Essential fish habitat (EFH) map on Potential recruitment areas for pikeperch was prepared in PanBalticScope project (co-founded by the European Maritime and Fisheries Fund of the European Union) http://www.panbalticscope.eu/

Pikeperch (Sander lucioperca) is a species of freshwater origin, which spawns predominantly in freshwater tributaries and has a relatively limited dispersal away from its recruitment area. Species distribution modelling studies have shown the importance of suitable environmental conditions for pikeperch recruitment. Due to lack of coherent data on pikeperch spawning and nursery areas across the Baltic Sea countries, the distribution of pikeperch recruitment areas was delineated based on areas with suitable conditions of depth, wave exposure, salinity, water transparency (Secchi depth) and distance to deeper (10 m) waters. The threshold values were obtained from literature. Temperature, although important for pikeperch, was left out due to high variation in timing of suitable spawning temperatures across the Baltic Sea. The map on pikeperch recruitment areas was originally developed within the HOLAS II project (HELCOM 2018) when it was approved by all HELCOM Contracting Parties in a dedicated review process after correction to Swedish waters. The map was subsequently considered by the Pan Baltic Scope project, who proposed adjustments to Estonian, German, Lithuanian and Polish waters.

Stock: Several, undefined

EFH type: Recruitment areas

Approach: Environmental window with national approach for Finnish waters, selected data points corrected for Estonian, German, Lithuanian, Polish, and Swedish waters.

Variables and thresholds: Depth < 5 m, Logged exposure < 5, Salinity < 7, Secchi depth < 2, Distance to deep (10m) water < 4km. Based on the model for the Finnish coastline, pikeperch recruitment areas were defined as: Unsuitable for reproduction: P(catch larvae) < 0.5, Suitable for reproduction: P(catch larvae) > 0.5, Important for reproduction: the smallest area where the expected cumulative larval abundance is 80% of the total expected abundance over study area.

Quality: Recruitment area here refers to essential habitats for young-of-the-year pikeperch (based on inventory data from spawning until the end of the first summer). The map is based on literature and environmental variables, derived from inventory data. The species distribution modelling studies, where the thresholds values for environmental variables have been obtained, are from the northern Baltic Sea. Also, the data layers on environmental variables are based on modelling. Here, same thresholds have been applied in the southern Baltic. Due to these constraints, the data layer should be considered as a rough estimation. In addition, temperature is important for pikeperch recruitment but was not included as a delineating variable due to high variation in timing. The data layer may underestimate pikeperch in Finnish waters with respect to habitats for young-of-the-year pikeperch, as it focused on newly-hatched larvae when the dispersal is more limited compared to later in the season.

Attribute information: Raster value representing the potential occurrence of pikeperch reproduction area (either 0 or 1).

References:

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- HELCOM (2020) Essential fish habitats in the Baltic Sea – identification of potential spawning, recruitment and nursery areas

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- Veneranta, L, L Urho, A Lappalainen, and M Kallasvuo (2011) Turbidity characterizes reproduction areas of pikeperch (Sander lucioperca (L.)) in the northern Baltic Sea. Estuarine, Coastal and Shelf Science 95:199-206