Local fishermen do not take their boats out for flounder in the bay. Researchers have been fishing there for a few decades. The latter's 30 nets yield different results depending on the day.

"Today's catch was rather poor, nothing to write home about. The nets yielded a few flounders, round goby and some ruffe. And then there were a lot of holes and chewed up bits of fish, meaning that the seals found our nets again last night," said Estonian Marine Institute ichthyologist Redik Eschbaum.

It turns out that the fact Küdema Bay is home to two species of flounder – Baltic flounder and European flounder – was only confirmed a few years ago. The two species are indistinguishable by appearance or taste. The only way to tell them apart is by genetically studying them.

The most important difference is that one species reproduces in the Baltic shallows, while the other undertakes a long journey to the island of Bornholm.

"They are both represented here and we would like to find out the species' relative abundance. They are different species and their reproduction areas are totally different. The European flounder goes to the deep places of the Baltic Sea to spawn," Eschbaum added.

Survey catches suggest that there are fewer flounder and younger specimens in the sea. The forecast isn't good for next year either.

Even though the round goby and flounder share the same menu, lack of food is not the reason the abundance of flounder is dwindling. Ichthyologists believe that the Baltic Sea's falling salinity and oxygen content as criteria crucial to the flounder's reproduction process are the main reasons.

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