The zebrafish (Danio rerio) were initially engineered to glow blue, green, or red for research purposes before developers started marketing them as pets, calling them Glofish, Science says. It adds that though their sale was banned in Brazil, some fish farms still breed them and stores still sell them.
Researchers from the Universidade Federal de São João Del Rei have studied the escaped fish to gauge whether they had enough resources to establish reproductive populations. As they reported recently in Studies on Neotropical Fauna and Environment, the researchers found that the fish were generalists, eating algae, plankton, and more, and that they have reproductive activity most of the year.
"They are in the first stages of invasion with potential to keep going," first author André Lincoln Barroso Magalhães from São João Del Rei tells Science.