INVASIVE SPECIES EDITION—Where we take a moment to explore the species that threaten the Great Lakes region.

 

They may not be what comes to mind when you think of invasive carp, but grass carp can have drastic and lasting impacts on aquatic ecosystems and water quality. Originally from eastern Asia, they have been introduced the world over as a biocontrol for aquatic weeds and can now be found in over 70 countries. 

This wide range is made possible by their versatility—not unlike the hydrilla they are sometimes employed to eliminate. Grass carp can live in water temperatures from below freezing to over 100ºF, can survive in brackish waters, and are able to tolerate low-oxygen environments. 

 
While they live mostly in slow moving and still waters, eggs are spawned in fast rivers, and must remain suspended for two to four days before they hatch. From there, grass carp grow quickly—as much as 10 inches in the first three months. An adult can grow to be upwards of 4 feet in length and more than 50 pounds on a diet of mostly aquatic weeds. But they have also been known to consume detritus, insects, and other invertebrates as well.  
 
Grass carp were first brought to the U.S. in 1963 when they were imported from Malaysia and Thailand to aquaculture facilities in Alabama and Arkansas. Their first release into the wild is believed to have happened three years later when some escaped from the U.S. Fish and Wildlife Service Fish Farming Experimental Station in Stuttgart, Arkansas. Planned introductions began in 1969 in an effort to control nuisance plants. By the end of the 1970s, grass carp had been introduced in 40 states. Today it can be found in 45 states, with well-established populations throughout the Mississippi River Basin.
 
Grass carp are a highly regulated species, and for good reason. Because they are so adept at consuming plants, there is a risk that these veritable aquatic lawnmowers might leave a waterbody completely devoid of plant life and wipe out the food supply for other fish, insects, and waterfowl. A lack of plant life can also spur on algal blooms, which in turn lower oxygen levels. And without roots to keep sediment secure, the water is likely to become muddied, and spawning beds for other fish can be destroyed. 
 
Because of these and other risks, grass carp used for weed control are sterilized by shocking the eggs with drastic changes in either temperature or pressure. But this process is not 100 percent effective, and fish sometimes escape into the wild. In some states, including Illinois, the use of grass carp is restricted to private ponds or pools. Those thinking about using the fish for personal use are encouraged to explore other weed-control options.  
 
 

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🌊 Boost Your Great Lakes Literacy in 3 Easy Ways!1️⃣ Read the Great Lakes Literacy Principles2️⃣ Join a Sea Grant professional learning event3️⃣ Explore Great Lakes educational resources📬 The summer edition of the Center for Great Lakes Literacy newsletter supports all three—and more!Perfect for educators, environmental leaders, and curious minds.👉 Subscribe today and dive into a world of Great Lakes learning: https://conta.cc/3ZtrIKc or the link in bio.
Don’t miss this opportunity to enhance your teaching skills and connect with fellow educators! Join us for a two-day, water-themed workshop on August 8-9, 2025, at the Dunes Learning Center located in Indiana Dunes National Park. Open to all 5-12th grade formal and non-formal educators, this event offers a chance to explore the natural world, network, and receive exclusive access to the newest Project WET Educator’s Guidebook: Water in Earth Systems.The registration deadline is July 18th.Learn more at the link in bio.
📣 Aquaculture Teacher Workshop – June 2025🗓️ June 26–27, 2025📍 Purdue University – John S. Wright Forestry Center🕐 Starts June 26 at 1 PM | Ends June 27 at 4:30 PM🌿 Optional Pre-Tour: June 26, 10:30–11:30 AMExplore Aquaculture & Aquaponics in Action!Perfect for science teachers looking to bring hands-on, real-world STEM into the classroom.What’s Included:✔️ Facility tours at Purdue & nearby✔️ Build-your-own aquaponics system (FREE to take home!)✔️ Hands-on labs & classroom integration ideas✔️ $250 stipend for travel or classroom supplies✔️ Open to formal and non-formal educatorsLearn how aquaculture is a powerful tool for engaging students in science, sustainability, and food systems!Spots are limited – register early!Learn more at the link in bio.
IISG is hiring a part-time pollution prevention outreach assistant. IISG’s pollution prevention team addresses water quality issues affecting the Great Lakes coasts and the inland waters of Illinois and Indiana, specifically focusing on contaminants of emerging concern like pharmaceuticals, microplastics and marine debris, and PFAS. This outreach assistant will support the pollution prevention team by developing outreach activities and engaging with communities to share that knowledge.Learn more and apply at the link in bio.
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