74 ILLINOIS BIOLOGICAL MONOGRAPHS [74 



the point where the schools were found. Every effort was made to equalize 

 the search over both shallow and deep water, and an equal length of time 

 was spent hunting for schools in water of the different depths. The results 

 are shown in table 14. Since the edge of the bar occurs in water between 

 5 and 6 meters deep, a total of 14.77% of the schools occurred upon the 

 bars as against 85.23% over the deep water. The difference is sufficient 

 to show a decided preference on the part of the fish for a pelagic habitat 

 over deep water. 



Table 14 



THE DISTRIBUTION OF SCHOOLS OF YOUNG LABIDESTHES OVER 



WATER OF DIFFERENT DEPTHS (OCONOMOWOC LAKE) IN JULY, 1923 



However, this distribution of immature fish undergoes a radical change 

 toward the end of July. This fact was discovered quite by accident while 

 investigating a very different problem — the distribution of the shore fish 

 at night as compared to daylight dispersal. Beginning late in June, 1923, 

 the writer collected the fish present along a given strip of shore line on 

 Oconomowoc lake after dark and again at noon over the same area and 

 listed the species found. This area was seventy-five feet in length and was 

 dragged with a twenty foot fine meshed minnow seine. Silversides were 

 found in almost every collection, but more commonly at night than in the 

 day time, and all the specimens were fully grown. It was decidedly interest- 

 ing, therefore, to find, on the night of July 10, five young silversides in the 



