FOOD OF THE SHORE FISHES OF CERTAIN WISCONSIN LAKES, 279 



IV. ADAPTABILITY OF FOOD HABITS. 

 ALTERNATIVE FOODS. 



Fish prefer certain foods and select from their environment. If the largest single 

 items are picked out from the dietaries of the fishes shown in Table i , the following results 

 are obtained: Nine species eat more dipterous larvee than any other single kind of 

 food; six, amphipods; five, cladocerans; four, fishes; two, adult hemipterous insects 

 (Corixa) ; two, Cyclops; and one species takes its chief food from gastropods, dipterous 

 pupae, May-fly nymphs, and ostracods. The next question to be answered is: What 

 will the different fishes eat if their favorite food is not available ? 



To answer this, the three foods taken in largest quantity (i. c, first, second, and 

 third choice) were selected for each of the 32 species shown in Table i. For example, 

 the golden shiner, Abramis crysoleucas, ate 57.6 per cent cladocerans, 16.5 per cent 

 copepods, 5.7 per cent dipterous pupae, and other foods. This species was, therefore, 

 put in a class "Cladocera — copepods — dipterous pupae." The classes and the number 

 of species of fish taking the same three chief items of food were as follows : 



Diptera larvae — Copepoda — Cladocera 3 



Cladocera — Diptera larvae — Amphipoda 3 



Diptera larvae — Ostacoda — Copepoda 2 



Cladocera — adult Diptera — Diptera pupae 



Cladocera — ^Copepoda — Diptera pupae 



Cladocera — Diptera larvae — algae 



Diptera larvae — cra^'fishes — Odonata nymphs 



Diptera larvae — Ostracoda — Cladocera 



Diptera larvae — Oligochaeta — plant remains 



Diptera larvae — fish eggs — Trichoptera larvae 



Diptera larvae — Oligochaeta — Copepoda 



Fish — crayfish 



Fish — adult Diptera — Diptera larvae 



Fish — frogs 



Amphipoda — Ephemerida nymphs — Diptera larvae 



Fish — Amphipoda — Hemiptera nymphs or Sphaeridae 



Amphipoda — Diptera larvae — Millipeds 



Amphipoda — Diptera larvae — Trichoptera larvae 



Amphipoda — Diptera larvae — Diptera pupae 



Amphipoda — Diptera larvae — Coleoptera larvae 



Gastropoda — plant remains — toad eggs 



Adult Hemiptera — Ephemerida nymphs — Diptera larvae 



Adult Hemiptera — Ephemerida nymphs — Cladocera 



Diptera pupae — silt and debris — Copepoda 



Cladocera — silt and debris — algae 



Ephemerida nymphs — Oligochaeta — Amphipoda 



Ostracoda — Diptera larvae — Amphipoda 



Thirty-two species of fishes thus show 27 classes. If only the two chief food items 

 are considered, the number of classes is reduced to 19, as follows: 



Amphipoda — Diptera larvae 4 



Diptera larvae — Copepoda 4 



Diptera larvae — Ostracoda 3 



Cladocera — Diptera larvae 3 



Diptera larvae — Oligochaeta 2 



