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Report, 2021

Essential fish habitats in the Baltic Sea : identification of potential spawning, recruitment and nursery areas

Bergström, Lena; Erlandsson, Mårten; Putnis, Ivars; Gatt Støttrup, Josianne; Kallasvuo, Meri; Bergström, Ulf; Jokinen, Henri; Plikšs, Maris; Taal, Imre; Kokkalis, Alexandros; Brown, Elliot; Husa, Stefan; Saks, Lauri; Selnes, Terje; Svirgsden, Roland; Sundström, Linda; Yurtseva, Anastasia O.; Ustups, Didzis


Fish, as well as other aquatic organisms, are highly dependent on the conditions of their living environ - ment to sustain health and viable populations. Maps that identify the location of important habitats for key species are a valuable tool for marine management. The habitat maps can, for example, support the planning of environmental man - agement actions or contribute to an ecosystem-based maritime spatial planning.

There has so far been a lack of regionally coherent spatial in - formation on fish habitats in the Baltic Sea. Mapping is typically restricted by data limitations, which is enhanced by the need to identify potentially coherent data at the regional scale, and by the challenge of depicting dynamic population properties in a representative way on the map.

In the following report, we explore the possibility to produce regionally coherent maps on essential fish habitats in the Bal - tic Sea based on currently available knowledge. Our focus is on widely distributed fish species, and on spawning, nursery and recruitment areas, which represent central ecological functions that need consideration in marine management and maritime spatial planning. Based on the results, we develop a set of re - gional habitat maps for selected fish species and life cycle stages. New Baltic-wide maps representing potential spawning areas of herring, sprat, European flounder and Baltic flounder, as well as potential nursery areas of flounders are presented. Additionally, previously available maps on potential cod spawning areas, as well as perch and pikeperch recruitment areas are re-evaluated and improved.

Data to support the mapping of essential fish habitats has been recently enhanced by national and joint Baltic projects, and this fact was an important enabler of the current work. The presented maps hence represent the best available information at a coherent Baltic Sea regional scale at their time of develop - ment, supported and further refined by a subsequent Helcom review process.

However, sufficient data for mapping was not yet available for some parts of the Baltic Sea and selected species. It is sug - gested that these gaps are filled in future work. Also, points for further improvement are identified for the presented maps. To give a fuller representation of essential fish habitats one should especially include more information for fish in coastal areas and in the western Baltic Sea. One should also consider additional life stages for some of the included species, since both spawn - ing, nursery, feeding and migration areas are important exem - plifications of essential fish habitats. Another key area for de - velopment is to develop a stronger understanding on how the current distribution of functional essential fish habitat is limited by human activities, and how to improve management in these situations. These needs are even more emphasized by climate change, which is expected to have dramatic influence on the dis - tribution of fish and fish habitats in the future.

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Publisher: Helsinki Commission