Meanwhile, almost two decades ago the zebra mussel, an invasive species, invaded the lough.

Almost two decades ago the zebra mussel invaded the lough.

Zebra and quagga mussels are both freshwater species, native to Eastern Europe, with the zebra mussel growing up to 2 inches in length, and the quagga mussel slightly bigger.

Recently, she said, she was warned about the possible presence of a small mollusk called zebra mussel in moss balls commonly used in fish aquariums.

Oregon - and much of the region - has largely avoided a zebra mussel invasion through strict monitoring of watercraft, according to Fish and Wildlife officials.