PROGRESS IN BIOLOGICAL INQUIRIES, 1931 473 



Tho results for the 233 bluegill stomachs were as follows : 



Average 

 Item percentage 



Plant material 25. 7 



Chironomus hirvsp 22. 



Ants 11.5 



Snails 9.7 



Hexagenia larvae 5. 1 



Amphipods 2. 8 



Total in 6 items 76. 8 



These results indicate that the bluegills are much more restricted in their 

 diet than either the rock bass or the perch. The 6 items listed in the table con- 

 stituted 7G.S per cent of the food material found in the bluegills as compared 

 with 57.8 per cent for 8 items in the rock bass and 67.6 per cent for the 8 

 items in the perch. The large percentage of plant material found In the 

 stomachs of the bluegills is also an important difference ; it amounted to 3.4 

 per cent in the perch, 5.0 per cent in the rock bass, and 25.7 per cent in the 

 bluegills. 



The menu of the 273 ciscoes was still more restricted, as indicated in the 

 following table : 



Average 

 Item percentage 



Cladocera 45. 6 



Copepoda 32.8 



Corethra larvae 2. 1 



Chironomus larva? 1. 8 



Total in 4 items 82. 3 



Two items, namely, Cladocera and Copepoda, make up more than 78 per 

 cent of the food material of the ciscoes. In 67 ciscoes obtained from Clear 

 Lake, 96.4 per cent of the food consisted of Daphnia. This table shows that 

 there is very little competition for food material between the ciscoes and the 

 other thi'ee species enumerated above. 



During the summer 2,643 fish from the various lakes were examined for 

 internal parasites. The perch were rather heavily infested in four of the live 

 lakes from which specimens were examined in considerable numbers. The 

 flesh and digestive organs of only 195 out of 652 perch were negative, and 

 164 of those that were negative came from Weber Lake. Excluding those 

 from Weber Lake, only 6 per cent of the specimens from the other four lakes 

 gave negative results. No explanation of the very small percentage of infesta- 

 tion in the Weber Lake perch has been found so far ; only 11 specimens out 

 of 175 harbored parasites. It may be mentioned in this connection that 7 

 specimens of sniallmouth black bass from Weber Lake also gave negative 

 results. A small trematode larva was found in the eyes of 96 per cent of the 

 perch from Trout Lake, in 98 per cent of those from Muskellunge Lake, and in 

 100 per cent of those from Nebish and Silver Lakes. 



The flesh and viscera of the rock bass yielded a high percentage of para- 

 sites ; the infestation varied from 88 per cent in Trout Lake to 100 per cent 

 in Nebish and Silver Lakes. The small trematode larva was found in the eyes 

 of only 30 per cent of the rock bass from Silver Lake, but this infestation 

 reached 90 per cent in Muskellunge Lake and 100 per cent in Nebish and 

 Trout Lakes. 



Trematode larvae were found in the viscera of all of the bluegills (180 

 specimens) from Muskellunge Lake, and 20 per cent of them also had cestode 

 cysts ; 92 per cent of them had trematode larvae in their flesh, and 60 per cent 

 had trematode larvae in their eyes. 



Thiity ciscoes from Silver Lake were examined for parasites, and cestodes 

 were found in the intestines of all of them ; 80 per cent of them also had 

 Acanthocephala. In Muskellunge Lake 80 per cent of the ciscoes contained 

 cestodes and 20 per cent were free of visceral parasites. In Trout Lake 

 16 per cent were negative, 82 per cent had cestodes in their intestines, and 10 

 per cent also had Acanthocephala. The ciscoes from Clear Lake, on the other 

 hand, were 96 per cent negative; only 2 specimens out of 60 examined yielded 

 any parasites. These fish were found to be feeding almost exclusively on 



