The herring in question, long known to Swedish fishermen as the Slåttersill, is visibly larger than its Baltic brethren. Now, in their latest Nature-published research, researchers from the University of Uppsala, Sweden, have proven that the Slåttersill is a genetically distinct type of herring from other herrings.
The Slåttersill resembles the Atlantic herring more than the typical Baltic herring, but unlike its Atlantic and Baltic cousins, it feeds not on plankton but on small fish. Scientists have observed at least two separate populations of this species in the waters near Stockholm - and note that it spawns in mid-June off the coast of Sweden.
Researchers suspect that piscivorous herring came from the Atlantic and evolved in the Baltic Sea over the thousands of years of its existence, changing its diet because of an opportunity to fill an ecological niche. This is because large predatory marine fish, such as mackerel or tuna, do not live in this sea.
Including the Szczecin and Vistula Lagoons, the Polish Baltic coast is 775 km long, and the area of this sea belonging to Poland (including internal waters) covers over 10,000 km2.
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Source: IAR, PAP