Zebra mussels, an invasive species that kills native mussels and chokes drinking water systems, have been discovered in the Saint John River in New Brunswick, the farthest east in Canada they've been positively identified. Fisheries and Oceans Canada said last week in a release that environmental DNA tests over the summer had detected the presence of the small Eurasian freshwater mussels with the telltale striped pattern in parts of the river as far apart as Edmundston, Grand Falls and Nackawic, communities that span more than 200 kilometres.