I dont know exactly the law about the collection of wild fish.
I think you should contact the Ministry of Environment for more information
http://www.ypeka.gr/Default.aspx?tab...language=el-GR
About the link:Not threatened does not mean it is not protected

Gambusia affinis you can find easily in many public parks in Thessaloniki (will surely find a lot to a park opposite the building of the ERT, in the center of the city )
*Your name Andras is a Greek word and means "Man"