The Three-Spined Stickleback takes over in the Baltic Sea

In recent years, the stickleback has increased dramatically in the Baltic Sea. According to an as yet unpublished study that Vetenskapsradion has taken part in, it is estimated that in some places there is eleven times as much stickleback as it was 20 years ago.

Marine ecologist Agnes Olin at the Swedish University of Agriculture is a co-author of the study and tells Vetenskapsradion that there are several reasons why the stickleback is increasing in number.

-It’s a good thing that there are fewer predatory fish both here on the coast but also in the lake, for example less cod that can eat the sticklebacks, says Agnes Olin.

The stickleback also benefits from overfertilization and from high temperatures.

In a worst-case scenario, the stickleback can take over more and more bays in the Baltic Sea until there is not much perch and pike left, whose eggs and fry the stickleback likes to eat.