Lindsay Chadderton, Nature Conservancy aquatic biologist
Are we on the verge of a global freshwater invasives explosion?
It's likely. Improved transportation, global trade and often unregulated importation of live organisms have meant that we're probably in the middle of another wave of damaging invasive introductions around the world, like the one that coincided with European colonization of the New World.
Here in North America, a wide variety of species and associated biological contaminants are being imported as live food, for aquaculture or for aquarium or water gardens, and we have very little understanding of the potential for these species to survive in the wild or what damage they can cause.
Give us an example.
Asian carps. That's a group of species imported for aquaculture purposes that have become established in the wild and threaten the biodiversity and fisheries of the Mississippi system.
Equally alarming is the seemingly innocuous sucker mouth catfish, a species imported as an algae cleaning fish for aquaria — they have become established in the wild in Florida and Mexico, reaching large numbers. These fish have been linked to disturbance of manatee and associated with declines in native fish species.
Most people have heard about zebra mussels and snakeheads. What are the top three aquatic invasive threats to the United States right now?
I think you have hit on two of the three and to these I would add the Golden mussel. They represent three invasive species at different stages of the invasion pathway.
First, I would lump zebra and quagga mussels together. After their initial introduction into the Great Lakes and spread into the Mississippi, North America is now going through a second major-range expansion of these mussels, following their establishment in the Colorado River systems.
Without drastic actions and changes in boating behavior, we are going to see these species rapidly spread across rivers and lakes of western United States and Canada, with potentially disastrous consequences for water supplies, agriculture, and biodiversity.
Second, snakehead are still in the early phases of range expansion. However, with the recent discovery of northern snakehead in Arkansas, we are on the verge of this species becoming permanently established in the Mississippi River, which would be a national disaster for this great river system and hundreds of endemic mussels, fish, reptiles and amphibians in this system — let alone the impacts on commercial and recreational fisheries.
Third, the golden mussel (Limnoperna fotunei) is an Asian shell fish that is presently not thought to have colonized North America — but it has invaded various streams in South America and has exhibited a wider environmental tolerance than zebra mussels, and similar ecological and industrial impacts. It could potentially colonize most of continental United States.