Full text of "Man's effect on the fish and wildlife of the Illinois River"

' L I B R A FL Y

OF THE
UNIVERSITY
or ILLINOIS

cop .2

"MUHAL HISTORY
SURVEY

V'.

MAN'S

EFFECT

ON THE FISH

AND WILDLIFE

OF THE ILLINOIS

RIVER

inois

Natural History Survey
Biological Notes No. 57
Urbana, Illinois
June, 1966

f^ATUHAi

mio,]f

JU/^ .-:

Harlow B. Mills, William C. Starrett, and Frank C. Bellrose

TE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION NATURAL HISTORY SURVEY DIVISION

Fig. 1. — Illinois Ri\< r and its drainam' basin, indicating
thr main features discussed in the text. Approximate limits
of the drainage basin arc indicated by the heavy broken lines.

LAKE
MICHIGAN

CHICAGO

COVER PHOTO: Natural History Survey crew taking dissolved oxygen readings with a galvanic oxygen analyzer. Photo
by George W. Bennett.

MAN'S EFFECT ON THE FISH AND WILDLIFE
OF THE ILLINOIS RIVER

Harlow B. Mills, William C. Sfarrett, and Frank C. Bellrose

THIS IS A DOCUMENTED REPORT on changes
in the Illinois Ri\er, primarily in the past 75 years,
with emphasis on the biological modifications which have
occurred and are occurring as a result of man's activities.

The Illinois Ri\er has been called the "most studied"'
ri\er in the world. Certainly there is a great heritage of
biological information obtained from this stream. We
have drawn freely on the observations of Kofoid, Forbes,
Richardson, and many others, and have included more
modern observations which we and some others have
been in a position to make.

The river has not shown steady changes from year to
year. Rather, many of them have occurred with great
rapidity and some have not been permanent. For ex-
ample, the acreage of water, which went up greatly due
ic) di\ersion from Lake Michigan in 1900, was reduced
almost to its pre- 1900 surface by 1913. This reduction
was due to the development of levee districts, which
claimed and drained large areas of the floodplain, and
subsequently to decreased lake water diversion in the
19.30's.

Most of the observations in this publication relate lo
the main stream and its lateral bottomland lakes, t)ul
these areas are only what the basin makes them.

THE RIVER AND ITS BASIN

Till' basin of the Illinois River and its ti ibutarii'S is
comprised of 32,081 scpiare miles, which is more than
half the area of the state of Illinois (Bariows 1910: 1).
The name "Illinois" is applied to that part of the chain-
age below the confluence of the Kankakee and Dcs
Plaines rivers southwest of Chicago, the Kankakee
rising in Indiana and the Des Plaines in Wisconsin. The
group of glacial lakes in the northeast part of the state
drains into the Illinois River through the Fox Ri\cr.
The Illinois River is 272.4 miles long, and ilii- cniirc
waterway from Lake Michigan lo the mouth of ihc
river is 327 miles long. 1 he livcr flows nearly west lo
Hennepin where it turns abiuplly southwest, arriving
at the Mississippi near Grafton, above St. Louis (Fig. 1 ).
Thus, it traverses a large section of l\ni slate, and is
affected by and affects the majority of the stale's citizens.

Barrows (op. cit.) referred to the Illinois valley as
the most conspicuous topographic feature of Illinois. Ilr
stated that, ". . . certain peculiarities of ihc lower Illinois

This j)apc'r is puhlishrct by aulhorily i>f the Stale of IltiiiiiiH. IR.S CM,
127, Far. .iH.Ili. It is a ( ntitriliutioii frtiiii tlie SectioiiN of A(|ii.'itir ftinltii^y
and Wildlife Kpsrarrli of the Illinois .Natural History .Survey. Dr. Harlow
B_. Mills is Clhief of the Survey. Dr. William C. Starrell i.s an At|iia(ir
Biologist, and Frank C. Bellrose is a Wildlife Spcrialist.

render it unic|ue among rivers, the region is one of par-
ticular interest. . . . The lower Illinois presents a second
peculiarity in its remarkably gentle fall. . . . The average
fall between Hennepin and Pekin, a distance of .5.'). 8
miles, is 0.82 inch per mile. The Illinois is a river of
relatively insignificant volume. Its natural low-water dis-
charge is less than that of the Rock River and but a
small fraction of that of the upper Mississippi and Ohio
rivers. The nearly level channel and the small volume
result in a very sluggish river, which has bei'n described
as a stream that 'more nearly resembles the Great Lakes
than an ordinary river,' and again as one that 'partakes
more of the nature of an estuary than of a river.' It is
wholly unecjual to the task of washing forward the sedi-
ment delivered by its headwaters and its numerous
tributaries. . . . The average fall of the lower Illinois is
less tlian that of the Mississippi below the mouth of the
Illinois. This is tin- reverse of the normal relation be-
tween tributaries and their main streams."

This unique condition for a river has been brought
about by the present stream flowing through much of
its lenglh in a valley developed in the late Pleistocene
epoch. During that lime a much larger water volume
produced by receding glacicis fashionetl llie present
physiogiaphy.

It might be well lu-ic lo describe the Illinois Ri\fr's
bottomland lakes (lateral levee lakes). The river, flow-
ing in its uimsually wide valley and carrying a silt load,
drops more of this silt at the quieter edges than in the
more rapid stream center. This builds u]3 low natural
levees along ils shores. Overflow of ihe river at high
water leaves large impoundments behind these levees
as the water recedes. Usually these impoundments are
shallowly connected with the river al iheir upper anil
lower ends.

Man's trealnienl of the i i\cr has tended lo aggravate
ils natural tendency to deposit sediment. The building
of several dams across the river for navigation purposes
iias lendfd lo slow the water even more. Also, the greater
tillage (if the agi icultural ujjland has increased the
amount of sill that is carried into the quiet mainstream
waters.

The Illinois River was the highway for exploreis of
the area, and early settlements were made on its shores.
Many early writers were impressed by it.

Following an ascent of the Illinois River in 1673,
Marquette (Kenton 192.5) wrote as follows: "We lia\e
seen nothing like this river that we enter, as regards to
its fertility of soil, its prairies and woods; ils cattle, elk,
deer, wildcats, bustards, swans, ducks, parroquets, and

even beaver. There are many small lakes and rivers.
That on which we sailed is wide, deep, and still, for
65 leagues."

Thomas Jefferson (1787:13) wrote "The Illinois is
a fine river, clear, gentle, and without rapids; insomuch
that it is navigable for batteaux to its source." In 1838
Captain Howard Stansbury described the valley as "one
to five miles wide, deeply overflowed in every freshet.
filled with bayous, ponds, and swamps, and infested with
wild beasts . . ." (Mulvihill and Cornish 1929:27).

To come down to the beginning of the present
century, Kofoid (1903:151-155) described the river
and its bottomland lakes at a high water stage in May,
as it was just above Havana: "As we leave the sandy
shore of Quiver we traverse the clear, cold, and spring-
fed water along the eastern bank with its rapidly grow-
ing carpet of Ceratophyllum [coontail], and in a few rods
note the increasing turbidity, rising temperature, and
richer plankton of the water which has moved down from
the more or less open and slightly submerged bottom
to the north. . . . The water [of the river] also appears
much more turbid by reason of silt and plankton, and no
trace of vegetation is to be seen save occasional masses
of floating Ceratophyllum or isolated plants of Lcmna,
Wolffia, or Spirodda [duckweeds]. ... As we plunge
into the willow thicket on the western shore we have to
pick our way through the accumulated drift lodged in
the shoals or caught by the trunks of the trees or the
submerged underbrush. . . . From this dark labyrinth we
emerge to the muddy but cjuiet waters of Seeb's Lake
with its treacherous bottom of soft black ooze. We next
enter a wider stretch of more open territory with scat-
teied willows and maples and a rank growth of semi-
aquatic vegetation, principally Polygonums [smartweeds].
The water is clearer and of a brownish tinge (from the
diatoms) , while mats of algae adhere to the leaves and
stems of the emerging plants. A flock of startled water-
fowl leave their feeding grounds as we pass into the wide
expanse of Flag Lake. We push our way through lily
pads and beds of lotus, past the submerged domes of
muskral houses built of last year's rushes, and thread
our way, through devious channels, among the fresh
green flags and rushes [probably river bulrush, Scirpii.i
fimnatilis] just emerging from the water. Open patches
of water here and there mark the areas occupied by
the 'moss' or Ceratophyllum, as yet at some depth below
ihc surface. The Lcmnaccae [duckweeds] are every-
whiic li>(li;(d in mats and windrows, and amidst their
green, one occasionally catches sight of a bright cluster
of Azolla [moscjuito fern]. The water is clear and brown-
ish save where our movements stir the treacherous and
mobile bottom. . . . Thompson's Lake, the largest ex-
panse of water in the neighborhood, is wont to be rough
in windy weather, but if the day be still we can see the
ricli aquatic vegetation which fringes its margin and lies
in scattered masses toward its southern end. Its waters
seem somewhat turbid, but more from pl.mklon lli.ui

from silt, though the deep soft mud which forms much
of its bottom is easily stirred. . . . The new vegetation
is already springing from the decaying and matted stems
of the preceding summer."

Later in the season when the water was at a low-
stage, Kofoid (op. cit.:155) noted, "The backwaters
have been reduced to the lakes, sloughs, bayous, and
marshes which abound everywhere in the bottom-lands."'
Flag Lake had lost its connection to the river and was
a "sea of rushes." Thompson Lake still maintained a
connection of sorts with the Illinois through a slough,
and was choked with vegetation at its southern end.
Quiver Lake was completely choked with aquatics ex-
cept for one narrow channel where clear, ojjen water
prevailed.

The present-day condition is well described by Star-
rett and Fritz (1965:88) : "Today Quiver Lake is de-
void of aquatic plants. The formerly deep basin of the
lake has been filled in with 4- to 8-foot deposits of
silt. Turbid water at depths of over 3 feet and a soft.
flocculent bottom prevent the establishment of aquatic
plants in the lake. Conditions in Quiver Lake are dupli-
cated in many of the other floodplain lakes of the Illinois
River: that is, in the past 35 years siltation has greatly
changed the ecology of these lakes."

HUMAN POPULATIONS AND ACTIVITIES

In the early days of exploration and settlement of
Illinois the rivers were the arteries of travel, communica-
tion, and commerce. It was not until the era of rail-
roads that the people of Illinois were in a great measure
emancipated from the rivers.

Little concern was shown about changes in. or the
changing of, the Illinois River for the first 250 years of
its use by white people. Its character seemed to remain
about the same, although the greatest flood ever re-
corded for the river was in the 1840's. Steamboats made
their way far up its reaches in the 19th centuiy. Cities
sprang up along its shores and. near the headwaters.
Chicago began its growth. Events happened rapidly
from the last ciuarter of the 19lh centuiy to tiie present
time.

To gi\e a simple illustration of the development in
(lie river's basin, the population of the counties which
are all or in part drained by the Illinois River changed
from about a half-million in 1850 to 1.629.738 in 1870.
Hv 1964 this figure had risen to 8.537.900 of a total state
population of 10.500.000.

Man has made several major changes in the river
itself. On January 1. 1900. the Sanitary and Ship Canal
was opened at Chicago, connecting the Des Plaines and
Illinois rivers with Lake Michigan. The great quantities
of water thus diverted flushed untreated domestic sew-
;ige and industrial wastes down the canal and into the
Illinois River system. This directed these materials
away from the lake, which the city used as a source for
its water supply.

Forbes & Richardson (1919:140-141) reported an
average rise of 2.8 feet at Havana as a result of this
diversion, and between Juno and September the level
rose an average of ;?.6 feet abo\e piediversion averages.
This flooding had several effects on the river. It penna-
ncntly inundated tliousands of acres, ultimately kilting
bottomland forests. Where trees like the pin oak
[Qucnus lialtistiis) and the pecan (Carya illinocnsi\)
were in\()l\ed, this meant a loss of food for mallards
and wood ducks, but tiiere was also a considerable in-
crease in water surface whicli was beneficial to the fish-
ery. Forbes and Richaidson (op. cit.:141) conunenlcd
that Thompson Lake increased in surface from 1,94;5 lo
5,072 acres. As late as 1940, dead snags from this
"drowned forest" were still in evidence, hut time and
man's later activities have erased most of the traces of
the old lakes, sloughs, and bottomland forests which
existed prior to the 1900 diversion.

These same authors (op. cit.:142) give a good ac-
count of the effects of this inundation : "This destruc-
tion of inshore and alongshore vegetation has been
especially conspicuous in the broad belt of deadened
trees and shrubs along the banks, especially in the middle
course of the stream from Peoria southward. Otiier im-
portant effects arc beginning to appear as these dead
trees weaken and fall into the water of the stagnant
lakes, fouling them, in the hottest weather, with the
products of vegetable decay."

In 1848 the Illinois-Michigan Canal was opened,
and in 1907 the Henne]3in Canal connected the Illinois
with the Mississipjji. Drainage of bottomlands for agri-
cultural purposes followed closely on the heels of the di-
version from Lake Michigan. Actually drainage started
in a small way prior to 1900 (Mulvihill and Cornish
1929:38), but most of the drainage enterprises were ini-
tiated between 1903 and 1920. The last levees were
started between 1918 and 1921. Initially there were
400,000 acres subject to overflow between La Salle and
Grafton. At the height of the drainage period iheic
were 38 drainage districts and three private drainage
areas aggregating 200,000 acres. Spring and Thompson
Lakes, long known for their fisheries and their concen-
trations of waterfowl, were eliminated as were a host
of smaller lakes and sloughs. How drainage and levees
have changed the floodplain near Havana is illustrated
by Fig. 2.

There has been some aliandoiunent of drainage
districts. Prior to 1920 the Partridge District, across
from Chillicothe, failed, and after the Hood of 1926
the Chaulauc|ua Levee District near Ha\ana and llie
Hig Praiiie Levee District near Heardslown were discon-
tinued. These abandonments resulted in a return of
8.000 acres to fish and wildlife habitat.

Another human activity has conspicuously changed
the river. Hefore 1900, low dams were buill at Mar-
seilles, Henry, Copperas Creek, La Grange, and Kamps-
ville. Because they were low, their greatest effect on the

stream was during periods of low water. During the
1930's. higher navigation dams were built at Dresden
Heights (22 ft ) , Marseilles ( 24 ft) , Starved Rock ( 19 ft j ,
Peoria (11 ft), and La Grange (10 ft). Moreover, a
navigation dam on the Mississippi at Alton raised water
levels in the Illinois River as far north as Hardin.

Barge traffic on the ri\er is now very heavy, and
there is a conseciuent effect on the turbidity of the water
in the main stream and adjacent waters.

Soil pollution has been present in Illinois River
waters since the recession of the last ice sheet. However,
the laying bare of the soil in agricultural operations has
greatly increased the problem.

A study of Lake Decatur, on the Sangamon River,
a tributary of the Illinois, showed that the rate of sedi-
mentation was about 20 percent greater in the decade
starting in 1936 than it was in the preceding 14.2 years
(Brown, Stall, & DeTurk 1947). In one county above
the impoundment row crops increased from 39 percent
of the total area in 1924 to 64.5 percent in 1943. There
is a probable cause-and-efTect relationship here. This
sedimentation is a serious matter to organisms that live
in the water as well as to those that use it. Further, it
displaces water. Where waters are stilled, the load of
silt is dropped, and the water is replaced by .soil.

In 1964, in the counties drained wholly or in part
by the Illinois River 6,220,200 acres were planted to
corn for grain which was valued at .$530,288,900. and
an additional 3,466,100 acres were planted to .soybeans
(Illinois Cooperative Crop Reporting Service 1965).
Thus, in these counties 47 percent of the land surface
in 1964 was in row crops which leave the soil vulnerable
to erosion.

The streams thai flow into the Illinois have a steeper
gradient than dfH-s the Illinois in its central and lower
reaches. Since the ri\er is impounded and the gradient
is low, it has difficulty carrying its silt load. Therefore
a tremendous amount of this turbid burden is deposited
in the remaining floodplain lakes when spring flood-
waters top the low natural banks. An example of the
seriousness of siltation is evident in the study made In-
stall & Melsted (1951) of Lake Chautaucjua, They
found that in a 23.8-year period the sediment had
reduced the storage capacity of this artificial lateral
bottomland lake by 18.3 jjercent. nearly one fifth. Other
bottomland lakes are steadily diminishing in size and
depth as sediments continue to be deposited in spite of
soil conservation measures.

The basic reason for the 1900 diveision of Lake
Micliigan water into the Illinois waterway was to dilute
sewage and transjjort it away from Chicago. Since that
time the treatment of sewage in the Chicago area has
been greatly impro\ed, but the rich effluent still affects
the waters of the waterway b(4ow the city (Keup. In-
gram, Geckler, & Homing 1965). Moreover, the other
cities within the Illinois River basin have grown, and
make their increasing demands on and contributions to
the stream.

b) — 1960

Fig. 2. — Illinois Rivci liottoiu near Havana, Illinois, a) as it was prior to lOl'J, and hi as it was in 1960. (From Starrrtt ..'<
Fritz, 1965.)

Domestic sewage and industrial wastes are not the
only source of organic ]jollution of our streams. With
the development of larger and larger cities, the paving
of more streets, parking areas, etc., the storm water
runofT adds a considerable amount of organic matciial.
A study by Wcibel, Anderson. & Woodward (1964) of
a sewered storm water runofT from a 27-acre, residential-
light commercial area in Cincinnati, Oiiio, disclosed that,
assuming a secondary sewage treatment plant effluent
at the population density and environmental conditions
of this area, the o.xygcn demand of the storm water
would equal about 60 percent of the oxygen demand of
the sewage effluent on a yearly basis.

Man is contributing other things to the Illinois
River. No one knows what all of these contributions
are, in addition to those from industry and farming op-
erations, or what they do to the environment. Usually
these additions come to the attention of biologists only
when there is a conspicuous deterioration of the biolog)'
of a stream.

Occasional accidents occiu" which affect the biology
of the ri\er, as, for example, when large quantities of
ammonia fertilizer inadvertently escaped into it below
Peoria in 1961.

With all that we are adding to the Illinois River, tin-
known and the unknown, it is certain that the river is
changing, and in some cases it is deteriorating rapidly
insofar as it affects the well-being of the animals and
plants that are dependent on it.

The following pages include a summary of some of
our observations on this important stream. While we
discuss some chemical and physical parameters to this
problem, we are basically interested in them as they
affect the fish and wildlife. It is probable that a greater
future emphasis on the biology of streams will be a
necessity in any intelligent water management program.
Without in any way detracting from the importance of
other fields of specialization, we believe that water biol-
ogy stands at the center of any water quality consider-
ation. In the words of Hynes (1961), "Pollution is.
after all. primarily a biological phenomenon, as the
things we need to know about water are almost all con-
cerned with living organisms. Can we or our animals
drink it? Will it be a good medium for brewer's yeasts?
Is it likely to carry disease? Will it smell nasty as the
result of biological degradation of organic matter? Can
fish live in it?"

TURBIDITY

As mentioned previously, the Illinois River was at
one time characterized as being clear. It has always
carried some silt load, of course, but prior to human
settlement of the basin this must surely iiave been a
nominal one, and doubtless was most obvious during
periods of high water. When the while settlers estab-
lished the intense agrarian culture in the area, their
plows and axes began a change in the river which still

goes on. Kofoid (1903:179) discussed the matter of
clarity as it was in 1896. He measured clarity by sub-
mciging a white plate of scmiporcelain. The depth at
which this plate disappeared from view was measured
in centimeters.

"As might be expected in the river environment," he
stated, "when floods occur the tmbidity is often extreme,
and is exceedingly variable according to the locality and
the river levels. The extreme range of our records
extends from 1.3 cm. ['A inch], in a Spoon River flood,
to 260 cm. [8'/? feet], in Quiver Lake, under the ice.

"In the [Illinois] river the great majority, about two
thirds, of the records lie between 20 and 50 cm. [8-20
inches], while the extreme range is from 2 cm. [% inch],
in the flood of May 1897, to 1 15 cm. [45 inches], in the
declining waters of July, 1896." The range for two-thirds
of his readings would be roughly estimated to equal
25-103 turbidity units (Jackson 1954:39).

Recent turbidity measurements have revealed how
much greater the silt load is in the waters of the ri\er
than it was about 70 years ago. In 1963 and 1964,
during periods of minimum flow when the silt load
would be lowest, the turbidity was determined to be
from 79 to 220 units in the La Grange Pool. Thus at
this low-river stage, the modern measurements were
at the lowest reading three times those of Kofoid's and
at the highest reading over twice the 1896 (igme. We
have already discussed in general terms what this silt
load is doing to water impoundments, and its relation-
ship to modern agriculture. The lower and middle
stretches of the river tend to be kept in a more turbid
condition because of the movement of tow boats up and
down the main stream (Starrett, unpublished). Tin-
increased turbidity of the Illinois River has come from
the greater exposure of the soil to precipitation and
resulting erosion, as discussed in the previous section,
and from the hastening of the How of the nmddy wateis
into the stream. Great marshes, for example, used to
impede the movement of rainfall to the ri\er. hut these
marshes are largely gone now.

That the silt load in the lower river tends to be
greater than in the upper stretches is indicated in the
following tabulation which lists the turbidity units by
navigation pools, beginning with the Alton Pool at the
river's mouth and ending with the Dresden Pool in the
Des Plaines River just below Chicago.

Narigalion Raii^r in

Pool Turbidily Units

Alton 71-320

La Grange 79-220

Peoria 15-140

Star\-cd Rock 1,5-52

Marseilles 15-28

Dnsclcn 15-27

These readings were made during the periods of min-
imum flow in the fall months of 196!^ and 1964. During
j)eriods of high water all of these readings would, of

course, be much greater; as high as 2,000 lurbidity units
have been noted by the Illinois Sanitary Water Board
in the lower river during flood conditions.

Turbidity in parts of Peoria Lake is sometimes in-
creased by large populations of minute floating plants
known as phytoplankton, but in general the river's lack
of clarity is due to suspended silt. Turbidity probably
affects the procurement of food by sight-feeding fish
(Starrett & Fritz 1965). It also affects production of
plankton, and the well-being of various larger forms
of aquatic plant and animal life (Ellis 1936).

DISSOLVED OXYGEN

Oxygen dissolves in water according to certain phys-
ical laws, and ac]uatic life has evolved to live and respire
within the normal limits of this solution. Suffocation
can take place if waters carry pollutants which will
oxidize and remove this gas faster than it can be
replaced. This makes too great a demand on the avail-
able oxygen, and fish, as well as other forms of ac]uatic
life, will die.

The requirements for oxygen on the part of different
aquatic species arc not the same. Trout, for example,
require more dissolved oxygen than do carp or goldfish.
It appears from Ellis's stu'dies (1937:372-37.3) that 5
parts per million (ppm) of dissolved oxygen is the lower
limit for maintaining a desirable fish fauna in a river.
Tarzwell (1958:19) believed that ". . . for a well-
rounded warm water fish population, dissolved oxygen
concentrations must not be below 5 p. p.m. for more
than 8 hours of any 24-hour period and at no time
should they be below 3 p. p.m." Diu'ing the winter
months on the Illinois River, Thompson (1925:431)
noted that carp and buffalo were found in water having
as little as 2.5 ppm of oxygen, but a variety of fish was
found where there were 4 ppm, or more, and the greatest
variety was found where there were 9 ppm. We also
have foimd fish living in water with below 3 ppm of
oxygen ; however, we believe that prolonged low oxygen
conditions are having a drastic effect on acjuatic orga-
nisms in the river.

Continuous low oxygen determinations indicate that
pollutants carried by the stream have a high biological
and chemical demand on the oxygen supply and that the
stream is in poor condition for fish life. Because the
quantity of dissolved oxygen in tlie Illinois River water
becomes an important limiting factor and has a strong
relationship to the health of the organisms living in that
water, it is important that we briefly review this factor.
That low dissolved oxygen is a present as well as a
past problem is indicated bv the readings presented in
Table 1.

Prior to 1800 the entire Illinois River syslcTu wilhoul
doubt carried enough oxygen to support a well-diversi-
fied, healthy, fish population. Possibly a turning point
occurred when the flow of the Illinois and Midiigan
Canal was reversed and began to biing sewage from

Chicago to a point in the river at La Salle in 1871. The
Peoria-Pekin area also began to develop along the
middle stretch of the river. Sewage and industrial wastes
coming into the river were untreated.

Kofoid (1903:199) estimated that the Illinois River
received the untreated waste from a population of
1,032.229 people in 1890. There were no statistics as
to the gallonage that this represented, but considering
the pumpage into the water systems of the cities as an
approximation of the sewage flow, he calculated that in
1897 the flow was 540.529,061 gallons per day. Kofoid
stated (loc. cit.:230) that before the Sanitary and Ship
Canal was opened in 1900 the nitrogenous material in
the Chicago sewage was in the process of rapid oxidation
in the upper reaches of the Illinois and Michigan Canal
near Lockport, and that the process was largely com-
pleted by the time the canal water reached the Illinois
River. He also said that in the summer months the
wastes from Peoria were well decayed before reaching
Havana, although in the winter the sewage was not so
well oxidized.

As mentioned earlier, the opening of the Sanitarv
and Ship Canal in 1900 brought into the Illinois great
quantities of sewage-laden lake water. Forbes & Richard-
son (1919:139) mentioned that in 1913 the flow of the
Sanitai-y and Ship Canal amounted to 85.7 percent of
the flow of the original river at Peoria.

By 1911 the upper part of the river was heavilv
polluted. Forbes (1911:5-6) stated: "Immediately
below the mouth of the canal we have in the Des Plaines
a mingling of these waters, and the Illinois River itself,
below the jimction of the Des Plaines and the Kankakee,
the septic contributions of the former stream are largelv
diluted by the comparatively clean waters of the latter.
Nevertheless, we had in July and .■\ugust what mav be
called se]3tic conditions for twenty-si.x miles of the course
of the Illinois from its origin to the Marseilles dam. At
Morris, which is on the middle part of this section, the
water, July 15, was grayish and sloppy, with foul, pri\y
odors distinguishable in hot weather. . . . Putrescent
masses of soft, grayish or blackish, slimy matter, loosely
held together by threads of fungi and densely covered
with bell animalcules, were floating down the stream ;
and chunks of this material, from the size of a walnut
to that of a milk pan, occasionally rose to the surface,
c\idently borne up by the gasses developing beneatii
them." He found that at that time the dissolved oxygen
at Morris was only 9.8 percent of satination. Sixteen
miles below Morris, at Marseilles, the oxygen was onlv
7.5 percent of saturation. However, in the unpolluted
Kankakee River 9 miles above Morris the dissolved
oxygen was 1 12 percent of satination.

The oxygen determinations gi\en in Table 1 show
how polluted the Illinois River was in 1911 and 1912
from Morris to Peoria.

Clonditions became men worse during and imme-
dintelv following World W.n 1. Purdy (1930:2), who

Table 1. — Summary of minimum dissolved oxygen determinations near surface in channel of the Illinois and Des Plaines rivers
during summer months of 1911, 1912, 1922, 1923, 1925, 1926, 1928, 1950, 1964, and 1965.

Nearest
Town

Dissolved Oxygen in Parts per Million

1911»

1912"

1922''

1923«

1925''

1926''

1928''

1950"

1964'

1965'

Lockport ... 0.01

Channahon ... 0.2

Morris 0.9 ... 0.2

Marseilles 0.5 ... 0.1

Ottawa ... 0.3

La .Salle ... 0.5 0.0 0.0

Peru 2.7 ... 1.7

Spring Valley 2.0 ... 0.0 0.3

Hennepin 2.2 1.8 ... 0.0 0.1

Henry 2.1 1.0 0.4 0.0

Lacon 2.1 ... 0.8 0.4

Chillicothe 2.3 2.7 0.4 0.0 0.3

Rome 1.9 ... 0.0 0,2

Narrows (Peoria) 4.3 5.7 2.6 3.0

Pekin 5.4 5.2 3.3 2.2

Kingston Mines 4.1 6.6 3.0 5.5

Havana 3.6 ... 1.3 3.8

Browning 3.7 . ... 3.9

Bcardstown 4.8 2 7* 2.3 2.7

0.3
1.2

0.5

0.4
0.4
0,1
0.0
2.4

0.6

0.1

0.2

0.1
0.0
0.5

2,4

2.9

5.3

3.9
2.9
3.9

4.9
3.5
2.9
5.1
4.8
5.0

2.3
2.3

1.6
4.1
2.5
2.8
5.1
4.9
5.1
3.8
3.0
2.7

1.0"

" Barlow (1913:40-45).

'' Hoskim. Ruchhoft, & Williams (1927:114-122) Lowest of monthly mean determinations for Julv and .August 1922.

■■ Greenfield (192.';:26-27 and 3(1-31).

•> BorufT & Buswell ( 1929:57-1U8) .

*■ Mondala. Chairman (Report of the Illinois River Pollution Commission. 195I:LA 41 Table I .-Xnalytiral Data of Illinois Sanitary Water Board).

t Starrelt (Illinois Natural History Survey data).

^' Mr. Ralph E\ans of the Illinois Water Survey furnished the data.

* Samples laiten in 1921 rather than 1922.

Studied the river in 1921 and 1922, said: "Growth of
the city of Chicago, with heavy increase in amount of
sewage and of stockyard waste overburdening the al-
ready polluted Illinois River, which, with reduced area
for overflow, limiting levees, and increased volume.
must therefore flow more rapidly in its narrowicl
channel, with the result that each succeeding year its
organic matter is carried fartiier downstream, before
the offensive organic content is sufficiently removed."
Richardson believed (1921b: 33) that in the 1915-1920
period the southward progression of this offensive condi-
tion in the Illinois Ri\i'r was iiitiviiig at the rate of 16
miles a year.

Conditions upstream from Peoiia are niut li (lillnciit
now from those of about 40 years ago, as a coin|)arison
of the oxygen determinations made in 1922 and 196.")
indicates (Table 1). This improvenifut is interesting
when one considers the gieat growth that has been
occurring in population and industiy in the Chicago
metropolitan area. The improvement may ha\e been
due to several factors, including the construction and
operation of the tremendous sewage treatment plants
by the Chicago Sanitary District through a program
instittited in 1922. and the lock and dam sy.stem l)uill
in the I93f)'s whidi slowed up the moMiiifiU of the
water. The adoplicjn of belter water pollution laws by
the state also had its effect.

Hoskins, Ruchlujft, & Williams (1927:2,5) stated
that the total combined domestic and industrial pollu-
tion cmiJtiicl into ihe Illinois Rivii in 1922 was the

equivalent of that from 6,211,471 people. Tlie popula-
tion ec|uivalent of domestic and industrial wastes entering
the river in 1960 (United States Public Health Service
1963) had been reduced to 2,417.000, in spite of ex-
panding human populations and increased industry in
the basin. This change reflects the great progress which
has been made in the treatment of wastes and indicates
the magnitude of work yet to be done.

In spite of the dramatic improvement described
above, our oxygen analyses made in 1964 and 1965
(Fig. 3) indicated that most of the river had less than
5 ppm dissolved oxygen. We consider the determinations
for the na\ igation pools to be (luite typical for nK)ining
samples during warm weathei. I he downward slopes
of the oxygon graphs below the clams (Fig. 3) are
similar for all pools but Starved Rock, which is affected
on the right bank by effluents from Marseilles and the
Fox River. The higher oxygen readings just below the
dams, and the declining curves as one proceeds down-
stream from each dam, indicate that additional oxygen
is added as the water |jasses over and tluough the dams
and locks, and that this is rapidly removed by the high
demand for the oxygen caused by the pollutants. Hartow^
(1913:36) noted a similar increase in oxvgen in the
river below the Marseilles Dam in 1912.

The similarity of the declines in oxygen below the
dams after the initial upsurge indicates that there arc
still high biological and chemical tiemands for the dis-
solved oxygen, and the amount available is at about a
breaking point insofar as fish life is concerned.

■"4.5

UJ4.0
O

X3.5
O

3.0
a

o 1.5

■STARVED ROCK

1 t:0CK a DA M :■!! ■•■

STARVED ROCK POOL
30 JULY 1965
0725 to 10*3 CST
TEMP 26 4 to 290"C.

.-V ,— '

UiR5£ILLES POOL
^9 JULf ,965
0650 10 1122 CST
TEMP 29 5° to 302° C,

196!

DRESDEN POOL

0835 10 1035 CST
TEMP 302* 10 32i"C.

\.'

230 234 238 242 246 250 254 258 262 266 270 274 278 282 286 290
MILES FROM MISSISSIPPI RIVER

RIP UF Annw
LOWER END PEORIA DETWEILLER PEORIA LAKE Ilqugh

PEORIA LAKE^^ / NARROWS P*"" LIGHT \^CHILLICOTHE__,/ LACON

LAKE SENACHW1NE
HENRY ^ HENNEPIN

VERMILION
PERU RIVER

SPRING VALLEY ' LASALLE

33.0r

PEORIA POOL .

6 8 7 AUGUST 1964 I 5 AUGUST 1965 '

0528 10 1113 CST 0808 to 0930 CST

TEMP 27 2° 10 29 7°c1tEMP 25 6" Io 26.8°C.

186 190 194 198 202

MILES FROM MISSISSIPPI RIVER

BEAROSroWN SANGAMON RIVER b„oWNINO

LIVERPOOL

MACKINAW
KINGSTON MINES RIVER

PCKHI ,

GRANGE H^HHH^^HBJI^^^^^H
|ldcx q dam -^i^^^^^^^^^^^^^^^^^^H

i^^mimlliii^g

L» BRMee POOL

M, 15, 16 JULY 1964 I 1 1 AUGUST I9G9
0517 to 1020 CST 0545 to ll56 CST

TEMP. 23.3° to 26.2° C.I TEMP. 25.0° to 25.7° C

MILES FROM MrSSISSIPPt RIVER

MISSISSIPPI RIVER
GRAFTON

M0NTE7UMa FLORENCE

NAPLES MEREOOSIA

«*»

g3.0

§2.0

ALTON POOL
12 AUGUST 1965
0530 to 1515 CST
TEMP. 23.9° to 27.1°

V,=

32 36 40 44 48

MILES FROM MISSISSIPPI RIVER

Fig. 3. — Dissolved oxygen determinations in the Illinois River from Brandon Road Lock and Dam to Grafton. Broken lines
represent readings taken in the summer of 1965; solid lines represent readings taken in the summer of 1964. (Illinois Natural His-
tory Survey data.)

The poor oxygen content in the La Grange Pool in
the summers of 1964 and 1965 (Fig. 3 and Table 1)
probably reflects the eflfects of additional wastes coming
into the river from the Peoria-Pekin area. Conditions
were particularly bad during the summer of 1965. This
has been a problem of some duration. Roruff & Buswell
(1929:54) in reviewing their own and other studies of
the BOD (biological oxygen demand) of the river prior
to 1928, stated: "Physical conditions, especially below
Peoria and Pekin and below this latter city for some
miles, tend to show each summer season signs of an
increasing pollution load. The extra load that is being
added to the river is due to the increased population of
the Pekin and Peoria districts, as well as to the veiy
marked increase in industrial wastes." BorufT (1930:5)
found that the dissolved oxygen content of the water
below Peoria and Pekin remained at a low level.

Our present study of the bottom fauna (Starrett &
Paloumpis, unpublished) and of the fishery indicates
that some improvement in conditions occurs below the
mouth of the Sangamon River at Beardstown. The pos-
sible influence of this tributary at times is clearly shown

in the cross-section oxygen readings made in 1964 (Fig.
4). In the entire cross section of the Illinois River at
Mile 89.3, just above the mouth of the Sangamon, dis-
solved oxygen was at a value of 2.4 ppm. The cross
section at Beardstown at Mile 88.6, also shown in Fig.
4, disclosed a high oxygen content on the left bank below
the Sangamon's confluence through Muscooten Bay, and
a low content on the right or opposite side. However,
our 1965 data do not reflect such beneficial effects from
the Sangamon River as were noted in 1964. Tiie longi-
tudinal section (Fig. 4) below the Sangamon's mouth
shows that the mixing of the high-oxygen Sangamon
water in 1964 did not reach midstream until about
Mile 88.

BOTTOM FAUNA

The bottom fauna ( benthos j consists of the macro-
scopic animals which spend all or a part of their lives
living on or in the bottom sediments. Certain benthic
organisms, such as insect larvae, fingernail clams, and
snails, are important food items for larger animals such
as fish and ducks (Starrett & Paloumpis, unpublished;

2.4-

CF?OSS SECTION

Left MILE 89.3 RigM

Bonk 1047 CST Bank

DISSOLVED OXYGEN- ILLINOIS RIVER

3 FEET BELOW SURFACE

16 JULY 1964

9,0

80-

7,0-

6.0

5.0

4.0

3.0-

2.0

6.0

5.0-

4.0-

3.0-

2.0-

CROSS SECTION

HIGHWAY
BRIDGE

Left MILE 88.6 RigM
B(»ik 1000 CST Bonk

MILE 89 3

RAILROAD
BRIDGE

ILLINOIS
RIVER

BEARDSTOWN

88.0

LONGITUDINAL SECTION
BELOW MOUTH OF SANGAMON RIVER

87.0

Fig. 4. — A continuous
scries of dissolved oxygen read-
ings made in the Illinois River
with a galvanic oxygen ana-
lyzer near the mouth of the
Sangamon River. The graphs
reflect the increase and mixing
of dissolved oxygen in the Illi-
nois River resulting from the
effects of a major tributary
having a higher dissolved oxy-
gen content. Cross section at
Mile 89.3 is above the mouth
of the Sangamon River, and
cross section at Mile 88.6 is
below. ( Illinois Natural His-
tory Survey data.)

MILES FROM

RIVER

Anderson 1959:338-339). Much of the Illinois River
(as well as its adjoining bottomland lakes) is now char-
acterized by populations of pollution worms of the
family Tubificidae. However, some of the original di-
versity of benliiic organisms, such as immature insects,
clams, snails, leeches, moss animals, and the like, does
exist in some parts of the river and its lakes.

Reduction in the abundance of the clean-water ani-
mals would be expected to have an adverse effect on
animals which rely on them for food, and, as we shall
see later, this undoubtedly has happened.

Changes which have occurred since 1913 in the zones
of pollution based on the bottom fauna are shown (Fig.
5). The chart shows that approximately half of the
river in the La Salle-to-Beardstown section in the 1913-
1915 period contained principally clean- water benthic
forms, whereas in the 1964-1965 period most of the or-
ganisms in the same section of the river were pollution
worms, which are poor food for fish and ducks.

Fingernail clams (Sphaeriidae) occurred in large
numbers in the Illinois River and some of its bottomland
lakes up to 1954 (Paloumpis & Starrett 1960:423-425,
and unpublished). The cause for the virtual dis-
appearance of these important food items is not
known, but there are strong indications that it was
a pollution complex of some kind. These tiny clams
(Fig. 6) still occurred in ihe river below the mouth of

the Sangamon at Beardstown in 1964 (Starrett &
Paloumpis, unpublished).

Snails of the genera Campeloma and Pleurocera also
occur at the present time in greater abundance in the
lower river than elsewhere, but we collected a few living
specimens (Campeloma) in 1964 from the river channel
below Henry by means of an otter trawl. In Quiver
Lake, above Havana. Paloumpis & Starrett (1960:425)
found that a small snail (Cincinttali tmarginata) disap-
peared simultaneously witii the fingernail clam. In the
lower part of this lake, which is properly a part of the
river, all species of snails decreased from 10.76 grams
per square foot (exclusive of shells) in 1952 to 6.07
grams per scjuare foot in 1954. and none in 1964 (Star-
rett & Paloumpis, unpublished) .

Starrett & Paloumpis did not take midge larvae
abundantly anywhere in the river in 1964 and 1965. At
times they were more abundant in fish stomachs than
in the benthic collections, especially in the Peoria Pool.
It is possible that seasonal variations and local concen-
trations of larvae may have accounted to some extent
for this disparity.

Burrowing mayflies (Hcxagciiia) were considered
by Richardson ( 1928) to be clean-water organisms in the
Illinois River. According to Hunt (1953:55) nymphs
of Hcxancnia limhata were unable to withstand stagnant
conditions when tlie dissolved oxygen dropped below 1

Fig. 5. — Historical rhango in
pollution of the Illinois River as
indicated by bottom fauna sam-
ples. (From Riehardson, 191iH,
and Starrett & Paloumpis, un-
published.)

MILES BELOW
LAKE

LOCATION MICHIGAN
LA SALLE 101.5

SPRING VALLEY 108.6

CHILLICOTHE 146.5

SPRING BAY 154.0

NARROWS

PEORIA NARROWS 161.0

HAVANA

BEARDSTOWN

207.0

238.0

1913 -1915*

EARLY

POLLUTIONAL

EARLY POLLUTION-
AL TO EARLY
SUB-POLLUTIONAL
IN I9II-I9I2

LATE
SUB-POLLUTIONAL

EARLY CLEAN-WATER
WHEN NOT AFFECTED
BY LOCAL SEWAGE

PRINCIPALLY
CLEAN-WATER

CLEAN-WATER

RATING OF TERMS FROM MOST TO

EARLY POLLUTIONAL
LATE POLLUTIONAL
EARLY SUB-POLLUTIONAL
LATE SUB-POLLUTIONAL
EARLY CLEAN-WATER
CLEAN-WATER

1920-1925*

PRINCIPALLY EARLY
SUB-POLLUTIONAL

EARLY

POLLUTIONAL

EARLY TO LATE
POLLUTIONAL

POLLUTIONAL TO
EARLY SUB-POLLU-
TIONAL ABOVE
COPPERAS CREEK
0AM, LARGELY EAR-
LY SIJB- POLLUTION-
AL BELOW

PRINCIPALLY LATE
SUB-POLLUTIONAL,
1920-1923, SHIFT-
ING TO EARLY
CLEAN-WATER AFT-
ER 1923

I I

LEAST POLLUTED.

1964-1965

»*

POLLUTIONAL
MAINLY TUBIFICID
WORMS AND
MIDGE LARVAE

HEXAGENIA NYMPHSi
AND SPHAERID
CLAMS APPEAR
HERE SAMPLES
ALSO WITH TUBI-
FICID WORMS AND
MIDGE LARVAE

* FROM RICHARDSON (1928:402)
**FROM STARRETT AND PALOUMPIS (UNPUBLISHED)

Fig. 6. — Finger-
nail clams, important
food items for some
fish and birds, have
virtually disappeared
from the river above
Beardstown.

ppm. In 1913 and 1915 Richardson (1925:381) col-
lected an occasional Hcxagcnia nymph in middle and
lower Peoria Lake; after 1915 he did not find any in
the river above Havana.

Mayfly emergences can be spectacular when millions
of these insects are drawn to lights and may concentrate
in such numbers as to be hazardous to traffic. Such
emergences have been characteristic of many parts of
the Illinois River. The last time we observed a large
emergence at Havana was in 1949. Paloumpis & Starrett
(1960:419) collected Hexagenia limbata nymphs in the
1950's at Quiver Lake, and in most summers during the
early 1950's they saw subimagos at or in the immediate
vicinity of the lake. Since the late 1950's we have not
observed any mayfly emergences at the lake and Star-
rett & Paloumpis (unpublished) did not collect any
nymphs there in 1964. They collected some Hcxagcnia,
though, in 1964, in the river below Beardstown and in
the Alton Pool.

The predominant organisms in the 1964-1965 bcn-
ihic sam]3les were jJoUution worms and these were quite
abundant, even in the samples from below Beardstown
where both mayfly nymphs and fingernail clams were
taken (Starrett & Paloumpis, unpublished). In 1915 at
Lake Matanzas, below Havana. Richardson ( 1921 a: 506-
507) collected only 4.4 worms \kv sc|uare yard, whereas
Paloumpis & Starrett (1960:430) in 1953 look 11.007
per scjuare yard in the same area.

Such drastic changes in the bcnlhic populations as
those described above can be accounted for only by the
accunuilative effect of pollution in the bottom muds of
tlie Illinois River waters. Such changes may not l)c
shown by chemical analyses.

AQUATIC VEGETATION

Within the last 15 years there have been unusual
changes in the aquatic vegetation of the Illinois River
and its bottomland lakes. Today there is a vastly dif-
ferent picture in the vicinity of Havana from thai

painted by Kofoid at the turn of the century. Flag and
Thompson lakes disappeared in the early 1920's, the
result of the building of levees, drainage, and cultivation.

Kofoid (19():i:236) slated: '"The ac|uatic environ-
ment at Havana im|}resses the \isiting biologist who for
the first time traverses its river, lakes, and marshes, as
one of exceedingly abundant vegelalion. indeed almost
tropic in its luxuriance. . . . He will find acres upon
acres of 'moss,' as the fishermen call it — a dense mat of
mingled Ccratophyllum and Elodca choking many of
the lakes from shore to shore, and rendering travel by
boat a tedious and laborious process. . . . The carpels
of Lcmnaccac will be surprising, and the gigantic growths
of the semiaquatic Polygonums will furnish evidence of
the fertility of their environment."

The first big change in aquatic vegetation came
shortly after Kofoid had completed his study, with the
1900 diversion of Lake Michigan waters into the ri\er.

Richardson (1921b:46) recorded the disappearance
of aquatic plants from Peoria Lake in 1920 as follows:
"The luxuriant growths of coarse aquatic plants ( Pola-
mogeton, Ceratophyllum, Scirpus, Vallisineria, etc.) that
covered several .square miles of Peoria Lake at mid-
summer and autumn levels between 1910 and 1914,
and their rich fauna of small invertebrates along \\ith
them have disappeared now altogether in the upper and
middle lake except for an occasional scraggly clump at
the very edge. In the lower lake, a thin patch of
Potamogeton and Ccratophyllum, covering less than two
acres, was still growing in a small springy slough, . . ."

Thompson (1928:304) reported that pondweeds
(Potamogctons) and other large aquatic plants in Peoria
Lake, the river, and connecting sloughs and lakes down-
stream, disappeared almost completely between 1915
and 1920. But about 1922 pondweeds began to reap-
pear and increase rather rajiidly in many areas of Peoria
Lake.

Purdy (1930:113) slated that in 1921 Peoria Lake
held some growths of pondweeds and algae, but these
were so slight as to be overlooked by the casual obseiA'cr.

From the late 1930"s to the middle 1950's, in some
places along the central stretches of river there was an
abiuulance of aquatic vegetation, but this has now al-
most completely disappeared. The reasons for this are
not clearly understood, Thcic may be some inimical
materials in the waters now, and it appears that the silta-
tion of the last decade has been a factor. Siltation affects
aiiuatic jjlants adversely in two ways: it produces a
tiubidity which reduces the penetration of light and in-
hibits photosynthesis, and it creates bottom conditions
which make it difficult or ini]Jossible for various species
of jilaiits to obtain anchoiage whc-n they are buffeted by
wave action.

The importance of wave and fish action in rc-
suspending sediment particles in Lake Chautau(|ua has
been jjointed out iiy Jackson & Starrett (1959). Dining
the spring of 1953 tliey found that, with an increase in

wind velocity from light to strong, suspended particles
increased more than fourfold (162 to 700 turbidity
units) . The actions of bottom-feeding fish also caused
a resuspension of sediment particles. Because it takes
from 7 to 12 days for much of this sediment to settle
from Lake Chautauqua, this lake (as with most such
lakes in the Illinois River valley) is in a highly turbid
state most of the time.

Sago pondweed (Potamogclon pcctinatus) is more
tolerant of reduced light than most other aquatic plants.
In spite of this, Bellrose (1941:261-263) found that
from 1938 to 1940 sago pondweed in Lake Chautauqua
did not thrive in water more than 48 inches deep, and
was absent in water more than 56 inches deep. Later,
at the same lake, Jackson & Starrett (1959:159) re-
ported that sago pondweed grew best when the maxi-
mum water depth was about 3 feet.

Sedimentation of Lake Chautaucjua was accelerated
by the great spring floods of 1943 and 1944. Beds of
aquatic plants, which had declined slightly from 1938
to 1942 (Bellrose 1941:243, and unpublished) were al-
most wiped out by the high turbid waters of the two
following flood years. Probably because additional silt
was deposited as a "false bottom" over the previous
"firm bottom," aquatic plants never did return to their
former luxuriance in Lake Chautauqua. For all practi-
cal purposes, longleaf pondweed (Potamogeton ameri-
canus), coontail (Ceratophyllum demersum) , and bushy
pondweed {Naias guadalupensis) were lost as important
items in the lake's ecology. Sago pondweed is the only
plant which has been common since the 1943 flood. It
varies in abundance in Lake Chautauqua annually, de-
pending on the depth of water in May and June; low
water during this period has favored a fair growth dur-
ing some summers. The most extensive recent growth
occurred with the low, stable water levels of 1956 when
the beds covered 1,237 acres early in the fall.

The Peoria Dam, put into operation in December.
1938, stabilized low water levels in Peoria Lake, and
coontail, bushy pondweed, and sago and longleaf pond-
weeds, as well as wild celery (Vallisencria spiralis), in-
creased greatly in the 1940's, with a peak abundance in
1949. Early in the autumn of that year aquatic plant
beds were lush, covering several thousand acres of this
10,000-acre lake. After 1949 these beds declined in
vigor and abundance until, following a small gain in
1952 and 1953, the lake has been almost completely
barren of these plants.

At first this deterioration was attributed to spring
floods, such as those that may have affected the Chau-
tauqua flora. However, aquatic plant beds failed to re-
cover when water levels were favorable to growth (with
the exception of 1952 and 1953), and this reduces the
possibility that floods were solely involved in tlioir de-
cline.

There is evidence that factors other than luriiiililv
may be responsible for the eradication of aquatic plants

in certain areas. Coontail, longleaf and sago pondweeds.
and wild celery have disappeared from the Starred Rock
Pool since the 1940's and have not returned, even though
in many years since then the transparency of the water
has been adecjuate for their growth. Their failure to re-
appear suggests that factors other than a lack of water
clarity were responsible; at other lakes increase in water
transparency has been simultaneous with an increase in
vascular aquatic plants.

The level of Rice Lake was artificially raised 2 or 3
feet in the mid- 1940's. When this rise occurred the
aquatic and marsh plants began to disappear. By 1950.
360 acres of river bulrush (Scirpus fluviatilis) had
dwindled to less than 100. By 1956 only 20 acres were
left. Both coontail and white waterlily (Castalia tuber-
osa) increased at first with lessened competition from
American lotus. However, as the marsh disappeared and
wave action increased, this churned up the bottom, and
coontail declined from 522 acres in 1950 to none in
1960. White waterlily went from 90 acres to zero in
the same period.

Several years ago water levels were raised in Spring
Lake, not now connected with the river, to enlarge the
lake area for recreation. This increased depth was ac-
companied by a loss of about 200 acres of coontail and
an equal area of river bulrush marsh.

Clearing of bottomland forests for agriculture elimi-
nated such food-producing trees as pecans and oaks
which furnished food for some ducks.

FISH

At Havana, on the middle stretch of the Illinois
River, some of the elderly citizens still talk of the special
trains that used to bring Springfield anglers to Havana
for a day's fishing. They also recall the carloads of live
fish that were once shipped out of Havana to the New
York City market.

Largemouth bass [Microptcrus salmoides) were
abundant enough in the river-bottom lakes so that one
could make wages by catching them with a cane pole
for the local market. In 1897. 13,061 pounds of bass
were handled commercially at the Ha\ana fish markets
(Cohen, Bartlett, & Lcnke' 1899: 71 . Between 1899 and
1908 the commercial yield of largemouth bass increased
322 percent (Forbes & Richardson 1919:149-150).

During the past half-century man has so seriously
damaged the habitat that the once great fishery at
Havana, and elsewhere along the river, is now but a
fraction of its former size. Increase in turbidity and
sedimentation, chronic pollution, decrease in aquatic
vegetation, virtual disapijcarance of fingernail clams,
and reduction of food h.ihilat through drainage have
contributed to this change.

Perhaps the most important change in the fish fauna
was the introduction of the carp (Cyprinns carpio) in
the 1880's. Carp fitted well into the new environment
and soon became the most important commercial s|iecies.

adapting to many of the changes in the river. The
fishery of the river reached its peak in 1908, when about
24 million pounds of fish were taken commercially.
Carp made up nearly two-thirds of this catch.

The great increase in the commercial fishery starting
at the turn of tlie century appeared to result from the
increase in water because of the diversion from Lake
Michigan, the increased nutrients made available to
fish-food organisms, and the population explosion of
the carp.

Since 1908 the Illinois River fishery has been de-
clining (Fig. 7) ; data in this depth are not available
for sport fishes.

The gains in water area available to fish, brought
about by the diversion of Lake Michigan water, began
to be offset after 1907 by the drainage of bottomland
lakes. The 1913 area was about the same as it was in
1897, prior to diveision (Forbes & Richardson 1919:
154). In addition to these losses due to draining, condi-
tions were further aggravated by the increase in sedi-
mentation discussed earlier. Pollution from the Chicago
and the Peoria-Pekin metropohtan areas has had serious
efl'ects on the fish and fish-food organisms since the peak
of the fishery in 1908. The upper river was more dras-
tically affected than the part below Utica. Between
1912 and 1917 pollution completely wiped out the fish
life above this city (Thompson 1928:301).

Forbes & Richardson (1913:517, 521-522) stated
that near Morris (Marseilles Pool) in August and Sep-
tember of 1912 the river "was practically destitute of
fishes, and the few taken were in close pro.ximity to the
Mazon slough. Moreover, some of the bullheads were
'fungused' or in otherwise unwholesome condition.

"The only other vertebrates taken here were a single
frog, two sna]jping turtles, and a soft-slielled turtle. The
search for moUusks yielded seven species of mussels, all
the specimens dead, however, except for one collection
made in Mazon slough. ... In August and September,
1912, [Marseilles] conditions were similar to those found
at Morris at the same time. Set-nets were raised every
day from August 13 to 17, but witiiout result; and a
dozen half-pound sticks of dynamite were exploded, hut
no fish were taken. . . . On the night of August 19, a
heavy rain, which flooded the small creeks, washed fishes
out into tlie river, where they became sick from sewage
and could be picked up easily with a dip-net."

In the summer of 1923 the ri\er was practically
anaerobic as far down as Cliillicothe, with conditions
virtually impossible for the existence of fish (Greenfield
1925:24-25).

There has been a change toward the better in the
upper river since then. Today fish are found living in
the river above Utica. The goldfish (Carrasius auratiis) ,
an exotic fish not present in tlie river prior to 1908, now
occurs commonly in the upper reaches, together with
carp, black bullheads (Iclalurus mclas) , emerald shiners
(Notropis atherinoides) , and other less abundant species.
The return of fish life to this part of the river dining
the late 1930's followed the better treatment of Ciiicago
wastes and the slowing of the river's current following
the building of the navigation dams.

From a comparison of modern studies with those
made befoie 1908, it appears that we may have lost 18
species of fish from the Illinois River (Starrett & Smith,
unpublished) . Many species now occur less abundantly
than in former years.

25.0

COMMERCIAL FISH YIELDS FROM
ILLINOIS RIVER 1894-1964

1894 1897 1899

1921 1922

' 1931 ^ 1950 1955 I960 1964

YEAR

Fig. 7.- — Changes in
coninurcial fish yield in
the Illinois River from
1894 to 1964. (Data
based on published fed-
eral fisheries statistics
and observations made
by the Illinois Depart-
ment of Conservation
and Natural History
Survey. Data for 1 955,
1960, and 1964 from
Starrett, Lopinot &
11, nth. im])iiblished. )

In the past 15 years the commercial fishery of the
middle river, from Hennepin to Beardstown, has shown
a sharp decline. The commercial yield in this stretch
has dropped from 5.07 million poimds in 1950 (Starrett
& Parr 1951:18) to 0.91 million pounds in 1964 (Star-
rett, Lopinot, & Harth, unpublished), a reduction of
4.16 million pounds. Because of the condition of the
water in the river, the commercial fishery above Hen-
nepin has been limited to the activities of one part-time
fisherman who fishes near the mouth of the Fo.x River
near Ottawa.

No attempt will be made here to discuss the condi-
tion of the populations of all fish species living in the
river, but certain important species are included for
closer scrutiny.

Carp

Since carp is the only species of fish that occurs
abundantly in all sections of the river it has been used
in our studies as an indicator of the effects of pollution.
Much of the decline in the commercial catch since 1950
has resulted from the scarcity of carp of commercial
size (17 inches or more in total length) in the middle

section of the river. Small carp are often abundant in
this section but most of them disappear before attaining
commercial size. The commercial catch of carp in the
Alton Pool has changed little since 1950.

1 here are two noticeable effects of pollution on this
species. First, the length-depth ratio of individuals goes
up with increasing pollution. By dividing the depth into
the standard length, an index is obtained which, if 3 or
greater, indicates that the fish is too thin for commercial
uses. Any index under 3 would indicate a satisfactory-
commercial fish. Second, carp exhibit a rachitic bone
malformation (an abnormality characterized bv mal-
formed heads and gill covers) known as a '"knothead"
condition. This becomes more conspicuous (Fig. 8)
with increased pollution.

Thompson (1928) found that carp developed the
knothead condition in association with the polluted
condition of the river during and following \Vorld War
I. Fig. 9 shows the percentages of the carp population
having the knothead condition in various parts of the
river, as reported by Thompson ( 1928:302) and in our
checks in 1963. Upstream from Peoria, conditions were
similar in 1926 and 1927 to those in 1963. The absence

Fig. 8. — Knothead condition
in carp. Left, normal: center,
moderate knothead condition ;
right, extreme knothead condi-
tion. (From Thompson, 1928.)

JOUET.

Fig.
heads i
Illinois
(Thoin
(lllinoi
data

9. — Percentage of knot-
n carp populations in the

River in 1926 and 1927

pson, I92fi) and in 1963.

Natural History Survey

BEARDSTOWN

100 120 140 160 ISO 200

MILES FROM MISSISSIPPI RIVER

Fig. 10. — Ratio betwctn
standard length and body depth
in carp in 1963 from Hardin to
Morris. Note the change in
length-depth ratio at Beards-
town. ( Illinois Natural History
Survey data.)

CARP

RATIO OF STANDARD LENGTH TO BODY DEPTH

BEARDSTOWN
MEREDOSIA . \

;2.60
270
^2.80
="2 90
^3 00

tSSSSMESS

THll I iroTHF SPRING VALLEY

chillicothe , ottawa |

peoriaX henry \utica

PEKINu^^^^

ILA GRANGE POOLl

11963

100 120 140 160 180 200

MILES FROM MISSISSIPPI RIVER

of fish life above Utica in the 1920's prevented Thomp-
son from extending his study as far upstream as we did
at the later date. The percentage of knothead carp
between Beardstown and the Peoria-Pekin area was
greater in 1963 than it was in 1926 and 1927, indicating
a greater pollution load in this stretch of the river.
Stating this another way, it appears that the pollutional
factors in the river responsible for this condition in carp
have not increased above the Peoria-Pekin area, but that
they have moved on downstream toward Beardstown
since Thompson's observations were made.

The length-depth ratios of carp caught in oiu'
autumn 1963 Illinois River collections clearly indicate
a sharp distinction between specimens taken above and
below Beardstown (Fig. 10). Those below this city had
ratios less than 3. and above it the ratios were 3 or more.
\Vc suspect that this dift'erence may be due in part to
ihc elimination of fingernail clams abo\e Beardstown.
Slarrett & Paloiimpis (unpublished) have found these
mollusca regularly in the stomachs of carp collected in
the lower river.

Carp in the niiddk- and upper river are subject to
lower dissolved oxygen conditions than those in the
lower river. It is possible that tlie life expectancy of the
fish above Beardstown is reduced because of periods of
stress resulting from oxygen deficiency. These two
factors — l(;ss of fingernail clams ]5lus low dissolved
oxygen — could explain the dearth of commercial-size
carp in the middle and up|)er reaches of ihc Illinois
River.

Catfishes

Black bullheads are still abundant in lh<' river, par-
ticularly in the middle and upper stretches. These fish,
together with carp, furnish most of the river fishing
for pole-and-linc fishermen from Morris downstream.
CMiaiincl catfish [Iclalurits jntnclalui) Iiave declined in
abundance in the river since 1899 as evidenced by the
following commercial fishing statistics: 241,000 pounds
in 1899 (Forbes & Richardson 1920:183). 105..5.54
jjounds in 19;')0 (Starrctt & Parr 1951:18), and about

98,000 pounds in 1964 (Starrett, Lopinot. & Harth.
unpublished). Mc.st of the catfish are now taken in the
lower river.

BufFalofishes

The bufTalofishes of the genus Iclobius are now
found mainly in the middle and lower sections of the
river. Commercial catch statistics indicate that these
important fishes have declined in the past 65 years, with
the decline being the most rapid in the last 15. The
1964 commercial catch was only about half that of
1950.

Crappies

()ur data indicate very little change in crappie
(Pomoxis annularis and P. nigromaculatus) populations
in the lower river since 1 942. However, the decline in
the middle river has been alarming. A Natural History
Survey crew in 1942 (Thompson & Hansen, field notes)
caught six times more crappies in nets than we were able
to take by the same method in the middle river in 1964.
\X Bath, by electrofishing. we caught 14 cra|)pies pei
30 mimites of fishing in 1962, and only 4 in the same
time in 1964. We suspect that the drastic decline has
been due to the low oxygen conditions in association with
the low water levels of the past few years.

Bluegill

The bluegill (Lcpomb macrochirui) has declined in
out river collections even more than have the crappies.
The take of bluegills in our 1942 fishing in all pools was
33 times greater ih.ui in 1961.

Largemouth Bass

W'c have aliiaily meiuioiu'd the abundance of this
fish at the turn of the centui-y. Other than in a few
bottomlaml lakes, sport fishing foi- laigemouth bass is
now rare in the Illinois River. In 1962 we made a few
sizable collections from some parts of the middle and
lower river. In 19615 and 1964 our electrofishing catch
was substantially less in most parts of the river. The
decline has been related to pollution and the loss of
good habitat, as in the ease of other spot t fishes.

WATERFOWL

Our emphasis, earlier in this report, on the great
reduction in the quantity of vascular water plants has a
special application here. These organisms form the base
of the food pyramid upon which many other kinds of
life depend. Crustaceans and aquatic insects occur abun-
dantly on water plants. Such animals, as well as the
plants themselves, form a part of the diet of various
aquatic birds. The absence of these and other aquatic
organisms can become limiting factors for some water-
fowl populations. The disappearance of the fingernail
clams and other bottom fauna created a drastic loss in
the food supply of most diving ducks that inhabited the
Illinois River valley.

Anderson (1959:316) found that mollusca made up
more than 85 percent of the diet of lesser scaup ducks
[Aythya affinis) . The ring-necked ducks [Aythya col-
laris) made mollusca about 25 percent of their diet, and
the food of canvasbacks {Aythya vallisincria) was made
up of about 9 percent mollusca.

The combined loss of aquatic plants and bottom
animals has drastically affected the numbers of diving
ducks that use the Illinois during their migrations. Just
as the loss of mollusca apparently caused problems with
the lesser scaup, the loss of vegetation in Spring Lake,
near Manito, has affected other species. Coontail pro-
vided food for several thousand redheads [Aythya ameri-
cana) during the spring migration. Now the redheads
are forced to seek food elsewhere. Peoria Lake, once the

scene of the greatest fall concentration of diving ducks
in Illinois, has suffered an almost complete loss of these
birds.

Many dabbling duck species as well, such as the
widgeon (Marcca amcricana) and the gadwall (Anas
strepera), are well known to be dependent on water
plants for food.

Let us briefly examine some f)opulation statistics for
a few important duck species.

Lesser Scaup

Fig. 1 1 shows the yearly change in lesssr scaup pop-
ulations in both the Illinois and Mississippi river valleys
from 1946 to 1964. Both rivers are included to indicate
the possibility of change of duck populations from one
valley to the other. Prior to 1955 the bulk of the fall
population of this species was concentrated in the Illinois
River valley. A tremendous decline occurred among the
lesser scaups stopping along the Illinois in 1955, and
numbers have remained insignificant since then. This
reduction is synchronous with the disappearance of
fingernail clams. It would appear that, after 1956. some
elements of the Illinois River scaup population gradually
shifted to the Mississippi. Although this shift could ac-
count for a part of the previous Illinois River popula-
tion, Fig. 1 1 indicates that the total population for the
state has been substantially reduced. ^Ve might infer
that the Mississippi Ri\ er docs not contain enough food
to support a population of lesser scaup such as was

LESSER SCAUP

2,520,000-1

ILLINOIS RIVER VALLEY
MISSISSIPPI RIVER VALLEY

1,200,000

> 1, 000,000

800,000

600,000

K
lij
SI

400,000

< 200,000-

1946 '47

1946 to 1954

1955 to 1964

Fig. 11. — Changes in Irsscr scaup duck populations on the Illinois and Mississippi ii\er valleys from 19-lti to 196.1. The reduced
populations after 1954 coincide with the virtual disappearance of the fingernail clams from the river above Bcardstown. (Illinois
Natural History Survey data.)

present on the combined rivers from 1946 lo 1954, for
iheir decline was greater than that for the flyway as a
whole.

Ring-necked Duck

Ring-necked ducks were at a peak in numbers in
1949 when aquatic plants reached maximum abundance
in Peoria Lake (Fig. 12). With the decline in abun-
dance of both aquatic plants and mollusca in the Illinois
River valley, populations of these ducks declined. In the
1955-1964 period the number of ring-necked ducks did
not decline proportionately so much as did the lesser
scaups. The ringneck seemed to be better able to use
the flooded moist-soil plants for food. Moreover there
was some decline in the populations of this species in
the Mississippi area for several years after 1955. The
decline probably reflects a known decrease in flyway
population from out-of-state causes, for there was no
commensurate deterioration in habitat conditions in the
Mississippi valley.

Canvasback

Populations of this species slumped as badly as did
those of the lesser scaup following the loss of plant and
animal food resources from the Illinois River valley
(Fig. 13). The canvasback population in the Mississippi
River valley increased during the 1955-1964 period, fol-
lowing the great disappearance of these birds from the
Illinois system, but the total population for the state is
still far below the pre-1955 level. Canvasbacks in the
Mississippi River section of Illinois are forced to feed
almost entirely on animal life because of the scarcity of

aquatic vegetation, yet food-habit studies (Anderson
1959; Cottam 1939) show their preference for aquatic
plant foods.

The paucity of plant-food resources in the Mississippi
River section probably limits the numbers of canvas-
backs to a level far below that accommodated by both
river valleys in the early 1950's.

Ruddy Duck

The ruddy duck {Oxyura jamaicensis) declined in
numbers with the decline in aquatic plants and mol-
lusca (Fig. 14), but this decline was proportionately less
than in other diving ducks, possibly because of this spe-
cies' propensity to feed on aquatic insect larvae (Ander-
son, loc. cit.). Insects have not as a group suffered
catyclismic losses as have the mollusca in bottomland
lakes. Therefore more animal food to the liking of ruddy
ducks remains available in this valley. The Mississippi
River seems to have absorbed a part of the Illinois River
population, as in the case of other diving ducks, but it
appears that the "carrying capacity" of the Mississippi
may not be sufficient to overcome the loss of the food
resources in the Illinois.

Mallard

Populations of this common duck (Anas plalyrhyn-
chos) in the Illinois and Mississippi river vallevs do not
show the same trends as do the dixing duck pojjulations,
or those of the dabblers dependent on aquatic vegeta-
tion. Although mallard populations declined after 1955,
this decline occurred almost equally in both valleys; no

RINGNECK

900,000

nn] = ILLINOIS RIVER VALLEY
■ = MISSISSIPPI RIVER VALLEY

150,000

1946 47

360,000-.

^ 300,000

,240,000

o 180,000

120,000-

60,000

1946 10 1954

1955 to 1964

Fig. 12. — The ring-ncrkrd durk drrlinrd in abund;inrr in the Illinois Ri\rr following thr loss of the- molUisi- food rcsourci- and
tlic reduction in aquatic vegetation. (Illinois .Natural History Survey data.)

drastic reduction occurred solely in the Illinois River
valley (Fig. 15).

The lower mallard population in Illinois following
1955 is attributed almost entirely to loss in production
resulting from drought on the northern plains breeding
grounds. The decline in mallard numbers in Illinois did
not parallel the loss of aquatic plant and animal food

resources. The mallard in Illinois feeds mainly on waste
corn and the seeds of moist-soil plants (Anderson 1959) :
its sustenance is more stable, being to a large extent in-
dependent of animal life or aquatic plants.

Mallards have sufTered a greater diminution because
of drought on the northern plains than have most of the
diving ducks; lesser scaup and ring-necked ducks in

CANVASBACK

360,000-

^ 300,000-

= 240,000-

g 180,000-

D
Z

sJi

m^Bu

? 120,000-

ilR

60,000-

010= ILLINOIS RIVER VALLEY
■ = MISSISSIPPI RIVER VALLEY

168,000

!^ I40P00-

Q 112,000-

84,000-

56,000-

< 28,000

1946 '47 '48 '49 '50 '51

Fig. 13. — Canvasback duck
aquatic vegetation and mollusca.

52 53 54 55 '56

populations declined drastically in the
(Illinois Natural History Survey data.)

61 62 63 64
Illinois River

alle

1946 lo 1954
following the near disa

1955 to 1964
ppearancc of

RUDDY DUCK

72,000

u 60,000-

i 48,000

£ 36,000

Z
-I

? 24,000

12,000-

\ \

El = ILLINOIS RIVER VALLEY
■ = MISSISSIPPI RIVER VALLEY

1946 47 48 '49 '50

36,000-1

Si; 30,000

a 24,000

18,000-

12,000-

< 6,000-

l»46 10 1954

1965 10 1964

lig. II. — Ruddy ducks feed on both .small mollusca and aquatic in.srct larvae. Because aquatic insect lar\ac did not decline in
abundance so much as the mollusca, these ducks persisted in greater numbers, proportionately, after 1954 than did other diving ducks.
(Illinois Natural History Survey data.)

MALLARD

7,200P00

6,000,000

4,800,000-

3,600,000

2,400,000-

1,200,000-

ILLINOIS RIVER VALLEY
MISSISSIPPI RIVER VALLEY

3.600.CX)0-

•

^3,000,000-

5 2, 400,000-

llJ

m 1,800,000-

o 1,200.000-

^^^

■.■.■.■.\-.-.

^^H

600,000-

1946 10 1954

1955 to 1964

Fig. 15. — The mallard duck feeds primarily on plant foods, largely seeds of moist-soil plant.s and waste crop grains, so its pop-
ulation was not affected by the loss in mollusca and aquatic vegetation. The population decline in Illinois reflects the continental
trend for this species. (Illinois Natural History Survey data.)

particular have escaped severe drought losses. In spite
of their greater productivity during this drought period,
the lesser scaups and ring-necked ducks, as well as other
diving ducks in the Illinois River valley, declined in num-
bers proportionately much more than the mallard.

The difference in the geographic and yearly popula-
tion change between the mallard and the diving ducks
fortifies our belief that the post- 19.55 diving duck popula-
tion loss is directly related to the loss in food resources
resulting from silting, and from inban and industrial
pollution of the Illinois Ri\er and bottomland lakes.

To generalize, it would appear that recent environ-
mental changes in the Illinois River, due to activities of
an enlarging human population, have produced dis-
astrous consecjuences on food resources for diving ducks
as wtII as for some dabblers. From the mid-1950's to
the present, a combination of soil pollution jjIus indus-
trial and domestic pollution appears to ha\c eliminated
as a functional ])art of the (•n\ir()nmcnt tin- important
aquatic plant and animal life necessary for the support
of populations of many species of ducks. 'I'hesc may not
be the only factors involved; we do know that in certain
[jlaces the raising of water levels, for examjjle, has con-
tributed to the decline of a(|uatic vegetation.

OTHER BIRDS

A study of any group of species of birds will show
fluctuations in numbers from year to year. Some of these
changes in bird populations in the Illinois River valley,

although rons])icuous. cannot be tiarcd to the deteriora-

tion of water ciuality in the river. For example, the pro-
thonotaiy warbler (Protonolaria citrca) was abundant
near Chautauqua Lake 15 years ago and is now moder-
ately rare. It is a cavity-nesting, insectivorous species,
and at the time of its abundance there were many dead
willows along the edges of the lake. The warblers used
holes in the trees for nesting. As the trees decayed and
fell, the numbers of the birds decreased, and the logical
explanation for this population reduction is the disap-
pearance of nesting sites.

Changes in some other sjJecies may have a moie di-
rect relationshi]) to changes in the river.

Cormorants

Each autumn during the 1940's and the early I950's
there was a large flight of double-crested cormorants
(Phalacrocorax auritus) down the Illinois River valley.
The migrants usually arrived between October 5 and 9.
Many thousands remained until early November, con-
ducting fishing drives in the larger bottomland lakes.
On October 16, 1950, we estimated that there were
15,000 cormorants on the lakes in the valley between
Spring Vallev and Meiedosia.

The largest single flight of cormorants was ob.served
on October 7, 1940, when an estimated 12,000 passed
Havana. Another flight of approximately 9.500 |jassecl
that city on October 9, 1949.

A rapid decline in the numbers of cormorants visit-
ing the Illinois River valley occurred after 1950. The
largest passage in 1955 occurred on October 14, w^hen
4,000 were estimated. By 1958 the great passage of cor-
morants had dwindled to onlv SOO which were observed

Table 2. — Approximate number of nests of great blue herons and American egrets in heronries in the Illinois Ris'cr valley. 1958-
1964, based on counts made from a circling light aircraft.

V 1958 1962 1964

Location of Great Blue American Great Blue American Great Blue American

Nesting Colony Heron Egret Heron Egret Heron Egret

LakeDepue 250 250 250 300 75 120

Wise's Lake 60

Pekin Lake 125 125 280 iM) 60 75

Clear Lake 110 100 110

Ingram Lake 250

Meredosia Bay 90 500 1 50

Total 775 375 J, 140 640 385 305

on October 5. From 1959 to 1965 veiy small numbers
of cormorants, usually fewer than 200, have been ob-
served at any one time in the autumn. On October 18.
1965, only 22 cormorants were observed on an aerial in-
ventory of water birds in the Illinois River valley. This
was the largest number seen in 1965.

We do not know the cause of this decrease in num-
bers of cormorants migrating through the Illinois River
valley, but somewhere along the line a great change in
their environment must have occurred.

Herons and Egrets

There is a subjective feeling that the great blue heron
(Ardea herodias) exists on the Illinois River in diminish-
ing numbers, and it appears fairly certain that although
the numbers of American egrets [Casmcrodius albus) in-
creased until 1962 there has been a decline since then.
Our data, however, cover such a short span of time that
they do not present a strong basis for evaluating long-
term population trends (Table 2). Nesting populations
of these two species have fluctuated considerably from
19.58 to 1964.

Counts of great blue heron and American egret nests
were made at several heroniies along the Illinois Ri\er
in June, 1939. A direct comparison of these nest conc<'n-
trations with those of more recent times is not possible,
for several of them have been vacated and new ones
created. However, the nest data suggest that the num-
bers of great blue herons ha\c declined and that the
numbers of American egrets have increased. Only 17
egret nests were found in four heronries in 1939, while
305 were located in three of the lieronries in 1964.

CONCLUSION

An attempt has been made in the preceding pages to
make comparisons which relate measurable changes in
fish and wildlife populations of the Illinois River and
its bottomland lakes to human activity during the past
ihrec-tiuarters of a century. Even though a tremendous

amount of biological data is available for the river, there
are still many areas where we know very little concerning
the organisms which li\ e in or have lived in this habitat.

Some things become apparent from this study. Noth-
ing in our physical environment ever remains static:
change is the rule. But in this period in historv" when
people are gaining more and more mastery over their
environment, they have bent their intelligence toward
making unusual changes that may benefit them temjx>-
rarily but may be deleterious when a longer period is
considered.

It is unrealistic to delay doing things which benefit
people until we know all of the possible side effects which
may go along with these actions. If we were to do this
there would never be any progress. But when such side
effects become apparent and are not good, and there are
ways of circumventing them, we do not use our intel-
ligence if we fail to make corrections.

It is difficult to believe that so much has happened
to the Illinois River and its floodplain since Kofoid pub-
lished his comprehensive work in 1903. Starting with
the diversion of Lake Michigan waters into the river in
1900. the ecology of this stream has been changed dras-
tically several times. This diversion added to the fish
liabitat in the lower stretches and remo\ed it completely
in the upper river. Drainage enterprises removed half of
the floodplain that the river once used and eliminated
fish and waterfowl habitat. Navigation dams created
new water areas while destrcning important waterfowl
marshes. Domestic pollution has fluctuated up and down
as new sewage treatment plants have been activated and
then found to be inadecjuate as the rising tide of human
population in the basin caught up with them. Chemicals
ha\e been released into the waters from developing in-
dustries on the river's banks and in the watershed.

Although these actions have caused conditions to fluc-
tuate widely, the net result has been an ever-diminishing
biological resource as the aquatic habitat and its inhabi-

Fig. 16. — A carp-goldfish
hybrid collected from the pol-
luted upper Illinois Ri\er. Note
the eroded tail and fin.s.

tants have been degraded by the activities of man (Fig.
16). Here and there man has tempered this degrada-
tion — wildlife refuges and public hunting and fishing
grounds have been established, and management of some
areas by hunting clubs has produced better habitats than
existed prior to this activity.

We trust that the deleterious trends now apparent in
the Illinois River can be changed. Some of the knowl-
edge of how to do this is now available. More must be
gained. There must be the desire on the part of agricul-
ture, municipalities, industn', and individuals to trans-
late present knowledge into action.

LITERATURE CITED

Anderson, Harry G. 1959. Food habits of migratory ducks in
Illinois. Illinois Natural History Survey Bulletin 27(4) :289-
344.

Barrows, Hari.and H. 1910. Geography of the middle Illinois
valley. Illinois Geological Survey Bulletin 15. 128 p.

Bartow, Edward. 1913. Chemical and biological survey of the
waters of Illinois: Effect of Chicago sewage on the Illinois
River. University of Illinois Bulletin 10(36), Water Sur\-ey
Series 10:30-45.

Bei.lrose, Frank C. 1941. Duck food plants of the Illinois
River valley. Illinois Natural History Survey Bulletin
21(8):237-288.

BoRUFF, C. S. 1930. Illinois River studies 1929-1930. Illinois
Water Survey Circular 9. 8p.

, and A. M. Busweli.. 1929. Illinois River studies

1925-1928. Illinois Water Survey Bulletin 28. 127 p.

Brown, Cari. B., J. B, Stall, and E. E. DeTurk. 1947. The
causes and effects of sedimentation in Lake Decatur. Illi-
nois Water Survey Bulletin 37. 62 p.

Cohen, Nat H., S. P. Bartlett, and A. Lenke. 1899. Report
of the Illinois state fish commissioner from October 1, 1896,
to September 30, 1898:3 42.

CoTTAM, Clarence. 1939. Food habits of North ,\merican
diving ducks. USDA Technical Bulletin 643. 140 p.

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(89820-8000— 6-66 >

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