Happy Fish Friday, everyone! It’s the end of Invasive Species Awareness Week, so I just wanted to highlight some fairly common, yet highly disruptive species.
Grass Carp (Ctenopharyngodon idella): Grass Carp are a large member of the minnow family. They are native to eastern Asia and Russia. They were first brought over to the US in 1963 as a biological control for vegetation at aquaculture facilities in Alabama and Arkansas. Soon after, the Arkansas stock escaped when the local rivers flooded their ponds. Since then, Grass Carp have spread far and wide due to stocking efforts, both legal and illegal. They are often sold for home or residential pond use, assumed to be triploid fish (meaning they cannot reproduce) but that is not a guarantee. If history repeats itself, which it does, the rivers flood, and the fish escape these ponds into a new system. Grass Carp have been found in at least 45 states and are highly established in a majority of them. These fish impact ecosystems primarily by removing aquatic vegetation. This removal leads to loss of cover, decreased aquatic macroinvertebrates (food), and increased turbidity from runoff. They grow to roughly 60 inches and have been recorded to weigh over 90 pounds!
A large Grass Carp taken from the Wabash River, IN. Credit: Paul DeRolf.
Range map for all/recent findings of Grass Carp. Credit: USGS NAS program.
Brown Trout (Salmo trutta): Brown Trout are members of the salmon family and possibly one of the most popular “sport” fish species out there. Native to Europe, northern Africa, and western Asia, fish from Germany were first brought over to the US in 1883 and stocked in the Pere Marquette River, Michigan by the US Fish Commission. They have been stocked in 47 different states, as well as multiple Canadian Provinces, most with little success in obtaining natural reproduction. This lack of success has led to periodic, even yearly, stocking events to maintain populations. The introduction of Brown Trout has been followed up with many negative impacts on native fishes. Brown Trout outcompete native Brook Trout for food and habitat, which forces them to move and be exposed to predators. Brown Trout have also led to the demise of other native trout, as well as minnow and sucker species, out west. These fish will continue to be stocked in our waters as long as recreational anglers are willing to pay for them. Browns can grow to 50 inches and over 100 pounds.
Brown Trout from a lake in central Vermont. Credit: Paul DeRolf.
Range map showing all/most recent areas where Brown Trout have been found. Credit: USGS NAS program.
Round Goby (Neogobius melanostomus): We have covered the Round Goby before but it never hurts to revisit something. They are native to the brackish water of Eurasia but can also be found in freshwater systems. The Round Goby first appeared in the US in 1990 where it arrived through the ballast water of cargo ships. They are widespread and continually reproducing in all of the Great Lakes, and have been slowly making their way into the numerous tributaries. Recently, they have been recorded outside of the Great Lakes system within the Illinois River watershed of Illinois. Round Goby have a generalist diet, meaning they eat just about anything, which allows them to outcompete and harm native species populations. Their expanding range could, and most likely will, lead to decreased diversity of Darters and Sculpin. These fish can reach lengths of roughly 9 inches and weigh less than a pound.
A Round Goby taken from the West Branch DuPage River, IL. Credit: Paul DeRolf
Range map showing the most recent areas occupied by Round Goby. Credit: USGS NAS program.
Please remember to never move fish, or anything, outside of their native range, and if they are already moved around don't spread them any further. No matter what, always make sure to enjoy, protect, and enhance our freshwater ecosystems!
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