Prairie Parkway Follow-Up

Summary of IDNR Surveyof Big Rock Creek

By Tom Schrader
Vice President, Friends of the Fox River

In the last issue of The Riffle, the potential impact of the proposed Prairie Parkway on Big Rock Creek was raised as an issue of concern for Friends of the Fox River. In early October, the Illinois Department of Transportation (IDOT) announced they had narrowed the potential sites of the Parkway to two options. The northern end of both options closely approximates the originally “protected” route that crosses Big Rock Creek twice and parallels it closely for a large portion of its length. Almost the entire length of the Parkway’s route (north of the Fox River) lies within the Big Rock Creek watershed.

As noted in the Fall 2005 Riffle, IDOT commissioned the Illinois Natural History Survey (INHS) to sample fish and mussels in Big Rock Creek and the Fox River at potential Parkway crossing sites. While the initial field work for the INHS study was conducted in July, more field work will be conducted in Spring, 2006 prior to INHS submitting their report to IDOT.

The focus of this article is on the methodology and results of a comprehensive sub-basin biological survey of Big Rock Creek and its tributaries that was conducted by the Illinois Department of Natural Resources (IDNR) Region II Streams office in August, 2002 and July, 2003 (click here for the full IDNR report).

Description of the Big Rock Creek Watershed

The Big Rock Creek watershed covers almost 125,000 acres (194 square miles) in three counties (DeKalb, Kane, & Kendall) in northeastern Illinois. In addition to Big Rock Creek proper, the watershed includes four main tributaries to Big Rock Creek: Little Rock Creek, West Branch Big Rock Creek, East Branch Big Rock Creek, and Welch Creek. Other named streams that are tributaries of the main tributaries mentioned above include Battle Creek (tributary of West Branch), Harvey Creek (tributary of Little Rock Creek), and Young’s Creek (tributary of West Branch). The mainstem of Big Rock Creek begins at the confluence of the East and West Branches, about 1 mile southwest of the village of Big Rock and flows generally south and slightly east to its confluence with the Fox River just south of Plano.

The Big Rock Creek watershed contains eight communities: (starting from farthest upstream in the watershed) Elburn, Kaneville, Troxel, Hinckley, Big Rock, Little Rock, Sandwich, and Plano. Of these communities, Elburn, Hinckley, Sandwich, and Plano discharge effluent from wastewater treatment plants into Big Rock Creek or one of its tributaries. Some effluent from the village of Big Rock also is discharged into Big Rock Creek.

The watershed consists primarily of agricultural land and low density residential areas. The riparian areas along the mainstem of Big Rock Creek consist of a combination relatively steep, wooded bluffs, forested flood plain, and pastureland.

Methodology Used in the IDNR Biological Survey of Big Rock Creek and its Tributaries

Fish sampling occurred at 14 stations located throughout the watershed during August, 2002. Nine tributary stations and 5 mainstem stations were selected through a careful reconnaissance process which ensured that the full range of habitat types present within the streams of the watershed was sampled. For the purposes of this article, our primary focus will be on the five mainstem stations on Big Rock Creek.

Upon arrival at a station to be sampled, the survey team carefully measured the length of the station (ranged from 700 to 870 feet at the five Big Rock Creek mainstem stations) and placed block nets (1/4” seine nets) completely across the creek at the upstream and downstream boundaries of the station. The purpose of these block nets was to prevent fish from escaping from or entering into the station while the actual collection of the fish was occurring. Once the station was measured and blocked, the sampling team would prepare to collect the fish.

On Big Rock Creek, the primary fish collection method used an electric seine. The electric seine consists of a 30-foot electric cable strung between two brails and powered by a single phase, 1600 watt AC generator that is floated behind the seine in a small boat. Two members of the survey team manned the brails, another member of the team pulled the boat which contains the generator and the tank where collected fish are kept, while the rest of the survey crew fanned out behind the seine with fiberglass-handled (non-conductive) dip nets to net fish that were stunned by the electric current. While fish collecting was proceeding, a final member of the survey crew sketched a map of the station that highlighted the physical features of the stream and surrounding riparian area and also measured the width of the stream and the depth of the channel at various point in the station. This crew member also measured and recorded the air temperature as well as the temperature, turbidity, and conductivity of the water in the station. All members of the survey crew wore insulated waders to protect them from the electric field generated by the seine.

The survey team started at the downstream block net and worked their way upstream to the block net at the upstream end of each station. In the case of this survey, the average length of time to work an entire station was about 48 minutes. Fish that were captured by the survey crew were put into an aerated holding tank in the boat and held for processing at the end of the collection period. During the processing, larger fish, sportfish, and unusual species were identified, weighed and measured and then were returned to the stream. Smaller fish, which were impractical to identify in the field, were preserved in a formalin solution for later identification in the laboratory. A voucher specimen for each species found in a station was kept and preserved to be sent to the Illinois Natural History Survey fish collection in order to officially record that that species occurred at that particular station in Big Rock Creek.

Mussel collection was conducted at each of the fish collection stations the following year (in July, 2003). Each station was sampled using a protocol developed by an IDNR mussel expert which used hand-grabbing techniques and/or visual observation of the mussels in shallow water. Each station was sampled for four man-hours. During the sampling period, mussels were collected and placed into mesh bags. At the end of the sampling period, the collected mussels were identified, counted, aged and placed back into the stream. As with the fish, voucher mussel specimens were collected that typically consisted of the shells of dead mussels that were representative of living species found in the station. These voucher specimens were used to officially document the occurrence of those species within the creek with the Illinois Natural History Survey.

Survey Results

Perhaps the most exciting result of the Big Rock Creek survey was the collection of a State-endangered* greater redhorse (Moxostoma valenciennesi). Until the 1980’s, this fish was considered to have been extirpated from the state of Illinois, the last specimen having been recorded from Salt Creek (DuPage County) in 1901. In recent years, however, a total 26 specimens of greater redhorse have been found in the Illinois River basin (Retzer & Kowalik, 2002). These specimens were found in Aux Sable Creek (another Class A stream that will be potentially impacted by the Prairie Parkway), the Vermillion River, the Illinois River, and the Fox River (also impacted by the proposed Parkway). The presence of a greater redhorse in Big Rock Creek is exciting because it marks another step in this fish’s comeback from the brink of extirpation in Illinois.

Another exciting result of the survey was the presence of two State-threatened* mussel species: the spike (Elliptio dilatata) and the slippershell (Alasmidonta viridis). Additionally, the ellipse (Venustachoncha ellipsiformas), a specie that is intolerant of poor habitat, was found at six stations in the survey. The presence of these rare and intolerant mussel species is a testament to the quality habitat provided by Big Rock Creek.

A total of 38 different species of fish were found in Big Rock Creek (40 species were found in the watershed overall). Eleven of these fish species were intolerant of siltation and other types of habitat degradation. In addition to the greater redhorse mentioned earlier, one of the more notable fish collected was the mottled sculpin (Cottus bairdi), which occurs very sporadically in Illinois outside of cool-water stretches of tributary streams in the Fox River watershed. Recent temperature data collected by the IDNR Region II Streams Office indicates that sections of Big Rock and lower Little Rock Creek provide cool water habitat not often found in this part of Illinois. This cool water is a result of relatively high levels of groundwater discharge into the creek.

Other intolerant fish species collected within the Big Rock Creek watershed included southern redbelly dace (Phoxinus erythrogaster), hornyhead chub (Nocomis biguttatus), rosyface shiner (Notropis rubellus), northern hogsucker (Hypentelium nigricans), smallmouth bass (Micropterus dolomieu), black redhorse (Moxostoma duquesnei), shorthead redhorse (Moxostoma macrolepidotum), slender madtom (Noturus exilis), and banded darter (Etheostoma zonale).

A total of twelve mussel species were collected during the survey. In addition to the State-threatened spike and slippershell and the intolerant ellipse, other species found included elktoe (Alasmidonta marginata), cylindrical papershell (Anodontoides ferussacianus), plain pocketbook (Lampsilis cardium), fatmucket (Lampsilis siliquoidea), white heelsplitter (Lasmigona complanata), creek heelsplitter (Lasmigona compressa), giant floater (Pyganodan grandis), creeper (Strophitus undulatus), and lilliput (Toxolasma parvus).

The diversity of the fish and mussel populations found in Big Rock Creek denotes the high quality of the habitat. The quality of the habitat (for fish) is quantified by the Index of Biotic Integrity (IBI; Smogor, 2002). The IBI takes into account a number of factors including the number of native fish species present, the number of native intolerant species present, and eight other factors which pertain to the fish sampled. These factors, in combination with stream demographics such as width, slope, and location are then put through an equation that results in a single score that can range from 0 to 60 (0 equating to the lowest quality; 60 the highest).

The stream’s IBI score is used as the basis for determining the letter-based Biological Stream Classification (BSC; Bertrand et al., 1996). The IBI scores for the five mainstem Big Rock Creek sampling stations ranged from 52 to 59. All of these IBI scores fall within the Class A (or Unique Aquatic Resource) on the BSC. Less than 5% of the stream stations surveyed in the State of Illinois receive a Class A rating on the BSC.


In order to become more effective stewards of our natural resources, we need to become educated about their characteristics. The report on the biological surveys of Big Rock Creek and its tributaries conducted by the IDNR provides us with a wealth of information. The full report contains information about the physical characteristics of the watershed, the sampling methods used in the survey, maps and detailed descriptions of each of the stations sampled, and tables detailing the types and numbers of fish and mussel species collected. Our thanks go to the IDNR biologists (Bob Rung and Steve Pescitelli) who worked hard to conduct this survey and make it possible for us to have access to this type of information.

The IDNR report documents the presence of threatened and endangered species and the diversity of fish and mussel species that truly mark Big Rock Creek as a unique resource. It’s our responsibility, as concerned citizens, to use the solid information provided by our expert biologists and to act to help preserve and protect the creek.

Call or write your legislators and let them know what you’ve learned about the creek. Refer them to this article and to the original IDNR report (also found on our website) so they can become more fully informed and in a better position to make decisions that impact this wonderful resource.

Friends of the Fox River and all friends of a healthy environment need to work to ensure that Big Rock Creek is protected and preserved as one of the truly unique natural resources we have within our watershed. Working together as informed citizens, we can make a difference.


*As declared by the Illinois Endangered Species Protection Board


Bertrand, W.A., R.L. Hite and D.M. Day. 1996. Biological Stream Characterization (BSC): Biological Assessment of Illinois Stream Quality through 1993. Illinois Environmental Protection Agency. IEPA/BOW/96-058. Springfield, Illinois.

Retzer, M.E. & Kowalik, C.R., 2002. Recent Changes in the Distribution of River Redhorse (Moxostoma carinatum) and Greater Redhorse (Moxostoma valenciennesi) (Cypriniformes: Catostomidae) in Illinois and Comments on Their Natural History. Transactions of the Illinois State Academy of Science, 95, 4, pp.327-333.

Rung, R.C. & Pescitelli, S.M., 2004. Biological Surveys of Big Rock Creek and Tributaries, August, 2002 and July, 2003. Illinois Department of Natural Resources, Region II Streams Office, Plano, Illinois.

Smith, P.W. 1979. The Fishes of Illinois, University of Illinois Press. ISBN 0-252-07084-4.

Smogor, R. 2002. Draft Manual for Calculating Index of Biotic Integrity Scores for Streams in Illinois. Illinois Environmental Protection Agency, Bureau of Water, Springfield, Illinois.