378 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 3 



applying copper sulfate have been only 

 partially satisfactory. 



A sample of water collected from the 

 lake was analyzed by the State Water 

 Survey, table 2. The presence of 1.7 

 parts per million of ammonium indicates 

 pollution from barnyard waste. Other 

 parts of this analysis, as compared with 

 similar analyses from many other Illinois 

 ponds, show that the water of Onized Lake 

 is somewhat softer than that of most other 

 ponds. 



Further indications of pollution from 

 the barn lot came to light in hoopnet fish- 

 ing operations in the terminal portion of 

 the main arm in the summers of 1938 and 

 1940. Most of the fish caught in hoop- 

 nets set in the shallow water of this arm, 

 and left overnight, died, while those 

 caught in other parts of the lake, and sim- 

 ilarly treated, lived. 



No loss of fish has been observed in 

 Onized Lake outside of nets, and it is 

 probable that fish move out of the upper 

 end of the larger arm or bay when periods 

 of oxygen reduction occur. Undoubtedly, 

 the waste from the barnyard has stimu- 

 lated the growth of fish food organisms 

 and, hence, the fish production of the lake. 



Evidences of Overfishing 



Onized Lake was stocked with 10,000 

 fingerling fish in 1934, from the state 

 hatchery near Lebanon. No record is 

 available of the kinds of fish used, but it is 

 believed that largemouth bass and crap- 

 pies predominated in this group. The next 

 year, 1935, 2,000 fish, species unknown, 

 from the Lebanon hatchery, were placed 

 in Onized Lake, when it was found that 

 the water level in a pond near Brighton, 

 for which they had been intended, was 

 dangerously low. Fishing in Onized Lake 

 was begun in 1937 and it is probable that 

 at that time, with 12,000 fish that had been 

 stocked plus their young of 1935, 1936 

 and 1937, the lake was overpopulated and 

 the fish already stunted. 



L. H. Nicolet of the Owens-Illinois 

 Glass Company estimates that over a 5- 

 year period an average of 125 families 

 fished the lake each year. Fishing permits 

 were issued to about 100 families in 1939, 

 and to a few less in 1940 and 1941. In 

 addition, approximately 95 special passes 

 were issued each year. 



Near the end of the fishing season of 

 1938, the Natural History Survey fur- 

 nished the Onized Lake caretaker with a 

 creel census record book in which records 

 could be made for each fishing trip, includ- 

 ing the date, name of fisherman, number 

 of hours of fishing, kinds of fish caught, 

 numbers caught and their total weight. 

 Mr. Conrad, in charge of the grounds, 

 was much interested in the returns from 

 fishing and checked each fisherman on 

 entering and leaving the area. Fishing 

 was heaviest on week-ends, beginning on 

 Friday and usually reaching a peak on 

 Sunday. Few fishermen appeared on 

 Monday. As the custodian was on duty 

 over the week-end, he was allowed a free 

 day on Tuesday. Although some Tues- 

 day fishermen were interested enough in 

 keeping records to inform Mr. Conrad of 

 catches made on that day, others did not 

 take the trouble to do so ; therefore, the 

 Tuesday record is not complete. No 

 attempt has been made to estimate either 

 the total Tuesday catch or the fishing 

 intensity for that day, so that figures listed 

 in the tables dealing with catch and fish- 

 ing intensity are somewhat lower than if 

 this information could have been included. 



The evidence for overfishing originates 

 from three sources: (1) a creel census; 

 (2) hoopnet samples of the population 

 and (3) comparison of the poisoned fish 

 population of June, 1941, with figures 

 from the creel census and the hoopnet 

 sampling. 



The first and probably the best evidence 

 of overfishing in Onized Lake is from the 

 creel census. A comparison of the total 

 weight of fish taken by anglers during the 

 fishing seasons of 1939 and 1940, table 3, 

 indicates that a considerable drop in yield 

 occurred in the latter year, after nearly 

 700 pounds of fish had been removed from 

 Onized Lake in 1939. Apparently the 



1939 catch was greater in pounds than 

 could be replaced by the assimilation of 

 the natural food supply. The fact that! 

 about 1,000 fewer fish were caught in 



1940 than in 1939 does not necessarily 

 mean that the actual number of fish pres- 

 ent in the lake had been reduced. No fig- 

 ures are available on the abundance of 

 natural spawn, but a. few successful indi- 

 vidual broods could easily have replaced 

 the numbers taken. It rather suggests 

 that the number of fish of desirable sizes 



