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Rapport2023Vetenskapligt granskad

Invasive species in the Baltic Sea and their impact on commercial fish stocks

Thor, P; Naddafi, R; Nadolna-Ałtyn, K; et al.

Sammanfattning

The brackish, semi-enclosed Baltic Sea is especially vulnerable to the possible negative impacts of invasive species. Here, we examine the effects on commercial fish stocks of four species established in the larger areas of the Baltic Sea. The round goby, established in all major basins of the Baltic Sea, has become an important prey for many predatory fish and birds, but it can also compete successfully with native fish for prey. Records of round goby feeding directly on commercial fish species are rare. The sea walnut, a ctenophore jellyfish, has invaded the southern part of the Baltic Sea, where it preys heavily on zooplankton, thereby potentially outcompeting planktivorous fish such as herring and sprat. Initial concerns that the sea walnut may prey on fish egg and larvae were put to rest after studies showed no such effects. The mud crab has become a stable component of benthic communities in most of the Baltic Sea. No negative effects of this invader have been reported; however, mud crabs have become an important prey for benthic fish in many areas. The fishhook water flea, a small planktonic crustacean, has invaded the Central Baltic Sea, and its role has become double-edged, in that it contributes significantly to the diet of herring, sprat and smelt in the Baltic Sea, while also competing with these other fish species for zooplankton as prey.

Publicerad i

ISBN: 978-92-9405-029-8Utgivare: European Commission