealand / New Zealand Shelf / South Island | 2008 | |
| Sabella spallanzanii | Portugal / Azores | To 1954 | |
| Sabella spallanzanii | Spain / Iberian Coastal | To 2003 | |
| Sabellaria spinulosa | Netherlands | 1938 | |
| Sabia conica | Israel | 1980 | |
| Saccharina japonica | France / Western Mediterranean | 1976 | |
| Saccharina japonica | Germany / North Sea | To 1980 | |
| Saccostrea glomerata | Italy / Adriatic Sea | 1984 | |
| Saduria entomon | Ukraine / Black Sea | 2009 | |
| Salmo salar | Turkey / Black Sea | 1992 | |
| Salpingella decurtata | Romania | 2012 | |
| Salpingella decurtata | Ukraine / Black Sea | 2002 | |
| Salpingella sp. | Ukraine / Black Sea | From 2002 | |
| Salvelinus fontinalis | Denmark / Baltic Sea | 1916 | |
| Salvelinus fontinalis | Denmark / North Sea | 1916 | |
| Salvelinus fontinalis | Finland | 1890 - 1899 | |
| Salvelinus fontinalis | Sweden / Baltic Sea | 1892 | |
| Salvelinus namaycush | Finland | 1960 - 1969 | |
| Salvelinus namaycush | Sweden / Baltic Sea | 1958 | |
| Sander lucioperca | Portugal / Azores | To 2004 | |
| Sarcodiotheca gaudichaudii | United Kingdom (Britain) / English Channel | 1974 | |
| Sarconema filiforme | Israel | 1945 | |
| Sarconema scinaioides | Greece / Eastern Mediterranean | 1980 | |
| Sardinella aurita | Bulgaria | 1980 - 1989 | |
| Sardinella aurita | Georgia | 1937 | |
| Sardinella aurita | Romania | 1980 - 1989 | |
| Sardinella aurita | Russia / Black Sea | 1980 - 1989 | |
| Sardinella aurita | Turkey / Black Sea | 1997 | |
| Sardinella aurita | Ukraine / Black Sea | From 1999 | |
| Sardinella gibbosa | Israel | 2008 | |
| Sargassum hornschuchii | Turkey / Black Sea | 1990 - 1999 | |
| Sargassum muticum | Belgium | 1999 | |
| Sargassum muticum | Denmark / Baltic Sea | 1984 | |
| Sargassum muticum | Denmark / North Sea | 1984 | |
| Sargassum muticum | France / Biscay Gulf | 1975 | |
| Sargassum muticum | France / Celtic seas | 1976 | |
| Sargassum muticum | France / English Channel | 1975 | |
| Sargassum muticum | France / North Sea | 1979 | |
| Sargassum muticum | France / Western Mediterranean | 1980 | |
| Sargassum muticum | Germany / North Sea | 1988 | |
| Sargassum muticum | Ireland | To 1995 | |
| Sargassum muticum | Italy / Adriatic Sea | 1992 | |
| Sargassum muticum | Netherlands | 1977 | |
| Sargassum muticum | Norway / North Sea | 1988 | |
| Sargassum muticum | Portugal / Iberian Coastal | 1989 | |
| Sargassum muticum | Spain / Iberian Coastal | 1985 | |
| Sargassum muticum | Sweden / Baltic Sea | To 2005 | |
| Sargassum muticum | Sweden / North Sea | 1985 | |
| Sargassum muticum | United Kingdom (Britain) / Celtic seas | 1971 | |
| Sargassum muticum | United Kingdom (Britain) / English Channel | 1971 | |
| Sargassum muticum | United Kingdom (Britain) / North Sea | 1981 | |
| Sargassum muticum | United Kingdom (Britain) / North Sea / Orkney Islands | To 2015 | |
| Sargocentron rubrum | Greece / Central Mediterranean | 2017 | |
| Sargocentron rubrum | Greece / Eastern Mediterranean | 1947 | |
| Sargocentron rubrum | Israel | 1945 | |
| Saron marmoratus | Israel | 2013 | |
| Sarpa salpa | Bulgaria | 1949 | |
| Sarpa salpa | Georgia | 1938 | |
| Sarpa salpa | Romania | 1949 | |
| Sarpa salpa | Turkey / Black Sea | 1998 | |
| Sarpa salpa | Ukraine / Black Sea | From 1999 | |
| Sarsameira parva | Turkey / Black Sea | 2009 | |
| Sarsamphiascus parvus | Russia / Black Sea | 1999 | |
| Saurida lessepsianus | Greece / Central Mediterranean | 1990 | |
| Saurida lessepsianus | Greece / Eastern Mediterranean | 1940 - 1945 | |
| Saurida lessepsianus | Israel | 1952 | |
| Savoryella lignicola | Ukraine / Black Sea | From 2001 | |
| Scageliopsis patens | Portugal / Azores | To 1989 | |
| Scageliopsis patens | Portugal / Iberian Coastal | From 2006 | |
| Scageliopsis patens | Spain / Iberian Coastal | To 2008 | |
| Scaliola elata | Israel | 1987 | |
| Scartella cristata | Denmark / Baltic Sea | 1934 | |
| Scarus ghobban | Greece / Eastern Mediterranean | 2014 | |
| Scarus ghobban | Israel | 2001 | |
| Scherocumella gurneyi | Israel | 2005 | |
| Schizobrachiella verrilli | Belgium | To 1905 | |
| Schizobrachiella verrilli | Germany / North Sea | 2011 - 2012 | |
| Schizobrachiella verrilli | Netherlands | To 2015 | |
| Schizoporella errata | Portugal / Azores | 2013 | |
| Schizoporella errata | Portugal / Iberian Coastal | 2016 | |
| Schizoporella errata | Portugal / Madeira | 1897 | |
| Schizoporella errata | Spain / Canary Islands | To 2003 | |
| Schizoporella japonica | Denmark / North Sea | 2021 | |
| Schizoporella japonica | Germany / North Sea | 2018 | |
| Schizoporella japonica | Ireland | To 2015 | |
| Schizoporella japonica | Netherlands | To 2018 | |
| Schizoporella japonica | Norway / Norwegian Sea | From 2014 | |
| Schizoporella japonica | Spain / Spain | 2017 | |
| Schizoporella japonica | United Kingdom (Britain) / North Sea / Orkney Islands | From 2011 | |
| Schizoporella pungens | Portugal / Madeira | 2010 | |
| Schizoporella unicornis | Australia / Bass strait | 1802 - 1880 | |
| Schizoporella unicornis | France / English Channel | 2000 | |
| Schizoporella unicornis | France / North Sea | 2000 | |
| Schizoporella unicornis | Portugal / Azores | From 2009 | |
| Schizoporella unicornis | Spain / Canary Islands | To 2003 | |
| Schottera nicaeensis | Australia / Bass strait | 1975 | |
| Schyzocotyle acheilognathi | Norway / Norwegian Sea | To 2012 | |
| Sciaenops ocellatus | China / Yellow Sea | To 2001 | |
| Sciaenops ocellatus | Israel | 1999 | |
| Sciaenops ocellatus | Italy / Central Mediterranean | 2016 | |
| Scolecetrix sp. | Ukraine / Black Sea | From 2001 | |
| Scolionema suvaense | Italy / Western Mediterranean | 1972 | |
| Scomberomorus commerson | Greece / Central Mediterranean | 2017 | |
| Scomberomorus commerson | Greece / Eastern Mediterranean | 2008 | |
| Scomberomorus commerson | Israel | 1935 | |
| Scrippsiella acuminata | Bulgaria | 1989 | |
| Scrippsiella acuminata | Georgia | 1985 | |
| Scrippsiella acuminata | Netherlands | To 2018 | |
| Scrippsiella acuminata | Romania | 1982 | |
| Scrippsiella acuminata | Russia / Black Sea | 2001 | |
| Scrippsiella acuminata | Turkey / Black Sea | 1990 - 1999 | |
| Scrippsiella acuminata | Ukraine / Black Sea | 1960 - 1969 | |
| Scrippsiella operosa | Bulgaria | 2008 | |
| Scruparia ambigua | Australia / Bass strait | 1881 | |
| Scruparia ambigua | Spain / Canary Islands | To 2003 | |
| Scrupocellaria scrupea | Australia / Bass strait | 1887 | |
| Scrupocellaria scruposa | Australia / Bass strait | From 1900 | |
| Scrupocellaria scruposa | Greece / Eastern Mediterranean | 1967 | |
| Scyllarus caparti | Italy / Adriatic Sea | 1977 | |
| Scytosiphon dotyi | France / Western Mediterranean | 1994 | |
| Scytosiphon dotyi | Greece / Eastern Mediterranean | 2013 | |
| Scytosiphon dotyi | Italy / Adriatic Sea | 1960 - 1977 | |
| Scytosiphon dotyi | Portugal / Iberian Coastal | 2016 | |
| Scytosiphon dotyi | Spain / Canary Islands | To 2004 | |
| Scytosiphon dotyi | Spain / Iberian Coastal | To 1998 | |
| Scytosiphon dotyi | United Kingdom (Britain) / North Sea | 1900 | |
| Scytosiphon lomentaria | Australia / Bass strait | 1971 | |
| Sebastes schlegelii | Belgium | 2008 | |
| Sebastes schlegelii | Netherlands | 2008 | |
| Sebastiscus marmoratus | Norway / North Sea | 2016 | |
| Sepia pharaonis | Israel | 2003 | |
| Sepioteuthis lessoniana | Greece / Eastern Mediterranean | 2009 | |
| Sepioteuthis lessoniana | Israel | 2004 | |
| Septifer cumingii | Greece / Eastern Mediterranean | 2010 | |
| Septifer cumingii | Israel | 2007 | |
| Serranus hepatus | Turkey / Black Sea | 2012 | |
| Sertularia marginata | Greece / Eastern Mediterranean | 1990 | |
| Sertularia marginata | Israel | 1949 | |
| Sertularia marginata | Spain / Iberian Coastal | To 1991 | |
| Sicyonia lancifer | Israel | 2015 | |
| Sigambra tentaculata | Georgia | 1978 | |
| Sigambra tentaculata | Ukraine / Black Sea | 1960 - 1969 | |
| Siganus fuscescens | Italy / Western Mediterranean | 2020 | |
| Siganus luridus | France / Western Mediterranean | 2008 | |
| Siganus luridus | Greece / Adriatic Sea | 2014 | |
| Siganus luridus | Greece / Central Mediterranean | 1973 | |
| Siganus luridus | Greece / Eastern Mediterranean | 1964 | |
| Siganus luridus | Israel | 1955 | |
| Siganus luridus | Italy / Adriatic Sea | 2010 | |
| Siganus luridus | Italy / Central Mediterranean | 2003 | |
| Siganus luridus | Italy / Western Mediterranean | 2004 | |
| Siganus rivulatus | France / Western Mediterranean | 2018 | |
| Siganus rivulatus | Greece / Adriatic Sea | 2014 | |
| Siganus rivulatus | Greece / Central Mediterranean | 2007 | |
| Siganus rivulatus | Greece / Eastern Mediterranean | 1925 | |
| Siganus rivulatus | Israel | 1924 | |
| Siganus rivulatus | Italy / Central Mediterranean | 2015 | |
| Silhouettea aegyptia | Israel | 1998 | |
| Sillago suezensis | Greece / Eastern Mediterranean | 2018 | |
| Sillago suezensis | Israel | 1977 | |
| Sinanodonta woodiana | Belgium | To 1999 | |
| Sinanodonta woodiana | Ukraine / Black Sea | 1999 - 2000 | |
| Sinelobus stanfordi | Belgium | 2006 | |
| Sinelobus stanfordi | France / North Sea | 2016 | |
| Sinelobus stanfordi | Germany / Baltic Sea | 2012 | |
| Sinelobus stanfordi | Germany / North Sea | To 2012 | |
| Sinelobus stanfordi | Latvia | 2015 | |
| Sinelobus stanfordi | Netherlands | 2006 | |
| Sinelobus vanhaareni | Belgium | To 2007 | |
| Sinelobus vanhaareni | Denmark / Baltic Sea | 2021 | |
| Sinelobus vanhaareni | Denmark / North Sea | 2021 | |
| Sinelobus vanhaareni | Estonia | 2010 | |
| Sinelobus vanhaareni | Finland | From 2016 | |
| Sinelobus vanhaareni | Germany / Baltic Sea | 2012 | |
| Sinelobus vanhaareni | Germany / North Sea | 2009 | |
| Sinelobus vanhaareni | Poland | 2014 | |
| Sinelobus vanhaareni | Sweden / North Sea | 2020 | |
| Sinotaia quadrata | France / Biscay Gulf | 2017 | |
| Sinotaia quadrata | Spain / Iberian Coastal | 2017 | |
| Siphonaria crenata | Israel | 1965 | |
| Siphonaria pectinata | Greece / Eastern Mediterranean | 1973 | |
| Sirpus monodi | Greece / Central Mediterranean | 2006 | |
| Sirpus monodi | Greece / Eastern Mediterranean | 2002 | |
| Sirpus zariquieyi | Turkey / Black Sea | 1982 | |
| Skeletonema subsalsum | Ukraine / Black Sea | From 1993 | |
| Skistodiaptomus pallidus | Germany / North Sea | To 2010 | |
| Smaragdia souverbiana | Greece / Central Mediterranean | 2012 | |
| Smaragdia souverbiana | Greece / Eastern Mediterranean | 1993 | |
| Smaragdia souverbiana | Israel | 1987 | |
| Smittina nitidissima | Israel | 1986 | |
| Smittina nitidissima | Italy / Central Mediterranean | 2014 | |
| Smittoidea prolifica | Germany / North Sea | 2011 | |
| Smittoidea prolifica | Netherlands | 1995 | |
| Solieria chordalis | United Kingdom (Britain) / Celtic seas | 1976 | |
| Solieria chordalis | United Kingdom (Britain) / English Channel | 1976 | |
| Solieria dura | Israel | 1954 | |
| Solieria filiformis | Australia / Bass strait | 1957 | |
| Solieria filiformis | France / Western Mediterranean | 1999 | |
| Solieria filiformis | Italy / Adriatic Sea | 2003 | |
| Solieria filiformis | Italy / Central Mediterranean | 1922 | |
| Solieria filiformis | United Kingdom (Britain) / English Channel | 1978 | |
| Solmundella bitentaculata | Turkey / Black Sea | 2010 | |
| Sorites orbiculus | Italy / Central Mediterranean | 2005 | |
| Sorites orbiculus | Turkey / Black Sea | 2010 | |
| Sorsogona prionota | Israel | 1946 | |
| Sousa plumbea | Greece / Eastern Mediterranean | 2017 | |
| Spartina alterniflora | France / Biscay Gulf | 1806 | |
| Spartina alterniflora | France / Celtic seas | 1960 | |
| Spartina alterniflora | France / English Channel | 1960 | |
| Spartina densiflora | Portugal / Iberian Coastal | 1986 | |
| Spartina densiflora | Spain / Iberian Coastal | 1950 - 1959 | |
| Spartina patens | France / Biscay Gulf | 1901 | |
| Spartina patens | France / Celtic seas | 1901 | |
| Spartina patens | France / Western Mediterranean | 1849 | |
| Spartina patens | Portugal / Iberian Coastal | 1999 | |
| Spartina patens | Spain / Iberian Coastal | To 1997 | |
| Spartina townsendii var. anglica | Belgium | 1920 - 1929 | |
| Spartina townsendii var. anglica | Denmark / Baltic Sea | 1948 - 1953 | |
| Spartina townsendii var. anglica | Denmark / North Sea | 1930 - 1940 | |
| Spartina townsendii var. anglica | France / Biscay Gulf | 1924 | |
| Spartina townsendii var. anglica | France / Celtic seas | 1894 | |
| Spartina townsendii var. anglica | France / English Channel | 1894 | |
| Spartina townsendii var. anglica | France / North Sea | To 1990 | |
| Spartina townsendii var. anglica | Germany / North Sea | 1927 | |
| Spartina townsendii var. anglica | Ireland | 1925 | |
| Spartina townsendii var. anglica | Netherlands | 1924 | |
| Spartina townsendii var. anglica | Sweden / North Sea | From 2007 | |
| Spartina townsendii var. anglica | United Kingdom (Britain) / Celtic seas | 1850 - 1859 | |
| Spartina townsendii var. anglica | United Kingdom (Britain) / English Channel | 1850 - 1859 | |
| Spartina x neyrauti | France / Biscay Gulf | 1897 | |
| Spartina x townsendii | France / Biscay Gulf | 1906 - 1910 | |
| Spartina x townsendii | France / Celtic seas | 1906 | |
| Spartina x townsendii | France / English Channel | 1906 | |
| Spartina x townsendii | France / North Sea | 2000 - 2010 | |
| Spartina x townsendii | Ireland | 1930 - 1934 | |
| Sparus aurata | Bulgaria | 1940 - 1949 | |
| Sparus aurata | Georgia | 1937 | |
| Sparus aurata | Portugal / Madeira | To 2002 | |
| Sparus aurata | Romania | 1940 - 1949 | |
| Sparus aurata | Turkey / Black Sea | 1942 | |
| Sparus aurata | Ukraine / Black Sea | 1987 | |
| Spatoglossum asperum | Israel | 1962 | |
| Spatulodinium pseudonoctiluca | Ukraine / Black Sea | From 2001 | |
| Spermothamnion cymosum | Italy / Adriatic Sea | 2010 | |
| Sphacelaria fusca | Australia / Bass strait | 1977 | |
| Sphaerococcus coronopifolius | Norway / North Sea | 1994 | |
| Sphaerococcus coronopifolius | Sweden / North Sea | To 1994 | |
| Sphaeroma serratum | Portugal / Azores | To 1990 | |
| Sphaeroma walkeri | France / Western Mediterranean | 1977 | |
| Sphaeroma walkeri | Greece / Eastern Mediterranean | 2015 | |
| Sphaeroma walkeri | Israel | 1971 | |
| Sphaeroma walkeri | Italy / Western Mediterranean | 2010 | |
| Sphaeroma walkeri | Portugal / Madeira | From 2015 | |
| Sphaeroma walkeri | Romania | 2004 | |
| Sphaerotrichia divaricata | France / Western Mediterranean | 1981 | |
| Sphaerotrichia divaricata | Portugal / Azores | 1991 | |
| Sphaerotrichia firma | France / Western Mediterranean | 1980 | |
| Sphenia rueppellii | Israel | 1978 | |
| Sphoeroides pachygaster | France / Western Mediterranean | 1991 | |
| Sphyraena chrysotaenia | Greece / Central Mediterranean | 2011 | |
| Sphyraena chrysotaenia | Greece / Eastern Mediterranean | 1995 | |
| Sphyraena flavicauda | Greece / Eastern Mediterranean | 2003 | |
| Sphyraena flavicauda | Israel | 1991 | |
| Sphyraena obtusata | Ukraine / Black Sea | From 1999 | |
| Sphyraena pinguis | Israel | 1931 | |
| Sphyrna zygaena | Romania | 1950 - 1959 | |
| Spirobranchus latiscapus | Spain / Iberian Coastal | To 2017 | |
| Spirobranchus tetraceros | Greece / Eastern Mediterranean | 1970 | |
| Spirobranchus tetraceros | Israel | 1976 | |
| Spirobranchus tetraceros | Italy / Central Mediterranean | 2016 | |
| Spirorbis (Spirorbis) marioni | France / Western Mediterranean | 1977 | |
| Spirorbis (Spirorbis) marioni | Greece / Eastern Mediterranean | 1997 | |
| Spirorbis (Spirorbis) marioni | Italy / Western Mediterranean | 1977 | |
| Spirorbis (Spirorbis) marioni | Portugal / Azores | To 1979 | |
| Spirorbis (Spirorbis) marioni | Portugal / Madeira | To 1995 | |
| Spirorbis (Spirorbis) marioni | Spain / Canary Islands | To 1980 | |
| Spisula solidissima | Netherlands | 1982 | |
| Spondylus nicobaricus | Israel | 2002 | |
| Spondylus spinosus | Greece / Eastern Mediterranean | 2008 - 2013 | |
| Spondylus spinosus | Israel | 1992 | |
| Spongoclonium caribaeum | France / Celtic seas | 1967 | |
| Spongoclonium caribaeum | France / English Channel | 1967 | |
| Spongoclonium caribaeum | France / Western Mediterranean | 1974 | |
| Spongoclonium caribaeum | Portugal / Azores | 2005 - 2007 | |
| Spongoclonium caribaeum | Spain / Canary Islands | 1970 - 1979 | |
| Spratelloides delicatulus | Israel | 1973 | |
| Spyridia hypnoides | Israel | 1937 | |
| Stenothoe georgiana | Italy / Adriatic Sea | 2017 | |
| Stenothoe georgiana | Italy / Central Mediterranean | 2016 | |
| Stenothoe georgiana | Italy / Western Mediterranean | 2013 | |
| Stephanolepis diaspros | Greece / Central Mediterranean | 2016 | |
| Stephanolepis diaspros | Greece / Eastern Mediterranean | 1943 | |
| Stephanolepis diaspros | Israel | 1925 | |
| Stephanolepis diaspros | Italy / Central Mediterranean | 1967 | |
| Stephanolepis diaspros | Italy / Western Mediterranean | 1983 | |
| Stephanopyxis palmeriana | Belgium | To 2006 | |
| Stephanopyxis palmeriana | Germany / North Sea | 1990 | |
| Stephanopyxis palmeriana | Netherlands | To 2006 | |
| Stephanopyxis palmeriana | Sweden / North Sea | To 2006 | |
| Stephanopyxis turris | Iceland | 1997 | |
| Stephos cryptospinosus | France / Biscay Gulf | 2010 | |
| Stephos marsalensis | France / Biscay Gulf | To 2014 | |
| Sternaspis scutata | United Kingdom (Britain) / English Channel | 1986 | |
| Sternodromia spinirostris | Italy / Central Mediterranean | 1969 - 1972 | |
| Sticteulima lentiginosa | Israel | 2004 | |
| Stictyosiphon soriferus | Australia / Bass strait | 1969 | |
| Stolephorus indicus | Israel | 2015 | |
| Stolephorus insularis | Israel | 2009 | |
| Stramonita haemastoma | France / English Channel | 2018 | |
| Stratiotes aloides | Ireland | From 1836 | |
| Streblosoma pseudocomatus | Italy / Western Mediterranean | 1981 | |
| Streblospio benedicti | Denmark / North Sea | To 2017 | |
| Streblospio benedicti | France / Biscay Gulf | 1982 | |
| Streblospio benedicti | France / Celtic seas | 1982 | |
| Streblospio benedicti | France / English Channel | 2009 | |
| Streblospio benedicti | France / North Sea | 2009 | |
| Streblospio benedicti | Germany / North Sea | To 2006 | |
| Streblospio benedicti | Netherlands | To 2006 | |
| Streblospio benedicti | Russia / Baltic Sea / Kaliningrad area | 1997 | |
| Streblospio eridani | Italy / Adriatic Sea | 2016 - 2017 | |
| Streblospio gynobranchiata | Romania | 2011 | |
| Streblospio gynobranchiata | Russia / Black Sea | 2001 | |
| Streptosyllis varians | Bulgaria | 1966 | |
| Strongylocentrotus intermedius | China / Yellow Sea | To 2001 | |
| Styela canopus | France / Western Mediterranean | 2019 | |
| Styela canopus | Portugal / Iberian Coastal | 2015 | |
| Styela canopus | Portugal / Madeira | 2006 | |
| Styela clava | Australia / Bass strait | 1976 | |
| Styela clava | Belgium | To 1986 | |
| Styela clava | Canada / South-eastern Scotian Shelf | 2012 | |
| Styela clava | Canada / Southern Gulf of St. Lawrence and Eastern Scotian Shelf | 1998 | |
| Styela clava | Denmark / Baltic Sea | 1981 | |
| Styela clava | Denmark / North Sea | 1981 | |
| Styela clava | France / Biscay Gulf | 1979 | |
| Styela clava | France / Celtic seas | 1968 | |
| Styela clava | France / English Channel | 1968 | |
| Styela clava | France / North Sea | 1970 | |
| Styela clava | France / Western Mediterranean | 2004 | |
| Styela clava | Germany / Baltic Sea | 2017 | |
| Styela clava | Germany / North Sea | 1997 | |
| Styela clava | Ireland | To 1971 | |
| Styela clava | Italy / Adriatic Sea | 2021 | |
| Styela clava | Netherlands | 1974 | |
| Styela clava | Norway / North Sea | To 2011 | |
| Styela clava | Portugal / Iberian Coastal | To 2003 | |
| Styela clava | Romania | 2004 | |
| Styela clava | Spain / Iberian Coastal | To 2005 | |
| Styela clava | Sweden / North Sea | To 2023 | |
| Styela clava | United Kingdom (Britain) / Celtic seas | 1953 | |
| Styela clava | United Kingdom (Britain) / English Channel | 1953 | |
| Styela clava | United Kingdom (Britain) / North Sea | To 1998 | |
| Styela clava | United Kingdom (Britain) / North Sea / Orkney Islands | 2020 | |
| Styela plicata | Australia / Bass strait | 1966 | |
| Styela plicata | France / Western Mediterranean | 1950 | |
| Styela plicata | Greece / Eastern Mediterranean | 1968 | |
| Styela plicata | Israel | 1955 | |
| Styela plicata | Italy / Adriatic Sea | 1953 - 1955 | |
| Styela plicata | Italy / Central Mediterranean | 1972 - 1982 | |
| Styela plicata | Italy / Western Mediterranean | 1822 - 1830 | |
| Styela plicata | Portugal / Azores | To 2010 | |
| Styela plicata | Portugal / Iberian Coastal | To 2009 | |
| Styela plicata | Portugal / Madeira | 1992 | |
| Styela plicata | Spain / Iberian Coastal | To 2016 | |
| Stylocheiron sp. | Romania | 1978 | |
| Stylochus flevensis | Netherlands | 1921 | |
| Stylonema alsidii | Australia / Bass strait | 1977 | |
| Stylonema cornu-cervi | Turkey / Black Sea | 2000 - 2009 | |
| Stypopodium schimperi | Greece / Central Mediterranean | 2008 | |
| Stypopodium schimperi | Greece / Eastern Mediterranean | 1994 | |
| Stypopodium schimperi | Israel | 1995 | |
| Stypopodium schimperi | Spain / Canary Islands | To 2002 | |
| Suberites massa | Netherlands | To 1989 | |
| Suberites massa | United Kingdom (Britain) / English Channel | | |
| Suberites massa | United Kingdom (Britain) / North Sea | To 2002 | |
| Sycon raphanus | USA / California Current | 2012 | |
| Sycon scaldiense | Netherlands | To 1975 | |
| Syllidia armata | Netherlands | 1943 | |
| Syllis gracilis | Netherlands | 1940 | |
| Syllis hyllebergi | France / Western Mediterranean | 2019 | |
| Syllis hyllebergi | Italy / Adriatic Sea | 2014 | |
| Syllis hyllebergi | Italy / Central Mediterranean | 2008 | |
| Syllis hyllebergi | Italy / Western Mediterranean | 2008 | |
| Syllis pectinans | Italy / Adriatic Sea | 2013 | |
| Syllis pectinans | Italy / Western Mediterranean | 2013 | |
| Syllis pectinans | Spain / Iberian Coastal | To 2017 | |
| Symphyocladia marchantioides | Italy / Western Mediterranean | 1984 | |
| Symphyocladia marchantioides | Portugal / Azores | 1971 | |
| Symphyocladia marchantioides | Portugal / Iberian Coastal | From 2003 | |
| Symphyocladiella dendroidea | France / Biscay Gulf | 2005 | |
| Symphyocladiella dendroidea | France / Celtic seas | 2018 | |
| Symphyocladiella dendroidea | France / English Channel | 2022 | |
| Symphyocladiella dendroidea | France / Western Mediterranean | 1995 | |
| Symplegma brakenhielmi | Greece / Eastern Mediterranean | 2015 | |
| Symplegma brakenhielmi | Israel | 1951 | |
| Symplegma brakenhielmi | Italy / Central Mediterranean | 2016 | |
| Symplegma brakenhielmi | Italy / Western Mediterranean | 2014 | |
| Symplegma brakenhielmi | Portugal / Madeira | From 2015 | |
| Synagrops japonicus | Italy / Western Mediterranean | 1987 | |
| Synanceia verrucosa | Israel | 2010 | |
| Synaptula reciprocans | Greece / Eastern Mediterranean | 1995 | |
| Synaptula reciprocans | Israel | 1971 | |
| Synchiropus sechellensis | Greece / Central Mediterranean | 2018 | |
| Synchiropus sechellensis | Greece / Eastern Mediterranean | 2014 | |
| Syngnathus acus | Turkey / Black Sea | 2000 - 2009 | |
| Syngnathus acus | Ukraine / Black Sea | 2006 | |
| Synidotea laevidorsalis | France / Biscay Gulf | To 1975 | |
| Synidotea laevidorsalis | France / Celtic seas | 1975 | |
| Synidotea laticauda | Belgium | To 2005 | |
| Synidotea laticauda | France / Biscay Gulf | To 1975 | |
| Synidotea laticauda | France / English Channel | 2017 | |
| Synidotea laticauda | Germany / North Sea | 2011 | |
| Synidotea laticauda | Netherlands | 2009 | |
| Synidotea laticauda | Spain / Iberian Coastal | To 1996 | |
| Synurella ambulans | Belgium | To 2016 | |
| Syphonota geographica | Greece / Central Mediterranean | 2002 | |
| Syphonota geographica | Greece / Eastern Mediterranean | 2014 | |
| Syphonota geographica | Italy / Central Mediterranean | 1999 | |
| Syracolithus dalmaticus | Ukraine / Black Sea | 1990 - 1999 | |
| Syrnola fasciata | Greece / Eastern Mediterranean | 2012 | |
| Syrnola fasciata | Israel | 1949 | |
| Syrnola lendix | Israel | 1994 | |
