Previous attempts to identify different populations of European sprat during the 1980-1990s were unsuccessful (Nielsen 1994). Gulf of Lyon and the Adriatic Sea populations have the “biggest genetic distance” within the Mediterranean and any population differentiation was found between the Baltic Sea, the North Sea and the Bay of Biscay (Debes et al. 2008). Genetic analysis showed a clear genetic distinction from the NE Atlantic Ocean and the Baltic Sea and a high differentiation of the Adriatic Sea population from all northern samples (Limborg et al. 2009). More recently, a “complex population structure is considered across the species’ distribution” (Limborg et al. 2012). Nevertheless ICES recommends the conduction of further studies to clarify this structure (e.g. apparent overlap between North Sea and English Channel spratts) thus here we consider the existing assessment units (ICES 2014):
- Celtic Sea and West of Scotland in Subarea VI and Divisions VIIa–c and f–k
- Skagerrak and Kattegat in Division IIIa
- North Sea in Subarea IV
- English Channel in Divisions VIId,e
- Baltic Sea in Subdivisions 22–32.