Table 1: the species is currently present in 6 of them (endemic, native, introduced);
Table 2: possible in 0 of them (stray, questionable);
Table 3: absent from 3 of them (extirpated, not established, misidentification, error).
Table 4: all reports listed together.
Distribution: Western Atlantic: Hamilton River, Labrador, Newfoundland, Canada to northeastern Florida, USA. Occurs occasionally in Bermuda and French Guiana (Ref. 7251). Northern Gulf of Mexico (Ref. 26938). In Europe: Baltic Sea. Landlocked populations in Lakes Ladoga and Onega (Russia), both now extirpated. Occasionally recorded from Great Britain and North Sea in Elbe drainage (Ref. 59043). Recent research revealed that this species existed in the Baltic Sea, but is now extirpated (Ref. 83384, 83385). Near threatened globally, but extirpated in Europe (Ref. 59043).
The literature species report in a country is represented by an icon (a circle) in the middle of the
country polygon. Important: a report in the literature does not necessarily mean that the species is currently
present in the country! There are errors in literature, misidentifications, and some species have
been locally or globally extirpated or eradicated.
The patterns and colours of the icon give 4 additional indications (see the legend under the map
for the signification of the different colours and patterns):
Presence status: the colour of the ring (green: Present; orange: Possible; red:
Absent)
Introduction status: a white 'i' in the middle of the circle indicates that the species has been introduced,
if the presence ring is green it means that the species established itself or that we don't know the current presence status,
if the presence ring is red it means that the species did not established itself.
Threat status: the pattern of the ring (not dashed: not threatened or no information;
dashed: any status indicating that the species has a national threatened). Important: This is the national threatened status, not the global IUCN one.
Salinity status = milieu: the colours in the middle circle (blue: Marine; green: Brackish;
light blue: freshwater; dark green: Land).
How to interpret the map
The icon in a country polygon indicates that the species has been reported at least once in
the country, BUT NOT NECESSARILY that it is present IN THE ENTIRE COUNTRY.
It is particularly the case for large country such as Brazil, USA, Canada, Russia, China,
India, Indonesia, Australia, etc.
For example, a number of freshwater species present in western European countries are
also present in the western part of Russia, but not beyond the Ural mountains. Still the
icon for Russia is placed in its Asian part.
The icon is placed approximately in the middle of the country, even for the species that
are marine only.
For marine species, it does not mean either that the species is present in all oceanic coasts
of the countries (e.g., Altlantic and Pacific for USA and Canada).
So the map needs to be interpreted carefully, but we think it helps to give a quick view
of the distribution by country, in a better way than the textual list of countries when it is
over a dozen countries.
Table 1: Present in 6 countries/islands (endemic, native, introduced)
The map in this page was supported by BioFresh that has received funding from the European Union's Seventh Programme for research, technological development and demonstration under grant agreement No 226874
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The map in this page was supported by BioFresh that has received funding from the