What’s up with that: Why are the big fish schooling near the NU bridge?


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.

The RoundTable could not get Northwestern to answer our questions, so the RoundTable took pictures of the fish and sent them to the experts at the Chicago’s Shedd Aquarium. According to Shedd fish and research teams, the fish are acting normal for what are probably common carp or grass carp based.

The Shedd scientists sent photographs back to the RoundTable explaining 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. They can grow as long as 4-5 feet.

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.

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