-by Tommy Palmgren
Likely to have been brought to the Baltic waters via ships’ ballast shifting, the Round Goby fish ( Neogobius melanostomus) is spreading through the Baltic Sea coastal areas.
The authors of Helcom Baltic Sea Environment Fact sheet 2012[1] points out
that the Round Goby is an invasive species[2], taking over the ecological site of the indigenous Gober niger , perfectly thriving in brackish environment and feeding on a variety of mussels, arthropods and small animals therefore also competing with other fish like flatfish and eelpout. It has also ousted Perch and Pike.[3] Itself being important prey for cod, perch, cormorants and Grey heron. Also actually considered tasty by Polish fischermen. It has in a few year spread along the Baltic first reported from The gulf of Gdansk and can now be found all the way from the Danish straits to eastern side of the Bothnian bay. It quickly has spread wherever introduced in brackish waters[4]
It has depleted or diminished locally the mussel banks.
In his article Increased spread of the fish round goby in the Baltic Sea, Magnus Thorlacius argues that it has been established that the new populations outside Gotland and Åland of Round gober consists of more active and aggressive individuals compared to the older from Hel and Swarzewo one of them just outside Gdansk. Round gober usually become very numerous in invaded areas. They investigated stress hormones in these populations and compared them to already long term- established ones. Surprisingly although they multiply to extreme densities in a few years individuals held in very high densities seem to have lower levels of stress hormones. It all complies to that this species will spread at a very high rate probably altering the ecology in costal marine areas.
Authors:
Monika Michalek – Departement of Aquatic Ecology, Maritime institute, Poland
Riikka Puntila – HELCOM Secretariat; Solvita Strake. Latvian Institute of Aquatic Ecology
Malin Werner – Swedish Institute of Agricultural Sciences,Department of Aquatic Resourcesm, Institute of ..Marine Research.
“Abundence and distribution of Round Goby”
Accessed 5 july 2016 [http://helcom.fi/Baltic-sea-trends/environment-fact-sheets/biodiversity/abundance-and-distribution-of- round – goby]
[1] In Swedish waters alone over 20 million tonnes ballastwater is discharged but on a worldscale three to four billion tonnes are shifted between different parts of the world.
Bernes, Claes. (2005). Changes beneath the surface-An in-depth Look At Sweden´s Marine environment. P 146
The Swedish Evironmental Protection Agency
[2] Ponto-Caspian origin
[3] Bernes, Claes(2005). Ibid p 148
[4] Also for instance to the Northamerican lakes with the ballastwater of freighters.
source the second article written by Magnus Thorlacius:
“Increased spread rate of the fish round goby in the Baltic Sea”
http:phys.org/news/2015-12-fish-goby-baltic-sea.html
[5] Thorlacius, Magnus (december 16,2015) Increased spread of the fish round goby in the Baltic Sea.
Discovery of a Sustainable Baltic Sea 