Few people see fish the way Josh Sherwood does. Sure, casual observers may notice the minnows that dart away as they look down from a bridge, and anglers learn the habits and haunts of the bass, catfish and other species they hope to catch.
But Sherwood, who's a fisheries research scientist with the Illinois Natural History Survey (INHS), looks at a different picture. He's interested in the entire gamut of fish that inhabit Illinois streams, and he's quick to point out they are much more diverse and striking than you might think.
For an example, he calls attention to the arrestingly colorful, 3-inch-long rainbow darter, which is common in appropriate habitat throughout the state. During the breeding season, a male rainbow darter's sides are marked by alternating bars of vibrant blue and orange, colors that dominate on its fins, too. Below, it may be yellow, green or red, and there's another splash of orange around its gills.
Most nonscientists never lay eyes on rainbow darters or the many other nongame fish that dominate our waterways — including myriad other darters, shiners, suckers and sculpins — because we can't see them where they live, and we don't have sufficient cause to pull them out of the water for a look.
Of course, pulling fish out of the water for a look constitutes a major part of the job for Sherwood and his colleagues.
Here's how they survey a reach of stream. Two people stretch a block net across the downstream end, taking care that it connects with the streambed. Then another team approaches them from upstream with a lightly electrified seine, which stuns fish as they approach. Other team members follow close behind and scoop up the fish with dip nets, then deposit them in live wells where they're held until the collection is finished. The scientists weigh the fish, measure them and record their species, then return them to the stream.
Currently, Sherwood is in charge of fieldwork and sampling for a survey of the fishes of Champaign County, a project with very deep roots. It has been run at intervals of about 30 years, going back to the late 1800s, and this is the fifth installment.
As they work on this project, Sherwood and company are building on the legacy of giants in their field. Their predecessors include Stephen A. Forbes, the first director of the INHS and an early definer of ecology as a field, and R. Weldon Larimore and Phillip W. Smith, who pioneered the statewide study of the ecology, distribution and conservation of fishes in the 20th century.
To date, Sherwood and his team have completed fieldwork at 65 of the 172 sites the survey will encompass, and they anticipate finishing work at the remainder next year. Most of the sites yet to be surveyed are in the Sangamon River watershed, but a few are smaller streams that were too dry for sampling thanks to this year's drought.
In the watersheds where fieldwork is largely complete — which include portions of the Kaskaskia, Embarras and Vermilion rivers — they have found roughly the same mix and numbers of fish that were found in the last survey, with one notable exception.
In the Saline Branch, just downstream of the Urbana-Champaign Sanitary District's northeast plant, and further downstream, in the Salt Fork of the Vermilion River, fish species diversity has increased dramatically.
In the Saline Branch alone, the number of species collected rose from about 30 in the late 1980s to 45 this past summer.
What accounts for the change? Sherwood hesitates to speculate, since much work with the data is to be done. But it's natural to focus on possible changes in the flow emanating from the UCSD plant, since it constitutes such a significant portion of the total in the stream.
When we spoke, Sherwood said it was his understanding that shortly after the previous survey, the UCSD began to remove chlorine (which is used as a disinfectant) from its discharge, and that would do a great deal to promote aquatic life.
Environmental Almanac is a service of the University of Illinois School of Earth, Society and Environment, where Rob Kanter is communications coordinator. Environmental Almanac can be heard on WILL-AM 580 at 4:45 and 6:45 p.m. on Thursdays.