wind velocity from light to strong, suspended particles 

 increased more than fourfold (162 to 700 turbidity 

 units) . The actions of bottom-feeding fish also caused 

 a resuspension of sediment particles. Because it takes 

 from 7 to 12 days for much of this sediment to settle 

 from Lake Chautauqua, this lake (as with most such 

 lakes in the Illinois River valley) is in a highly turbid 

 state most of the time. 



Sago pondweed (Potamogclon pcctinatus) is more 

 tolerant of reduced light than most other aquatic plants. 

 In spite of this, Bellrose (1941:261-263) found that 

 from 1938 to 1940 sago pondweed in Lake Chautauqua 

 did not thrive in water more than 48 inches deep, and 

 was absent in water more than 56 inches deep. Later, 

 at the same lake, Jackson & Starrett (1959:159) re- 

 ported that sago pondweed grew best when the maxi- 

 mum water depth was about 3 feet. 



Sedimentation of Lake Chautaucjua was accelerated 

 by the great spring floods of 1943 and 1944. Beds of 

 aquatic plants, which had declined slightly from 1938 

 to 1942 (Bellrose 1941:243, and unpublished) were al- 

 most wiped out by the high turbid waters of the two 

 following flood years. Probably because additional silt 

 was deposited as a "false bottom" over the previous 

 "firm bottom," aquatic plants never did return to their 

 former luxuriance in Lake Chautauqua. For all practi- 

 cal purposes, longleaf pondweed (Potamogeton ameri- 

 canus), coontail (Ceratophyllum demersum) , and bushy 

 pondweed {Naias guadalupensis) were lost as important 

 items in the lake's ecology. Sago pondweed is the only 

 plant which has been common since the 1943 flood. It 

 varies in abundance in Lake Chautauqua annually, de- 

 pending on the depth of water in May and June; low 

 water during this period has favored a fair growth dur- 

 ing some summers. The most extensive recent growth 

 occurred with the low, stable water levels of 1956 when 

 the beds covered 1,237 acres early in the fall. 



The Peoria Dam, put into operation in December. 

 1938, stabilized low water levels in Peoria Lake, and 

 coontail, bushy pondweed, and sago and longleaf pond- 

 weeds, as well as wild celery (Vallisencria spiralis), in- 

 creased greatly in the 1940's, with a peak abundance in 

 1949. Early in the autumn of that year aquatic plant 

 beds were lush, covering several thousand acres of this 

 10,000-acre lake. After 1949 these beds declined in 

 vigor and abundance until, following a small gain in 

 1952 and 1953, the lake has been almost completely 

 barren of these plants. 



At first this deterioration was attributed to spring 

 floods, such as those that may have affected the Chau- 

 tauqua flora. However, aquatic plant beds failed to re- 

 cover when water levels were favorable to growth (with 

 the exception of 1952 and 1953), and this reduces the 

 possibility that floods were solely involved in tlioir de- 

 cline. 



There is evidence that factors other than luriiiililv 

 may be responsible for the eradication of aquatic plants 



in certain areas. Coontail, longleaf and sago pondweeds. 

 and wild celery have disappeared from the Starred Rock 

 Pool since the 1940's and have not returned, even though 

 in many years since then the transparency of the water 

 has been adecjuate for their growth. Their failure to re- 

 appear suggests that factors other than a lack of water 

 clarity were responsible; at other lakes increase in water 

 transparency has been simultaneous with an increase in 

 vascular aquatic plants. 



The level of Rice Lake was artificially raised 2 or 3 

 feet in the mid- 1940's. When this rise occurred the 

 aquatic and marsh plants began to disappear. By 1950. 

 360 acres of river bulrush (Scirpus fluviatilis) had 

 dwindled to less than 100. By 1956 only 20 acres were 

 left. Both coontail and white waterlily (Castalia tuber- 

 osa) increased at first with lessened competition from 

 American lotus. However, as the marsh disappeared and 

 wave action increased, this churned up the bottom, and 

 coontail declined from 522 acres in 1950 to none in 

 1960. White waterlily went from 90 acres to zero in 

 the same period. 



Several years ago water levels were raised in Spring 

 Lake, not now connected with the river, to enlarge the 

 lake area for recreation. This increased depth was ac- 

 companied by a loss of about 200 acres of coontail and 

 an equal area of river bulrush marsh. 



Clearing of bottomland forests for agriculture elimi- 

 nated such food-producing trees as pecans and oaks 

 which furnished food for some ducks. 



FISH 



At Havana, on the middle stretch of the Illinois 

 River, some of the elderly citizens still talk of the special 

 trains that used to bring Springfield anglers to Havana 

 for a day's fishing. They also recall the carloads of live 

 fish that were once shipped out of Havana to the New 

 York City market. 



Largemouth bass [Microptcrus salmoides) were 

 abundant enough in the river-bottom lakes so that one 

 could make wages by catching them with a cane pole 

 for the local market. In 1897. 13,061 pounds of bass 

 were handled commercially at the Ha\ana fish markets 

 (Cohen, Bartlett, & Lcnke' 1899: 71 . Between 1899 and 

 1908 the commercial yield of largemouth bass increased 

 322 percent (Forbes & Richardson 1919:149-150). 



During the past half-century man has so seriously 

 damaged the habitat that the once great fishery at 

 Havana, and elsewhere along the river, is now but a 

 fraction of its former size. Increase in turbidity and 

 sedimentation, chronic pollution, decrease in aquatic 

 vegetation, virtual disapijcarance of fingernail clams, 

 and reduction of food h.ihilat through drainage have 

 contributed to this change. 



Perhaps the most important change in the fish fauna 

 was the introduction of the carp (Cyprinns carpio) in 

 the 1880's. Carp fitted well into the new environment 

 and soon became the most important commercial s|iecies. 



14 



