LLINOIS STREAMS: A Classification Based on 
heir Fishes and an Analysis of Factors Responsible 
or Disappearance of Native Species 
ILLINOIS HAS MANY different drainage systems. 
is bounded on the west, south, and southeast by 
eat rivers and on the northeast by Lake Michigan. 
jithin its borders it has many creeks, rivers, ponds, 
id artificial lakes, plus a few glacial lakes in the 
mtheastern corner of the state. Thus it is not sur- 
ising that almost 200 species of fishes have been 
corded in the state. The great number of streams 
\d variety of stream habitats are primarily responsible 
r the richness of the Illinois fauna. 
As a group, fishes are tolerant and adaptable or- 
nisms that can survive considerable habitat abuse, 
it the ecological tolerances of the many different 
ecies vary tremendously. The presence of fish indi- 
tes little about the condition of a stream, but a 
owledge of the assemblage of species and _ their 
merical relationships provides the ichthyologist with 
excellent biological picture of the water course 
d its well being. When such information is available 
er a long period of time, fishes can be one of the 
st sensitive indicators of the quality of the aquatic 
vironment. 
From time to time for more than a hundred years, 
thyologists at the Illinois Natural History Survey 
1 other agencies have conducted censuses of Illinois 
les so that, in a sense, changes in the aquatic envi- 
ment have been monitored all this time. A particu- 
y thorough collecting program spanned the period 
m 1876 to 1905 and culminated in publication of 
classic “Fishes of Illinois” (Forbes & Richardson 
8). The collecting stations are shown in Eigwl; 
ther program, begun in 1950 and recently com- 
ted, was even more thorough, thanks to modern 
isportation facilities. The collecting stations are 
wn in Fig. 2. A wealth of information on changes 
ish populations and aquatic habitats in Illinois has 
n assembled by comparing distributional patterns 
census data from the two surveys, and this in- 
nation is available to interested agencies. 
Analysis of these data has made it possible to as- 
| virtually all of the streams in the state ratings 
xcellent, good, fair, or poor. The ratings are based 
the species composition of the hundreds of collec- 
Ss available. It has also been possible to detect 
term changes, and to identify factors that are 
———— 
his paper is published by authority of the State of Illinois, 
Ch. 127, Par. 58.12. It is a contribution from the Section 
aunistic Surveys and Insect Identification of the Illinois 
ral History Survey. Dr. Smith is a Taxonomist and Head 
€ Section of Faunistic Surveys and Insect Identification. 
Philip W. Smith 
responsible for each stream’s deterioration and each 
species’ change of status. 
Owen F. Glissendorf, Technical Editor of the Sur- 
vey, edited the manuscript. Lawrence M. Page aided 
in the analysis of data and critically read several pre- 
liminary drafts of the manuscript. He and R. Weldon 
Larimore provided counsel in many areas. Douglas 
W. Schemske compiled the counts of species known 
from each drainage system by consulting species dis- 
tribution maps. Since 1962, Alvin C. Lopinot and his 
staff in the Division of Fisheries of the Illinois Depart- 
ment of Conservation have deposited in the Survey 
collection hundreds of fish collections made through- 
out the state. I have made free use of information 
assembled in the series “Surface Water Resources” for 
Illinois counties issued by the Division of Fisheries 
and recommend these publications to anyone inter- 
ested in more specific detail about his own county. 
CLASSIFICATION AND 
DESCRIPTION OF STREAMS 
The following annotated list of stream systems rates 
each stream on the basis of fishes presently known 
to occur in it and its potential for harboring others. 
A rating of excellent signifies that the expected species 
are still present in a numerical relationship to each 
other that indicates little modification of the stream 
from its original condition. Good, fair, and poor are 
self-explanatory. Consideration has been given to the 
varying adequacy of sampling different stream Sys- 
tems. Unusual species and habitats, if present, are 
noted, and sources of problems in the stream, if they 
can be identified, are indicated. 
The order of treatment is roughly north to south. 
Stream systems are numbered and can easily be lo- 
cated on the accompanying map (Frontispiece). Tribu- 
taries of the river cited are discussed only if their 
condition differs from that of the main stream. Near- 
by small streams that are not tributaries are some- 
times included because of their proximity and simi- 
larity. For example, Menominee, Smallpox, and 
Sinsinawa creeks are not tributaries of the Galena 
River, but they are close to the Galena River, and it 
is convenient to treat the four streams as one unit. 
The Mississippi, Ohio, Wabash, and Illinois rivers are 
not included in the annotated list, but their species of 
fishes are included in the counts for the stream systems 
if records are available for sites near mouths of the 
streams. 
