The Mystery of Catfish in the Study Pond

Pauline pond-dips

This week, while preparing for a pond-dipping program at Volo Bog’s study pond, our Conservation Education Representative Pauline noticed schools of little black critters swimming around in the pond. At first we assumed they were tadpoles, but the schooling behavior was unusual - upon further inspection, we realized they had little fins and whiskers. She hadn’t found hundreds of tadpoles, she’d found baby catfish!

Northeastern Illinois is home to a few different species of catfish. But how did they get in there to breed in the first place? The study pond is at a higher elevation than the bog and isn’t connected to any other bodies of water. And not only is it populated by catfish fry; we also observed schools of minnows in the sunlit water.

If you’ve visited other ponds, you may have witnessed this sort of thing before. Fish appear seemingly out of thin air. Of course, we know that spontaneous generation is a myth of the past, but how then to account for this?

As it turns out, the secret may be birds. Some fish have sticky eggs that can attach to the legs of waterfowl and be transported to new bodies of water. Both minnow and bullhead catfish eggs fit this description. While uncommon, it’s very possible that our baby catfish’s parents landed in the study pond when their eggs got stuck to a duck.

Baby catfish in the Study Pond

The mystery may be solved, but now we ask: what will become of all these baby catfish? Unfortunately, the vast majority of them will probably not survive to adulthood. The pond is too small to support dozens of full-sized adult catfish. The good news is that this is very common in nature; many animals have lots of offspring without expecting them all to reach adulthood. The study pond is frequented by herons and other wildlife that will happily eat small fish, so the young that don’t survive will still strengthen the local food web.

All of this is a great reminder of nature’s ingenuity. Fish get into places you’d never expect in surprising ways, and their numerous young are a valuable food source for several different predators. It’s all part of the cycle of life.