109] STUDY OF SOUTHERN WISCONSIN FISHES— CAHN 109 



by the fact that the bars are much less regular here than along the north 

 and south shores, and the schools go south at the west end and north at the 

 east end over a scattered territory. The figures show conclusively that the 

 line of travel is well laid down. There is at present no explanation for the 

 phenomenon; there is no evidence of oxygen, carbon dioxide, hydrogen-ion 

 concentration, light or temperature changes to account for it, nor can it 

 be a reaction to current, for down the north shore the fish are following the 

 current caused by the incoming Oconomowoc river, while along the west 

 and south shores they are going against the current caused by the outflow 

 of the Oconomowoc river at the northwest corner of the lake. It is difficult 

 to see in what way it could be linked to the food habits, for certainly the 

 entomostraca have no such migratory movement. 



However, that the movement of the fish is intimately connected with 

 their food habits is indicated by the fact that a migrating school can be 

 stopped by an abundant food supply. This fact is well known to the 

 winter fishermen who utilize it to their benefit by dropping oatmeal flakes 

 into the water. Upon the descending flakes and the accompanying dust 

 the fish feed ravenously, and a series of schools can be held under the holes 

 in the ice for weeks at a time while hundreds of fish are caught from the 

 schools by means of a small "white bait" or a gold bead. Once the school 

 has been stopped in this way, the stomachs show nothing but oatmeal — 

 the normal food habits are entirely abandoned. Any small object descend- 

 ing slowly through the water is taken into the mouth, but if it be not 

 satisfactory it is ejected again with astonishing rapidity. This oatmeal 

 diet is not injurious to the fish, though the flesh is noticeably softer after 

 the fish have been feeding upon it for some weeks. A few years ago meat 

 scrap was used instead of oatmeal; it was eaten even more ravenously than 

 the meal, but resulted in diarrhea and in the death of many fish, so that 

 its use had to be prevented by law. (Fig. 5.) 



One further point should be noted in this connection. In the lakes of 

 the north, where lumbering causes a constant distribution of sawdust over 

 the water, the writer has found dead Leucichthys floating at the surface, 

 with stomachs containing a solid mass of sawdust. These descending 

 particles are no doubt taken in with the water, strained out by the gill 

 rakers, mass in the stomach and eventually kill the fish which is unable 

 to void the debris. 



CONSERVATION 



It is generally said that the cisco will bite only during the winter, but 

 this is not correct as the writer has often proven. Still no one fishes for 

 them in the summer, which is just as well. Cisco fishing has been a winter 

 sport in the county for forty years and the catches are astonishing. No 

 less, certainly, than 15,000 are taken from Oconomowoc lake each winter, 



