From the Archive: Carp eat other fish out

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October 19, 1929 | Vol. 16 | No. 445

Carp eat other fish out

Carp get the better of other fish whose waters they invade, literally by eating them out of house and home. This has been disclosed by the drainage of a small, carp-infested lake in southern Wisconsin, which was studied by Dr. Alvin R. Cahn of the University of Illinois. His results are reported in Ecology.

As the waters went down in the lake, all the fish were captured and counted. Out of a total of 6,006 fish, 5,891 were carp. More desirable species, like perch, black bass and pike, were notable for their absence or scarcity. By way of contrast, a similar total taken from a lake containing no carp had a good representation of several desirable game and food species.

The most notable difference between the two lakes, Dr. Cahn states, was to be seen in the plant population, which of course forms the ultimate food of all fishes. In the carp-less lake there was an abundant growth of many kinds of plant life, in the carp-filled water there wasn’t a weed. The restless, avid, all-eating mouths of the carp had destroyed every green thing.

The muddy bottom of the lake was entirely covered with little semi-round depressions about a quarter of an inch deep. These had been made by the carp, “mouthing” the mud to get the last traces of anything fit even for a carp to eat. Incidentally, of course, this constant stirring of sthe bottom effectually prevented the germination of any seed of a water plant that might have fallen into the lake, and also kept the water constantly roiled and muddy.

UPDATE | July 2, 2011

A new carp comes to town

Bighead carp swim freely in tanks at Chicago’s Shedd Aquarium, but major efforts are under way to keep this and other species out of the Great Lakes.

History indeed repeats itself, but — in the case of invasive carp — things may be worse the second time around.

Sometime during the 1800s, the common carp was intentionally introduced into American waters as a potential food source. As Alvin Cahn found in the 1920s, escaping carp did well in muddy-bottomed lakes, rooting around for food, making the waters turbid and damaging the ecosystem from the bottom up.

Today, there’s a new invader. In the 1960s, catfish farmers brought Asian carp to American ponds to clean up algae. Again, the fish escaped. Bighead and silver carp now reign in the Mississippi and other Midwest river systems.

Great efforts are under way to make sure the fish, which can grow to 100 pounds and reportedly eat between 20 and 120 percent of their weight in plankton and algae each day, stay out of the Great Lakes — where they’d probably sink the $7 billion fishing industry.

Control strategies include electrical underwater barriers and carp hunting. (Carp-seekers beware: This game jumps and has been known to break noses.) Some say the best solution is for people to eat the Asian carp. Though its common cousin couldn’t capture and retain the interest of American diners, perhaps the new invader will. In which case the present may break from the past after all. — Elizabeth Quill

Credit: M. Spencer Green/AP photo