Catfish are being used to help remove pollution from the Chicago River. A nonprofit group called Friends of the Chicago River has been putting the fish into the river system as a way to measure the effects of water pollution and clean up the river.
In 2011, the city of Chicago took a mandate from the Environmental Protection Agency to start the cleanup of the notoriously polluted river system. Since then, work on cleaning up the river has been intense. Earlier this year, the Friends of the Chicago River group released more than 195,000 baby channel catfish into the river. They also created 400 nesting cavities from permeable concrete tubes that are designed to mimic submerged logs.
This fish release represents the largest such release in the history of the river. Experts say that they should notice the effects of the catfish by the time they mature to adulthood in about four to five years.
While the catfish are native to the waters of the region, they have been limited in number because of the river’s poor water quality and the lack of appropriate habitats. The water in the river has become largely degraded because of the high presence of nitrogen and phosphorus, which has resulted in an overabundance of algae.
Hydrologist Dale Robertson explains, “At first, the nutrients help the algae to grow over-abundantly, and the fish can eat more. But then the algae becomes so much, then it dies and decomposes, taking the oxygen out of the water. It’s like putting food into an aquarium. If you put too much in, you have problems.”
Currently, the Chicago River has too much algae, and while it serves as a food source for the catfish, the algae is starting to go rotten. With too much nitrogen and phosphorus, algae has run amuck in the river. These materials are largely the result of sewage that is being dumped into the river. Now, the city is working to disinfect its treated wastewater before it is dumped into the river.
By adding catfish into the river, officials are hoping that the creatures will be able to clean up the excess algae. Additionally, officials have also started using the algae itself in wastewater treatment plants. The algae is said to consume excess phosphorus, making the water cleaner. Together, the catfish and the algae will work as a team to clean up the water in the Chicago River.