Checklist of Baltic Sea Macro-species - IOW

1. Introduction
1.1 Checklists
Checklists are comprehensive lists covering all
species of a certain group known to occur in a specific
area. They are of great importance in providing
an overall view of an area’s diversity, its species
composition and its biological history.
In the field of biology, checklists have a longstanding
tradition stretching back to the early
naturalists. The list functions as a living document;
species being added or, in some cases, removed
as time passes and new species are discovered or
established species become extinct or are merged
with other species. As science progresses there
are also changes in taxonomy, especially following
the major advances in genetic research. For some
groups this means that over time the same species
can have several, sometimes as many as twenty,
synonyms in the literature. This information is also
added to the checklists and enables researchers to
track the occurrence of a species through historic
literature. At times scientists and researchers work
consecutively on the same checklist ensuring it is
up to date both in terms of species composition
and nomenclature. In this way they make sure that
it can be used in the present although it has its
roots a hundred years back.
1.2 HELCOM checklist of Baltic
Sea species
In 2009, the Helsinki Commission was tasked with
creating a comprehensive Red List of Baltic Sea
species. One of the first steps in compiling such a
list was to establish which species are present in
the Baltic Sea. To achieve this, expert teams were
set up to prepare checklists for each of the following
groups: macrophytes, benthic invertebrates,
fish and lamprey species, waterbirds and marine
mammals.
To date most checklists have concentrated on a
particular group of species. For example, checklists
have been compiled for species within a certain
family or order, or for species that are found in
a particular region (e.g. within certain national
borders). The HELCOM checklist of the Baltic Sea
species goes further in that it aims to cover all
macro-species simultaneously and the Baltic Sea in
its entirety. In this sense the HELCOM checklist is
unique.
The HELCOM checklist compiles information on the
taxonomic group, the scientific name and author,
synonyms, a minimum of one valid taxon code in
taxonomic databases or other taxonomic reference,
distribution data and a minimum of one reference
confirming the occurrence (historic and/or present)
of the species in the Baltic Sea.
If a species is included in the HELCOM checklist, it
does not automatically mean it was present in the
Baltic Sea at the time the checklist was published.
Some observations are historical and the only way
to confirm the presence of a species is to undertake
new inventories in the area previous occurrence
1.3 Work on the checklists
In the HELCOM checklist, the Baltic Sea species
have been divided into five groups: Macrophytes,
Benthic invertebrates, Fish and lamprey species,
Baltic breeding birds, and Marine mammals. Each
group was assigned its own team of experts. The
teams were comprised of experts from countries all
around the Baltic Sea and they worked to collect
data from the whole Baltic Sea area. This document
combines the checklists that were compiled
by the experts and functions as the HELCOM
checklist of Baltic Sea species. The experts in each
team are listed at the start of the corresponding
chapters.
Although other checklists have also focused on the
Baltic Sea and its species (e.g. Nielsen et al. 1995),
these lists have all been regional and/or focused on
a specific group of species. The existing checklists,
as well as literature studies, databases, personal
communications and data provided by the various
Baltic States, have all been used to draw up the
five checklists reported here. For transparency,
each observation included in the present checklists
has been allocated a reference code and the corresponding
reference can be found in either the
relevant documentation section (see Chapters 2 to
6) or by contacting the experts listed in Annex 1.
Because the starting point for each checklist is
slightly different, some aspects of the checklists
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