At seven centimetres, the Chinese mystery snail may look big for an aquatic snail. But it's fairly unassuming.

However, Ken Donnelly of the Nova Scotia Invasive Species Council says this species can quickly outcompete other snails and change the water quality of ponds and lakes, making it a concern for Nova Scotian ecosystems. 

Donnelly says they are being seen more often over the past month. He said even his organization was surprised when it found several of the snails in its fishnets on a rece…