OREGON STATE UNIVERSITY
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Crayfish are one of the most threatened groups of animals in the world. About 45 percent of North American crayfish species are considered to be at risk of extinction. However, a few crayfish species are among the world's most invasive freshwater organisms. Taking into consideration that invasive crayfish are the leading cause of decline in native crayfish populations, it seems that crayfish's greatest threat is other crayfish. Species Guide (PDF) | Related Activities | Video | Additional Resources |
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The American bullfrog is a highly reproductive aquatic species that is native in the central and eastern United States and southeastern Canada. This species was first introduced to western America as a food source (frog legs!); since then, it escaped aquaculture ponds and has spread widely. Bullfrogs lay up to 20,000 eggs each season and are voracious predators: they eat anything that fits in their mouth. Bullfrogs can be recognized by the large, round eardrums behind their eyes.
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The red-eared slider, also called the red-eared terrapin, is an American breed of turtle widely spread across the USA and is quickly becoming an invasive species in many parts of the world. It is also the most popular breed of pet turtle in the US and is widely kept as a pet around the world. This breed is the most commonly traded turtle of its kind. Species Guide and Related Activities | Video | Additional Resources |
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What ancient animal in modern times has a primitave spinal cord that may resemble the first vertebrates on earth, spends most of its life stuck to a boat or rock, produces an exoskeleton made of cellulose and is more associated with plants than animals? Tunicates are marine invertebrate filter feeders that colonize underwater substrates and can also be invasive. They can be spread by boats, fishing gear and aquaculture activities. |
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Colonies of millions of quagga and zebra mussels foul and clog pipes, water treatment plants, and dam turbines and give a competitive boost to toxic algae. It takes only one contaminated boat and the right conditions for zebra and quagga mussels to infest a new watershed; once they have been introduced and start to flourish, they are virtually impossible to control. | Related Activities | Video | Lesson Plan | Additional Resources |
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Knotweeds are a group of closely related invasive plants from Asia. They can grow to over three meters tall, with bamboo-like hollow stems and heart-shaped or lance-shaped leaves. They spread quickly and form tall, dense thickets. Knotweeds dominate stream banks, sides of roads, gardens, and other sunny, moist, and disturbed sites. |
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The nutria is a large, semi-aquatic rodent native to South America. Nutria were introduced to the United States for their fur. After a boom in nutria ranches during the 1930s, the animals escaped or were released from fur farms in the Pacific Northwest, Louisiana and other states, where they are now considered a threat to native wildlife, wetland habitats, water quality and human health. | Related Activities | Video | Lesson Plan | Additional Resources |
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Asian carps—fish in the Cyprinid family—have been part of our culture for centuries. We use them as ornamental aquarium fish (goldfish and koi) and food fish, and to help keep aquaculture ponds clean. However, when Asian carps escape into natural waterways, they can cause big problems for human health, the economy, and the environment. Four species of Asian carps have escaped in the United States and are of concern: grass carp, silver carp, bighead carp, and black carp. | Related Activities | Video | Lesson Plan | Additional Resources |
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The Chinese mitten crab was first identified in the south San Francisco Bay in 1992 by commercial shrimp trawlers, and quickly spread to the Sacramento and San Joaquin Rivers. The Chinese mitten crab threatens ecosystems, earthen structures, and fisheries by preying on and competing with many species, including fish eggs, clams, and mussels; and by eroding riverbanks, wetland edges, and levees. | Related Activities | Video | Lesson Plan | Additional Resources |
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Hydrilla and Brazilian elodea are invasive aquatic plants that occupy freshwater habitats. While hydrilla is native to Asia, Africa, and eastern Australia, and Brazilian elodea is native to South America, both plants are invasive to North America. Because these plants are related and both have pointed green leaves that whorl up the length of the stem, they may be difficult to distinguish at first glance. | Related Activities | Lesson Plan | Video | Additional Resources |
