Please handle this volume with care. The University of Connecticut Libraries, Storrs 3 T153 DDTDfiflflb 7 Digitized by the Internet Archive in 2013 http://archive.org/details/smallbottomshoreOOrich Donated By LYLEM. THORPE STATE OF ILLINOIS DEPARTMENT OF REGISTRATION AND EDUCATION DIVISION OF THE NATURAL HISTORY SURVEY STEPHEN A. FORBES. Chief Vol. XIII. BULLETIN Article XV. The Small Bottom and Shore Fauna of the Middle and Lower Illinois River and its Connecting Lakes, ChiUicothe to Grafton: its Valuation; its Sources of Food Supply; and its Relation to the Fishery BY ROBERT E. RICHARDSON GOVEKNiVltNT RECEIN1 APR 2 6 UMIVERS1TY l| UHjV£F31TY OF CX PRINTED BY AUTHORITY OF THE STATE OF ILLINOIS V URBANA, ILLINOIS June, 1921 983 BRARY NNECTiCUT CONTENTS PAGE Introduction 363 General summary 366 Hydrography and bottom fauna, Illinois River, Chillicothe to Grafton, July— October, 1915 376 (a) Chillicothe to foot of Peoria Lake (18.5 miles) 376 (b) Foot of Peoria Lake to Pekin (9 miles) 386 (c) Pekin to Copperas Creek dam (16.2 miles) 388 (d) Copperas Creek dam to Havana (16.8 miles) 392 (e) Havana to Lagrange dam (42.5 miles) 398 (/) Lagrange dam to Grafton (77.5 miles) 404 (g) General summary, Illinois River bottom fauna, July — October, 1915 409 The bottom fauna of the lakes and ponds of the Illinois River bottom- lands between Copperas Creek dam and Lagrange, July — October, 1914—1915 418 The weed fauna of the 1 — 4 foot zone of the Illinois valley lakes, and the combined bottom- and weed-fauna average, August — October, 1914 431 The bottom and weed1 fauna of the littoral zone of the deep glacial lakes of northeastern Illinois, August — October, 1916 433 Comparison with outside bottom- and weed-fauna valuations -435 The food of certain small bottom-invertebrates in the river channel at Havana and the general composition of the detritus 439 The nitrogen, organic carbon, and other oxidizable matter in the bottom muds of the river and lakes below Chillicothe, 1913 — 1914 444 The plankton and other limnetic oxidizable matters carried by the Illi- nois River channel at Chillicothe and Havana, 1909 — 1914 448 General comparison of the Illinois River and the connecting lakes in the food resources of a fishery and in fish output 462 The reproductive rate of the bottom animals 472 Changes in the quantity of the bottom-fauna stocks between 1913 and 1915 474 Detailed valuation tables: I. Bottom Fauna, Illinois River, 1915 477 II. Bottom fauna of the lakes of the Illinois valley, Copperas Creek dam to LaGrange, 1914 — 1915 494 III. Weed fauna, 1- to 4-foot zone, lakes and backwaters in vicinity of Havana, 1914 512 IV. Bottom and weed fauna, littoral zone of glacial lakes of north- eastern Illinois, 1916 515 Bibliography 522 Profile of Illinois River, Chillicothe to Lagrange dam. Maps of Illinois River and bottom-land lakes, Chillicothe to Grafton. Article XV. — The Small Bottom and Shore Fauna of the Middle and Lower Illinois River and its Connecting Lakes, Chillicothe to Graf- ton: its Valuation; its Sources of Food Supply; and its Relation to the Fishery. By Robert E. Richardson. Introduction The present paper, so far as it relates particularly to the valuation of the bottom and shore animals, brings together the results of three sum- mer-autumn seasons of dredging operations in the Illinois River and its connecting backwaters, July, 1913, to October, 1915. The work in the river proper and in the wide expansion of its waters known as Peoria Lake included forty cross-sections, at intervals ranging from one to about eleven miles, covering the lower one hundred and eighty miles of the river, or about 80 per cent, of the total distance- between the mouth and the head of navigation at La Salle ; and embraced a total of three hundred and eighty-seven dredge and dipper collections. The dredging opera- tions in the more inclosed bottom-land lakes were mainly confined to those in the middle Illinois valley district of about fifty-nine miles river length between the Copperas Creek and Lagrange dams, in the lakes and other backwaters of which region three hundred and eighty-five dredge and dipper hauls were taken during the three working seasons. In addition to the collections of the bottom animals for the valua- tion studies, sieved samples of the mud deposits on the floor of both the river and the lakes were taken in 1913 and 1914 and analyzed for such indications as they might contain of reasons for differences in productiv- ity of different bottom areas. Between M.arch, 1914, and February, 1915, also, standard sanitary chemical analyses of water samples from a lim- ited number of stations in the upper, middle, and lower river were car- ried on continuously at weekly intervals with a view particularly to obtaining data on the nitrogen load of the waters and on the rate of progress of its nitrification. Such comparisons as are undertaken Avith plankton production are with reference mainly to data collected in 1909 and 1910, the most recent seasons devoted at all extensively to plankton operations in the region of the river covered by" the present paper. Some principal conclusions from the plankton work of these two years in the river and lakes at Havana, as also from the sanitary chemical analyses of 1914-1915, have already been reported upon in papers by Prof. Forbes and the present writer (Forbes and Richardson, 1913; 1919). Apparatus. — The collection of the bottom fauna was begun in the summer of 1913 with our ordinary iron dredges (modified "Blake" or 364 "Naturalist's" type (see pages 367, 368), supplemented in some situa- tions where there was unusually soft mud and where the heavier framed iron dredges were inclined to sink too deeply and fill too quickly, with a lighter framed dredge following closely a recent design by Ekman which was intended for quite a different purpose. (See Fig. 3 and 4.) Although there was no expectation early in the work of making more than a very rough quantitative application of the biological data obtained, all the dredge hauls were, from the first, of a previously de- termined and recorded length. The introduction into use in the summer of 1914, for work in water under eighteen feet in depth, of the "mud- dipper" (see Fig. 5), an instrument bearing some resemblance to the Walker dipper-dredge as used by Baker (1916, 1918), and the adop- tion of finer meshed inner bags for it and the dredges, was the means of what appeared to be rather more accurate work that year than in the first season, while at the same time its use in parallel test hauls of differ- ent lengths alongside the iron dredges suggested that averaged results from measured drags, under certain limits of length, with either, had a greater quantitative value than we had at first believed. It was found, in brief, that with a 22" X 6" front iron dredge we took on the average as many bottom animals by hauling five feet as by hauling ten, and with a 6-inch mud-dipper as many in two feet as in four, but that in hauls under two or five feet, in either case, we got less. As the aver- age 5-foot haul with the dredge was in the neighborhood of ten times the 2-foot drag of the dipper, and the 2-foot dipper haul about five times a quick deep dip of the mud-dipper to a depth of about three inches (ap- proximate area covered, 25 square inches), it was an easy step to the con- clusion that on a rough average, if a few apparently aberrant cases be excluded, the most of the 5- to 10-foot dredge hauls might be safely taken to represent an effective drag of about one square yard, and the 2- to 4-foot hauls of the dipper an effective drag of about 0.1 square yard (125 to 130 square inches). Still more recent parallel tests of the dipper alongside a new Petersen self-closing bottom sampler have not served materially to change these conclusions. The method used for collecting the small weed animals in the zones of densest vegetation (usually in water under four feet deep) was in- complete, taking in only the small fauna within the 0 to 9-inch depth line. A large bucket of known depth and diameter was lowered about the tops of the plants, the stems were cut off underneath, and then the bucket was brought into an upright position quickly ; after which the weed-tops were shaken out in the water saved, and that was finally passed through a 120-mesh sieve. Pulling up the weeds entire in- water over two and a half feet deep had shown that the attached weed animals, whether snails, insect larvae, or Crustacea, were, in bulk at least, decidedly most abun- dant nearer the top. And the adoption of the method also followed, by necessity, some unsatisfactory experience in the use of a small 3-legged caisson and pump — which involved the handling of vastly more material 365 than was practicable, with also an annoying tendency to in-leakage of outside water at the bottom. Valuation. — The determination to undertake a valuation of the bot- tom invertebrate populations that come within the feeding horizon of our ordinary bottom-feeding fishes in terms of pounds per acre was made some time after the conclusion of our field work in 1915, and has been carried out on a basis of estimated average-sized specimens of the va- rious species as they ran in a relatively small number of typical midsum- mer collections weighed after more than a year's preservation in alcohol and formalin. An average correction of 25 per cent, for loss in weight in alcohol (on a base of body weight only for Mollusca, and on a base of gross weight for other groups) has been made, after a limited number of experimental weights, in the preserved and the fresh state, of a few snails and insect larvae. The final valuation figures, so far as they in- clude insects, their larvae or other immature forms, worms, or Crustacea, represent gross rough weights, but in the case of the Mollusca (Gastrop- oda, Sphaeriidae, or young Unionidae) represent the body weight only, after deduction of shell weights at rates determined separately for each species by actual weighing. Sponges, Bryozoa, and other smaller in- crusting invertebrates are not included in the valuation figures ; as are not also crayfish or pearl-button mussels, except the young. Acknowledgments. — For many of the hydrographical and physical data we are indebted to the U. S. Army Engineers' survey of 1902 — 1905 (House Document 263, 59th Congress, 1st session, and accompanying charts) ; as well as to Alvord and Burdick's recent excellent report (1915) on the Illinois River and its bottom-lands; and, in a lesser de- gree, to the Report of the Legislative Committee on submerged and shore- lands (1911). Thanks are also due Dr. Edward Bartow, Chief of the State Water Survey, for his interested cooperation in obtaining the san- itary chemical analyses of river waters in 1914 ; and to Prof. S. W. Parr for supervising the analysis of the bottom mud samples taken that year and the year preceding. To Mr. Charles A. Hart is owing a special debt for his assistance in the determination of much of the more unfamiliar biological material of the earlier collections, taken in the preliminary field work of July-September, 1913. Mr. F. C. Baker has contributed both facts and opinions that have made possible rough valuations, for comparison with our own, of the littoral bottom fauna areas of the lower south bay of Oneida Lake, New York, reported upon by him in two very interesting and valuable papers in 1916 and 1918. To these two papers and to Dr. C. G. Joh. Petersen's several recent contributions on the valua- tion of sea-bottom off the Danish coast (Reports of Danish Biological Station, 1911-1918), I owe not a few ideas which have cast illumination in more or less dark places. The general plan into which the present piece of work is intended to fit, the directing force behind it, and the sup- ply of means and general suggestions as to methods for its execution, have been the work and care for many years of the Chief of the Natural 366 History Survey, Professor Forbes, without whose aid in these more pro- foundly important respects the present investigation would doubtless neither have been conceived or carried out in its present scope and form. Illustrations of Apparatus. — Fig. 1. Iron dredge, showing canvas protector • covering posterior bobinet bag, and forward coarse-mesh bag hung backward inside. Fig. 2. Iron dredge, showing canvas protector rolled back to un- cover bobinet bag, and forward coarse-mesh bag pulled out in front of frame. Fig. 3. Ekman dredge, showing canvas protector covering pos- terior bobinet bag, and forward coarse-mesh bag hung backward inside ; front mud shoes of Ekman design omitted. Fig. 4. Ekman dredge, disposed as iron dredge in Figure 2. Fig. 5. Mud-dipper, showing bobinet bag pulled out in front of thimble, and canvas protector in position for drag. Fig. 6. Apparatus used in 1914 for collecting samples of the thin bottom ooze for study of the composition of the lighter detritus and the microorganisms entering into the food supply of the small bottom animals. General Summary It is the purpose of the studies here reported to make an estimate, based on many quantitative collections, of the total store of animal life on and in the bottom sediments of different sections of the middle and lower Illinois River and its bottom-land lakes and on the plants of their shal- lower, marginal waters, to trace the causes of the wide differences in this respect between river and lakes and between different sections of the stream, to estimate, also quantitativly, the food resources which the bottom muds contain for the animals inhabitating them, and thus to trace in a gen- eral way the successive steps by which the organic materials in the muds and waters of the river system* are converted into forms available as food for man. This is, in fact, to be regarded as essentially a soil survey of these aquatic public properties, for the beds and weedy margins of rivers and lakes are a natural soil of various fertility, of which the animals, mainly univalve mollusks and a few kinds of insect larvae, are the crop, harvested chiefly by fishes, these being harvested in turn by man. From this point of view the upper Illinois River is, under present conditions, mainly a mass of plant and animal weeds — forms which occupy the pol- luted waters to the practical exclusion of everything useful to human kind — but the current of this section carries elements of a normal fertility to the lower reaches of the river, depositing a large part of them finally in the silts and sediments of river and lake in forms available for the nutrition of normal aquatic life, but bearing also an immense quantity to the mouth of the stream where it escapes unutilized into the Mississippi. The river system below Chillicothe varies enormously in the produc- tiveness of its different parts, the richest of them being the weedy margins 367 368 369 bo c 3 be di3 c .to bCO o CD O -t-> w O M ft «w O ft "" CD «S W 03 > c bOoj II 0 bo CD 370 3 e bo C o & fc «j < o C5 fc N o H H O o w O CO W o o Ph Is d n o3 O d +- O IS o.2 o o3 » g 8 o S aJ a I s £ s-i S 5 ■3 ^ CD oS T3 •i— i o 00 Tfl cm T-i CO CO c^ o rH O CO T*t lO CO os rH o rH CM Ph o 02 ^ «2 o O +j P=h 02 Si CD Jh id «* O ^ d o> O -M «M O £ *■< p- CD <1Ph rH h o N 00 Tt* CaI rH co CO rH t- o to rH O ^1 CO Tfl CO CO Tt< o rH (?q •Tin CO ■>* t- C- OS C5 O to rH tO oq CO 00 oo to CO to T-i ■«*" T-i rH t- to •'t1 OS to to o o oo to OO CO TjH CO T-i CO t~ CO t-^ TjH OS "^ CO CO ""* rH CD ^ o3 J c3 •1—1 i-t o cu Ph «(-l 0) ° ^ -+-J •i-H O r* O 72 =<— < 02 _ c o i— i 03 ° s O ■+-> o ^ «M (X) ^H o d ^ o ^ I— 1 M •H O CD ^, ,d CD (> CD OPh <1Ph 386 (b) Foot of Peoria Lake to Pekin (9 Miles) Hydrography. — After- passing over the high bar above the mouth of Farm Creek (foot of Peoria Lake) the river follows a comparatively swift and narrow channel to Pekin, the average velocity at a flood gage of eighteen feet, Peoria, being 191.64* feet per minute for the 9.8 miles between the foot of Main St. and the wagon bridge at Pekin, and the width (at low water of 1901) usually under six hundred feet. The aver- age slope of the water surface at the low levels of 1901 was two inches per mile, and 4.36 inches per mile at the high water of March, 1904. These average slopes and velocities are much greater than are met with in any other considerable section of channel in the one hundred and twenty-five miles between Chillicothe and Florence, and are four to seven times the figures for the 18.5 miles between Chillicothe and the foot of Peoria Lake. Decline in Elevation of Water Surface Reach Stage of river Interval miles Av. slope inches per mile Low water Foot of Peoria Lake to Pekin 1901 Flood stage 9.2 . 2.00 (< Mar. 15, 1903 9.2 3.45 Flood stage it Mar. 31, 1904 Low water 9.2 4.36 Chillicothe to foot Peoria Lake 1901 Flood stage 18.3 0.26 << Mar. 31, 1904 18.3 0.64 The channel floor is sand and shells, nearly denuded of mud, for most of the nine miles. At our 1915 collecting stations between Wesley and Pekin the bottom was hard, but opposite Pekin the hard bottom was overlaid with a very thin covering of soft silt. Between the 4- and 7- foot lines at Wesley in 1915 hard gravel bottom washed clean of mud was found both on the east and west sides. At the shore stations below the wagon bridge at Pekin six inches of soft mud was found on the west side and 12 to 36 inches on the east. Shore vegetation, except an occa- sional narrow fringe at the bank edge, is wanting. At the low water of 1901 the bank to bank width of the river be- tween Peoria and Pekin was usually between 400 and 600 feet, only a very short stretch just below the mouth of Farm Creek much exceed- ing 600. Depths in the wider and shallower stretches ranged from 7 to %y2 feet; and in the deeper and narrower ones between 10 and 13 feet. Average depths at recent low levels (gage of July-October, 1910-1914) have been about 3^ feet more than these figures. The connecting lake * Table, p. 377. 387 acreage (113.6 acres per mile at the low water of 1901) is little more than a third of that which occurs between Chillicothe and the foot of Peoria Lake (299.9 acres per mile) ; and is under the rating of any other section of the river between Chillicothe and Kampsville.* Widths and Depths, Foot of Peoria Lake to Pekin, Low Water, 1901 Miles above Grafton Station Width, ft. Depth ft. max. 161.9 160.7 159.9 159.0 158 0 50 yds. below mouth Farm Cr. P. &. P. U. R. R. bridge 100 yds. below Wesley 347 915 640 402 514 586 640 515 439 475 8.1 6.6 11.8 8.3 7 5 157.0 7 5 156.0 7 2 155 0 8 5 153 9 12 4 153 3 10 3 153.0 Pekin, at wagon bridge 11.2 Bottom Fauna. — The bottom collections made in cross-sections at Wesley and Pekin in 1915 included four channel hauls and four hauls in the 4r-7-foot zone. In neither depth zone was a fauna indicated quite so rich as that of the channel and shore zones between Peoria and Chilli- cothe, the average channel poundage amounting to 253.8 lbs. per acre, and that of the 4-7-foot zones to only 206.3 lbs. Larvae of caddis-flies (principally Hydropsyche sp.) were decidedly more abundant in the swifter stretches of channel between Peoria and Bottom Fauna, Channel, Wesley to Pekin, 1915 Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Number per sq. yard, Average 87.7 16.7 129.0 Pounds per acre, av. 224.6 8.3 20.9 Total 233.4 253.8 collec- tions 4 collec- tions Per cent, of total, (By weight) 88.6% 3.2% 8.2% * See table, p. 378. 388 Pekin than above Peoria, and the Sphaeriidae less sp. The larger Gas- tropoda (Viviparidae and Pleuroceridae) made up about the same per- centage of the average weight of collections as above Peoria (88.6%). In the 4-7-foot zone the Sphaeriidae showed the heaviest poundages (66.2% of totals), and the insect larvae and the larger snails were rela- tively much less abundant than in channel collections. Bottom Fauna, 4 — 7-foot Zone, Wesley to Pekin, 1915, Average Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard 20.0 272.5 56.5 349.0 4 collec- tions Pounds per acre 60.0 136.7 9.6 206.3 4 collec- tions Per cent, of total, (By weight) 29.2% 66.2% 4.6% (c) Pekin to Copperas Creek Dam (16.2 Miles) Hydrography. — Following the swift run from the foot of Peoria Lake to Pekin, where the low-water slope in 1901 was 2.00 inches per mile, the effect of the dam at Copperas Creek became very distinct be- low Pekin at those low levels, and the average slope of water surface between Pekin and the dam fell to 0.14 inch per mile. Although this average low-water decline is not much more than half that between Chillicothe and the foot of Peoria Lake (0.26 inch per mile for 18.2 miles), at ordinary spring flood-levels the slope rate is multiplied ten times or more (1.40 inches per mile at gage 18 ft., Peoria), and the aver- age flood velocity (114.40 feet per minute at gage 18 ft., Peoria) rises to a figure more than double that between Chillicothe and Peoria.* This circumstance — a consequence of the fact that at flood stages the sweep of the current tends to follow the old lines of slope of water sur- face as they existed before the low-crested dam was put in — accounts for the generally well-scoured channel floor that we find throughout this reach of 16.2 miles, not even excepting its lowermost portion just above the dam. The only important stretch of soft mud bottom in the channel in the 16 miles is the deposit occupying less than a mile of channel length just above the mouth of the Mackinaw. With the exception of that and of about a mile of dirty sand which ends a mile above the dam, the gov- * Table, p. 377. 389 Decline in Elevation of Water Surface Reach Stage of river Interval miles Av. slope inches per mile Pekin to Copperas Creek dam (above) Low water - 1901 16.2 0.14 Pekin to Copperas Creek dam (above) Flood stage Mar. 15, 1903 16.2 1.36 Pekin to Copperas Creek dam (above) Flood stage Mar. 31, 1904 16.2 1.43 ernment borings of 1902-1905 showed hard bottom at all channel sta- tions, the upper layer of sand, gravel, or sand and shells having depths of from five to twenty-nine feet. In the shore zones within the 7-foot line mud bottom was found by us in 1915 at all the collecting stations. There is no shore vegetation worth mentioning in the 16 miles. Between Pekin and Copperas Creek dam at the 1901 low levels, bank to bank widths averaged rather greater than in the Peoria-Pekin section, being usually over 600 feet, and for short distances 700 feet and over. The greatest depths at these levels were under 15 feet, and in a Widths and Depths, Pekin to Copperas Creek Dam, Low Water, 1901 Miles above Grafton Station Width, ft. Depth, ft. max. 153.0 152.8 Pekin at wagon bridge 695 • 750 440 677 384 600 610 695 700 549 732 622 586 530 550 586 570 677 549 11.2 13.0 152.5 7.1 151.7 10.2 150.5 11.0 149.9 8.6 149.3 14.1 149.0 9.0 147.9 12.6 146.8 7.4 145.6 145.2 8.7 14.7 144.6 7.0 143.9 8.4 142.9 8.3 141.3 11.6 139.0 8.4 138.3 14.5 137.7 9.3 137.2 10.4 136 95 11.0 136.8 Dam 390 large part of the section ranged between 7 and 9 feet. Recent maximum low-water depths have been mostly 2 to 3^ feet more than these. The connecting lake and pond acreage in this section at the low levels of 1901 (219.0 acres per mile) was about twice that between Peoria and Pekin per mile of river length, but was not much more than two thirds that between Chillicothe and the foot of Peoria Lake, and was less than half that between Copperas dam and Havana.* Bottom Fauna. — A total of 14 channel collections and 16 shore col- lections were made between Pekin and the dam in 1915 at stations as shown below. Miles above Grafton Station • Channel 4 — 7— ft. zone 1 — 3-ft. zone 151.5 iy2 miles below Pekin 2 2 145.6 Opposite Kingston 6 3 3 141.9 Opposite Spring Lake canal 4 4 4 136.8 100 yards above dam 2 Total 14 The average valuation figure for the channel fauna in the section (144.8 lbs. per acre) was lower than in any other important stretch of channel between Chillicothe and Havana. The weight of the average channel collection was not far from equally divided between the Sphaeriidae and the larger Gastropoda, the first contributing 43.7%, the Bottom Fauna, Channel, Pekin to Copperas Creek Dam, 1915 Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average 28.8 126.9 49.8 205.5 14 collec- tions Pounds per acre, Average 73.3 63.4 8.1 144.8 14 collec- tions Per cent, of total, (By weight) 50.6% 43.7% 5.7% * Table, p. 378. 391 latter 50.6%. The insects, worms, and small Crustacea made up the re- maining 5.7%, the greater part of which was composed of the larvae of the commoner channel caddis-flies. In the shore zones both numbers and weight valuations were con- spicuously higher than in the channel, the average poundage in the 4-7-foot zone being 695 per acre and that in the 1-3-foot zone 391. Con- trary to the rule found usually to hold good in the river, the larger Gas- tropoda (Viviparidae principally) here showed larger poundages and much larger percentages of valuation totals (74 to 91%) both in the 1-3- and 4-7-foot zones than did the Sphaeriidae. The insects, worms, and Crustacea contributed less than one per cent, of the average pound- age figures in the 4-7-foot zone. In the hauls taken inside the four-foot line, leeches and chironomid larvae were especially abundant, and these with a few worms and small Crustacea added, made up over 8% of the weight of the average haul. Bottom Fauna, 4 — 7-ft. Zone, Pekin to Copperas Creek Dam, 1915 Viviparidae and Pleuroceridae ■ Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average 177.6 104.0 34.4 316.0 9 collec- tions Pounds per acre, Average 638.0 ■ 52.4 5.1 695.5 9 collec- tions Per cent, of total, (By weight) 91.7% 7.5% 0.8% Bottom Fauna, 1 — 3-ft. Zone, Pekin to Copperas Creek Dam, 1915 Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average 108.4 135.7 116.8 360.9 Pounds per acre, Average 292.4 67.8 31.2 391.4 Per cent, of total, (By weight) 74.7% 17.0% 8.3% 392 (d) Copperas Creek Dam to Havana (16.8 Miles) Hydrography. — One is at first surprised to find that although at the low water of 1901 there was a decidedly greater decline in elevation of water surface between the foot of the dam at Copperas Creek and Havana (o.j8 inch per mile for 16.8 miles) than between Pekin and the head of the dam (0.14 inch per mile for 16.2 miles), average flood velocities in the section below the dam are less than in the section of similar length above it. The average velocity at a gage of 18 feet, Peoria, March, 1903, was 83.81 feet per minute between Banner — about 2 miles above the dam — and Havana; and was 114.40 feet per minute between Pekin and Banner. The average slope of high water surface, however, is in close correspondence with these flood velocities — equal- ing 1.43 inches per mile between Pekin and the dam, as compared with 1.18 inches per mile between the dam and Havana at a gage of 22.6 feet, Peoria, March 31, 1904 ; and 1.36 inches per mile between Pekin and the dam, compared with 1.11 inches between the dam and Havana at a gage of 19.0 feet in March, 1903. As the low flood velocities through Peoria Lake are a joint consequence of the high bar above the mouth of Farm Creek and the unusual opportunity for expansion in the broad and low flats above it, the retardation of the flood current between Cop- peras Creek dam and Havana may be explained also as due jointly to the increased impounding area in this section* and to the high mud bar, superimposed upon an older sand bar, which attains its summit about a mile above the mouth of Spoon River. The top of this bar has an elevation only 0.6 foot below the level of the channel floor just below the dam at Copperas Creek, and is 13.8 feet higher than the deepest part of the channel between Liverpool and Havana. The artificial pool behind the dam at Copperas Creek, on the other hand, lies toward the lower end of a stretch of river with relatively steep natural slope, and at the higher gages the flood water moving through that section tends to follow the old slope-lines of water surface as they existed in the years antedat- ing the construction of the dam. Quite consistently with what has just been noted, both at flood stages and at the 1901 low levels, average slope and current are ap- preciably greater in the first than in the second half of the 16.8 miles be- low the dam, the average velocity (66.00 feet per minute) in the eight miles immediately above the Havana bar at a flood gage of 18 feet, Peoria, being in fact not much more than half that in the first eight miles (105.01 feet) and less than that of any other considerable reach of channel in the whole river below Peoria. In the first seven miles of channel below Copperas Creek dam the upper bottom stratum as shown by the government borings of 1902-1905 was sand and shells or plain sand to a depth of 4 to 21 feet for the greater part of the distance; though dirty sand or sand and shells oc- curred .at a few of the boring stations and was found by us just above * Table, p. 378. 393 H M O o H !> Q O o o s M P P3 & o o 1-1 H t—t •l-H a © r-i © id © rH * w CD a © 00 © © to to * 02 CD • l-H a CO <*■ rH O iH r-l 1— I • l-H a cd cc CD O bees to1 th '» CO o . O *h 00 r-j r-i • : CO tH CD .4 cd ft o 1—1 cc cd bJO Jh CD CO CD O o . O *H r* as rH r-j rH • • CO CO rH CD ^ tH £rH O OO O © rH CO © rH © I— 1 >• 0) PI R oq rH 00 o OS oq to o oS Pi a > d o a H3 M CD O U o cc d cd a o O Copperas Creek dam to 1 mile above Liverpool I c$ H o l-H o o A u CD CD > O c3 CD c3 3 Pi a g rH a a M CD CD U o m u CD A A O O o .a 3 CD fin w CD +-> +J ei o cp as (T( p -d h o CO p > u ~— ' CO rr! Ul ^H 0) D ,P a W a cti n 0> 0 >, +-> -l-> cd CJ «H o n -O crt bJO a) P CO TJ p P O a ?H 71 CD CO P f-| P h oi O o pq +-> n> CO +-> (1) Sh Ul r^ o a; u ^ a o * a o 394 and just below Senate Island in 1915. In the nine miles of deeper chan- nel between Mile 129 (1 mile above Liverpool) and Havana, the bottom is uniformly mud. The depth of the mud layer is nearly everywhere more than 8 feet, and in extreme instances 13 to 17 feet. The thickness of the mud stratum diminishes to about 7 feet opposite Havana, and a quarter mile farther south the mud quite gives way to a layer of mud and shells, which description of bottom continues nearly uninterrupted for the next 14 or 15 miles. The bottom soils found in the shore zones between Havana and Copperas Creek in 1915 were dark-colored soft mud throughout the 16.8 miles. Between the dam and Liverpool, bank to bank widths at the low water of 1901 were much as between Pekin and Copperas Creek — usually 550 to around 700 feet ; while the greatest depths were under 12 feet. Below Liverpool the river narrows and deepens decidedly, as far as Mile 122.4 — the beginning of the expansion formerly known as Havana Lake. In this six miles, widths at the 1901 low levels ranged from 329 to about 500 feet, and depths from 14 to 21 feet. Opposite Havana, for a distance less than half a mile above the mouth of Spoon River, the wide water spread over the Havana bar (Havana Lake) showed an extreme width in the summer of 1901 of about 1,300 feet; while maximum channel depths in the 3 miles above Mile 121 (1 mile above Havana) tapered off southward from more than sixteen to about seven feet. Recent extreme depths at midsummer low gages in the lower half of this reach have ranged from 4 to 5 feet more than the low-water depths given. Widths and Depths, Copperas Creek Dam to Havana, Low Water, 1901 Miles above Grafton Station Width, ft. " Depth, ft. max. 136.6 136.0 500 yards below dam 677 695 475 586 549 603 586 528 439 439 402 340 329 457 475 586 1,299 514 7.5 7 7 134.3 8 6 133.0 8 3 132.5 129.8 1 mile below foot Senate Island 11.8 10 0 129.0 128.5 1 mile above Liverpool 10.8 11 6 128.0 Liverpool 14 6 126.9 17 0 126.5 16 7 126.0 14 0 125.7 19 0 125.4 17 0 125.0 5 miles above Havana 21.0 124.0 15.7 123.0 122.4 Middle of "Hogfat Bend'' ....... 16.3 10 8 121.0 120.0 Upper end "Havana Lake" C. P. St. L. Piers, Havana 7.0 12.2 395 Connecting lake-acreage per mile of river-length between Copperas Creek dam and Havana at the low gages of 1901 largely exceeded that in any other section of river above or below, the figure of 472.1 acres per mile being 57 per cent, more than between Chillicothe and the foot of Peoria Lake and 23 per cent, more than between Havana and the Lagrange dam — the two other reaches with the highest ratings. (Table, p. 378.) Though the eight or nine mile stretch of river just above Havana has had more shore vegetation at recent summer levels than any other section below Peoria Lake, the amount of vegetation bordering on chan- nel of normal width (excluding such areas as Havana Lake) has not in any recent season been very important. In a local fiat stretch of a quarter mile on the west side above Liverpool, where there was more shore vegetation both in 1913 and 191-1 than anywhere else between the dam and the head of Havana Lake, the extreme width of the weed strip was about 35 feet, a little less than 5% of the bank to bank width at the time (about 750 feet) ; while for most of the distance it was not more than 15 feet. Nowhere else between Copperas Creek dam and the head of Havana Lake was there in 1913 or 1914 shore vegetation for any im- portant distance that occupied more than a ten-foot strip next the bank, and there were long stretches with much less than that amount. In the shore zones of the wide water above the mouth of Spoon River there are several acres of Potamogeton on the west side in the most favorable seasons ; and on the east side a narrower strip, sometimes up to 50 or 60 feet wide, in a stretch of about 300 yards along the edge of Cook's Island. Even these local areas, relatively to the vastly greater river acreages wholly without aquatic vegetation in the 16.8 miles, are extremely smiall, and revert largely to open water in all but the driest seasons. Bottom Fauna. — A total of 16 channel collections and 23 collections in the shore zones (within the 7-foot line) were made in July-October, 1915, between Copperas Creek dam and Havana in cross-section: at Bottom Collections, Copperas Creek Dam to Havana july-october, 1915 Channel 4— 7-ft. zone 1— 3-ft. zone 1. Copperas Creek dam to Mile 129 Mile 135.2, opposite head of Senate Island Mile 133.6, opposite foot of Senate Island 4 4 2 2 2. Mile 129 to Havana Mile 128.5, y2 mile above Liverpool Mile 123.0, 3 miles above Havana 5 3 5 8 4 2 'Total 16 17 396 two stations in the shallower swifter section of 7.8 miles between the dam and Mile 129 (1 mile above Liverpool) ; and at two stations in the deeper more stagnant section of 9 miles between Mile 129 and Havana. Although the entire section of over 16 miles is on the average richer in small bottom animals than any other sections heretofore treated, biologically, as well as in its hydrographical characters, it is sep- arable into two well-distinguished portions, the half with the richer channel bottom fauna being the deeper muddier section below Mile 129 and more immediately above the high Spoon-River bar. The average of the poundages per acre at the channel stations in the lower half of the sec- tion (5,156.0 lbs.) was in fact nearly six times the average valuation of channel above Mile 129 (878.3 lbs. per acre), and almost fifteen times the average valuation at the channel stations between Chillicothe and the foot of Peoria Lake, Peoria Narrows excepted (345.1 lbs.). Bottom Fauna, 1915, Copperas Creek Dam to Havana pounds per acre (average total) Channel 4 — 7-ft. zone 1 — 3-ft. zone 1. Copperas Creek dam to Mile 129 (7.8 miles) 878.3 1,436.2 No collections 2. Mile 129 to Havana (9 miles) 5,180.8 2,122.0 919.7 In the channel collections both above and below Liverpool the larger Viviparidae made* up more than 99% of the weight of the average collection. The Sphaeriidae and the smaller Gastropoda amounted in weight to a mere trace in comparison; while the insects, worms, and small Crustacea accounted for less than half of one per cent, of the average poundages. Bottom Fauna Channel, Copperas Creek Dam to 1 Mile above Liverpool, 1915 Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average 263.4 0.3 28.3 292.0 8 coll.'s Pounds per acre, Average 874.2 878.3 8 coll.'s Per cent, of total, (By weight) 99.5% trace 0.4% 397 Bottom Fauna, Channel, 1 Mile above Liverpool to Havana, 1915 Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average 1,294.0 3.0 171.8 1,468.8 8 coll.'s Pounds per acre, Average 5,156.0 0.1 24.7 5,180.8 8 coll.'s Per cent, of total, (By weight) 99.5% 0.4% Average bottom-fauna poundages in the, 4— 7-foot zone above Mile 129 in 1915 (1,436.2 lbs. per acre) were nearly twice those in the chan- nel opposite (878.3 lbs.). Below Mile 129, where they were 2,122.0 lbs. they were less than half the average channel valuation (5,180.8 lbs.). No collections were taken above Mile 129 within the 4-foot line, but be- tween Liverpool and Havana six collections in the 1-3-foot zone showed an average valuation of 917.7 lbs. per acre. In the 4-7-foot zone, both above and below Liverpool, Sphaeriidae were relatively much more abundant than either in the channel or the 1-3-foot zone, making 40 to 80% of the average weight of collections. In the 1-3-foot zone below Mile 129 the weight-composition of the bottom fauna was on the whole nearly identical with that of the channel (Viviparidae and Pleuroceridae 96%; Sphaeriidae and smaller Gastropoda 2.3%; insects, etc., 1.1%). Bottom Fauna, 4 — 7-foot Zone, Copperas Creek Dam to 1 Mile above Liverpool, 1915 Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average 302.2" 1,212.5 96.0 1,610.4 4 coll.'s Pounds per acre, Average 814.3 606.2 15.7 1,436.2 4 coll.'s Per cent, of total, (By weight) 56.6% 42.2% 1.0% 398 Bottom Fauna, 4 — 7-ft. Zone, 1 Mile above Liverpool to Havana, 1915 . Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average 120.8 3,537.3 172.0 3,830.1 13 coll.'s Pounds per acre, Average 319.3 1,776.7 28.0 2,122.0 13 coll.'s Per cent, of total, (By weight) 15.0% 83.7% 1.2% Bottom Fauna, 1 — 3-ft. Zone, 1 Mile above Liverpool to Havana, 1915 Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average Pounds per acre, Average Per cent, of total, (By weight) 230.6 887.6 -96.5% 38.5 21.6 2.3% 81.0 10.5 1.1% 350.1 6 coll.'s 919.7 6 coll.'s (e) Havana to Lagrange Dam (42.5 Miles) Hydrography. — While the 42.5- miles of channel between Havana and Lagrange has on the whole a swifter flow than the flatter reaches above Havana, it is separable into three subdivisions which show dis- tinct differences in slope and current : 1. The 17.2 miles between Havana and Sheldon's Grove (approxi- mately Sharp's Landing), which has a low-water slope about the same as Liverpool-Havana (0.53 inch per mile, low water, 1901), and a flood velocity more than twice as great (140.91 feet per minute, March, 1903). 2. The 13.3 miles between Sheldon's Grove and one mile above Beardstown, which had a low-water slope in 1901 (1.08 inches per mile) about double that of the first 17 miles, but a flood velocity (116.06 feet per minute, March, 1903) less than that of the first section. 399 3. The 12.0 miles between a point one mile above Beardstown and the dam at Lagrange, where the slope of water surface in July, 1901, was only 0.10 inch per mile, but the flood velocity (152.04 feet per second in March, 1903) greater even than between Havana and Sheldon's Grove. Decline in Elevation of Low-Water Sueface, 1901; and Flood Velocity Average slope Flood velocity (av. ft. Reach Interval inches per minute, gage, miles per mile 18 ft., Peoria) Havana to Sheldon's Grove 17.2 0.62 140.91 (17.2 miles) Sheldon's Grove to 1 mile above Beardstown 13.3 1.08 116.06 (14.3 miles)* 1 mile above Beardstown to La- grange dam 12.0 0.10 152.04 (11.0 miles)* The principal part of the first subdivision (the 13.8 miles between Havana and the foot of Grand Island) as well as the lower 19.5 miles of the reach (Browning to the dam), together making more than three fourths of the entire reach of 42.5 miles, is comparatively wide and shal- low, and has almost entirely sand or sand and shell bottom channel. The muds found at the shore stations in 1915 were both lighter in color and also less soft and deep than the soft shore deposits found above Havana. At the low levels of 1901, depths in the channel between Havana and the foot of Grand Island were as a rule 8 to 10 feet and ran at most a little over 12; while below Browning they ranged usually between 10 and 12 feet and for short distances reached 13 to 15. Depths at recent midsum- mer low levels have been 2 to 3 feet greater than these. Widths at the low water of 1901 of single channel between Havana and the foot of Grand Island were mostly 600 to 700 feet, and exceeded 750 feet for short stretches ; and between Browning and the dam were usually over 700 feet and for good distances between 800 and 1,000. The central section of about 9 miles of channel lying immediately above the mouth of the Sangamon River (approximate foot of Grand Island to 1 mile above Browning) is much narrower and deeper than the stretches of channel above and below it, and. has a mud bottom. Depths in this section of channel at the 1901 low levels were nearly everywhere 15 to 20 feet; while bank to bank width was usually under 600 feet and fell for good distances under 500. The deep natural pool lying above the Sangamon River bar is a homologue of those above the great Farm Creek and Havana bars already described, and is of less mo- ment biologically, in the respect of furnishing a very rich soil for bottom animals, only because the entrance of this large tributary occurs in the very midst of a 'long stretch of river with naturally steep gradient, where * Nearest corresponding- velocity-reaches (Van Ornum float tests, March, 1903) stop at Beardstown. 400 both increased velocities and increased flood volumes retard sedimen- tation and keep the summit of the bar lower than in the other two cases. Lake and other backwater acreage per mile between Havana and the Lagrange dam (382.1- acres) exceeded at the low water of 1901 that of any other reach of river except the 16.8 miles between Copperas Creek dam and Havana.* The densest distribution of pond acreage oc- curs in the 9 miles between the foot of Grand Island and the mouth of the Sangamon and falls within the boundaries of greatest channel depths, least flood velocity, softest and darkest-colored bottom deposits, and richest bottom fauna, as shown by our collections of 1915. Widths and Depths, Havana to Lagrange Dam , Low Water, 1901 Miles above Grafton Station Width, ft. Depth, ft. max. 119.0 118.1 1 mile below Havana 658 768 549 640 530 732 712 457 514 658 475 582 439 494 878 750 732 658 1,006 1,000 514 841 732 732 805 933 8.5 8.7 10.7 10.0 12.5 8.3 9.0 9.1 7.0 11.0 14.7 12.4 18.4 15.6 20.4 17.0 13.4 8.7 8.3 10.2 13.2 12.8 10.2 13.1 12.1 8.5 10.5 11.7 15.0 11.8 11.7 1. Havana to foot of Grand Island. Shal- 117.5 low section 116.0 115.0 114.0 113.5 111.9 Head of Grand Island 110.0 West channel only 108.0 106.5 106.2 104.0 1/3 mile above foot of Grand Island.... Foot of Grand Island 2. Foot of Grand Island to Browning. Nar- 102.8 101.6 row, deep section 98.0 98.2 Mouth of Sangamon.. 97.0 95.7 93.0 1/4 mile below Brown- iy2 miles below 3. Browning to Lagrange dam. Wide, shallow section 90.3 89.1 - 88.2 86.2 1/4 mile below wagon bridge, Beardstown 84.2 83.6 82.6 81.5 80.4 78.8 78.6 77.7 250 yards above La- * Table, p. 378. 401 Bottom Fauna. — A total of 58 bottom collections, at 9 stations, in cross-section, were taken in 1915 between Havana and the Lagrange dam, distributed between the channel and the shore zones and from north to south as shown in the following table. Collections, Havana to Lagrange Dam, 1915 Miles above Station Channel 4 — 7— ft. zone 1 — 3-ft. zone Grafton 1. Havana to foot Grand Island (13.8 miles) 114.7 Opposite foot Matanzas Lake 500 yards above head of Grand 3 2 113.7 Island 3 2 8 2. Foot Grand Island to Brown- ing (9.0 miles) 101.0 Opposite foot of Stewart Lake 1 4 2 97.0 1/4 mile below Browning 1 6 2 3. Browning to Lagrange dam (19.7 miles) 89.5 1 mile above Beardstown 1 6 2 84.0 Brigg's Landing 2 83.2 Reich's Landing 2 80.3 Lagrange Landing 2 77.7 200 yards above dam 1 2 6 Total 16 22 20 With* reference to the bottom fauna this reach of 42.5 miles may be described as a whole as a section of exceedingly poor channel, bor- dered on either side by a comparatively rich shore fauna. The average channel poundages of bottom animals taken in 1915 between Havana and the dam at Lagrange was only 22 lbs. per acre, or not much more than one fifteenth of average channel valuation between Chillicothe and the foot of Peoria Lake (345 lbs.), and less than one two-hundredths of the average between Liverpool and Havana (5,180 lbs.). While the channel fauna was about equally poor throughout the 42.5 miles in 1915, the shore fauna (bottom animals within the 7-foot line) was distinctly rich- est in the central deeper section of river above the mouth of Sangamon River, where the 4-7-foot zone showed figures (365.6 lbs. per acre) about 30% over the average of the 4^7-foot zone for the 42.5 miles, and the 1-3-foot zone a rating (1,613.4 lbs. per acre) nearly four times the 42-mile average, or more in fact than was found anywhere else at that depth between Chillicothe and Grafton. The greater part of the weight of the average collections in the 42 miles, whether from channel or shore zones, consisted of the larger snails (Viviparidae). Though larvae of caddis-flies and nymphs of May-flies were relatively commoner than above Havana, they were not numerous enough anywhere to contribute 402 importantly to weights, making up at the best only about 6 pounds of the total acre valuation. Bottom Fauna, 1915, Havana to Lagrange Dam pounds per acre, average totals Reach Channel 4 — 7— ft. zone 1— 3-ft. zone 1. Havana to Lagrange dam (42.5 miles) 22.0 282.6 435.5 2. Foot of Grand Island to Browning (9 miles) 12.5 365.6 1,613.4 Bottom Fauna, 1915, Channel, Havana to Lagrange Dam (42.5 miles) Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average 5.5 6.0 3.7 15.2 16 coll.'s Pounds per acre, Average 16.0 3.0 3.0 22.0 16 coll.'s Per cent, of total, (By weight) 72.7% 13.6% 13.6% Bottom Fauna, 1915, 4 — 7-foot Zone, Havana to Lagrange Dam (42.5 miles) Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average 73.0 88.0 31.1 192.1 - 22 coll.'s Pounds per acre, Average 234.8 42.1 5.7 282.6 22 coll.'s Per cent, of total, (By weight) 83.0% 14.8% 2.0% 403 Bottom Fauna, 1915, 1 — 3-foot Zone, Havana to Lagrange Dam (42.5 miles) Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea "Total Number per sq. yard, Average 99.3 91.1 18.3 208.6 20 coll.'s Pounds per acre, Average 385.7 44.6 5.2 435.5 20 coll.'s Per cent, of total, (By weight) 88.5% 10.2% 1.1% Bottom Fauna, 1915, Channel, Foot of Grand Island to Browning (9 miles) - Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average XI 2.5 1.0 6.2 2 coll.'s Pounds per acre, Average 1.5 5.0 6.0 12.5 2 coll.'s Per cent, of total, (By weight) 12.0% 40.0 % 48.0% Bottom Fauna, 1915, 4 — 7-foot Zone, Foot of Grand Island to Browning ( 9 miles ) Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average 92.4 106.4 10.3 209.1 10 coll.'s Pounds per acre, Average 309.7 53.2 4.5 365.6 10 coll.'s Per cent, of total, (By weight) 84.2%, 14.5%, 1.2% 404 Bottom Fauna, 1915, 1 — 3-foot Zone, Foot of Grand Island to Browning (9 miles) • Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Number per sq. yard, Average 327.4 186.2 26.1 539.7 4 coll.'s Pounds per acre, Average 1,516.0 93.1 4.3 1,613.4 4 coll.'s Per cent, of total, (By weight) 93.9% 5.7% 0.2% (f) Lagrange Dam to Grafton (77.5 Miles) Hydrography. — The average velocity in the 77.5 mile stretch of channel between the Lagrange dam and the mouth of the river in March, 1903, at a gage of about 18 feet, Peoria, (172.30 feet per minute), was more than three times that between Chillicothe and Peoria at the same time (51.94 ft. per minute) ; more than twice that between Copperas Creek dam and Havana (83.81 ft.)*; and exceeded that of any other sec- tion of channel below. Chillicothe except the 9 miles between Peoria and Pekin. The average decline in elevation of water surface at the 1901 low gages between Lagrange and the dam at Kampsville (0.85 inches per mile) was more than three times the average through Peoria Lake; and Decline in Elevation of Low-Water Surface, 1901; and Flood Velocity Reach Interval miles Av. slope inches per mile Flood velocity (av. feet per minute), gage, 18 feet, Peoria* Lagrange dam (below) to Grafton 77.5 172.30 Lagrange dam (below) to Kampsville dam (above) 46.1 0.85 164.24 Lagrange dam (below) to Florence 21.9 1.26 146.92 Florence to Kampsville dam (above) 24.2 0.49 183.85 Kampsville dam (below) to Grafton 31.4 2.44 186.91 * Van Ornum float tests, March, 1903. 405 in the 31 miles below Kampsville (2.44 inches per mile) was more than in the short swift stretch between Peoria and Pekin. A comparatively well-scoured channel bottom is found most of the way from Lagrange to the mouth, sand, mud and shell, or dirty sand prevailing, and such mud bottom as occurs being usually hard and covered at most with only a very thin layer of recent silt. Inside the 7-foot line in 1915 a soft light-colored silt 2 inches to more than 12 inches deep was found at most of our collecting stations. The most im- portant local stretches of muddy channel in 1915 were 6 miles imme- diately above the Kampsville dam; and about 4 miles just above the mouth of the river. A less important short section of muddy channel, in Widths and Depths, Lagrange Dam to Grafton, Low Water, 1901 Miles above Grafton Station Width, ft. Depth, ft. max. 77.0 72.7 y2 mile below Lagrange dam 658 805 586 658 1,006 658 1,006 787 951 823 567 1,024 1,025 658 975 1,116 933 1,317 1,409 1,482 1,043 1,354 1,180 1,317 1,006 1,079 1,134 1,116 1,208 768 1,061 732 1,189 1,610 1,098 1,263 768 677 13.1 8.2 72.3 14.0 71.6 12.7 71.5 68.0 Meredosia 9.1 15.7 66.5 10.3 65.5 • 64.0 8.7 6.9 62.5 9.3 61.4 15.3 59.0 6.9 55.5 Florence 8.8 54.5 15.6 53.5 9.0 47.5 10.9 44.0 10.3 41.2 2 miles below Pearl 10.5 39.2 12.3 36.7 10.2 34.5 . 14.5 33.0 31.8 31.3 29.8 1 mile above Kampsville. . . . 500 yards above dam 300 yards below dam 11.3 13.7 10.0 20.0 25.8 9.2 21.3 20.3 8.1 6.5 16.9 7.2 12.3 14.7 11.5 8.1 10.0 19.2 8.5 7.8 7.3 6.5 Foot of Six Mile Island 8.7 14 0 5.5 14 2 4.0 14 4 3.0 18.4 406 the first mile below Six Mile Island — a local section with little drop in levels at low water — had a deep deposit of light-colored mud in 1913, but apparently much less two years later. In the 46 miles between Lagrange and Kampsville extreme depths in the channel at the low water of 1901 ranged from 9 to 11 feet as a rule, and did not anywhere exceed 15 feet. Widths at these levels were be- tween 1,000 and 1,400 feet for good stretches, and did not fall below 800 feet for any important distance. Below the Kampsville dam widths were seldom' under 800 feet, ranging between 1,000 and 1,200 feet for most of the way, and reaching a maximum of 1,600 in the sluggish section just, below Six Mile Island. Connecting lake and other backwater acreage per mile between La- grange and the mouth of the Illinois at the low levels of 1901 (219.6 acres per mile between Lagrange and Florence; 180.0 between Florence and' Kampsville; 86.9 between Kampsville and the mouth) compared unfavorably with that of most of the river between Chillicothe and Havana.* The greater part of this backwater was leveed and drained between 1901 and 1913, resulting, no doubt, in recent years in a some- what better scoured channel even than is indicated by the government borings made between 1901 and 1905. As in the 42 miles above the Lagrange dam, shore vegetation between Lagrange and the mouth of the river has in recent years been a negligible quantity. Bottom Collections, Lagrange to Grafton, 1915 Miles above Grafton Station Channel 4— 7-ft. zone 1— 3-ft. zone 71.7 60.0 55.6 54.5 47.7 43.2 36.5 33.0 31.6 Y2 mile above Mered'osia iy2 miles below Valley - Opposite Florence 1 mile below Florence Total % mile below Bedford Opposite foot Pearl Island %-way Apple Creek to Panther Cr. 1 mile above Kampsville 300 yards above Kampsville dam 4 2 1 6 1 5 1 6 1 1 25.7 20.6 11.5 9.3 8.5 7.3 Total. . Opposite (west) head Diamond Is- land y2 mile below Hardin 1 mile below foot Mortland Island Opposite Bloom's Landing Opposite head Six-Mile Island Below foot Six-Mile Island 5 17 1 1 2 1 4 2 1 4 1 2 Total Grand total 7 16 12 31 12 28 * Table, p. 378. 407 Bottom Fauna. — In August, 1915, a total of 75 collections of the bottom animals were made in cross-section at 15 stations between La- grange dam and the mouth of the river, as shown in the preceding table. The bottom-fauna valuations indicated between Lagrange and Graf- ton by our collections of August, 1915, were almost uniformly poor both in the shore zones and in the channel — the average of the sixteen channel collections being only 6.7 lbs. per acre; that of 31 collections between 4— 7-feet, 16.7 lbs. ; and that of 28 collections within the 4-foot line, 16.9 lbs. The best local figures for the shore were obtained in the 4-7-foot zone opposite Meredosia, where two hauls averaged 57.5 lbs. per acre ; and in the 1-3-foot zone below Kampsville dam, where twelve collections averaged 27.9 lbs. Both in the channel and in the shore zones, if we except the 4-7-foot zone collections opposite Meredosia, Mollusca con- tributed less or very little more to the average weight of collections than did insects, worms, and small Crustacea, which together made up 63 to 65% of the average weight of collections in those depths zones, with the noted exception. Of the latter group (non-Mollusca) the most im- portant in weight were the larvae of caddis-flies in the channel, and the immature stages of Ephemeridae (willow-flies) in the shore zones. As these were principally of the new broods hatched from eggs deposited by the adults which emerged only a month to six weeks earlier, they contributed less to the weight of collections than they would have done in the same numbers earlier in the summer or later in the fall. The larger snails (Viviparidae and Pleuroceridae) amounted nowhere be- low Lagrange to more than 5 or 10% of the weight of collections. Bottom Fauna, 1915, Lagrange to Grafton pounds per acre (average total) Reach Channel 4— 7-ft. zone 1— 3-ft. zone 1. Lagrange dam to Florence (21.9 miles) /,* 57.5 2 10.1 8 2. Florence to Kampsville, above dam (24.2 miles) 12.4 5 16.6 7.5 8 3. Kampsville above dam to Grafton (31.4 miles) 6.5 7 10.3 2 27.9 12 Lagrange to Grafton (77.5 miles) 6.7 16 16.7 21 16.9 28 * The Italic figures give the number of collections. 408 Bottom Fauna, Channel, Lagrange to Grafton, 1915 pounds per acre Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Lagrange dam to Florence 4 coll.'s .... .... .... trace Florence to Kampsville 5 coll.'s 5.0 1.5 5.9 12.4 Kampsville to Grafton 7 coll.'s 2.6 3.9 6.5 Lagrange to Grafton 16 coll.'s 0.3 1.6 3.5 5.4 Per cent, of total (by weight) 5.5% 29.6% 64.8% Bottom Fauna, 4 — 7-foot Zone, Lagrange to Grafton, 1915 pounds per acre Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Lagrange dam to Florence 2 coll.'s .... 57.5 57.5 Florence to Kampsville 17 coll.'s 0.6 10.3 5.7 16.6 Kampsville to Grafton 12 coll.'s .... 4.8 5.5 ■ 10.3 Lagrange to Grafton 31 coll.'s Trace 11.2 5.2 16.4 Per cent, of total (by weight) 68.2% 31.8% 409 Bottom Fauna, 1 — 3-foot Zone, Lagrange to Grafton, 1915 pounds per acre Viviparidae and Pleuroceridae Small Gastropoda and Sphaeriidae Insects, worms, Crustacea Total Lagrange dam to Florence 8 coll.'s .... 9.2 0.9 10.1 Florence to Kampsville 8 coll.'s 2.4 0.1 5.0 7.5 Kampsville to Grafton 12 coll.'s 0.3 6.3 21.3 27.9 Lagrange to Grafton 28 coll.'s 0.8 5.3 10.8 16.9 Per cent, of total (by weight) 4.7% 31.3% 63.9% (g) General Summary, Illinois River Bottom Fauna, July-October, 1915 1. distinction of main reaches If we have regard only to the larger average differences in weight of the bottom-fauna stocks of 1915, the 180.5 mile stretch of river be- tween Chillicothe and Grafton separates into four principal subdivi- sions : — First, a section of 43.7 miles between Chillicothe and the dam at Copperas Creek which bears a fairly rich channel- and .a similarly rich shore-fauna (channel average, 239 lbs. per acres ; 4 — 7-foot zone, 372 lbs. ; 1 — 3-foot zone, 225 lbs.). Second, a short stretch between Copperas Creek dam and Havana which has an exceedingly rich channel fauna (3,029 lbs. per acre) and a shore fauna far above the average (4 — 7-foot zone, 1,960 lbs.; 1 — 3-foot zone, 920 lbs.). Third, 42.5 miles between Havana and the dam at Lagrange with very poor channel (22 lbs. per acre) but with shore as rich as in the first 60 miles (4 — 7-foot zone, 282 lbs. ; 1 — 3-foot-zone, 435 lbs.). Fourth, in the lower 77.5 miles, a long reach that is extremely poor both in shore and channel (channel, 6 lbs. per acre; both shore zones, 17 lbs.). Whether in the shore or the channel zones, so far as is shown by the data of 1915, the richest stocks of small bottom-invertebrates are present in the reaches with the least flood slope and velocity, these 410 factors clearly influencing — more particularly, of course, in the channel — both the depth and softness of the bottom deposits (regarded as a medium or as a substratum for the bottom population), and also the food supply of the bottom animals so far as it is brought to them by sedi- mentation. In the two richer reaches of river above Havana the average flood velocity in recent years (around 0.9 miles per hour) has been only about Ys of that between Havana and Lagrange (1.5 miles per hour), and less than half the average between Lagrange and Grafton (1.9 miles per hour). Though there is usually, both in the slower and swifter reaches of the river, if we except the cases of some sharp bends, some retardation of current between mid-channel and shore, with accompanying increase in sedimentation and noticeable differences in the composition of the bot- tom populations, these differences in the less rapid sections above Havana are neither very important quantitatively nor correlated so far as can be seen. The average poundages per acre of bottom animals between Chilli- cothe and Copperas Creek dam in the channel and the shore zones (chan- nel, 239 lbs.; 4— 7-foot zone, 372 lbs.; 1— 3-foot zone, 225 lbs.) are in fact so nearly the same that little if any significance can be attached to the differences; while in the 16.8 miles between Copperas Creek and Havana (channel, 3,029 lbs.; 4 — 7-foot zone, 1,960 lbs.; 1 — 3-foot zone, 920 lbs.) the differences in weight between the shore and channel stocks are in the reverse of the direction that might be expected. There is, however, a decidedly sharper contrast below Havana between the physical characters of the channel and shore zones, and in and to either side of the stretch of comparatively hard-bottomed channel between Havana and Lagrange a corresponding contrast in the richness of the bottom fauna that is without much question connected with it. In this section of 42.5 miles the 4 — 7-foot zone (282 lbs. per acre) had stocks thirteen times as rich as those of the channel (22 lbs.) ; and there was a further large in- crease shown in the stocks in the 1 — 3-foot zone. Certain special influences that may affect the bottom-fauna yields in the river below the Lagrange dam are discussed in a following sec- tion. 2. ALL-ZONE AVERAGES AND TOTAL STOCKS All-zone averages of the bottom-fauna stocks of the four main river reaches below Chillicothe based upon rough acreage-weightings show a figure for the first 43.7 miles below Chillicothe (264 lbs. per acre) about the same as the average for the entire 180.5 miles between Chillicothe and Grafton (261 lbs.) ; for the 16.8 miles between Copperas Creek dam and Havana about ten times that (2,693 lbs.) : for the 42.5 miles be- tween Havana and Lagrange a rate of yield (88 lbs. per acre) about one third of the general river average and about one thirtieth of the rate in the richest section; and for the 77.5 miles below Lagrange (10.4 lbs. per acre) less than one twenty-fifth of the 180 mile average and less 411 w O <1 a t> <1 H fe O N a H Ph 02 O < P O H H O PQ Average velocity miles per hour O O •p-i OS Average velocity flood gage 18 ft. Peoria ft. per mm. tr- oo o 00 tH OO CO OO t- co CO tH o CO CM* t- iH «H CD CO fl 1 N 2*- LO CM CM C© o CM OS <2> ©2 CO £©J 1 N so GO CM tr- ee O ©2 ©3 CM OO CM >H so 0) Eh CD el e 03 O u * so OS CO CM Ci CM © co~ CO CM CM co CO 02 s CO 00 tH LO CM* 1 to rd o3 CD XJ1 03 U CD a ft o O o CD 03 o ^ O CD ■rH £) S rH o o3 o3 > o3 w O a o3 rH* o 02 o3 rH CD a ft o O CD bfi o3 rH bfi 03 o +-> 03 n o3 > 03 o o3 rH o o CD bJD rH 03 rH bJO o3 as fl o H-> O o 02 1—) CD o l-H • I— t o a o LO rH O CO 00 rQ rH fej 3 Eh co rC 4-> CO > r_l tun o3 -u 02 O CO H rH 3 bo «C 412 than one two-hundredth of the rate between Copperas Creek dam and Havana. Figures for the total stocks present in the combined channel and shore acreage below Chillicothe July-October 1915 (table, p. 18), based on these all-zone weight valuations and on approximate acreages for average July-October levels in 1910 — 1914, show that out of total stocks equaling 6,988,103 pounds for about 26,700 acres, 92.7 per cent., or 6,480,952 pounds, were in the 60.5 mile section of river above Havana — this constituting only one third of the total length of river studied and less than one third of the total river acreage. Again, of the total bottom- fauna stocks 53.9%, or 3,770,200 pounds, were in the 16.8 miles of river between Copperas Creek and Havana — which comprises less than one tenth of the total distance between Chillicothe and the mouth, and only about one twentieth of the total acreage. The stocks between Havana and Lagrange, 396,880 lbs., for 42.5 miles, made up but 5.6% of the grand total ; and those between Lagrange and Grafton, 110,271 lbs., for 77.5 miles, only 1.5 per cent. Bottom Fauna, Illinois River, 1915. Acreage-weighted All-Zone Averages pounds per acre Reach Miles Approx. acres Gage, 8 ft. Havana Estimated part of total under 7 ft. deep Bottom fauna lbs. per acre (average) Chillicothe to Copperas Creek dam 43.7 10,268* 1/3 264 80f Copperas Creek dam to Havana 16.8 1,400 1/4 2,693 39 Havana to Lagrange 42.5 4,510 1/5 88 58 Lagrange to Grafton 77.5 10,603 2/5 10.4 15 Chillicothe to Grafton 180.5 26,782 261 252 Average Chillicothe to Copperas Creek dam, 555 lbs. Average Copperas Creek dam to Lagrange, 705 lbs. 3. COMPOSITION OF THE BOTTOM FAUNA In the section of river above Lagrange dam, both in the channel and in the shore zones, the great bulk of the bottom-fauna poundages was made up of Mollusca (Gastropoda and Sphaeriidae), the percentages by * Includes Peoria Lake. t The Italic figures give the number of collections. 413 o H fa < o o H fa W H O o H Hi M H w o Hi H o Q o s ^ K OS B « w § I > H CO M o o Eh E~ co" o oo c» to" OS CO o" 1-i T-i CO o oo" oo OS SO* tH LO CO t>^ b- CM Th" o oo o t^" to tH Tin" CM LO cn o" oo to" Bottom fauna lbs. per acre tO CM CO OS cm" oo oo © rH T-I to CM OS LO CM LO o LO LO LO Approx. acres Gage, 8 ft. Havana ■X- 00 to CM o o o ■>* o T-H LO CO o to o tH CM OO to" CM U0 to" T-i T-{ T- 1 os LO OO to tcv tH co CO oq tD LO CM LO LO O OO tH oo to CO •tH CO OS LO LO O to A u o3 CD Ph a o3 CD CD o co b3 Hi CD ft ft O O o -H> CD o CD l-H l-H •l-H o o3 d 03 K o -H> a 03 M CD CD Hi o m o3 Hi CD ft ft O O a o3 T3 CD CUD d o3 Hi faJD 03 O -H> o3 d 03 > o3 M d o -H> «HI o3 Hi O o a T3 CD d o3 H W) o3 d o -H> «M 03 H o o -Hi CD Hh -H> o CD I-H xi O d o -H> «HI c3 Hi O o -H> . a OS TJ H^ CD CD H CO o3 Hi CD ft a o O a CO CD d o3 H COD 03 HH o ■+J a" o3 U O CO o3 H CD ft ft O o 03 d 03 > a o -H> CD -Hi O o d Q H O 0) fn ho 414 weight running in these reaches from 86 to over 99%, and falling below 90% only in the 1 — 3-foot zone above the Copperas Creek dam. Below the Lagrange dam, where the large Ephemeridae (May-flies) were rela- tively much more abundant than farther north, the Mollusca percentages dropper to an average range between 35 and 68%. In the sections above Lagrange, if we except the 4 — 7-foot zone between Copperas Creek dam and Havana, the larger snails (Viviparidae and Pleuroceridae) accounted for 70 to nearly 100% of the Mollusca totals (by weight). Below Lagrange the Viviparidae (and Pleuroceri- dae) were largely replaced by Sphaeriidae in all zones, the weight per- centages of that group rising to a range between 84 and 100%. Bottom Fauna, Illinois River, 1915 Percentages of Average Total Valuations by Weight . contributed by mollusca Channel 4— 7-ft. zone 1— 3-ft. zone Chillicothe to Copperas Creek dam 96.7 97.3 92.1 Copperas Creek dam to Havana 99.5 98.8 98.8 Havana to Lagrange 86.3 98.1 98.9 Lagrange to Grafton 31.6 65.8 35.8 Bottom Fauna, Illinois River, 1915 Composition of Mollusca Totals. (Percentages by Weight*) Viviparidae and Pleuroceridae Sphaeriidae and small Gastropoda Reach Channel 4— 7-ft. zone 1— 3-ft. zone Channel 4— 7-ft. zone 1— 3-ft. zone Chillicothe to Copperas Creek dam 78.5 78.1 70.7 21.5 21.9 29.3 Copperas Creek dam to Havana 100.0 22.5 97.7 trace 77.5 2.3 Havana to Lagrange 84.3 84.8 89.7 15.7 15.2 10.3 Lagrange to Grafton 15.8 none 13.2 84.2 100.0 86.8 * Pound values on which these percentages are based are shown in following tables. 415 &H « «l a s a 02 s ■" fc Cm u U ki S o m Ph H o «r| k H fc r-l hJ rJ <3 h- 1 fe § o K o pq +J c5 a © CJ P CO LO CO rH OS 00 iH -* CO OS OS C3S CO Csj o LO a o C5 OS OS OS OS- OS OS Oi 00 LO ""*! 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CD rH O r-H ft B CO CD r> <1 u £ fc Ph O 3 K fa r^ ^ a CO rH CO > CC r£ CJ cc Cti . rH M rQ A 3 O 02^ * O 416 \H M <3 m § fc 3 c p N 0} H ^^ O O N H 1 M t> U < ■<* tf as W iO Ph os m .> & « p o Ph P H >■ M Ph O a & o H H O PQ ■kJ d d ° 1 cu eg •* CO tH eg CO 00 LO OS t- CO CO oo 00 o LO CO OO Ph^ OS os OS OS OS OS OS OS OS o CO -* CO CO tH TfH zo CO LO cq o Tfrl co LO " co CO -tfl d t- tr- CO LO tH ^. 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Hydrography and Physical Features In the midsummer and autumn months of 1914 and 1915 a total of 266 bottom collections, principally with the mud-dipper, were made in the lakes and ponds and other backwaters in the river bottoms between the head of Clear Lake and the foot of Sangamon Bay, covering a river distance of 39 miles, and representing an ex-river acreage (about 16,000 acres) at a gage of 8 feet, Havana, around one third of the total prevailing at the time between the Copperas Creek and Lagrange dams (about 52,000 acres). The lakes and backwaters studied, separate naturally on a basis of physical and hydrographical features into five classes : I. The deeper lakes of the all-bottom-land type, with flat muddy banks on both sides, and with maximum depths at recent midsummer levels between 7^ and 9 feet. The five lakes of this class examined — Clear — Mud, Liverpool, Thompson, Dogfish, and Sangamon Bay — have deep soft black mud bottom in the central deeper portions, and only rarely a little sand near shore. The vegetation, principally Potamogeton and Ceratophyllum, is confined to the rather wide shallow margins, the most of it well within the zone of 0 — 6 feet. These lakes ranged in size at the low water of 1901 (4.2 ft., Havana) from 275 to about 1,800 acres, and represented in all at that gage about 3,390 acres. At the average gage of July — October, 1910 — 1914 (approximately 8 ft., Havana), their acreage is somewhere near %y2 times the 1901 figures, or over 8,000 acres, which is close to one seventh of the total lake acreage between Copperas Creek dam and Lagrange, and more than the total river acreage at the same gage in the same distance (about 6,000 acres). II. The deeper, sand-beach type, bordering on one side against the sandy bluff, and with sandy shore on that side, but with flat muddy banks opposite. The two lakes of this type studied (Quiver and Matanzas) had a total acreage at the low water of 1901 of more than 600 acres), and maximum depths at recent midsummer levels of 8J^ to 12 feet. In Quiver Lake there is some sand and large quantities of old shells mixed with the mud in the deep "channel" which is kept open by the water from Quiver Creek during freshets. In Matanzas Lake the central open por- tion has all a soft black mud bottom. The vegetation in these two lakes is in its character and in its distribution not essentially different from that of the lakes of Class I, though it is inclined to be rather less dense on the average. These lakes receive a comparatively large amount of spring water from the sandy bluff on the east side, and their waters average somewhat clearer and (except at times of invasion by river water) poorer in plankton than the lakes of the all-bottom-land type. 419 III. The comparatively shallow, weedy lakes, with maximum depths at gage 8 feet, Havana, of about 5 feet. The lakes of this class in which collections were made in 1914 and 1915 (Flag, Seebs, Stewart) represented a total acreage at the low water of 1901 of about 1,500 acres, and at 8 feet, Havana, somewhere near 4,000. All of these lakes went completely dry in seasons of extreme low water before 1900. Both in the shallower and the deeper portions the black bottom deposits con- tain a much larger percentage of partially decayed dead vegetation than is found in the open waters of the lakes of Class I. In recent midsummer seasons, up to 1914, Flag and Seebs lakes have been almost completely filled with growing vegetation. In Stewart Lake at the same time some open water was to be found in the central deeper portion toward the foot, but much less relatively to the total area than was the case in such lakes as Thompson and other deeper lakes of its type. IV. The very shallow, very weedy lakes, with greatest depths at the low water of 1910 — 1914 between o1/^ and 4 feet. These lakes (Duck, Dennis, Crane) were little more than lily or flag ponds before 1900, going wholly dry at low water in most seasons before the opening of the Chicago Sanitary Canal. Between August and October, 1914, Duck and Dennis lakes were so filled with mixed vegetation that it was difficult to pass through them with a skiff, even the fallen dead stems of the coarse water-plants being blanketed with living filamentous algae. Crane Lake in 1914 and other recent years has been a vast lily- bed, with its rather more open, but densely shaded bottom sprinkled with dead lily stems and "yorkey-nuts". These three lakes had a low- water acreage in 1901 around 1,200 acres. V. The shallow dead timber and brush areas first permanently submerged after the opening of the Sanitary Canal in January, 1900. These shallow backwaters, ranging in depth from 1}4 to 4 feet over most of their areas, have alternating opener and densely weeded stretches, the prevailing vegetation being Potamogetom and Polygonum. Their location on the ridges between such lakes as Flag and Thompson, and on similar ridges between these lakes and others and the river, makes them in reality littoral, either of the river or of lakes of the pre- ceding classes, as the case may be. Their bottom soil still contains abundant traces of the sticks and dead leaves contributed by the willows and mallows and button-bushes that grew there 20 years ago. The area represented by waters of this type can only, for the present, be roughly estimated. The total area under 4 feet in depth at the July-October levels of recent years between Copperas Creek and Lagrange dams (about 29,700 acres) made up over 50% of the total ex-river acreage, while careful estimates in the case of Thompson Lake as flooded to the same elevation (approx. Havana 8 ft.) indicated that on that gage in this lake these areas made up about 30% of the total land flooded. The dead timber and brush areas studied by us in 1914 and 1915 were all in the vicinity of Havana and were variously contiguous with Clear, Flag, Thompson, Dogfish, and Quiver lakes. 420 2. Bottom Fauna of the Lakes, by Classes Class I. — Fifty-three collections from open water over 6 feet in depth in the deeper all-bottom-land lakes of Class I in 1914 and 1915 averaged 222 pounds per acre of bottom animals, after deducting shells of Mollusca. An average about twice as great (441 lbs.) was shown by 78 collections from the 1 — 6-foot zone, 21 of these hauls coming from open bottom and having an average of 696 lbs. per acre, and 57 from more or less weedy bottom, with an average of 347 lbs. The average of the total of 131 collections from the five lakes, all depths, in both seasons, was 352 pounds. Forty-two of the total 131 collections were taken in 1914 and 89 in 1915. Thompson Lake, both in 1914 and 1915, easily outranked the other lakes of its class studied in the richness of its bottom fauna, its average of over 540 lbs. per acre, in either season, being more than double the best other lake average in this class, (Dogfish,) and nearly three times the lowest (Liverpool). Class II. — The two sand-beach lakes (Quiver and Matanzas) showed a combined average for 1914 and 1915, for open water over 6 feet, of 1,667 lbs. per acre, for a total of 27 collections. Of these, 18 were from Quiver Lake, with an average of 2,471 lbs., and 9 from Matanzas Lake, with an average of only 58 lbs. per acre. The combined average of 37 collections, from the 1 — 6-foot vegetation zone, was 251 lbs., the average of Matanzas again being lower than that of Quiver. The general average, for the total of 64 collections, both lakes, both years, and all depths, was 848 lbs. per acre, or more than twice that of the lakes of Class I. It will be noted, however, that the very high average for this class and for Quiver alone, was largely due to a few enormous hauls of large Viviparidae in the deep "channel" in 1914. These were much reduced in numbers and weight per acre in 1915. Classes III, IV, V. — The shallow weedy lakes of Class III, Flag, Seebs, and Stewart, averaged only 57 lbs. per acre, combined average of 45 collections, all depths, both seasons ; and the very shallow, very weedy lakes (Duck — Dennis, Crane) only 94 lbs. per acre for a total of 10 collections. As will be shown in the next section, however, it was in these shallower, weedier lakes, and in other weedy backwaters, that the shore animals in the weeds (above the bottom) reach their highest figures. In the dead timber and brush areas the bottom-fauna average of 16 collections, 1914 — 1915 (187 lbs.) was better than in weedy lakes of Classes III and IV, approaching, in fact, the average of the open water of the deep lakes of the all-bottom-land type (222 lbs.). 421 rH .05 P < O pq K M 3 CD 6 CO LO LO ■* LO ^ U5 •-C +-> CD pj tH tH rH rH r-i T-i rH o3 3 o OS 05 05 05 05 , 05 05 P O 2 rH tH tH rH r-{ rH r-i CD i -^ d CD g C5Q 05 co 1-i ©3 lO so ?- tH "* LO -* lO CM •o o3 | O 05 rH CM t- "* (>• . i— i CD -t-J lO Tfl CO rH 05 v CO rj< cd ad~ ■ 5 > cm rH Tin LO CO rH CO , T3 to ? 2 >H d '£ >H ?- ■ ©2 §£ « .2 • • CM co O O rrj CO t- LO CO CO CTJ O -I-' • • o 05 CO CO CM 05 CO >H d lO -s >H . *H rH o CO t> CO CM "«f -* <^ co LO r-i l-H cm' t^ CO 05 CM CO TJH TfH m TJH UO LO o cm LO LO CM r-{ rH CO JH o3 Jh CD ft «M CD +j 03 l-H * c^-? so f£ co GO CO 00 00 GO >~t CO id CO cm t>- CO ■* O CO CM Sh LO cm o CO CO CM CO CM CM d g CD > tH TH T-{ 05 CM LO o CM rH CO "* rH tH ft © o +j «j — i a -t-J -U -M ■+J -(-5 -s-> -t-> CD 00 ?H> CO CO rH"- ctS o3 CD ft ^M >> f-t . -M CD CD- ,^-s^ ^-N 03 1 03 o 03 * O 03 o o 03 LO o3 lO Oj ^5 CO CM o o CO CO t> O fa. iH oo CO oo •i-T CO T-4 rH rH CM l-H o o ,0 ft CD CD ~ Q CD r-1 M CO CO T3 d CD 6X) a d d d 03 O f>; o o o o ?H | O a u CD CO ft CO ft rd ^ a CD > B a CO • cd CO ed 03 cuo < CD ' \> o o bJ3 bfi a l-H rd -d O o o3 O J H Eh P Q CQ w a o o ■|H bfl w CO $H bfl CD 422 1—1 CD r-{ OS fa o H H O PQ CO W fa w > CD 6 CO Th LO uo -U 03 £ tH rH rH c$ r-H o OS OS OS Q o •rH -t-> rH rH rH -1-3 f-H ^ ■**• ?^ CD ci >H >H to so CD 0 CXO -rH CO oo OS rH oo io t- lO CD CO rH CM ° 53 «5 T3 co bfi g CD ° r> '-3 o3 PI'S 53.5 ; ; ; fa r© . . 53 02 55 CO ©3 2> io " d. so >M >"H CO r-H O r-i "* CO i 1 *rH fa CM CD oo CM t- CO -* ■U LO CM 00 CD rH CO fa u 03 fn fa 1-1 gj 2^- *"H CO so CD CO t>- OS ft «f O oo o6 (^ T~i CO N oo ia t- uo T3 tH CO r-i CM 53 53 O rH * fa CD jj ^ CO Id ?^ >H so C3S ©2 o r-i CD uo CO OO t- rH o o .!£> CD 53 CD oo oo CO CD > cm" fa ft O o rd^i -M =t-H m ft -u -ri -r-i CD oo tH > rH -t-> CD CD z-v ,4 rr* TO i — 1 rH ^ d d cd CD o o o CO CO OS CD .a r— I CM CM CO o3 TO ft CD - CD Q fa i— i CD CO CO l-H ■a CD bfl 03 o CO o3 rH CD * CD rH CD 53 > < > •i-h > H-> 53 'B b3 a a S w rl 53 423 O H Eh O PQ CO w M «i 63 co *-< T^ LO TJH LO LO Dal colle tior rH tH iH tH tH OS OS as OS OS vH iH tH l-H T-H ■4-3 ck »C ©3 LO ■<-> rj oo *H 2^ CO *-i S*- ft o OS OS O OS 00 <3 | bkd -i-h > O t^ "* LO CO Jt- Fh^ t- cq LO a) CO .2 ^ CO O h3 0) O c3 ; ' • ; Pn 43 O ■+-> • • * 3 02 z — CO 'Pi LO — 1 O ■<*■ <3l^ O- ■+J LO CO CD Fh C C3 +j * lo C3<> LO Fh 54-1 CD so >H E- oo >-i ~^ CD ft ^ © OS OS © OS OO o [^ "* LO CO t- co 1 N t- CM C\l cq b- LO ^3 tH r-\ S S Fh o CD ; Ph .lj -s-J fS CD Fh Eh CD CD b» a o • \ • -*-J tM ft CD GO +j -j-j H-i +J • T3 «(-! «(-) «H «M «M • M t> LO LO LO LO LO . c3 cd ^M ft f — i Fh CD CD ^™N d reag wat 901 d d n d >> *3 o o CO o o o >> CO C£> iS> Fh CD > OS p* o 73 43 \ Ul | 1— i 1 1— 1 i h- 1 CD co bJO bo 42 42 p < ctf ec3 CD CD CD r-H CD CD -(-> fe fe GQ Ul m w a o -i-H o CD i — i O o rH ari ■ S 'C! m CD ch O +j dr d.£ O nd • Ph r^ • • d 02 55 XIX £ o ^H O . . *«H i — 1 •!-! . . 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Since the general average of 848 lbs. per acre for the Class II lakes (Quiver, etc.) applied to but 620 acres at the low water of 1901, while the average of 352 lbs. per acre for the Class I lakes covered 3,390 acres at the same gage, it is evident that a simple average of this sort is unfair and likely to be unduly high. As we have not complete acreage figures for different depths at recent gages pre- vailing in midsummer, and lack, in particular, exact figures on the dead timber acreage, a close general average of all the lakes and backwaters studied in the two years, based on accurate acreage weightings, can not now be figured. If we assume, however, that on the average the ex- pansion in lake acreage between 4.2 and 8 feet, Havana, is about the same in all of the first four classes of lakes except Class II, we shall not go far wrong in weighting the class average of I to IV, excluding the dead timber and brush areas, with the low-water acreage for 1901. The general bottom-fauna average for Classes I — IV, inclusive, figures out in this way at 285 lbs. per acre. If, again, we assume that the usual ratio of adjacent dead-timber acreage to the total acreage of lakes and backwaters at gage 8 feet, Havana, is about the same as in Thompson Lake (around 30%, estimated), and weight the Class I — IV average (285 lbs.) and the Class V average (187 lbs., dead timber and brush areas) with "per cent." acreage figures on this basis, we obtain a gen- eral average of bottom fauna for the two years, for all classes of lakes and backwaters, all depths, of 255 lbs. per acre, or almost exactly the general river average for 180.5 miles below Chillicothe (261 lbs.), but only about one third of the all-zone river average for the 59.3 miles be- tween Copperas Creek and Lagrange dams (705 lbs.). 426 LO LO LO LO LO T-* tH tH T-H tH ate llec- ons OS cs OS C5 OS tH T* tH iH tH P§5 «*< TJH «* "* rH tH tH tH tH T-f OS OS os OS OS m iH iH tH rH tH a ,Q •4-5 =1 — t 0) c3 *>- ?- »-o O CO +J o*? -£ £ *o GO *"5j" "M >H a & o b- tH t- -* t- 0J a 1 fcfl.rH tH LO LO OS oo o 02 a p. rr o CD -t-J !> CO Cxi rH 02 ft fl 02 >rH o T3 02 O n3 PL, X2 feiO g 0) o CO OS CO ; '; ; 02 +-> an 3 55 02 . lo 02 >H o> O CO *o io r-H O >"H co »<7* >-i >H 0*2 CKJ rH t- LO LO lo TH LO C5 oo 00 LO «# CO 00 rH oq oq T5 tH 02 02 OS u fl T-l on < u oo ?>■ to C5 CO y, CO 1 02 ?- GO -=t" >i >~i k P < Pa «? £ tH rH t- ■«*l t- o rjn LO LO OS oo fcc X N TH CnI rH a3 02 H ifl O o o *H <^ H &H 02 +J, go ?- -J— O 02 ►> a o o to CnJ ©3 CO C «W o In a 02 02 oo T3 -t-> o o i-l r OS oq LO ^H -* <*l X >■ *H «H > d c— iH • H-i CO CO LO iH t- 02 C2 fe. T-l CO iH tH C£> 0) > 02 02 ^ at a a 02 5 >> >> ^i <_J -t-5 >> pQ > > bt ►d a C2 >J 02 !> d HH o 02 02 1— 1 a o C3 02 Id 02 T3 02 02 o o3 02 +- 02 02 +-) M 02 o o O 02 ^ 02 02 o3 02 * a 02 a 02 03 02 ^ o3 <1 < 02 02 ^ 02 Q Q GQ > Q 1— 1 1— 1 i— i 1—4 > h- 1 > 427 4. Composition of the Bottom Fauna The proportion of Mollusca to associated animals in the lake col- lections of 1914 — 1915 did not run so uniformly high as in the river series of 1915. The Mollusca percentages are highest in the open water of the deeper lakes of Classes I and II, where they run from 84 to 96%. In the weedy zones (1 — 6 feet) of the deeper lakes the Mollusca per- centages were noticeably lower (77%). In the shallower weedy lakes of Classes III and IV the insects and small Crustacea are much more abundant relatively, and the Mollusca ratios drop to 36 and 50%. Per Cent. Mollusca by Weight (to Total Weight of Collections), Lakes, 1914—1915 Zone over 6 feet 1—6 ft., 1—6 ft., open water no vegetation vegetation Class I 84.1 89.8 77.8 Class II 96.8 • . . * 77.5 Class III • • • • • » . . 50.7 Class IV • • • « 36.4 Class V .... 79.7 The snail fauna of the lakes, like the insect fauna, presents in the average somewhat greater variety than that of the river. Viviparidae made up1 the largest percentage of the Mollusca totals in the deeper lakes of Classes I and II. In the shallower weedy lakes and in the dead timber areas the ratios of Viviparidae were lower. The smaller snail fauna (smaller Gastropoda, Sphaeriidae) less rarely than in the river consisted almost exclusively of Sphaeriidae' — the Valvatidae and Amnicolidae being well represented in most of the lakes studied, and exceeding Sphaeriidae in some cases, in the shallower weedier lakes, both in num- bers and weight. Further details of the composition of the lake bottom-fauna are shown in the detail tables at the end. Pee Cent, of Viviparidae, by Weight, to Total Weight of all Mollusca, Lakes, 1914—1915 Zone over 6 ft. open water 1—6 ft., no vegetation 1—6 ft., vegetation Class I Class II Class III Class IV Class V 56% 99% 85% 86% 88% 62% 61% 77% 428 Illinois Valley Lakes, 1914 — 1915, Bottom Fauna pounds per acre I. Deep Bottom-land Type. (Zone over 6 feet) Lake No. col- lections Large Viviparidae etc. Sphaeriidae etc. Insects etc. Total Per cent. Mollusca Clear— Mud, 1915 8 17.1 186.8 11.7 215.6 94 Liverpool, 1915 6 24.3 96.7 21.2 142.2 85 Thompson, 1914 8 76.5 140.0 94.2 310.7 69 Thompson, 1915, 8 413^9 64.6 18.1 496.6 96 Dogfish, 1914 3 8.0 3.1 12.3 23.4 47 Dogfish, 1915 12 67.1 18.5 66.4 152.0 56 Sangamon, 1915 10 51.2 41.4 14.0 106.6 86 Average 53 104.6 82.2 35.2 222 84.1% Illinois Valley Lakes, 1914 — 1915, Bottom Fauna pounds per acre 1. Deep Bottom-land Type. (1 — 6-ft. Zone. No Vegetation) Lake No. col- lections Large Viviparidae etc. Sphaeriidae etc. Insects etc. Total Per cent. Mollusca Thompson, 1914 10 687.1 80.3 : 135.8 903.2 85 Thompson, 1915 * 7 610.5 24.9 12.2 647.6 98 Sangamon, 1915 4 145.3 109.5 10.2 265.0 96 Average 21 558.3 67.3 70.6 696 89.8% 429 I. Deep Bottom-land Type. (1— 6-ft. Zone. Vegetation) Clear— Mud, 1915 12 121.7 110.7 17.7 250.1 93 Liverpool, 1915 9 117.0 4.2 28.2 149.4 85 Thompson, 1914 16 210.0 28.4 193.1 431.5 55 Thompson, 1915 12 481.9 10.0 20.4 512.4 95 Dogfish, 1914 5 336.0 19.1 42.4 397.5 89 Dogfish, 1915 3 none 7.3 - 126.9 134.2 5 Average 57 233.9 36.1 77.0 347 77.8% Illinois Valley Lakes, 1914 — 1915, Bottom Fauna pounds pee acre II. Deep, Sand-Beach Type. (Zone over 6 feet) Lake No. col- lections Large Viviparidae etc. Sphaeriidae etc. Insects etc. Total Per cent. Mollusca Quiver, 1914 15 2,754.6 2.9 47.5 2,805.0 98 Quiver, 1915 3 800.0 none 3.1 803.1 99 Matanzas, 1915 9 i none 40.6 18.0 58.6 69 Average .27 1,619.2 15.1 32.7 1,667 96.8% II. Deep, Sand-Beach Type. (1— 6-ft. Zone Vegetation) Quiver, 1914 17 329.7 33.4 25.2 388.3 93 Quiver, 1915 14 35.5 9.3 113.9 158.7 28 Matanzas, 1915 6 • 58.4 9.6 9.9 77.9 87 Average 37 174.3 20.4 56.2 251 77.5% 430 Illinois Valley Lakes, 1914 — 1915, Bottom Fauna pounds per acre III. Shallow, Weedy Type. (Depth 1—5 ft.) T , No. col- lections Large Viviparidae etc. Sphaeriidae etc. Insects etc. Total Per cent. Mollusca Flag, 1914 3 none 25.7 45.2 70.9 63 Flag, 1915 15 5.0 none 22.9 27.9 18 Seebs, 1914 7 14.0 15.5 94.5 i 124.0 j 24 Seebs, 1915 8 18.5 1.8 5.6 25.9 78 Stewart, 1915 12 41.0 24.4 8.4 73.8 | 1 88 Average 45 18.0 10.9 28.1 57 50.7% Illinois Valley Lakes, 1914 — 1915, Bottom Fauna pounds per acre IV. Very Shallow, very Weedy Type. (Depth 1 — 4 ft.) Lake Large No. col- Viviparidae lections | etc. Sphaeriidae etc. Insects etc. Total Per cent. Mollusca Duck — Dennis, 1914 5 none 12.4 97.9 110.3 11 Crane, 1915 5 42.0 14.3 22.7 79.0 71 Average 10 21.0 13.3 60.3 94 36.4% V. Dead Timber and Brush Areas. (Depth 1 — 4 ft. Vegetation) Vicinity Havana, 1914 6 29.8 87.1 44.0 160.9 72 Vicinity Havana, 1915 10 167.5 1.3 33.6 202.4 83 Average 16 115.8 33.4 37.5 187 79.7% 431 The Weed-Fauna of the 1— 4-foot Zone of the Illinois Valley Lakes, and the Combined Bottom- and Weed-Fauna Average, August— -October , 1914 1. Weed Fauna of the Lakes near Havana In the autumn of 1914 a series of quantitative collections of the small invertebrates attached to and scattered between the leaves and stems of the denser growths of coarse vegetation about the margins of the bottom-land lakes near Havana, in depths 1 to 4,y2 feet, were made at seven stations. These collections were made by inclosing the tops of the plants .in a large bucket, lowered about them to a depth of about 9 inches, cutting off the stems a little below the 9-inch level, shaking them out thoroughly in the water obtained by righting the bucket, and then passing the water saved through a fine sieve. Though these collections represent but a fraction of the total "weed fauna", omitting the small insects and other animals occurring between the bottom and the lower limit of the bucket hauls (a distance of 1 to 3 feet), the average valua- tions obtained in this way were very much above the average bottom valuations from the same lakes in any zone, with the single exception of a few hauls from the bottom of the Quiver Lake "channel" in 1914. The general average for the seven stations was in fact 2,118 lbs. per acre, or more than eight times the general average of bottom fauna for the five classes of lakes and backwaters between the head of Clear Lake and Beardstown studied by us in 1914 and 1915 (255 lbs.). The smaller snails (Amnicolidae, Physidae, and Valvatidae, prin- cipally) formed about 50% of the average total by weight. The ap- proximate half of the collections made up of insects (larvae and nymphs) consisted principally of immature Odonata (Agrionidae and small Libel- lulidae). The only large snails were a few adult Planorbis trivolvis, the great bulk of the material being of quite small size and easily avail- able, in that respect, for use as food by young to half-grown as well as adult fishes. 2. Combined Average Valuation of the Bottom- and Weed-Fauna Stocks, and Total Stocks in the Acreage For the purpose of calculating a general average, and also the total stocks, both of the bottom and weed animals, for the entire lake and other backwater acreage between Copperas Creek dam and Lagrange (approximately 52,700 acres at 8 feet, Havana — the average gage in July — October, 1910 — 1914), I have assigned the general bottom-fauna average of the twelve lakes studied (255 lbs.) to the entire acreage, as with no levees, and the weed-fauna average of the lakes in the imme- diate neighborhood of Havana (2,118 lbs.) to the approximate 29,700 acres with depths under 4 feet in the district. An acreage-weighted general average figured in this way stands at 1,447 lbs. per acre, or at 432 fa Q W <1 > «! >i E-i H M u H of w «H g CM -<* Tt< o .2 tH rH T~\ +j CD t- CM co Q8 bJD bJO bJO -t-> O O o O O ps <1 p <1 o O pi _i_j o3 $ OO S ,5 CO OS CO tH CO -* t- o r— ( 00 rH OS CM TJH »* CM LO fH O CD b-J o to OS CM ■^ CO OO o3 CO l>- t- OO LO LO CO 00 -u OS rH o OO o CO LO i-H O lo lO LO "tf CO CM rH T-H H Cxi CM CM CM CM iH rH CM 02 o CM CM co o O tJ< O ^3 OS CO CO CO TtH LO CO rH CM CO 00 lO T— . 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Of the total, 13,- 453,800 lbs., or 17.6%, represents the bottom animals of the full acreage; and 62,904,600 lbs., or 82.3%, represents the small weed animals of the upper 9 inches only, in the rather more than 50% of the total acreage within the 4-foot line. Bottom- and Weed-Fauna Stocks, Lakes, Coppeeas Creek Dam to Lagrange (59.3 miles) Approx. acreage 8 ft., Havana (No levees) Average valuation* pounds per acre 1914—1915 Total stocks for acreage in first columnf Per cent. of total Bottom fauna stocks — all depths 52,760 a. 255 13,453,800 17.6% Weed fauna stocks — 1 — 4 ft. 29,700 a. 2,118 62,904,600 82.3% Bottom and weed stocks 52,760 a. 1,447 76,358,400 The Bottom- and Weed- Fauna of the Littoral Zone of the Deep Glacial Lakes of Northeastern Illinois, August — October, 1916 1. Bottom Fauna The general average of 119 mud-dipper collections from the zone of 1 — 7 feet in eight of the deep glacial lakes of northeastern Illinois in August — October, 1916, was only 82.8 lbs. per acre. The six isolated lakes studied (Deep, Cedar, Zurich, Crystal, Long, and Sand lakes) showed the better average (105.8 lbs.), while the two large lakes (Fox and Pistakee) directly open to the channel of Fox River averaged only 54.2 lbs. Sparse vegetation, principally species of Potamogeton, with some Chara, chiefly within the 3-foot line, were present at most of the col- lecting stations. The bottom varied from sand, gravel or sandy mud, to soft black mud or yellow clay. On the windward side (southeast or west) of most of these lakes there is a more or less sterile clay zone with very * Based on data from 12 lakes representing around half of the total acreage, t Equals approximately that of 1908. (Table originally made for comparison with 1908 fish yields.) 434 scanty vegetation, or none at all, lying between the weedy shore zone and the deep open water, part of it sometimes extending within the 7- foot line. Valuations considerably better than the average were obtained in restricted areas with more nearly uniform bottom in four of the isolated lakes, the average for clay bottom overlaid with fine decayed vegetation, in Deep Lake being 320 lbs.; for sand and clay, in Cedar Lake, 251 lbs.; for gravel and sand, in Deep Lake, 220 lbs. ; and for gravel and sand, in Lake Zurich, 212 lbs. In its composition the littoral bottom-fauna of these lakes differs most strikingly from that of the Illinois Valley bottom-land lakes in the relatively much lower percentages of Mollusca. Snails made up only Lakes, Northeastern Illinois, August — October, 1916, Bottom Fauna pounds per acre Littoral Zone, 1 — 7 feet. Some Vegetation Lake Number of col- lections Large Viviparidae etc. Sphaeriidae etc. Insects etc. Total Per cent. Mollusca Deep Cedar 24 169.0 208.8 24.2 135.6 159.8 v 19 15 Zurich 13 9.9 10.0 49.2 69.1 23 Crystal 6 16.0 40.4 56.4 28 Long 6 1.7 50.7 52.4 3 Sand 10 0.6 13.1 13.7 4 Average 66 1.8 16.7 $7.1 105.8 17.4% Pistakee 29 10.8 26.0 42.6 79.4 46 Fox 24 2.3 3.6 18.0 23.9 24 3m 435 17.4% of the average weight of the hauls at 66 stations in the six iso- lated lakes; and only 41.8% in the two lakes traversed by the Fox River channel. The snails belonged almost entirely to the smaller-sized species, the larger Pleuroceridae ' and Viviparidae occurring only very rarely and in small numbers in the hauls. The most abundant families were the Sphaeriidae, Amnicolidae, Valvatidae, and Physidae. The most important insects, measured by weight, were the Trichoptera (caddis- flies), Chironomidae, and large Ephemeridae (May-flies). (A more complete report on these collections, including also the dredgings in deep water, is being planned for publication later.) 2. Weed Fauna In August, 1916, we found the shore vegetation of the isolated glacial lakes so generally thin and sparse, as compared with the dense growths of Potamogeton and Ceratophyllum in the Illinois River bottom-land lakes, that it was practically impossible to employ the bucket method of collecting the weed animals used at Havana in 1914. Along the north shores of Pistakee and Nippersink lakes, however, beds of mixed Potamogeton, Myriophyllum, and Ceratophyllum were not uncommon that were fully as dense and that carried not far from as rich a fauna as that of such lakes as Flag and Thompson. The average for the upper 9 inches at two stations in Pistakee and Nippersink lakes in August, 1916 (1,665 'lbs. per acre), was only 26% less than the average of the seven weed-fauna stations in the vicinity of Havana in 1914 (2,118 lbs.). Both insects and mollusks constituted an almost insignificant part of the totals, 85% of the weight in one case, and 95% in the other being made up of a single small crustacean — the little fresh-water shrimp, Hyalella knickerbockeri. (Table, p. 436.) Comparison with Outside Bottom- and Weed-Fauna Valuations 1. Bottom- and Weed- Faun a of Oneida Lake. (Baker, 1918) In the Lower South Bay of Oneida Lake, New York, in 1916, Baker found the richest bottom-fauna within the 6-foot contour. Averaged by weight*, in pounds per acre, sand bottom showed the highest valua- tions, 143 sixteen square-inch units examined, averaging 387 lbs. Gravel bottom, with 207 lbs., clay bottom, with 188 lbs., and sand and clay, with 210 lbs., were well under sand bottom in richness, but were all much 436 tH Oh OS _ pa Eh a W o CO H M < t- 00 tH tH 03 o3 6JD bO Q 3 < 3 <1 +f <3 Pi -H 82 10 U3 OS 00 *H C3 > f^ffi ■*"* r« S " CD o s PL."-1 ■<-> S? 8 s CO T^ ^ r^ 5 5 ph^i 1— c cq O LO d -T-i as • to -t-> O Eh OS 00 CO rH „ o3 - r— j CO o © i— 1 +J ,2 O o o CO CO to cfi '® +J CO oo K -rt CD •--' "t^ Jir lH o O +J «iH O u ri E? -£ ■rH CO • sis* oo CO • • 0) c3 ^ •"■H ?H O • . m c3 -u • • # a v • • . > > & S1 ® # ■ CD CD CO CO . 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Attached micro- organisms a o +j M i=l o3 Protozoa Algae Rotifera etc. to a O a o a l-H r-j O CO e3 a o a o 13 a o3 i— i ,a 03 o3 cj • l-H rH rH O O T3 a 03 p2fL i— i ft o .»— ( -t-> CD a a i— i bJD a •pH •1— CO a a CO CD 13 CD a CD O Ul CO a co CD T3 CD a CD CD Ul a a u CO 03 1— c CD O U CO a a CD 'C CD a CD CD CD Ul CO 02 o o3 Q Cyclotella Melosira Navicula etc. CO CD •i-H CD CD ft CO >> a o3 03 Jh •H CO CO ■— ' 0) CD Navicula Cyclotella Melosira cells Fragilaria cells Surirella 2. Bacteria CD a o ui ; CD • 1. Fine organic detritus (dead matter) CD a o CD a o CD a o 5 CD a O CD a !-• H CD CO CD CD ft Larva of caddis-fly (Hydropsyche sp.) • > u i— i t3 CD a^ £> O a o3 • pH o3 a o3 An •§5 PH CD W) bfi o3 CD a 443 tH OS rH ^ 1-1 P 1-3 «< fe «! > GQ «l P3 K Q fc |Zi P H H o H e4 fa Q E fa ph o ■Tt) ce H O W n K '«! a o i— ( H 02 r/7 W fe H H < M Q M ^H w fa P o fa > Q O i— i o § fe O H H O PQ fa o 2 O O 5. Attached micro- organisms i U O 4— o O e- Jh CO a d CD O Pleurococ- cus? t Rhizoclo- nium - a o M d .+_> +-> -H o o o Ph^ -I— CO 03 d O S cfl O 03 FJ ° ,d o3 O Ph • 03 ft o CD a •i— i i— i ho a CD Pediastrum Coelastrum Scenedesmus f • CD CO CO a o o3 3 Navicula Synedra Cyclotella Melosira f Navicula Synedra Cyclotella Melosira f *1s 4— 4— 4— 4— 4— 4— 4— 4- 4— 1. Pine organic detritus (dead matter) 4— 4— 4— 4- 4— 4— 4— 4— 4- t a P •p- a a •a "c a e a CO © '§ 9 CO O =0 £ o •1— 1 o d a c 444 The Nitrogen, Organic Carbon, and other Oxidizable Matter in the Bottom Muds of the River and Lakes below Chillicothe, 1913—1914 1. Bottom Muds of the Illinois River Channel, 1913 Mud samples taken in the Illinois River channel between Chillicothe and Kampsville in March and July — October, 1913, showed a rather wide variation in the amounts of nitrogen present, as expressed in terms of percentage of dry matter, but both in early spring and late summer agreed in showing a higher average above than below Havana. In percentage figures, as stated, five samples from above Havana, all months taken together, averaged 0.306% nitrogen, or 61% richer than the five samples taken on approximately the same dates at stations be- low Havana, which averaged 0.189%. A lesser actual difference in average nitrogen content is shown for the stations above and below Ha- vana, when we take into account the specific gravity and the moisture percentages of the samples and calculate average values of nitrogen by weight for a given area to a depth (3 inches) supposed to approximate the average depth of cut into the soft bottom by the dipper in taking the samples. The average number of pounds of nitrogen to the acre, figured in this way, was 1,918 for the stations above Havana; and only 26% less, or 1,417 lbs. per acre for the stations between Lagrange dam and Kampsville, in which the specific gravity was visibly higher and the moisture-content lower. The organic carbon per acre figures out, both above and below Ha- vana, at about 8 times the nitrogen, the averages standing at 14,111 lbs. per acre for the stations above and 11,322 lbs. for the stations below Havana. The total oxidizable matter (which includes both the nitrogen and the organic carbon,- as well as various other substances, some of them of a mineral nature), figured in the same way, averaged 48,345 lbs. per acre to a depth of 3 inches in the river channel above Havana, and 31,869 lbs. per acre below Havana. Compared with the stocks of nitrogen and total oxidizable matter (dry weight) in the muds either above or below Havana, the total acre- poundages of dry matter or nitrogen represented by the bottom inverte- brate population of July — October, 1913, are extremely small, however liberally figured. Taking the average bottom-fauna stocks of the river between Chillicothe and Havana (the richest section) as 555 lbs. per acre (see table, page 412), and assuming a dry-matter content of about 10% and a percentage of nitrogen to dry matter of 7%, the dry weight of the average stock of bottom fauna on one acre would stand at 55 pounds, or about 1/900 of the dry weight of the total oxidizable matter per acre in the channel mud of that reach, and the contained nitrogen at less than 4 pounds, or about 1/500 of the total nitrogen per acre. 445 CO rH OS i-5 o > H al oxidiz- e matter March o CM o ■* CD CO C» oo rH -M ,-H ■— ' *tf CO O ,Q H g3 rH i-{ TJH to ctf ,Q cm o rH O £x0 ?— i 1 o O u o3 >> 1-^ CO o «3 1-9 tjT rH- rH rH CD " CO oo OS t- Q O rH OO T-\ 5-H 1 CO Oi rH ""* •- h o rH O rH 4J . Dry weigh 1 liter eq bfl OS u CD 00 o rH rH Jh i—i CD " >> O «2 Jh CD ft-d ^ CD a • >> T3 ctf Wet" weight 1 liter o lo bJO O c© X 02 O CD ft o ft d v— • '•~t rt — ■ ture CM 02 a u CD CO JH A CO 03 a u CD """^ CO *H rd ctf ft CD o -M c3 ft CD CO CO -*-> -t-j d CD O S3 02 -M d CD CJ &H h -d CD o >> 02 13 f-c CD d tr- ee CD Ph d CD (3 Ph d o ft JH r-i O r-i Ph m w> Ph rd o cS CD tf o CD . • CD t— < CS 02 & 5 +j d o cd 1— 1 Cd 6 . CD g bjn O 446 2. Bottom Muds of the Lakes between Copperas Creek Dam and beardstown Comparison of samples from the central portions of eleven lakes be- tween the head of Clear Lake and Browning, May — October, 1914, on the dry-weight percentage basis shows the shallow weedy lakes highest in bottom nitrogen. The average of Flag, Seebs, and Stewart lakes (Class III lakes) in terms of percentage of dry matter, was 0.39%, com- pared with an average of 0.27% for seven of the deeper, more open lakes of Classes I and II; and with 0.26% for Crane Lake — a lake of the very shallow, very weedy type. The general average of all of the 19 mid-lake samples from eleven lakes of 4 of the five classes (0.32%) was some- what more than the average for the river channel stations above Havana (0.306%) and nearly twice the river average below Havana (0.189%). The general average of organic carbon in mid-lake samples was 3.89%, comparing with 2.41% for the river channel above Havana, and with 1.51% for the channel below Havana. In organic carbon as in nitrogen,, the shallow weedy lakes of Classes III and IV (with 4.30% and 5.19%) averaged well above the deeper lakes of Classes I and II (with 3.67% and 3.09%). Both in Thompson and Quiver lakes, May — October 1914, the ni- trogen and organic carbon figures were considerably highest in samples from the shallower water, the percentages of average difference as be- tween samples from under and over 6 feet in depth amounting in the case of the nitrogen to over 30%, in both Thompson and Quiver lakes, and in the case of the organic carbon to 15% in Thompson and to 52% in Quiver. Nitrogen and Organic Carbon in Muds, Thompson and Quiver Lakes, May — October, 1914 Nitrogen Per cent. (in terms of dry matter) Organic carbon Per cent, (in terms of dry matter) Thompson Lake Quiver Lake Thompson Lake Quiver Lake Depth over 7 feet Average 0.325 8* 0.320 4 4.83 8 3.46 4 Depth 1—6 ft. Average 0.42* 7 0.440 4 5.56 7 5.27 4 All depths Average 0.373 15 0.400 4 5.17 15 4.67 4 * The Italic figures give the number of samples. 447 Nitrogen, etc., in Mud of Illinois Valley Lakes, May — October, 1914 samples from middle, in deepest water per cent. in terms of dry matter - Lake Samples Nitrogen Organic carbon I. Deeper Clear— Mud 2 0.23 2.93 bottom-land lakes Liverpool 1 0.29 2.52 Thompson 4 0.32 4.83 Dogfish 1 0.30 3.46 Sangamon 1 0.22 4.86 Average (5 lake averages \ 0.27 3.72 II. Deeper Quiver 4 0.32 3.46 sand-beach lakes Matanzas 1 0.24 2.73 Average (2 lake averages) 0.28 3.09 III. Shallow, Flag 1 0.52 5.48 weedy lakes Seebs 1 0.35 3.78 Stewart 1 0.31 3.66 Average • « 0.39 4.30 IV. Very shallow, very weedy lakes Crane 1 0.26 5.19 General average, 0.32 3.89 448 Nitrogen, etc., in Bottom Muds, 1913 — 1914, Illinois River Channel and* Lakes in Vicinity of Havana Nitrogen Organic carbon Total oxidizable matter * + * t * t River channel Chillicothe to Kampsville .247 100 1.87 100 6.32 100 River channel, above Havana .306 123 2.41 128 7.71 121 River channel, below Havana .189 76 1.51 80 4.25 67 Eleven lakes, vicinity of Ha- vana, middle .320 129 3.87 206 Thompson Lake, middle .325 131 4.83 258 Thompson Lake, shore, 1 — 6 ft. .428 173 5.56 297 Thompson Lake, all depths .373 151 5.17 276 Quiver Lake, middle .320 129 3.46 185 Quiver Lake, shore, 1—6 ft. .440 178 5.27 281 Quiver Lake, all depths .400 161 4.67 249 The Plankton and other Limnetic Oxidizable Matters carried by the Illinois Eiver Channel at Chillicothe and Havana, 1909—1914 1. Stocks of Plankton Carried past Havana September, 1909 — August, 1910 Calculations of the total plankton that passed Havana September, 1909 — August, 1910, from the silk-net figures of that year, increased in * This column gives per cent, in terms of dry matter. t This column gives percentage on base of Illinois River channel, Chillicothe to Kampsville. 449 the average ratios found by Kofoid* to hold between silk-net and filter- paper volumes in 1896 — 1899, show a figure for the twelve-month period (200,477 tons) almost exactly treble the amount (67,750 tons) that was carried in the average year just prior to 1900. Of the twelve months' total about 89 per cent. (179,916 tons) was accounted for during the four months of the spring season, March to June inclusive, during which period 1,474 tons passed every twenty-four hours. The 14,025 tons that passed during the five months July to November inclusive, made up only 6.9 per cent, of the total for the year, but this amounted to ninety-one tons every twenty- four hours, and was enough if all settled to the bot- tom to supply 1,698 pounds per acre for every acre in the river below Copperas Creek dam at the average gage of that season and year (7.8 ft., Havana). The December — February plankton (6,536 tons) was less than half that of July — November, and only 3.2 per cent, of the total. The full twelve .months' total, over 400,000,000 pounds, amounted to 24,279 pounds per acre for each acre of the approximate acreage in the river below Copperas Creek dam at recent under-bank-full stages (8 ft., Havana) ; or to nearly a hundred times the wet weight of the total bottom-fauna stocks of July — October, 1915, shells deducted, between Copperas Creek and. Grafton (4,277,351 pounds). The dry weight of this plankton at two to five per cent. (8,000,000 to 20,000,000 pounds) was twenty to fifty times the estimated dry weight (at 10 per cent.) of the total bottom stocks of 1915 below Copperas Creek (427,735 pounds). Complete figures for the plankton stocks produced in the full 120 miles between Havana and Grafton would doubtless also include, in ad- dition to the Havana figures, new stocks of no small size added on the way down stream, both as a result of normal multiplication and lake and other backwater contribution. I do not take the fact that all of our down-stream plankton series between 1899 and 1910 showed a large de- crease in volumes southward of Havana as ruling out the inference of continued though hidden increase, at a rate merely slower than the rate of decrease due to consumption and settling. The average time of pas- sage between Havana and Grafton was 6.7 days at the average gage of July — November, 1909 (7.81 ft., Havana), and was 4.82 days at the average gage of March — June (Havana, 12.04 ft.). During upward pulses, rates of increase in plankton volumes (c.c. per m3) were several times recorded both by Kofoid and the writer for the river channel at Havana and for Thompson Lake, both in spring and autumn months, 1896 — 1910, that amounted to over 25 per cent, in one day; while in ex- treme cases the increases ran to 60 to 70 per cent, in a single day, or 400 to 500 per cent, in a week. * Bui. 111. State Lab. Nat. Hist., Vol. VI., Art. II., 1903, pp. 552-554. 450 o Oi CO p o p <4 o as a H Ph W 02 > M CO CO Ph o H ►H Ph hh «l Eh O d o '3 CO P • - 2,2 co a *j _ ^ ^ ft M . >■ i-i ^ ft o3 <£ co Ifld) Ooj bjQHH s^ CO I"*"1 42 tH ^°5o cd o o 5 ^ d O 0^ -t-5 i— i Q ^ o .2 3£ft Ph ?H co Ph » CO CD _h CO a^ C<1 W « fe S 5-1 d X =s CD !^ CO CO CO fr- ee CO CD d CO « a O K CO CD CO > Si Oi CO O CD "* CO CXj CO~ o OO CO CXI CM -^ S>- CD^CXJ CO K5 OO tH 00_ rH lo co © pq o © oo" • CO co n^ a d ?H O OPhH o o o o" CM co Oi tH S ^ i—h O CD •+-> ^ M I> CO ^ co O rt . a rH i— ( o ft a ^ d o _ O^j o tH ^3 +■» n CO U -H +j co Ph ^ c- o d d oo ■— 1 ■+-> co CO ft ft s ^ O CD ja-K » CO o •--H CI a © —i o ft 42 CD fe d | o CO fn K co s >» CD •2 « 02 a^ CD "* Q OS OO OO Oi CD OS OO 00 CD t>- tH t> Oi^ Cxf OS~ CO t- OO i-l oi" " 10 . co . 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Stocks of Total Nitrogen and Nitrates in the River Channel at Chillicothe, 1914 — 1915 Comparison of the plankton figures obtained at Havana September, 1909 — August, 1910, with the total nitrogen and nitrate figures for Chillicothe, March, 1914 — February, 1915, does not suggest that plank- ton production in the river between Havana and Peoria has been at all in danger of limitation by the nitrogen supply at any season during re- cent years. The total nitrogen that passed Chillicothe in the twelve months (67,722 tons) was sufficient, if all metabolized without loss, to produce more than ninety times the actual stocks of plankton that passed Havana in the year 1909 — 1910 (based on a dry-matter per cent. = 5; nitrogen per cent, in dry matter = 7) ; while the stock of unused nitrogen in the form of nitrates (22,345 tons) was capable of producing under the same conditions more than twenty times the total plankton that actually passed Havana in 1909 — 1910. At the dry matter and ni- trogen ratios assumed, only about 1,431,983 pounds out of the total of 35,444,859 pounds of nitrogen that passed Chillicothe in the year 1914 — 1915 would be accounted for as nitrogen in the form of living matter in 400,000,000 pounds of plankton (the approximate amount that passed Havana September, 1909 — August, 1910). If we could distribute the total nitrogen that passed Chillicothe over a river acreage of 26,782 acres (the estimated acreage below Chilli- cothe at about 8 ft., Havana, the average gage of July — November, 1910 — 1914), we would have 2,442 pounds per acre in the March — June pe- riod; 1,495 pounds per acre July — November; 1,119 pounds per acre De- cember— February; and a total of 5,057 pounds per acre for the year. The nitrates, similarly distributed with correspondingly lesser poundages for the separate seasons, would amount to 1,668 pounds per acre for the twelve months on the same acreage. The Peoria discharge data entering into the various tables following are the rating-table figures of Jacob A. Harman, as published in the special Report of the Illinois State Board of Health on Sanitary In- vestigations of the Illinois River, 1901, and more recently used by Alvord and Burdick in the Report of the Rivers and Lakes Commission on the Illinois River and its Bottom-lands, 1915. These figures are consider- ably higher than recent figures of the U. S. Geological Survey, which we did not have at hand, except in fragmentary form, when the manu- script for the present article was being prepared. 452 lo tH OS i-i OS w H O o H H w o o M 02 0Q *% d M d rft O OS t- Total nitroge pound: per 24 hrs CXJ d 03 OS rH os >t! 0} v* +j tH t- id Tota itrog pouni per cu. f CXI CX| T-H LO • "Eh o3 o a r? « PH r* CO *Eh ! o . 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OS P rH r- 1 P rH 00 00 CO to d M rC O o CO rQ CD M 03 O 01 B rH CD > s ^PM 454 M m w. < no H <(j LO « tH H OS H Z tH 1 1 OS W o ki as «* rH k? cc o H H ^H u H 1-1 o ki Ph <1 h-1 rr, Ph W > < H H O no H H 0 „ fc o o H M OS H Eh C 0) LO 02 02 02 02 fig. oo^ 02 45 tH 42 05 ,Q 02 4J a 0) -<-> as ^ fl — < Pi rH 0 *f O rH o o rH O rH -^ co o 1 OS H-> as +J ^ ^, o CO Nitr Chilli 1914- co CO -co CO OS oo 5^ - o 00 t- c*ia LO ,-H o rH CM rH rH 02 02 02 02 42 42 X5 42 d a o ft 5 -2 o I— 1 I— I i — i l-H CD t- O CO O fl rf CO jvq OO T-t CO 00 CO rH l~l °t - is*'* £ a13 to LO o ■r^ rH 00 o CO w rH rH rH tH 02 02 02 02 42 42 rO 42 o i— ( i— ( i—( l-H Total plankton passing Havana 1909—191 O rH cxf OO eg rH CO o OS t- rH LO C- CO IO LO © CO 00 as" oo" O r-i LO eg o CO rH o s=?rH Equals times actual plankto 909—19 rH as OS rH rH LO OS OS CD CO X X X X r-i 02 02 02 ID 42 42 42 42 . O i— H i— i l-H ■ — i H-> P3 OO o O o o a O * u co a ^ t-i u 42 CO a 02 ^ 42 o 02 fa 1 02 Pj a o3 J3 02 g> 02 Zt3 a> Sh 02 H, !>> 02 o> >> 1 « 42 CO 1 ^ Q O CN3 CO rH 1 CO >,LO ■— • rH a 1-3 CO CD 455 3. Total Stocks of Oxidizable Matter in the River at Chillicothe, 1914 — 1915 Not only the plankton, but in addition all the other oxidizable matter carried in the stream-flow, whether suspended or dissolved, may be re- garded as potential detritus or as potential microorganisms, some portion of which, in some form or other, may be useful as food to the bottom animals or to the organisms on which they themselves feed somewhere in the course of the stream below the sampling point. If the total oxidiza- ble matter at Chillicothe 1909 — 1914 was in about the same ratio to the' total nitrogen as in 1900 — 1902 (about ten times total nitrogen in the winter and spring months, and seven to nine times the nitrogen figures in midsummer and autumn), we would have had passing Chillicothe in the entire year, March, 1914, to February 1915 a total of 617,137 tons, or over 1,200,000,000 pounds total oxidizable matter, dry weight, or some sixty to a hundred and fifty times the total dry weight of the plankton that passed Havana in the twelve months September, 1909, to August, 1910 (eight million to twenty million pounds). If this enormous total load could be settled out and apportioned equally to the approximate 26,780 acres of river between Chillicothe and Grafton at gage 8 ft., Ha- vana, each acre would receive in the course of the year 46,086 pounds, an average equal to more than seventeen hundred times the average dry weight poundage (about 10 per cent.) of bottom animals per acre (twenty-six pounds) found in the summer of 1915 between Chillicothe and the river's mouth. The employment of vertical instead of surface chemical samples for the determination of loss on ignition would with little question, also, show still higher values of total oxidizable matter than those here figured, particularly in seasons of recession from flood, when the dead suspended organic matter increases heavily in concentra- tion from the surface downward. (See table on p. 456.) 4. The Portion of the Plankton Settled out or Consumed Basing the computations on percentage decreases in silk-plankton vol- umes (c.c. per m.3) between Havana and Grafton in June and August 1910, and on rates of increase in discharge between Havana and the mouth of the river in the spring and midsummer months, but taking no account of normal multiplication, there is found for the nine-months growing season, March — November, 1909 — 1910, a total loss of plank- ton in the 120 miles below Havana of 243,503,139 lbs., or almost exactly two thirds of the total stocks that passed Havana during the period (387,883,000 lbs.). The dry weight of this lost plankton at 5% (12,- 175,156 lbs.) amounts to nearly 30 times the dry weight, estimated at 10%, of the bottom animals found in 1915 in approximately the same reach of river in which the loss occurred (total bottom-fauna stocks Copperas dam— Grafton, 1915, 4,277,350 lbs; dry weight at 10%, 427,- 735 lbs.). 456 n Q 10 OS OS l-l M w o o xn m < Ch Pi fa H rH T*< os -HjH T3 ,Q c^i S £ OS O o3 • * • rH CO 5 3 O &H o> 1-H o3 b O o t- t- o oo o oo •r-| ^ ^3 o lO o l©^ Tj qj >— ' od o CO -* 'G -*i i-i io o t- °0S os" o OS lO oo CO ri 3 Fh * o3 iH T-l X X X • « o PI > o o3 in 2 n3 Fh Sm a> rO a> t» a> rQ 1 s 1 Ft 03 2 K-9 O ,Q | fc -M £ S ,3 1 o o 0) p U f-. 1-3 Csl tH G O jn -. aj i-H o +J fi c rrt 0J w o F* G +j CO rQ TJ -1) *r— | 2 > ^ >» 0) U +J (11 > << +j o +J PI ni C c-i Oo 4J OS i-l c 1 Ml •i-i o o <7i O rH K G 0J ■pH o 1 1 on G TJ O ^ 457 That the greater part of the plankton lost, or all of it, was settled out or consumed by larger organisms, rather than that it perished be- cause of any failure of the food supply (particularly nitrogen), is forci- bly suggested by two or three considerations : that the losses took place at the greatest rate during the hot season, when the current was least and settling easiest, the rate of loss in August 1910 being 98% ; and that in- stead of there appearing any evidence that the losses were due to dim- inution in food, both the total limnetic nitrogen and the. nitrogen in the form of nitrates increased down-stream both in the spring and midsum- mer— autumn months in 1914, the nearest year for which we have nitro- gen figures. I note here that incomplete studies on the succession of Algae, Protozoa, Rotifera, and Entomostraca in some of our down- stream series of plankton-catches suggest that a good part of the loss in plankton below Havana in the spring months during rising pulses of En- tomostraca may be due to internal consumption, within the plankton population itself. In May, 1899, in fact, these four groups of micro- organisms showed a progression in reaching their maximum abun- dance, each at a station farther down stream. In the circumstances the presumption seems strong that each pound of Cyclopidae or Rotifera taken near the mouth of the river represents several pounds of smaller plankton species eaten farther up stream. (See tables, pp. 458, 459.) 5. Coincidence of Richer and Poorer Plankton and Bottom- Fauna Reaches in the River below Chillicothe The fact that there are shown, on a basis of the plankton and bot- tom-fauna figures (1899 — 1915), such close coincidences between the location and extent of the richer and poorer plankton and bottom-fauna reaches between Chillicothe and the mouth of the river is not, I think, to be taken too quickly as in itself dependable evidence that the bottom fauna is to any certain and large extent a simple function of the vol- ume or weight o*f plankton above it. Not only, however, does it appear that both in its bottom fauna and its plankton stocks the sixty odd miles of low-sloped river channel between Chillicothe and Havana is far richer on the average than the lower river reaches, but the decrease down stream, on a broad scale, is in each case found to be progressive, and in fact in substantially similar ratios, if the comparison is made with the midsummer plankton figures. (Table, page 460.) The finding, on the contrary, in August 1913, in a local section of low-sloped channel in the lower river, of a rich plankton-consuming population of Sphaeriidae that was apparently not far from as rich as the best found in 1915 in the middle Illinois Valley district suggests that the very general lack of a suitable substratum for small Mollusca in the channel of the Illi- nois below Lagrange may have more to do with the decrease of the bottom fauna in the lower river than the decrease in the stock of plank- ton above it. Other influences that may have some bearing on the aver- age very poor showing made by the bottom fauna in the lower river in 1915 will be taken up farther on. 458 o H o < < H pq c H Ph ft o DE3 GG C d o -m _ r-H —i -i-j CD *r? £ ^ ^ rH t- CM co OS co 02 O d o d ^ d 05 o OS CI CO CO (>. rH ft5^ a cm o o o CO o *T $ & ^ CO CM LO o >• ^ ° eg W CO oq CO cq CM 02 o J O +J »i*— ■+J t-l oo CXI plank g Gra ound's CO CO CO lo OS 00 CO .l-H CO ■^f O m 1-\ Eh g ft * X! *-" CD •£ frt x. inc charg a to S Islan 903 & ^ O » B ^H ^£ cd > 5h * OSS, c.c. 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Per cent. on base of Reach I o o so 2- Pounds per acre OO T-H OS tH -J— i-i - tH « A. tH o tH of d d o3 a o o pq Per cent. on base of Reach 1 o o tH tH CNI All-zone average pounds per acre 00 OO o tH Flood velocity 18 ft. Peoria % basis o o tH 03 o o t-H 03 o o o CNI m o3 d o CD rd B d d d o d a i— i Ph June, 1910 August, 1910 (Forbes & (Forbes & Richardson) Richardson) o o tH so OO so CO O o r-i GO 00 CO so tH May, 1899 (Kofoid) * o o tH CO tr- rd u o3 03 I Chillicothe — Havana 60.5 mi. II Havana — Lagrange 42.5 mi. ill Lagrange — Grafton 77.5 mi. CD ten xn £ CD H U So* +-> CD 461 6. The Plankton of Thompson Lake, 1909 — 1910 As shown by volumes per cubic meter of silk plankton, based on vertical samples, the middle of Thompson Lake and the river channel at Havana averaged nearly the same in plankton content during the four months March — June, 1910 (Thompson, 12.77 c.c. ; river, 13.98 c.c.) ; while in the July — November period of five months Thompson Lake (5.21 c.c.) averaged about six times as rich as the river (0.87 c.c). Expressed in terms of pounds per acre to a depth of one meter, these volumes of plankton amount to around 114 lbs. for the lake and 124 lbs. for the river in the March — June period, and to 46 lbs. for the lake and 8 lbs. for the river in July — November. If these quantities of silk plankton are multiplied, both in the case of the river and the lake, by the Kofoid silk-filter-paper ratios for river samples, 1897 — 1899, the pound- ages for March — June would be about twice those just given, and for July — November about four times those figures. On the other hand, if depth is taken into account, and total amounts of plankton standing over an acre in the river and the lake to the full average depth at the collecting station are figured, the river acre in March — June will be found to have more plankton standing over it at a given time than an equal area in the central portion of Thompson Lake ; and in July- — November, about half as much, instead of only one sixth as much, as an acre in the lake. Plankton Thompson Lake and Illinois River, Havana, 9 months, March— November, 1909—1910 Gage, Havana average Depth coll. sta. feet, av. Depth coll. sta. meters, av. Silk plankton c.c. per m3 Silk plankton lbs. per acre to depth 1 meter March — June incl. Thompson L. 12.04 12.23 3.7 12.79 114 Illinois River 12.04 22.23 6.7 13.98 124 July — November incl. Thompson L. 7.81 8.00 2.4 5.21 46 Illinois River 7.81 18.00 5.4 0.87 8 462 General Comparison of the Illinois River and its Connecting Lakes in the Food Resources of a Fishery and in Fish Output Bottom and Limnetic Nitrogen, Plankton, etc. In the fact that the Illinois Valley lakes, only in a lesser degree than the river itself, are in the spring or later flood-seasons of all but very ex- ceptional years open to receive the sewage-laden water from the upper Illinois River and the Chicago Sanitary Canal, they differ materially from the isolated glacial type of lake and from ponds or other waters which are closed throughout the year to outside sources of nutriment. Such supplies as the river lakes receive, they are able to retain in great measure when their outflow is reduced to little or nothing by the falling of the water levels, but the acquired resources of the river are contin- ually drained away by the current, these losses being especially heavy when the bottom sediments are being stirred up and scoured out in times of flood. Hence the river, as we have seen, is not able to accumulate and hold, even in the reach of extremely low-slope between Copperas Creek dam and Lagrange, surplus stocks of these substances and the resi- dues from their decay as large as the stocks found in the lakes, whether in their deeper open, or in their weedy littoral portions ; while in the relatively swifter channel below the Lagrange dam the difference is still further emphasized. So far as the plankton alone is concerned, the sur- plus stocks on hand at a given time per cubic meter of water in Thomp- son Lake in 1909 — 1910 exceeded those in the richest part of the river at Havana, opposite, at whatever season, with the percentage of differ- ence in favor of the lake largest during the more critical season of low productivity, July — November. . That the central Illinois Valley lakes are also to a considerable ex- tent their own furnishers, through the growth and decay of shore vege- tation, of their permanent stocks or organic food-materials, is suggested by the size of the annual crops or aquatic vegetation, some of which is rooted, in their shallower zones ; as well as by the fact that the stocks of nitrogen, organic carbon and other oxidizable substances in the upper layer of bottom soil are appreciably larger in the weedy littoral than in the deeper open water. The river, whether in the Havana district or above or below, has as offset extremely little weedy shore, where rich stocks of similar kind can originate and decay, or where permanent lodgment can be furnished for settling suspended organic matters carried in from points up stream. Bottom and Shore Fauna In the case both of the plankton and of the various other food sub- stances directly or indirectly usable as food by the bottom and shore ani- mals, our data, as far as they go, point clearly to the presence at all 463 times, both in the river and in the lakes, of surplus stocks of a size far more than sufficient to supply the immediate needs even of vastly richer bottom and shore populations than we found in 1914 — 1915. But though the river, at least in the region of low slope between Chillicothe and Ha- vana, could thus theoretically produce as large poundages of bottom and shore fauna as the lakes, or even larger, the figures for stocks on hand in the two years mentioned, as well as other evidence, tend rather to prove that the lakes are over their average acreage the better producers, and that their richest fauna is developed in the weedy littoral, where also occur the largest deposits of nitrogen, organic carbon, and other oxidiza- ble matters. As the margin between the bottom and shore fauna stocks on hand in 1914 — 1915, even in the most productive lake and river areas, and the food requirements, in kind, of a normal fish population, as of 1908 and neighboring years, seems clearly to be very much smaller than that be- tween the supplies and the needs of the bottom and shore fauna itself, it may- be supposed that figures for stocks on hand after four or five months' feeding by fishes can not be accepted as they stand, quite as confidently as plankton and nitrogen figures for use as an index of actual total productivity. If this is the case, and if it is also true, as we have reason to think, that the lakes rather than the river are not only the favorite feeding-grounds of the greater part of the large bottom- feeding fishes during the 9-months growing season but also the largest producers of fish flesh, then we should expect that complete figures for total annual yield of bottom and shore invertebrates for the river and lake acreage in the Havana district would show a yet greater difference in favor of the lakes than is shown by the figures of stocks on hand as of July — October, 1914 — 1915. A further point in favor of the lakes is the fact that the very heavy bottom-fauna poundages of the river channel just above Havana consist largely of heavy-shelled snails, which we can not believe are easily made use of as food by any but the largest bottom-feeding fishes. Looked at in this way, the richest river valua- tions may represent accumulation in the presence of light feeding ; while the lower poundages of bottom animals in the lakes opposite may be looked upon as residues from originally much larger stocks, fed down to a closer point than the river stocks, in consequence both of a relatively greater size-availability and of their location within the main-feeding range. Fish Yields On a plain acreage basis the total river acreage, at a gage of 10 feet, Beardstown*, between La Salle and Grafton, with equal productivity as- sumed in both river and lakes, should in 1908f have supplied around 18% of the total fish yield of that year, and the lakes about 82%. In * Gage selected by Alvord and Burdick as that prevailing- on an average one half of the year, 1900 — 1913. t Last year for which we have full figures for fish yields. 464 the same year the river between Copperas Creek dam and Lagrange dam, where the lake acreage is largest relatively to the total, should have furnished about 10% of the total fish yield; the river between La Salle and Copperas Creek dam, about 17% ; and the river below Lagrange, about 37%. That the river and lake yields of fish per acre are not equal, however, is suggested with considerable force by more than one consid- eration. The first of these is the fact that in all the recent years for which we have records the largest poundages of fish per acre have been taken in the reaches with the largest quotas of connecting lake-acreage. Taking the year 1908 as an illustration, and using the figures for sep- arate shipping points obtained by the Illinois Fish Commission in that year, we find for the 59.3 miles of river and lakes between Copperas Creek dam and Lagrange dam, with about 90% of its acreage consisting of lakes and ponds, an average fish-yield per acre for water levels pre- vailing half the year, of 178.4 pounds; for the 87 miles from La Salle to Copperas Creek dam, with about 83% lakes, 130.4 pounds; and for the lower 77 miles, Lagrange to Grafton, with around 63% lakes, only 69.8 pounds. If, again, we seek to reach conclusions concerning fish yields for the central Illinois Valley district from the bottom- and shore-fauna data of 1914 — 1915 we can only suppose that the average yield of the river per acre in recent years between the Copperas Creek and Lagrange dams (with 705 lbs. bottom fauna average) has amounted to less than half the average yield of the lakes opposite (with 1,447 -f- lbs. bottom- and weed-fauna average). Or, to put it another way, while the river's quota of the total fish catch in this reach on a plain acreage basis in 1908 was 10%, its capacity on a basis of the bottom- and shore-fauna figures of 1914 — 1915 uncorrected, stands at about 5% of the total. That both the river and the lake yields of fish per acre have been lower in recent years in the reach above Copperas Creek dam and in the reach below Lagrange than in the district between, is suggested both by our bottom-fauna data from the river and by such incomplete figures as we have from Peoria Lake and Meredosia Bay (1913 and 1914), and also by the fact that the differences in fish yield per acre in 1908 between those two reaches and the Havana section are much greater than the difference in the ratios of lake to total acreage. That, however, the per cent, decrease in fish-yield in the lakes in these two reaches is less than the decrease in the river may perhaps be accepted as circumstantially proven by the greater decrease in the river bottom-fauna figures than in the figures of fish yield themselves. 465 S o hrl Q O H Eh O p H O <5 H M O <3 H M «} H H o W hi H 03 d i£> o3 o3 3 tH -i-} +-> ci a oi 03 03 W hrl -tf 'O 2 1 <2> CD w 1 O hH CD ■+-> CD <2> CD +J CD rj CD OS • TJH i— ( 02 ftrH ft TH ft S 02 CO a rH a °£ 2 o o d o o d O ^H H- 1 i— i PQ c3 d J3 03 + CD 03 C35 O h *-1 rH LO © CO o T-i a «.£: CNJ fc- O X5 ?h -f-> ■— I +J o eq CD CO • bfiO "S <£<=* o d CD i-H >-H c> Oi © h .. - C3i >-H •H-CO O o >— i OS tH CS a3 c3 cm" o cd hi O CD CD ° oo O^ CO 03 O i— i _,_> CO S * d ■5 cd d 1-1 Jh o 4— <2> .dc^S so C5 Ci 2» S ©3 catc" per Fish missi* "* TH oo o CO OO CO rH tH & CO . co & Zl T* -• HH R a cd a T3 o3 CD T3 bfl M CD CD hi d o3 hi bJO o3 a d o rd o CD u CO o3 CD h« 1 tf ft ft 03 1 a O 1 ® hi co 5.2 ^ CD I-H 1 *a CO "rt 03 d hi CD -rH bJO d d a o3 t-I CD CO 03 LO GO ^ ft£ hi h* J J 1 . U J £5 o3^=S +j CD O CD Co ^ s - CD CD CD cd CM Oi -f-3 Ph rH CO r-i CO OS ■S s CD ^h Ah OO cm OO © as cm' CO 1-j cm' OO Total acreage 1908 acres o o o o OS_ rH CO O o ©_ CO~ LO O o 00 CM o © oo~ CO Lakes 1908 acres o o LC5 C5 CO o o © 00 rH O o CO ©~ © o LO CO rH rH River 1908 acres * o o oq oo" O o Ci LCB O O CM o o3 CD Ph a 03 n3 03 o> m o3 d 03 S-c bO a 1 a o3 fH u. . sa 03 CO ft05 A a d 03 LO o3 L d o +j 5tH 03 Sh ia o3M 03 3 TO £* > +-> M 03 S Z ft h ft o 5 1 r o > CD 'ScPh rrJ-O 03 +-> CO cij 03 +J.2 O o 43 rj Q3 ^ Hn, 'u'S «w CO •r J w ? ?h 03 P-l 03 C(3 °^^ 03 < +-> ^ ^^ 03 3 ^ft£ * W 4— 467 Fish Catch, Illinois River and Lakes, 1908 (III. Pish Comm.) La Salle to Copperas Creek dam La Salle to Hennepin 520,000 lbs. Henry to Lacon 852,000 " Chillicothe 350,000 y " Peoria 2,800,000 " *Pekin (one half) 1,700,000 " Total 6,222,000 lbs. Copperas Cr. dam to Lagrange dam *Pekin (one half) Havana Bath Browning Beardstown Total 1,700,000 3,800,000 1,900,000 1,700,000 1,950,000 lbs. 11,050,000 lbs. Lagrange dam to Grafton Mered'osia Naples to Pearl Kampsville to Grafton Total 684,000 lbs. 409,000 " 905,000 " 1,998,000 lbs. Grand total 19,270,000 lbs. * Pekin catch divided between adjacent reaches because of heavy fishing- by Pekin crews in Spring Lake. Bottom- and Shore-Fauna Valuations, 1915, in Terms of Months' Supply for Annual Increment in Fish-Weight of 150 Pounds per Acre How close to a critical minimum, from the point of view of the fish- ery, the stocks of bottom invertebrates in the lower Illinois River had dropped in July — October, 1915, after 5 to 8 months' feeding, is most clearly seen after we have changed the bottom-fauna valuations into terms of months' supply of food for an annual yield of fish somewhat nearly equal to the average for the year 1908 on the acreage estimated to prevail during half of the year. In the tables next following, these calculations are shown as they come out for an annual weight increment of 150 lbs. per acre, the year's feeding being completed in 9 months (March — November), animal food only being used, and an average consumption of five pounds of bottom and shore invertebrates (shells of mollusks deducted) for one pound increase in fish weight being as- sumed. The feeding ratio (5:1) adopted is the estimate of Walter* for carp and carp-like fishes, living on wild animal food, and is close to the * Die Fischerei als Nebenbetrieb des Landwirtes u. Forstmannes. 1903. 468 ratios estimated by Otterstrom* and Kronheimy for trout fed on raw fish or "mostly animal food". The rate of consumption of bottom (or shore) invertebrates per month for the nine-months "year" works out at about 83 pounds : 150 X 5 = 83.3 9 Expressing the bottom- and shore-fauna valuations of 1915 in mul- tiples of the average monthly consumption rate, we find that in July — October of that year there were 120 miles of the Illinois River below Havana whose average supplies of free-living bottom-invertebrates were sufficient to last at such a rate only 30 days or less beyond the date of collection ; and 77.5 miles below Lagrange dam in which there were sufficient stocks to last only 3 days. The much richer stocks in the river above Havana, in" spite of the exceedingly low valuations in the lower river, were sufficient to bring up the average supply for the entire 180.5 miles between Chillicothe and Grafton to a figure of 3.1 months — which was also the average for the 60.5 miles between -Chillicothe and Cop- peras Creek dam. In the reach of 59.3 miles between Copperas Creek and Lagrange, where an average supply sufficient for 8.5 months was found, there was a short stretch of 16.8 miles (immediately above Ha- vana) where the stocks were sufficient to last for over 30 months, but a relatively much greater part of the bottom fauna in this locally very rich section was made up of large heavy-shelled Mollusca than was the case in any other part of the river. In contrast with all of these river figures except those for the 16.8- mile reach between Copperas Creek and Havana, the average stock of twelve lakes between Copperas Creek and Lagrange in July — October, 1914 — 1915, included a three months' supply of bottom fauna only for the whole acreage, a minimum^ of 25.5 months' supply of shore animals living above the bottom in the weedy acreage within the 4-foot line, and a combined average supply of bottom- and shore-animals sufficient for 17.4 months. (See table, p. 469.) Supplies of bottom animals that were well above the average of all the lakes studied, were shown by the Class I and Class II lakes (of the type of Thompson and Quiver respectively) : average of five deeper bottom-land lakes, 4.2 months ; average of two deep, sand-beach lakes, 10.2 months. Thompson Lake in 1914 had in August to October a 6.5 months' supply of bottom invertebrates over its entire acreage, and a 25.7 months' supply of weed animals in the 1 — 4-foot zones — or a com- bined average supply, on a rough acreage basis, sufficient for 20.8 months. The low v rating of bottom- fauna stocks in the very shallow weedy lakes, such as Flag, Duck, Dennis, (0.6 to 1.1 months' supply), * Fiskerei beretning, 1911, pp. 244 — 254. t Bibl. der Gesamten Landwirtschaft, Bd. 34, 1907. % "Weed fauna" catches cover the upper 9 inches only. 469 was of little importance by comparison with the very high weed-fauna figures from these lakes, the combined bottom and weed fauna averages (if Crane Lake be excepted) apparently including a supply sufficient for not less than 25 to 30 months. (See table, p. 470.) Bottom and Shore Fauna as Food for Fishery 1. Illinois River, July — October, 1915 Italic figures=months' supply, at 83 lbs. per month, for 9 months' growing season for fish-weight-increment of 150 lbs. per acre, feeding ratio 5:1. Miles Bottom fauna all-zone av. lbs. per acre Months' supply remaining on date of col- lection* Chillicothe — Copperas Cr. dam 43.7 264 8.1 Copperas Cr. dam — Lagrange 59.3 705 8.5 Copperas Cr. dam — Havana 16.8 2,693 824 Havana — Lagrange 42.5 83 1.0 Lagrange — Grafton 77.5 10.4 0.1 Chillicothe — Grafton 180.5 261 8.1 Hypothetical Fish-Yields for the River and Lake Acreage be- tween Copperas Creek Dam and Lagrange, on Basis of Bottom- and Shore-Fauna Stocks of July — October, 1914 — 1915 In the table on page 471 are shown figures representing the po- tential value in fish, at the Walter ratio (5:1), of the bottom- and shore-fauna stocks remaining unconsumed in the central rich district between Copperas Creek dam and Lagrange July — October, 1914 — 1915, after 5 to 8 months of feeding. The total hypothetical yield of the un- consumed stocks of food thus figured (16,103,580 lbs. of fish, from 80,517,900 lbs. bottom and shore animals), is greater by about 50% than the actual fish catch of 1908 (a banner year) in the same district. Of this total, 831,900 lbs., or 141 lbs. per acre, accrues from about 6,000 acres of river, bearing over 4,000,000 lbs. of small bottom animals ; and 15,271,680 lbs., or 289 lbs. per acre, from about 52,000 acres of lakes and other backwaters, bearing not less than 76,000,000 lbs. of small bottom- and shore-animals, of which over 60,000,000 lbs. comes from the upper levels in the shallower, more densely weeded acreage. * Dates of collection, July — October (after 5 to 8 months' feeding). 470 LO rH OS 02 05 fe £9 fe O fa p «! 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No Vegetation (Eight collections, mud bottom; two collections, sandy) Number per square yard Pounds per acre Campeloma subsolidum Lioplax subcarinatus Vivipara contectoides 83.0 63.0 72.5 218.5 249.0 75.6 ■ 362.5 687.1 Amnicola limosa A. emarginata Valvata spp. Musculium transversum Pisidium sp. 40.0 31.0 362.0 79.0 442.5 954.5 2.2 1.1 19.9 . 39.5 17.6 80.3 Small Oligochaeta Small leeches Chironomid larvae (large spp.) Caddis larvae 10.0 72.0 180.0 33.0 295.0 0.3 12.2 120.0 3.3 135.8 Total 1468 903.2 All north of "cut-road." 497 Thompson Lake, Aug. 12 — 20, 1914. Bottom Fauna 12 Collections,* Depth, 1 to 6 ft. All in Vegetation (Eleven collections, mud bottom; one collection, sandy) Number per square yard Pounds per acre Campeloma subsolidum Lioplax subcarinatus Vivipara contectoides 28.7 2.0 38.3 69.0 86.1 2.4 191.5 280.0 Amnicola limosa Valvata spp. Musculium transversum Pisidium sp. 0.8 69.5 65.4 35.8 171.5 trace 3.8 32.7 1.4 37.9 Small leeches 9.5 1.6 Planarians 2.5 trace Chironomid larvae (large spp.) 268.0 311.2 179.5 183.5 Chironomid larvae (small spp.) 2.5 €.3 Caddis larvae 17.5 1.7 Caenis nymphs 0.8 trace Hyalella knickerbockeri 10.4 0.4 Total 551.7 501.4 All north of "cut-road." Thompson Lake,* Aug 12 — 20, 1914. Bottom Fauna 4 Collections, Depth, 2 to 4 ft. All in Vegetation Number per square yard Pounds per acre Chironomid larvae (large spp.) Small oligochaetes 330 30 221.1 1.1 Total 360 222.2 * Foot of lake, below "cut-road." 498 Thompson Lake, Aug. 12 — 20, 1914. Bottom Fauna 3 Sand-Bottom Collections,* Depth, 1 to 5 ft. (Some vegetation) Number per square yard Pounds per acre Campeloma subsolidum Lioplax subcarinatus Vivipara contectoides 46.6 23.3 51.6 121.5 139.8 27.9 258.0 425.7 Valvata spp. Musculium transversum Pisidium sp. 96.6 55.0 150.0 301.6 5.3 27.5 6.0 38.8 Chironomid larvae (large spp.) Small leeches Caddis larvae Caenis nymphs Large libellulid (nymphs) Hyalella knickerbockeri 10.0 18.3 26.6 3.3 3.3 41.6 103.1 6.7 3.1 2.6 0.2 8.2 1.6 22.4 Total 526.2 486.9 * All above cut-road. These three collections, arranged separately here, are also included in tables preceding-. Thompson Lake, Aug. 28, 1915. Bottom Fauna 5 Collections,* Depth, 7 to 9 ft. No Vegetation Number per square yard Pounds per acre Campeloma subsolidum Lioplax subcarinatus Vivipara contectoides 23.0 11.2 66.3 100.5 69.0 13.4 331.5 413.9 Valvata spp. 54.7 3.0 Musculium transversum 106.5 53.2 372.7 64.6 M. jayanum trace Pisidium sp. 211.5 8.4 Small leeches 27.0 4.5 Small Oligochaeta 1.2 48.7 trace 18.1 Chironomid larvae (large spp.) 20.3 13.6 Caddis larvae 0.2 trace Total 521.9 496.6 * All above "cut-road. 499 Thompson Lake, Aug. 28, 1915. Bottom Fauna 7 Collections,* Depth, 1 to 6 ft. (No vegetation; all mud bottom) Number per square yard Pounds per acre Campeloma subsolidum Lioplax subcarinatus Vivipara contectoides 32.7 19.5 97.8 150.0 98.1 23.4 489.0 610.5 Valvata spp. Musculium transversum M. jayanum Pisidium sp. 43.5 30.2 trace 188.1 261.8 2.3 15.1 7.5 24.9 Small leeches Chironomid larvae (large spp.) 19.5 32.9 13.4 3.3 12.2 8.9 Total 444.7 647.6 All above "cut-road." Thompson Lake, Aug. 28, 1915. Bottom Fauna 7 Collections,* Depth, 1 to 6 ft. All in Vegetation (Three collections, mud bottom; four collections, sand and mud) Number per square yard Pounds per acre Campeloma subsolidum Lioplax subcarinatus Vivipara contectoides 117.0 11.4 137.0 265.4 Amnicola limosa 42.8 2.3 Valvata spp. 109.2 6.0 Musculium transversum 11.5 240.6 5.7 17.0 Musculium jayanum trace Pisidium 77.1 3.0 Chironomid larvae (large spp.) 11.7 7.8 Caddis larvae 2.1 55.7 0.2 14.5 Small leeches 37.7 6.4 Planarians 4.2 0.1 Total 372.3 296.9 * All above "cut-road." 500 Thompson Lake,* Aug. 28,. 1915. Bottom Fauna 5 Collections, Depth, 2 to 6 ft. All in Vegetation . Number per square yard Pounds per acre Vivipara contectoides 157 785.0 Pisidium sp. 12 0.4 Small leeches 169 28.7 Total 338 814.1 * Foot of lake, below "cut-road." Thompson Lake, Aug. 28, 1915. Bottom Fauna 4 Sand-and-mud Bottom Collections,* Depth, 1 to 6 ft. (All in vegetation) • Number per square yard Pounds per acre Campeloma subsolidum Vivipara contectoides Lioplax subcarinatus 31.5 54.0 96.2 10.7 94.5 270.0 377.3 12.8 Valvata spp. Amnicola limosa Musculium transversum Pisidium sp. 118.7 50.0 243.9 5.2 70.0 6.5 2.7 14.6 2.6 2.8 Small leeches 57.5 9.7 Planarians 7.5 83.2 0.2 19.9 Chironomid larvae (large spp.) 14.5 9.7 Caddis larvae 3.7 0.3 Total 423.3 411.8 * All above "cut-road." These four collections, averaged separately here, are also included in a preceding table. 501 Dogfish Lake, Aug. 18, 1914. Bottom Fauna 3 Collections, Depth, 6.5 to 7 ft. No Vegetation Number per square yard Pounds per acre Vivipara contectoides 1.6 1.6 8.0 8.0 Musculium transversum Pisidium sp. Valvata spp. 3.3 33.3 5.0 41.6 1.6 1.3 0.2 3.1 Leeches (small spp.) Chironomid larvae (large spp.) 16.6 170.0 186.6 0.9 11.4 12.3 Total 229.8 23.4 Dogfish Lake, Aug. 18, 1914. Bottom Fauna 5 Collections, Depth, 2 to 6 ft. All in Vegetation Number per square yard Pounds per acre Vivipara contectoides Campeloma subsolidum 66.0 2.0 68.0 330.0 6.0 336.0 Musculium transversum Pisidium sp. Valvata spp. Amnicola limosa Planorbis, small sp. 10.0 128.0 160.0 2.0 2.0 302.0 5.0 5.1 8.8 0.1 0.1 19.1 Leeches (small spp.) Chironomid larvae (large Chironomid larvae (small Small libellulid nymphs Caddis larvae spp.) spp.) 12.0 40.0 20.0 2.0 8.0 82.0 2.0 26.8 2.8 10.0 0.8 42.4 Total 452.0 397.5 502 Dogfish Lake, Aug. 31, 1915. Bottom Fauna 12 Collections, DErTH, 7.5 to 8.5 ft. No Vegetation Number per square yard Pounds per acre Vivipara contectoides Lioplax subcarinatus Campeloma subsolidum 10.6 5.0 2.7 18.3 53.0 6.0 8.1 67.1 Musculium transversum Pisidium sp. Valvata spp. Amnicola emarginata Planorbis (small sp.) Physa (small sp.) 10.5 74.5 165.3 37.5 1.6 1.1 290.5 5.2 2.9 9.0 1.3 0.1 trace 18.5 Leeches (small spp.) 38.8 6.5 Chironomid larvae (large spp.) 88.0 155.0 58.9 66.4 Small Oligochaeta 11.6 0.4 Hyalella knickerbockeri 16.6 0.6 Total 463.8 152.0 Dogfish Lake, Aug. 31, 1915. Bottom Fauna 3 Collections, Depth, 1 to 6 ft. Very Little Vegetation Number per square yard Pounds per acre Pisidium sp. Valvata spp. Amnicola emarginata 33.3 66.6 66.6 166.5 1.3 3.6 2.4 7.3 Leeches (small spp.) Chironomid larvae (large spp.) Small Oligochaeta 50.0 176.6 16.6 243.2 8.5 117.9 0.5 126.9 Total 409.7 134.2 503 Sangamon Bay, Sept. 8, 1915. Bottom Fauna Collections, Depth, 6.5 to 7.5 ft. No Vegetation Number per square yard Pounds per acre Campeloma subsolidum Lioplax subcarinatus Vivipara contectoides 9.1 13.7 1.5 24.3 27.3 16.4 7.5 51.2 Musculium transversum Valvata spp. 81.8 9.2 91.0 40.9 0.5 41.4 Leeches (small spp.) Chironomid larvae (large spp.) Caddis larvae Hexagenia nymphs 16.3 15.6 5.6 0.5 38.0 2.7 10.4 0.5 0.4 14.0 Total 153.3 106.6 Sangamon Bay, Sept. 8, 1915. Bottom Fauna 4 Collections, Depth, 1.5 to 6 ft. No Vegetation Number per square yard Pounds per acre Campeloma subsolidum Lioplax subcarinatus Vivipara contectoides Pleurocera sp. 35.7 12.7 4.0 2.5 54.9 107.1 15.2 20.0 3.0 145.3 Musculium transversum Valvata spp. 217.5 15.0 232.5 108.7 0.8 109.5 Leeches (small) Chironomid larvae XlarSe spp.) Palpomyia larvae Caddis larvae Hexagenia, etc. (nymphs) 27.0 3.7 0.7 11.5 2.5 45.4 4.5 2.4 trace 1.1 2.2 10.2 Total 332.8 265.0 504 2. Deep, Sand-Beach Type (Quiver, Matanzas) Quiver Lake, Sept. 30 to October 12, 1914. Bottom Fauna 15 Collections, Depth:, 7 to 12 ft. No Vegetation Number per square yard Pounds per acre Campeloma subsolidum Lioplax subcarinatus Vivipara contectoides Vivipara subpurpurea Pleurocera sp. 58.2 48.0 462.0 trace 177.3 745.5 174.6 57.6 2,310.0 212.4 2,754.6 Amnicola emarginata Musculium jayanum Pisidium sp. Young Unionidae 1.3 3.3 1.0 0.6 6.2 1.7 trace 1.2 2.9 Chironomid larvae. Small leeches Large leeches Small Oligochaeta Caddis larvae Agrionid nymph Asellus sp. (small spp.) 24.0 52.6 10.0 54.0 2.6 0.6 11.3 161.1 3.3 8.9 32.0 1.8 0.2 0.3 1.0 47.5 Total 912.8 2,805.0 505 Quivek Lake, Sept. 30 to October 12, 1914. Bottom Fauna 17 Collections, Depth, 1 to 6 ft. (Most in vegetation) Number per square yard Pounds per acre C'ampeloma subsolidum 24.7 74.1 Lioplax subcarinatus 11.1 85.1 13.3 329.7 Vivipara contectoid'es 48.2 241.0 Pleurocera sp. 1.1 1.3 Amnicola emarginata 42.3 1.5 Amnicola limosa 8.2 0.4 Valvata spp. 9.4. 0.5 Physa, small 7.6 124.0 1.7 33.4 Young Unionidae 6.3 12.6 Musculium transversum 32.0 16.0 Pisidium sp. .18.2 0.7 Chironomid larvae, large red Chironomid larvae, small Palpomyia larvae Caddis larvae Hexagenia nymph Agrionid nymph Large libellulid nymph Small leeches Large leeches Small Oligochaeta Hyalella knickerbockeri 1.1 4.4 0.3 trace 0.4 0.5 4.0 5.7 7.0 0.4 1.4 25.2 Total 38.8.3 Quiver Lake, Aug. 30, 1915. Bottom Fauna 3 Collections,* Depth, 7 to 10 ft. No Vegetation Number per square yard Pounds per acre Vivipara contectoides 160 160 800 800 Small leeches Caddis larvae Asellus sp. 8.6 6.0 11.6 26.2 1.4 0.6 1.1 3.1 Total 186 2 S03.1 All opposite Bishop's. 506 Quiver Lake, Aug. 30, 1915. Bottom Fauna 14 Collections, Depth, 1 to 6 ft. Most with Vegetation Number per square yard Pounds per acre Vivipara contectoid'es 7.1 7.1 35.5 35.5 Amnicola limosa Musculium transversum 16.0 1.0 17.0 8.8 0.5 9.3 Small leeches Chironomid larvae (large Chironomid larvae (small Agrionid nymph spp.) spp.) 11.9 162.8 13.5 2.1 -190.3 2.0 109.0 1.9 1.0 113.9 Total 214.4 158.7 Matanzas Lake, Sept. 4, 1915. Bottom Fauna 9 Collections, Depth, 6.5 to 8.5 ft. No Vegetation Number per square yard Pounds per acre Musculium transversum Pisidium sp. Valvata spp. 63.3 206.6 284.3 14.4 31.6 8.2 40.6 0.8 Small Oligochaeta Small leeches Chironomid larvae (large spp.) Palpomyia larvae 4.4 30.7 58.4 18.6 4.7 0.1 5.2 18.0 12.4 0.3 Total 342.7 58.6 507 Matanzas Lake, Sept. 4, 1915. Bottom Fauna 6 Collections (in Ceratophyllum and Potamogeton), Depth 2 to 6 ft. (Some vegetation at all stations) Number per square yard Pounds per acre Campeloma subsolidum Pleurocera sp. Vivipara contectoides 5.0 1.6 8.3 14.9 15.0 1.9 41.5 58.4 Musculium transversum Pisidium sp. Valvata spp. 15.0 48.3 3.3 66.6 7.5 1.9 0.2 9.G Leech, small Chironomid larvae (large spp.) Hexagenia, etc. (nymphs) Caenis nymph 13.8 2.3 6.6 3.3 26.0 2.3 1.5 5.9 0.2 9.9 Total 107.5 77.9 3. Shallower, Weedy Type (Flag, Seees, Stewart) Flag Lake, Oct. 6, 1914. Bottom Fauna 3 Collections, Depth, 4 to 5 ft. All in Vegetation Number per square yard Pounds per acre Musculium transversum Pisidium sp. Valvata spp. Amnicola limosa Physa, small sp. 6.6 93.3 276.6 20.0 46.6 443.1 3.3 3.7 15.1 1.1 2.5 25.7 Leech, small sp. Chironomid larvae Chironomid larvae Agrionid nymph Caddis larvae (large spp.) (small spp.) 33.3 33.3 110.0 3.3 6.6 186.5 5.6 22.1 15.4 1.5 0.6 45.2 Total 629.6 70.9 508 Flag Lake, Aug. 27 — 30, 1915. Bottom Fauna 15 Collections, Depth, 3.5 to 5 ft. Little Living Vegetation Number per square yard Pounds per acre Vivipara contectoides 1.0 1.0 5.0 5.0 Leech, small Chironomid larvae (large spp.) Chironomid larvae (small spp.) 37.8 23.3 8.4 69.5 • 6.4 15.4 1.1 22.9 Total 70.5 27.9 Seebs Lake, Oct. 13, 1914. Bottom Fauna 7 Collections, Depth, 2.5 to 5 ft. Some Vegetation Number per square yard Pounds per acre Vivipara contectoides 2.8 2.8 14.0 14.0 Musculium transversum Pisidium sp. Valvata spp. Amnicola limosa Amnicola emarginata Physa, small sp. 8.5 57.1 130.0 233.0 27.5 5.7 4.2 4.2 2.3 7.1 1.5 0.3 0.1 15.5 Leeches (small spp.) Leeches (large spp.) Chironomid larvae (large spp.) Small Oligochaeta Libellulid nymph (small sp.) Hyalella knickerbockeri 8.5 18.5 48.5 480.0 702.5 4.2 142.8 1.4 36.0 32.5 16.8 94.5 2.1 5.7 Total 938.3 124.0 509 Seebs Lake, Sept. 4, 1915. Bottom Fauna Collections, Depth, 2 to 5.5 ft. Little Vegetation Number per square yard Pounds per acre Vivipara contectoides 3.7 3.7 18.5 18.5 Valvata spp. 34.0 34.0 1.8 1.8 Leeches (small spp.) Chironomid larvae (large spp.) 24.2 2.3 26.5 4.1 1.5 5.6 Total 64.2 25.9 Stewaet Lake, Sept. 7, 1915. Bottom Fauna 12 Collections, Depth, 2 to 5.5 ft. All in Vegetation Number per square yard Pounds per acre Campeloma subsolidum 8.7 26.1 Lioplax subcarinatus 12.0 20.8 14.4 41.0 Vivipara contectoides 0.1 0.5 Musculium transversum 21.0 10.5 Musculium jayanum 3.5 1.9 Pisidium sp. 7.8 69.8 0.3 24.4 Valvata spp. 32.5 1.7 Young unionid 5.0 10.0 Small Oligochaeta 2.5 0.1 Leeches, small 36.0 6.1 Chironomid larvae (large spp.) 1.6 54.0 1.0 8.4 Chironomid larvae (small spp.) 6.6 0.9 Palpomyia larvae 4.0 0.2 Hyalella knickerbockeri 3.3 0.1 Total 144.6 73.8 510 4. Very Shallow, very Weedy Type (Duck, Dennis, Crane) Duck — Dennis Lake, Oct. 2, 1914. Bottom Fauna 5 Collections, Depth, 2.5 to 4 ft. All in Vegetation Number per square yard Pounds per acre Valvata spp. Physa, small sp. Amnicola limosa A. emarginata Pisidium sp. 188.0 6.0 8.0 12.0 2.0 216 Small leeches Small Oligochaeta Chironomid larvae (large spp.) Chironomid larvae (small spp.) Agrionid nymph Libellulid nymph Corixa, small sp. Hyalella knickerbockeri 2,0 12.0 106.0 72.0 6.0 4.0 12.0 62.0 276 10.3 1.3 0.4 0.4 trace 0.3 0.4 71.0 10.0 3.0 10.0 0.8 2.4 12.4 97.9 Total 492 110.3 Ceane Lake, Sept. 7, 1915. Bottom Fauna 5 Collections, Depth, 1 to 3.5 ft. Some Vegetation Number per square yard Pounds per acre Campeloma subsolidum 14.0 14.0 42.0 42.0 Musculium transversum 28.0 14.0 34.0 14.3 Valvata spp _ 6.0 0.3 Chironomid larvae ( small spp.) 6.0 0.8 Leeches (small spp .) 26.0 4.4 Chironomid larvae (large spp.) 4.0 78.0 2.6 22.7 Palpomyia arvae 16.0 1.1 Hexagenia, etc. (n- ymphs) 14.0 12.6 Caddis larvae 12.0 1.2 Total 126.0 79.0 511 5. Dead Timber and Brush Areas Dead Timber and Brush Areas, Vicinity of Havana,* Aug. 18 to Oct. 16, 1914 Bottom Fauna 6 Collections, Depth, 1.5 to 4 ft. Some Vegetation Number per square yard Pounds per acre Campeloma subsolidum 1.6 6.6 4.8 29.8 Vivipara contectoides 5.0 25.0 Amnicola emarginata 45.0 1.6 A. limosa 10.0 0.5 Valvata spp. 531.6 29.2 Physa, small sp. 6.6 1.5 Planorbis trivolvis 1.6 724.5 1.1 87.1 Planorbis, small sp. 3.3 trace Young Unionidae 1.6 3.2 Musculium transversum 98.2 49.0 Pisidium sp. 26.6 1.0 Chironomid larvae (large spp.) Chironomid larvae (small spp.) Palpomyia larvae Caddis larvae Small leeches Small Oligochaeta Hyalella knickerbockeri 26.8 8.6 0.7 0.3 2.2 trace 5.4 44.0 Total 1,000.9 160.9 lakes. Head Quiver Lake; head Dogfish Lake; ridge between Flag and Thompson Dead Timber and Brush Areas, Vicinity of Havana,* Aug. 31 to Sept. 11, 1915. Bottom Fauna 10 Collections, Depth, 1.5 to 3.5 ft. Some Vegetation Number per square yard Pound's per acre Vivipara contectoides 33.5 33.5 167.5 167.5 Valvata spp. Small Planorbis sp. Musculium jayanum 13.0 1.0 1.0 15.0 0.7 0.1 0.5 1.3 Chironomid larvae (large Small leeches Hyalella knickerbockeri spp.) 41.0 37.0 present 78.0+ 27.4 6.2 33.6+ Total 126.5+ 202.4+ * Head of Clear Lake ; head of Dogfish Lake ; ridge between Quiver and Dogfish lakes ; ridge between Flag and Thompson lakes. 512 III. Weed Fauna, 1- to 4-Foot Zone, Lakes and Backwaters in Vicinity of Havana, 1914 Dead Timber Ridge between Flag and Thompson Lakes, Oct. 6, 1914, Opposite "Warner's Cut," in Ceratophyllum and Algae Weed Fauna, Upper 9 Inches (Depth, 2 ft.) No. per sq. yard Pounds per acre Valvata spp. Amnicola limosa Physa (small spp.) Planorbis trivolvis 22,500 4,500 1,500 750 1,347.5 209.0 2,164.0 82.5 525.0 Chironomid larvae (small spp.) Pelocoris Hyalella knickerbockeri '750 270 3,000 52.5 256.5 429.0 120.0 Total 33,270 2,593.0 Head of Flag Lake, Oct. 7, 1914, in Smartweed and Scirpus Weed Fauna, Upper 9 Inches (Depth, 1.5 ft.) No. per sq. yard Pounds per acre Physa (small spp.) Amnicola limosa Valvata spp. Planorbis trivolvis 3,750 1,500 150 300 206.2 57.0 481.4 8.2 210.0 Chironomid larvae (small spp.) Agrionid nymphs Small libellulid nymphs Pelocoris femoratus Hyalella knickerbockeri 4,500 1,500 750 375 6,000 315.0 750.0 375.0 2,036.2 356.2 240.0 Total 18,825 2,517.6 513 Middle of Duck Lake, Oct. 2, 1914, in Potamogeton pectinatus Weed Fauna, Upper 9 Inches (Depth, 4 ft.) No. per sq. yard Pounds per acre Valvata spp. Amnicola limosa Planorbis trivolvis Pliysa (small spp.) 37,500 1,500 375 75 2,062.5 55.5 . 2,421.7 262.5 41.2 Chironomid larvae (small spp.) Hyalella knickerbockeri 375 1,500 26.2 86.2 60.0 Total 41,325 2,507.9 Foot of Thompson Lake, West Side, Aug. 12, 1914, in Potamogeton pectinatus Weed Fauna, Upper 9 Inches (Depth, 3.5 ft.) No. per sq. yard Pounds per acre Physa (small spp.) Planorbis (small spp.) 9,600 120 528.0 534.6 6.6 Caenis nymphs Agrionid nymphs Chironomid larvae (small spp.) Hyalella knickerbockeri 1,920 2,400 6,000 4,500 153.6 1,200.0 1,953.6 420.0 180.0 Total 24,540 2,488.2 514 Foot of Thompson Lake, East Side, Aug. 14, 1914, in Ceratophyllum, Smartweed, and Algae Weed Fauna, Upper 9 Inches (Depth, 2.5 ft.) No. per sq. yard Pounds per acre Physa (small spp.) 6,000 335.0 Planorbis (small spp.) 240 13.2 Planorbis trivolvis 600 420.0 991.4 Valvata spp. 2,400 132.0 Amnicola limosa 2,400 91.2 Pelocoris femoratus 240 228.0 , Small libellulid nymphs 1,200 600.0 Agrionid nymphs 600 300.0 1,314.0 Caenis sp. (nymphs) 1,200 96.0 Small green chironomid larvae 600 42.0 Hyalella knickerbockeri 1,200 48.0 Total 16,680 2,305.4 Middle of Flag Lake, Oct. 6, 1914, in Potamogeton, Ceratophyllum, and Algae Weed Fauna, Upper 9 Inches (Depth, 4 ft.) No. per sq. yard Pounds per acre Amnicola limosa Physa (small spp.) Valvata spp. 13,125 750 375 498.5 41.2 560.3 20.6 Small libellulid nymphs Agrionid nymphs Chironomid larvae (small spp.) Hyalella knickerbockeri 375 450 750 6,000 187.5 225.0 705.0 52.5 240.0 21,825 1,265.3 515 . - Foot of Thompson Lake, Middle, Aug. 14, 1914, in Potamogeton pectinatus Weed Fauna, Upper 9 Inches (Depth, 4.5 ft.) No. per sq. yard Pounds per acre Amnicola limosa Physa (small spp.) Valvata spp. 6,000 960 720 228.0 52.8 320.4 39.6 Pelocoris femoratus Agrionid nymphs Caenis sp., nymphs Chironomid larvae (small spp.) Hyalella knickerbockeri 60 480 480 600 2,400 57.0 240.0 38.4 833.4 402.0 96.0 11,700 1,153.8 IV. Bottom and Weed Fauna, Littoral Zone of Glacial Lakes of Northeastern Illinois, 1916 1. Bottom Fauna Deep Lake, August — October, 1916. Bottom Fauna 7 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation Number per square yard Pounds per acre Pisidium spp. Amnicolidae Valvatidae Physa Planorbis 4.0 13.9 2.9 3.6 15.4 39.8 Leeches, small spp. 12.5 • 2.1 Chironomid larvae (small spp.) 59.6 8.3 Caenis nymphs 3.0 0.2 Hexagenia, etc. (nymphs) 47.0 42.3 Caddis larvae (on Chara) 56.5 5.6 Sand-case caddis larvae 91.0 18.2 510.7 169.0 Libellulid nymphs 22.0 11.0 Agrionid nymphs 28.1 14.0 Gomphid nymphs 12.5 42.5 Pelocoris femorata 19.3 18.3 Hyalella knickerbockeri 156.2 6.2 Asellus sp. 3.0 0.3 Total 1,006.9 208.8 516 Cedar Lake, August — October, 1916. Bottom Fauna 24 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation Number per square yard Pounds per acre Sphaerium striatinum 4.4 3.0 Musculium transversum 11.0 5.5 Pisidium spp. 24.2 0.9 Amnicolidae 37.4 121.0 2.0 24.2 Valvatidae 22.0 1.2 Physa spp. 11.0 2.5 Planorbis 6.6 0.3 Unionidae, young 4.4 8.8 Oligochaeta (small spp.) 4.4 0.1 Chironomid larvae (small spp.) 46.2 6.4 Palpomyia larvae 1.1 0.1 Polycentropus larvae trace Sand-case caddis larvae 26.4 5.2 Caddis larvae (on Chara) 41.8 4.1 Misc. caddis larvae 19.8 1.9 430.1 135.6 Hexagenia, etc. (nymphs) 85.8 77.2 Agrionid .nymphs 17.6 8.8 Libellulid nymphs 15.4 16.5 Gomphid nymphs 2.2 7.4 Beetles, small 11.0 0.7 Hyalella knickerbockeri 143.0 5.7 Asellus sp. 15.4 1.5 Total 159.8 517 Lake Zurich, August — October, 1916. Bottom Fauna 13 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation Number per square yard Pounds per acre Campeloma subsolidum 3.3 3.3 9.9 9.9 Pisidium spp. Amnicolidae Valvatidae 21.3 84.5 84.5 190.3 0.8 4.6 4.6 10.0 Oligochaeta (small spp.) 3.3 0.2 Leeches (small spp.) 6.6 1.1 Chironomid larvae (small spp.) 94.6 13.2 Palpomyia larvae 6.6 0.5 Corethra larvae 13.4 0.5 Sand-case caddis larvae 38.7 226.6 7.7 49.2 Polycentropus larvae 1.5 0.3 Agrionid nymphs 1.5 0.7 Sialis larvae 1.5 0.9 Hexagenia, etc. (nymphs) 25.3 22.8 Hyalella knickerbockeri 33.6 1.3 Total 420.2 69.1 Crystal Lake, August — October, 1916. 6 Collections, Littoral Zone, 1 to 7 ft. Bottom Fauna Some Vegetation Number per square yard Pounds per acre Amnicolidae 58.5 3.2 Valvatidae 58.5 168.0 3.2 16.0 Planorbis sp. 47.5 2.6 Unionidae, young 3.5 7.0 Chironomid larvae (small spp.) 3.5 0.5 Ceratopogon larvae 3.5 0.2 Hexagenia, etc. (nymphs) 11.0 9.9 Libellulid nymphs 3.5 1.7 Gomphid nymphs 3.5 340.0 11.9 40.4 Agrionid nymphs 3.5 1.7 Caddis larvae (on Chara) 3.5 0.4 Sand-case caddis 11.0 2.2 Hyalella knickerbockeri 297.0 11.9 Total 508.0 • 56.4 518 Long Lake, August — October, 1916. Bottom Fauna 6 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation Number per square yard Pounds per acre Sphaerium sp. 3.5 3.5 1.7 1.7 Chironomid larvae (small spp.) Hexagenia, etc. (nymphs) Sand-case caddis larvae Caddis larvae (on Chara) Sialis larvae Gomphid nymphs Hyalella knickerbockeri 36.5 11.0 80.5 22.0 7.2 3.5 29.3 190.0 5.1 9.9 16.1 2.2 4.3 11.9 1.2 50.7 Total 193.5 52.4 Sand Lake, August — October, 1916. Bottom Fauna 10 Collections, Littoral Zone, 1 to 5 ft. Some Vegetation Number per square yard Pounds per acre Amnicolidae Valvatidae 2.2 8.8 11.0 0.1 0.5 0.6 Oligochaeta (small spp.) Chironomid larvae (small spp.) Sand-case caddis larvae Agrionid nymphs Gomphid nymphs 2.2 ' 13.2 13.2 2.2 2.2 33.0 0.1 1.8 2.6 1.1 7.5 13.1 Total 44.0 13.7 519 Pistakee Lake, August — October, 1916. Bottom Fauna 29 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation Number per square yard Pound's per acre Goniobasis sp. 18.0 18.0 10.82 10.82 Sphaerium sp. Pisidium sp. Amnicolidae Valvatidae Physa spp. Planorbis spp. Unionidae, young 5.9 53.7 260.9 38.5 4.4 0.6 2.2 366.2 2.9 2.1 14.3 2.1 0.2 trace 4.4 26.0 Oligochaeta (small spp.) 5.3 0.2 Planarians 13.6 0.5 Small leeches 67.3 11.4 Chironomid larvae (small spp.) 49.9 6.9 Sand-case caddis 16.5 383.3 3.3 42.6 Hexagenia, etc. (nymphs) 9.0 8.1 Agrionid nymphs 4.4 2.2 Sialis larvae 2.2 1.3 Asellus sp. 2.2 0.2 Hyalella knickerbockeri 212.9 8.5 Total 767.5 79.6 520 Fox Lake (Including Mineola Bay), August — October, 1916. Bottom Fauna 28 Collections, Littoral Zone, 1 to 7 ft. Some Vegetation Number per square yard Pounds per acre Campeloma subsolidum 0.8 0.8 2.3 2.3 Musculium transversum Musculium jayanum Sphaerium sp. Pisidium sp. Amnicolidae Valvatidae Physa spp. 0.8 1.6 0.8 5.5 40.6 25.1 4.6 2.2 0.4 0.8 0.4 0.2 3.6 1.4 0.3 0.1 Oligochaeta (small spp.) 15.6 0.5 Planarians 1.6 0.1 Leeches (small spp.) 14.7 2.5 Leeches (large spp.) 0.8 1.5 Chironomid larvae (small spp.) 9.2 1.3 Palpomyia larvae 0.8 0.1 Sialis larvae 0.8 278.2 0.5 18.0 Caenis larvae 7.7 * 0.6 Caddis larvae, misc. 0.8 0.1 Agrionid nymphs 3.1 1.5 Libellulid nymphs 0.8 0.4 Asellus sp. 0.8 0.1 Hyalella knickerbockeri 221.5 8.8 Total 319.6 23.9 521 2. Weed Fauna Head of Pistakee Lake, August 17, 1916, in Ceratophyllum Weed Fauna, Upper 9 Inches (Depth, 3.5 ft.) No. per sq. yard Pounds per acre Amnicola limosa Physa sp. 1,440 1,920 480 54.7 81.1 26.4 Chironomid larvae (small spp.) Small beetle Plea striata Caddis sp. (basket case) Hyalella knickerbockeri 720 120 120 58,080 120 57,000 23.7 6. 8.4 2,330.1 12.0 2,280.0 60,000 2,411.2 North Side of Nippersink Lake, August 18, 1916, in Potamogeton and Ceratophyllum Weed Fauna, Upper 9 Inches, (Depth, 3.5 ft.) No. per sq. yard Pounds per acre Amnicola limosa Physa spp. 600 840 240 22.8 36.0 13.2 Chironomid larvae (small spp.) Hyalella knickerbockeri 2,880 22,080 19,200 95.0 863.0 768.0 Total 22,920 899. 522 BIBLIOGRAPHY Alvord, John W., and Burdick, Chas. B. '15. The Illinois River and its bottomlands. Rep. 111. Rivers and Lakes Commission, p. 1 — 141. Baker, F. C. '16. The Relation of mollusks to fish in Oneida Lake. N. Y. State Coll. Forestry, Syracuse Univ., Tech. Pub. No. 4, p. 15 — 366. '18. The productivity of invertebrate fish food on the bottom of Oneida Lake, with special reference to mollusks. N. Y. State Coll. Forestry, Syracuse Univ., Tech. Pub. No. 9, p. 1 — 264. Board of Officers of the Corps of Engineers, U. S. Army '05. Report upon a survey for a navigable waterway from Lock- port, 111., to the mouth of the Illinois River. House of Repre- sentatives, Doc. No. 263, 59th Congr., 1st Session, p. 1 — 544, and charts. Forbes, Stephen A., and Richardson, R. E. '13. Studies on the biology of the upper Illinois River. Bui. 111. State Lab. Nat. Hist., 9 (Art. X) : 481—574. '19. Some recent changes in Illinois River biology. Bui. 111. Nat. Hist. Surv., 13 (Art. VI): 139—156. Legislative Investigating Committee '11. Report on the submerged and shore lands. Published under direction of House of Representatives, 47th General Assembly, State of Illinois. Vol. I, p. 1—191. Muttkowski, R. A. '18. The fauna of Lake Mendota. A qualitative and quantitative survey, with special* reference to the insects. Trans. Wis. Acad. Sci. Arts and Letters, 19 (Pt. I) : 374—482. Petersen, C. G. Joh., and Jensen, P. Boysen '11. Valuation of the sea. I. Animal life of the sea bottom, its food and quantity. Rep. Danish Biol. Station, 20 (1911) : 1—76. Petersen, C. G. Joh. '14. Valuation of the sea. II. The animal communities of the sea bottom and their importance for marine zoography. Rep. Dan- ish Biol. Station, 21 (1913) : 1—44. '18. The sea bottom and its production of fish food. A survey of the work done in connection with valuation of Danish waters from 1883 to 1917. Rep. Danish Biol. Station, 25 (1918) : 1—62. PROFILE OF A SECTION OF THE ILLINOIS RIVER Profile of the Illinois River from Chillicothe to Lagrange dam, showing elevations of water surface at low gage of 1901, channel depths, and general character of upper layer of bottom soils and sediments. The profile marks out clearly the three deep, flat-sloped, mud-bottomed, natural pools in which the richest accumulations of small bottom-animals were found both in 1913 and 1915, viz.: the Peoria Lake pool, lying behind the great bar thrown up by Farm Creek; the Havana pool, behind the great natural wier formed by the wash from Spoon River; and the Sangamon pool, lying behind the high bar thrown up by the mouths of the Sangamon. The data here used (elevations, soundings, and borings) are from the report of the U. S. Engineers' Survey for a deep waterway, House Document No. 263, 59th Congress, 1st session, Washington, 1905. 5094 096 HBP m ■-■-■■■■•*••- flrs it ■*•'"'■' *'.■>■■' ■''* '-'•■'■• 3M ■ .■ •'-'-■ ■-■'■"■■■•■•'■:''■". k " - : I ' " . ■ £ > . ■ • :" ' HkH •-'■.- * , . • Kwl " ' ' ' * i ,'■■'■' 9 •■■■• ''■■--■ 1 ; • • ' ■ ".'■'. ■■'<■'■ ■ Hi ■•..;■....'■, '•■■»■•■-; ■.■•■■■:-.■ ■ -;■'■:>-*■■■■■■■ ■I SlfiB INDEX SHEET to the following maps of Illinois River and bottom-land lakes, Chillicothe to Grafton. (After U. S. Engineers' Survey, 1902-1905, House Doc. 263, 59th Congr., 1st Session, 1905.) & mss&z Hall . » ■ i&U ■*:>:■■■ ?r v. ■.->:.- ■•:. feS] i SSl •■ -'v ■-':■» -v\; ^: v.- r;: "<*'-■:>■■ £* •■ .■■.•cv'» 1. Grafton sheet. 2. Kampsville sheet. 3. Meredosia sheet. \-£ol GroLTtcfe Dam. <& Jtyile. 73.&Oio &6.30 s&EARBSrOWhh 4. Beardstown sheet. SR0WMIN6 V fuH # V ^ ^ ^ ,00 i Grand. IsleS. . <*fc<^I MaiaTuicts^aJkm^ J3*2hLa&e SATW \ A(iU se^ou isj.s 5. Havana sheet. 6. Liverpool sheet. e> KINGSTON ^ PEORIA J) C^ wescev M p£o« <* PS.HIN Jtfile HS.S to 7ttS _^L 7. Peoria sheet. *r \. ■* \ ROME CHILL ICOTHE_ V- \J{ile173.3to/$6 LACON Q' 8. Chillicothe sheet. -- M ::•::. . :l: ^H~ .a._. :TF , .L University of Connecticut Libraries