30 ILLINOIS BIOLOGICAL MONOGRAPHS [30 



little evidence to show for it. Nets drawn in Lac La Belle have shown me 

 only two brook trout, but this may be due to the smaller size of the fish 

 and their consequent escape through the mesh of the nets. However, I 

 am inclined to believe that the species shows less tendency to migrate 

 than either of the other common trout — the rainbow and the brown. 



Order APODES 



Family anguillidae 



11. Anguilla rostrata (La Sueur). Eel. 



The eel is a rare fish in the Waukesha county lake district. During 

 the years I have been gathering data on the fishes I have seen but five 

 eels taken in the county, though there are records of an equal number at 

 least that have been hooked, lost or seen. Four of the fish I have handled 

 come from Lac La Belle, under the falls at the outlet of Fowler Lake. 

 These fish measured: 2 feet 9 inches, 3 feet 6 inches, 3 feet 7 inches, and 

 4 feet 2 inches in length. Two were caught at night by men fishing for white 

 bass in late May, worms as bait; the other two were speared. The fifth 

 specimen came from the Oconomowoc river at the outlet of Lac La Belle 

 and was speared. I have no doubt but that eels are more plentiful than 

 these data seem to indicate, but these are all the records I have. 



Order EVENTOGNATHI 

 Family catostomidae 



12. Ictiobus cyprinella (Cuv. & Valen). Big-mouth Buffalo; Buffalo-fish. 

 This, the commonest of the buffalos, is found in those streams tributary 



to the Rock River, in which water it is more common than in any of the 

 Waukesha county streams. Found also abundantly in the Fox river, 

 particularly south of the city of Waukesha. A fish of considerable size, 

 often reaching ten pounds, it is taken in nets during carp seining and never, 

 so far as I know, on hook and line. I have seen the fish taken from the 

 Oconomowoc river near its entrance to the Rock, and in Lac La Belle, 

 but never in numbers. My figures show an average of 91 carp (Cyprinus 

 carpio) to 1 of this species. The food consists almost entirely of vegetable 

 matter — algae, leaves and seeds of aquatic plants (Potamogeton, Elodea, 

 etc.), together with a considerable number of zooplankton organisms, insect 

 larvae (Chironomus) with mollusca represented occasionally by small 

 Sphaerium. These forms are all sucked in and strained out of the water 

 by the gill rakers which pass the mud and silt out with the water. Locally 

 the fish are not looked upon with much favor as a food fish, there being 

 plenty of bass and other high grade food fish available, but they bring a 

 good price when shipped by commercial fishermen. 



13. Ictiobus urus (Agassiz). Round Buffalo; Mongrel Buffalo. 



The various species of buffalo fish inhabiting local waters are not 

 distinguished by local fishermen. This species is far less common than 



