Holy carp! Another invasive carp threatens to invade U.S.

The Prussian carp has quietly spread through waters of southern Alberta and can easily be mistaken for a wild goldfish.

A Prussian carp looks like a goldfish but is often silver. The fish is invasive and has found its way to Canada. Photo: George Chernilevsky - Own work, CC BY-SA 3.0

A Prussian carp looks like a goldfish but is often silver. The fish is invasive and has found its way to Canada. Photo: George Chernilevsky - Own work, CC BY-SA 3.0

In the Great Lakes region, conservationists and anglers have been keeping close tabs on the Chicago Area Waterway System for two decades.Two species of Asian carp – silver carp and bighead carp – have made their way north up the Illinois River and could potentially invade the Great Lakes by swimming through a series of locks and electrical barriers.

Asian carp have been in North America since the 1970s, and the first step to preventing the spread of invaders is to stop them from arriving here in the first place. Improved regulation of live animal imports may help, but in the meantime new invaders continue to arrive. 

The Prussian carp was first discovered in a small lake in Alberta in 2006.  Since then it has spread to nearly two dozen southern Alberta waterways and firmly established breeding populations. A recent study reported that the U.S. Fish & Wildlife Service considers northern states bordering Alberta to be at high risk of invasion. Other northern states and southern provinces are a good match for the climate preferred by Prussian carp. The Great Lakes region would likely support breeding populations if Prussian carp were introduced.

Although not closely related to high-profile Asian carp species (silver carp and bighead carp), the Prussian carp also eats zooplankton. Prussian carp have invaded many water bodies in Europe and the Middle East, and they have caused damage to other plankton-eating fish populations in some waters.

In appearance, the Prussian carp is very similar to a wild goldfish. In fact, it can be hard to tell them apart. Although they are classified as different species, Prussian carp and goldfish are in the same genus and they can cross breed. Prussian carp are smaller than Asian carp, with a maximum weight of about 11 pounds.

The strange thing about Alberta’s carp invasion is that no one knows quite how it started. The fish must have been imported into Canada at some point, perhaps along with a shipment of goldfish. The original fish may have been destined for pet shops or breeding in aquaculture facilities that raise goldfish and koi.

Aquarium hobbyists should take this as a reminder to never release live fish, plants, or invertebrates into the wild. In addition to being a problem in their own right, introduced fish can carry new diseases and parasites that harm native fish.

Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University and its MSU Extension, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 33 university-based programs.

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