They can eat up to 100 percent of their body weight or more in plant matter every, day-denying that food to native fish-but they only digest about half,leaving the rest as waste.And some may carry parasites (寄生虫) that infect native fish.
●Bighead carp:An Arkansas fish farmer first brought bighead carp to the US from China in 1972 to clean out algae from fish farms. By the early 1980s,a few began appearing in open waters of the Mississippi and Ohio rivers after escaping from fish farms.Bighead carp are now found in at least 18 states,but their desire to eat algae hasn’t always been that strong-they prefer zooplankton
(small animals present in the water)
to phytoplankton
(small plants present in the water).
●Silver carp:Introduced in the 1970s,most likely via another Arkansas fishfarm escape,silver carp are now legendary for launching themselves into the air when scared, often at the sound of motorboats.Their forceful leaps can injure any people on the water. If you’re a skier, you can’t ski where there are a great many silver carp. That just wouldn’t be smart.But it isn’t the only threat from silver carp-their main food is phytoplankton,the tiny algae that mussels (河蚌) need to survive.
●Black carp:Although black carp aren’t officially established in the US, many fishermen from the Gulf Coast to Illinois and Missouri have reported catching them more often lately. While their relatives feed themselves on plants and plankton overhead,black carp stay low to hunt snails and mussels,causing a great danger to Great Lakes mollusks (软体动物) that are already hurt by other invaders.
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