What is big, scarily unattractive and gathering underneath and on both sides of the bridge connecting Northwestern University’s campus with the lake fill area?
The RoundTable was surprised at the answer.
But really, the RoundTable was just generally surprised at the behavior of the fish: More big fish than could easily be counted were bunching up on either side of the bridge, stymied from going into the artificial lake because of the rocks forming a dam, but ignoring the open access to the bigger waters of Lake Michigan.
Northwestern did not provide an answer, so the RoundTable sent photos of the fish to the experts at Chicago’s Shedd Aquarium. According to Shedd fish and research teams, the fish are probably common carp or grass carp.
The Shedd scientists explained the differences between the two types of carp:
- Common carp have an elongated dorsal (top) fin, barbels or whiskers on either side of the mouth and a thicker body structure.
- Grass carp are thinner, have no barbels near the mouth and no scales on their head and a single dorsal fin.
- Both species can grow up to five feet long.
According to the Clean Lakes Alliance website, carp can weigh as much as 80 pounds and live an average of 20 years. (Who knew?) Spring to early summer is their breeding season and “female carp can produce hundreds of thousands of eggs during the breeding season.”
Carp are edible, though they have a strong flavor and darker meat. (Traditionally, carp is one of the primary ingredients in gefilte fish. Pro tip: Ambitious cooks, if you make your own gefilte fish from scratch, may we strongly advise you befriend a local fishmonger and order deboned and ground carp.)
The RoundTable also asked the Shedd why the carp were acting in a way that seemed counter-intuitive to the fish’s health and welfare.
Johnny Ford, the Shedd’s Director of Public Relations, forwarded the scientists’ response. It said: “Common carp prefer shallow water with soft bottoms and because they root around eating a variety of foods, which includes aquatic vegetation, and insects from the bottom, they often stir up the sediment.
“Sounds like they aren’t stuck in there, but rather are likely taking advantage of food and are feeding in there and will swim out later. They usually hang out near the bottom of the water column, which might explain why you don’t usually see them. Maybe because it’s so clear right now, that’s why you’re seeing them recently.”
Glad we asked. Now we know.
The carp are doing the same behavior at the south end of the Chicago Botanic Garden in the big pod south of the prairie. They act there like they are breeding, stirring up a lot and being real close together.
Grass carp are one of the Asian carp and are considered invasive, aren’t they? I had thought that none of the Asian carp species had yet reached Lake Michigan, but I may not have the most current info. Do we know whether grass carp have been found in Lake Michigan yet?
Very interesting! Although it is disappointing to read “scarily unattractive” within the first five words. They’re fish. Just … fish. There’s already a big enough problem of people being disconnected from, afraid of, and oblivious to the nature in this town, and we shouldn’t add to it by calling fish scary and unattractive just because they’re existing.
Thanks so much! This has been a question that has fascinated me every time I walk by.
Super interesting. I always enjoy watching them. Thx!