38 U. S. BUREAU OF FISHERIES 



following lakes was animal: Andes, Madison, Byron, Clear, North 

 Red Iron, Tetonkaha, and Oakwood. Two-thirds of the stomach 

 content of the single specimen from Lake Kampeska was animal. 

 These lakes, except Tetonkaha and Oakwood, were filled with 

 abundant vegetation. This vegetation, however, is the favorite 

 haunt of most of the insects and crustaceans. In these cases, where 

 both plant and annual foods have been available, the bullheads have 

 taken the animal food and rejected the plant material. In the last 

 two lakes both vegetation and the animal life usually supported by 

 it were scarce, and the stomachs of most of the fish were either 

 empty or contained little save bits of hardened mucus. It was 

 found that some specimens had taken large pieces of unaccustomed 

 food, such as parts of cray fish, whole minnows, and pieces of perch 

 that were used as bait. 



In only three lakes — Poinsett, Cottonwood, and Sand — had the 

 fish eaten enough plant material to make it an unportant part of the 

 diet. In Sand Lake 45 per cent of the stomach content was plant; 

 in Cottonwood, 37.1 per cent; and in Poinsett 23.5 per cent. A large 

 part of this plant food was filamentous algae, Potamogeton, and 

 Ruppia. 



ALTERNATIVE FOODS 



If it were not for the fact that the plant tissue was digested, at 

 least partly so, and that there was such a large proportion of it, it 

 might be supposed that the fish had not eaten it for food, but rather 

 by accident when browsing about for larvae, pupas, snails, and crus- 

 taceans crawling about over the Ruppia and Potamogeton (not many 

 were found on the algae). The writer is inclined to believe that bull- 

 heads do not take food in any such haphazard manner, but that they 

 deliberately select certain foods and reject others. Several years ago, 

 at the writer's home, a number of bullheads w^ere kept in a tank 

 during the summer months. Water plants were growing on the 

 bottom of the tank, and the bullheads were observed to snatch up 

 mouthfuls of the plant material in which w^ater beetles were hiding. 

 Then perhaps the bullheads remained ciuietlj" in the same place or 

 swam leisurely away, but after a moment they opened their mouths 

 and the plant material was ejected. Considermg these facts, it is 

 difficult to understand why bullheads w411 take almost anything 

 from a hook that normally they do not include in their diet. 



Vegetation was abundant in Lake Poinsett and Sand Lake, which 

 in a sense accounts for such a large percentage of it being consumed 

 by the fish. This does not account for the fact that though much 

 animal life was present in the lake it composed little more than one- 

 half of the food found in the specimens from these lakes. There was 

 very little vegetation in Cottonwood Lake and almost a total absence 

 of crustaceans. As the bullheads consumed a large per cent of plant 

 material, it would appear that thej^ are able to choose this food as an 

 alternative to animal tissue under certain conditions. Insufficient 

 data are at hand, however, to determine exactly what these con- 

 ditions are, for under similar conditions at Lake Tetonkaha and 

 Lake Oakwood the bullheads were found to have eaten animal food 

 almost exclusively. 



