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PRI's Environmental News Magazine

Midwestern Salmon Adapt

Air Date: Week of March 21, 1997

Every year, Lake Michigan is stocked with thousands of farm-raised Chinook salmon where the fish are a favorite among sportfishermen Recently, some of these salmon have started to naturally reproduce in a most unlikely place. As Steve Frenkel of the Great Lakes Radio Consortium reports, they've found ideal spawning grounds in the wastewater of a sewage treatment plant.

Transcript

RUDOLPH: Every year, Lake Michigan is stocked with thousands of farm-raised Chinook salmon. The fish are a favorite among sport fishermen. Recently, some of these salmon have started to naturally reproduce in a most unlikely place. As Steve Frenkel of the Great Lakes Radio Consortium reports, they found ideal spawning grounds in the wastewater of a sewage treatment plant.

(Running water)

FRENKEL: Chemical plants, steel mills and refineries line the south shore of Lake Michigan. But among all this industry is a small, tranquil stream. Rushes and young trees crowd the banks, and although the waterway seems natural it's not. The stream is manmade and the clear water coursing through it out to Lake Michigan is actually treated outflow from the filtering pools at the East Chicago sewage treatment plant. Christie Waldschmidt is an aquatic researcher at the plant. Recently, on a visit to the stream, she was surprised to find 2 Chinook salmon swimming in the clear shallow water.

WALDSCHMIDT: Every single day I come out here and I look for this kind of stuff. I track it in my field notebook and this is great. See, they're going up the pipe. That's exactly what we're looking for. That's amazing; I think it's amazing.

FRENKEL: Salmon need clean water to spawn. Some scientists say the fish are attracted to the sewage treatment plant because the water flowing from it is nearly as pure as a pristine stream. Roger Klocek is the conservation curator with Chicago's Shedd Aquarium.

KLOCEK: Here they've stumbled onto this springlike water. Even though it's manmade it's very much like a natural spring in the sense that the water quality is really good and the salmon sense this and know it and spawn successfully.

FRENKEL: Water quality at the East Chicago facility vastly improved in 1989 when new equipment was installed to meet stricter Environmental Protection Agency standards. Tim Early, director of the Aquatic Research Center in nearby Hammond, Indiana, says salmon began spawning in the treatment pools within a year after the plant stopped using chemicals.

EARLY: This plant disinfects with ultraviolet radiation rather than with chlorine or with ozone, which are chemicals that disinfect the water very, very effectively. But they produce a residual which is toxic. The ultraviolet light, in contrast to that, destroys harmful bacteria, and there's no toxic residual to be carried downstream.

FRENKEL: The absence of chlorine is important because even tiny traces of it can repel salmon.

(Gushing water)

FRENKEL: Salmon are legendary for battling fierce currents in their biologically programmed search for good spawning waters. To reach the plant, operations manager Peter Bararnyai says the salmon must swim up miles of polluted rivers. Their final hurdle is an enclosed manmade waterfall, or weir.

BARARNYAI: Salmon will come up from Lake Michigan, up the US Ship Canal, the Grand Calumet River, up 200 feet of our 60-inch discharge pipe, come to this weir that we're at now, and leap up 4 to 4 and a half feet into the disinfection content chambers.

FRENKEL: Inside the concrete pools where the water is disinfected, the salmon feed on dead bacteria and lay their eggs among the snail shells and freshwater sponges, possibly brought by other fish attracted to the plant. However, not all scientists credit East Chicago's treatment process for luring the salmon. Jim Francis is a fisheries biologist with Indiana's Department of Natural Resources.

FRANCIS: The salmon spawning is not necessarily due to clean water being produced by the treatment plant. What the sanitary district is doing is eliminating the sedimentation, which is allowing the salmon to spawn. It's not necessarily a water quality issue.

FRENKEL: But aquatic researcher Tim Early says if such skeptics are right, salmon would spawn in other streams that are free of sediment, and that's not the case.

EARLY: You can have an area that's totally free of sediment but has low dissolved oxygen. You can have an area that's free of sediment and has high dissolved oxygen but the water is toxic. This is very deadly to salmon eggs and to baby salmon. So you have to look at all the conditions and not just one.

FRENKEL: The treatment plant's manmade stream has created a wildlife habitat that's attracted more than salmon. Beaver, fox, rare migratory birds, and other species of fish have been spotted in or near the stream. Tim Early says other wastewater treatment plants could produce cleaner water and restore wildlife habitats if they follow East Chicago's lead and purify without chlorine.

EARLY: We can take this process and reproduce it elsewhere. And this becomes very important when you're dealing with other areas that discharge water to impaired or damaged environments. Because now we have the model by which we can take those damaged environments and start to reclaim them, bring them back to their good state of health.

(Flowing water)

FRENKEL: Meanwhile, the staff in East Chicago will be watching their waters closely. They began tagging young salmon born at the plant in 1995, and are hoping some of those fish will return to their birthplace to spawn as early as next fall. For Living on Earth, I'm Steve Frenkel.

 

 

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