Parks Canada says genetic traces of zebra mussels found in a recent water sample taken from Clear Lake aren’t cause for undue concern. Although tests for environmental DNA for the invasive species came back positive last month, it could have come to the lake on a boat, water toy or other source, without the transfer of any living mussels. Living organisms like zebra mussels, which originated from the lakes of southern Russia and Ukraine and were introduced to many countries worldwide in the 1980s, shed DNA all the time, says Borden Smid, resource conservation manager with Parks Canada.