With a large-scale study, researchers want to investigate the effects of the increasing number of cormorants on the cod population in the western Baltic Sea. For this purpose, the excretions of the birds in Schleswig-Holstein, Mecklenburg-Western Pomerania and Denmark are to be examined, said the fisheries expert Christopher Zimmermann of the German Press Agency.
Fishermen in particular suspect cormorants of being responsible for the decline in stocks by eating young cod. They therefore demanded action against the birds. Zimmermann, head of the Thünen Institute for Baltic Sea Fisheries in Rostock, was less convinced. After the birds had almost become extinct, mainly due to environmental pollution, their population had recovered to such an extent that, according to Zimmermann's personal assessment, their protection status was no longer justified. "But to decimate them now in any form, without knowing what impact they have at all, in the absence of data, makes no sense at all from our point of view."
The study, financed by the state of Schleswig-Holstein, is scheduled to start in the summer. The aim is to determine what the animals have eaten based on the indigestible remains of fish in the excrement. In addition, an automated method using genetic analysis is being sought.
In addition to the herring of the western Baltic Sea, the cod was traditionally considered one of the bread fish of the German Baltic Sea fishermen and was important for their livelihood. In the meantime, its population has been decimated to such an extent that it can no longer be specifically caught. A few days ago, the International Council for the Exploration of the Sea (ICES) published its recommendations for the EU Commission on determining catch levels in the Baltic Sea. A closure of the fishery is still recommended for herring and cod in the western Baltic Sea, said Zimmermann, who is an ICES member.