My young son, Eli, and I ran to the river to see what was splashing. We arrived to see the flashing caudal fin of a fat goldfish spawning in the lush outgrowth of arrowleaf and elodea. This was a happy sound. The whole scene was bittersweet and happy.

The emergent and submerged aquatic plants are new growths along our section of the Chicago river channel near Montrose. Possibly because of the dry spring weather, water levels and flow rates have been low. Silt has settled, and the waters have become less turbid, more clear. Light reaches the bottom, encouraging dormant seeds to sprout and stretch for the surface. I saw five different aquatic plants: elodea, a milfoil, a pondweed, the tiny floating duckweed, a curly leaved thing I couldn’t place, and the brilliant, floating arrow-shaped leaf of Sagittaria. A matrix of destructive environmental changes–unseasonal fluctuations of water level, toxic pollutants, and excessive siltation–have chased these weeds from most of the Illinois waterway system over the last century. No weeds means no habitat for aquatic insect larvae, no shade for spawning and feeding fish, and consequently less food for dabbling and diving waterfowl. A big circle of dependencies has been broken and altered. The halting recovery currently taking place in the river system is pulling back together a few pieces of the hoop.

Eli sees and hears the thrashing, but can’t see the fish. Can’t turn his head fast enough. It’s like a trick, like being teased. I tell him it’s a fish doing that, squeezing out eggs into the milfoil. But it’s a mystery to him, this hidden underwater cosmos.

What’s going on with the fish in the Chicago river system? Sam Dennison, fisheries biologist for the Metropolitan Water Reclamation District (MWRD), has been surveying fish populations in our river system for more than 20 years. Systematic assays of fish communities are reliable indicators of stream quality. Numbers, quantities alone, are one part of the assay. “Over the past ten years we’ve seen a ten- to hundredfold increase in fish populations,” says Dennison. “Of course we were starting from a pretty low baseline. But these kinds of increases are certain evidence of improvement in fish habitat.”

It’s been almost ten years since our waste-treatment plants stopped chlorinating sewage effluent that is dumped into the North Channel at Howard Street. Since then alien species of carp, exotic, runaway goldfish, and their hybrids have been thriving. And the system has grudgingly allowed an increase in species diversity.

Last year 24 species were collected from the North Shore Channel, inspected, identified, and recorded. Each collection event was indexed to indicate biologic stream integrity using 12 metrics, or standards, and then assigned to one of six stream-quality classes. The scoring ranges from 0 (no fish) to 60 (Unique Aquatic Resource, i.e., an unperturbed, natural site). The metrics include species diversity; weight of catch; mix of insectivorous, omnivorous, and carnivorous fish; and percentage of fish diseased or abnormal. Fish catches for the North Shore Channel in 1993 ranged from a score of 20 (“poor” stream quality), just one point above the “very poor” classification, to a high of 34, “fair.” By weight 63 percent of these were carp, goldfish, or their offspring, but the catch also included some struggling natives and some welcome surprises, including golden, emerald, spottail, and spotfin shiners; bluntnose and fathead minnows; longnose dace; black bullhead; rock bass; green sunfish; pumpkinseed and orange spotted sunfish. A wonderful list. To finally meet families who had lived in the area for 50,000 years!

Damrong Mangkorn and Bernie Nessler stand on insulated pads on the bow of MWRD’s fishing boat, long-handled nets at the ready. Dennison is in the pilot’s chair, commanding the course of this odd-looking rig and monitoring the current flow from the 230-volt generator Sherry Sullivan has started up. The electrodes dangle into the water from two long Plexiglas booms extending forward into the shoreline weeds. The current stuns fish trapped within the range of the electric field. They loll to one side and are scooped up by the netters, then dropped, kersplash, into a tub of river water laced with a tranquilizer called Trance. We spend an hour fishing before returning to the larger Pollution Control Boat Number One to inspect and identify the catch.

“Carp. No knot head. Male, in flow, 490 centimeters, 4,200 grams.” Dennison moves methodically through his task. Sullivan records the data. “Knot head” refers to a vitamin deficiency common to carp in polluted streams that disfigures the head and gill area. “In flow” means flowing with milt, semen. As Dennison holds this magnificent fish, I see why carp are the subject of so many paintings in China and Japan, their homeland. This one weighs almost ten pounds; it’s coppery, gray green in color, with imperious trailing barbules, large scales decorated with fanlike markings, and prominent sharp spines leading the dorsal and anal fins. Just the size of this creature is impressive, the image of him lurking so silently by the shore.

“Carp–goldfish hybrid, humpback.” Dennison shows me the vestigial barbules that distinguish this fish from a goldfish. He counts the lateral-line scales to confirm that there are fewer than the 36 or more that characterize carp. “Humpback” is not a well understood abnormality, a growth just behind the head.

“White sucker. Dorsal and pectoral fin rot, hemorrhaging, 188 grams. This is what a lot of these fish are up against in this type of environment–constantly fighting off an abundance of bacterial and viral infections.” That’s part of what limits diversity, the inability of many species to thrive in an unpredictable eutrophic stew.

We find a golden shiner and one small but healthy bluegill, and many, mostly healthy goldfish. One large carp has an edema in the abdomen; it pisses out water through its urogenital pore, losing weight as it’s weighed. “Kidney failure,” Dennison says, looking deep into the fish’s gaping mouth. He tosses it, like all the rest, off the back of the boat into the soup, where they’ll shake off their stupor and reenter the mysterious rest of their lives.

The channelized, manhandled Chicago and Illinois river system is an anomaly that defies description or comparison to a natural watershed stream. To speak of restoring the system to a natural ecology is to speak of something that is not possible. Like restoring the State of Illinois Building atrium to a natural state by adding more potted plants. The North Shore Channel has no natural catchment area. Its watershed, its “headwaters,” are the toilets, sink drains, and gutters of a million urban homes. These waters carry their load of dissolved and suspended nutrients into the venous system of sewer trunk lines and arrive at the system’s “wetlands,” its kidneys, the water-reclamation plant at Howard Street in Skokie. There much of the nutrient load is removed and detoxified. What’s left is poured into the channel and comprises the main source of water and current in the North Channel. Upstream of the treatment plant, the channel waters are in a no-flow linear lake condition unless the sluice gates in Wilmette are opened to allow lake water to flush the system.

The poet Vincent Ferrini titled his book Know Fish. “The pitch is that only when we connect with the interior fishes are we discovering and extending life by the innate rules of the Earth, and thereby saving the self, the family, the city, and the planet.” What we have in the Chicago river system is one of the world’s largest aquarium and septic-system hybrids. It’s much more interesting and complex than the carefully controlled displays at the Shedd Aquarium. It’s our real-life, real-world experiment place, where a zillion players impact and interact. Dennison and his crew floated me through my first close encounter with the wild fish of my neighborhood.

Our stewardship of the Chicago River and the North Shore Channel over the past century leaves a lot to be desired. It’s like when you brought home your first goldfish in a bowl from Riverview and watched it slowly fade and go belly-up. And you learned at its expense that its water needs oxygen and green plants and snails. We won this real-life aquarium and all the stuff to put in it. Now we have to know it, tend to it, make it beautiful.