276 BULLETIN OF THE BUREAU OF FISHERIES. 



Summary. — Food: Insect larvae, 33.7; pupae, 12. i; adult insects, 11; mites, 0.3; ostracods, o.i; 

 amphipods, 26.9; copepods, 2.7; snails, 0.8; algae, 3.5; silt and d6bris, 7. 



Station 25; June 17; number examined, 10. Length: Maximum, 84; minimum, 42.5; average, 

 49.3. Food: Chironomid larvs, 2; Libellula luctuosa nymphs, 10; chironomid pupae, 2.5; Haliplus 

 adults, 2.5; Corixa adults, 5; mites, 3; ostracods, 32.2; Cyclops, 7; Chydorus, 1.5; Simocephalus, 4.6; 

 Planorbis, 5.5; Limnaea, 3.5; oligochaetes, 6; filamentous algae, 1.2; Pleurococcus, 9; silt and debris, 4.5. 



Summary. — Food: Insect larvae, 12; pupae, 2.5; adult insects, 7.5; mites, 3; ostracods, 32.2; 

 copepods, 7; cladocerans, 6.1; snails, g; oligochaetes, 6; algae, 10.2; silt and debris, 4.5. 



Station 28; July 2; number examined, i. Length: 47.5. Food: Oxyethira larvae, 10; carabid- 

 beetle larvae, 10; Odontomyia vertebrata larvae, 10; ostracods, 5; Hyalella, 60; Cyclops, 5. 



Summary. — Food: Insect larvae, 30; ostracods, 5; amphipods, 60; copepods, 5. 



Station 25, in ditch along road; number examined, 14. Length: Maximum, 25.2; minimum, 15.1; 

 average, 20.6. Food: Insect larvae, 0.3; chironomid larvae, 5; Chironomid tentans larvae, 5.3; Pal- 

 pomyia longipennis larvae, 0.3; Cricotopus trifasciatus larvae, 7; Caenis diminuta nymphs, 0.7; beetle 

 larvae, 3.5; dascyllid larvae, 8.5; midge pupae, 3.5; adult bug, 1.8; insect remains, 0.3 ; adult midges, 

 4.6; Naucoris adult, 4.4; Collembola, 0.8; mites, 0.3; Hermannia bistriata, 5.6; ostracods, 12.2; 

 Cyclops, 11; Canthocamptus, i; chydorid, o.i; Planorbis, 2; Limnaea, 5.2; oligochaetes, 7; rotifers, 

 1.3; Oscillaria, 0.7; Volvox and other algae, 0.3; filamentous algae, 0.1; Pleurococcus, 4.3; sand, 1.4. 



Summary. — Food: Insect larvae, 30.6; pups, 3.5; adult insects, 11. 9; mites, 5.9; ostracods, 12.2; 

 copepods, 12; cladocerans, 0.1; snails, 7.2; oligochaetes, 7; rotifers, 1.3; algae, 54; sand, 1.4. 



Station 23; August 14; number examined, i. Length: 51. Food: Hyalella, 25; C>'clops, i; 

 Chydorus, i; plant remains, 73. 



Grand summary for igi4 and igiS- — Number examined, no. Length: Maximum, 179; minimum, 

 15. i; average, 41.9. Food: Insect larvae, 21.9; pupae, 2.1; adult insects, 10.9; spiders, 0.1; mites, 

 1.2; amphipods, 6.5; ostracods, 23.1; copepods, 3.6; cladocerans, 1.3; snails, 2.3; Sphaeridae, 0.1; 

 oligochaetes, 2.9; leeches, i.i; nematodes, 0.4; rotifers, 2; protozoans, 0.2; plants, 2.5; algae, 11. i; 

 silt and debris, 1.4; unidentified, 3.8. 



The mud minnow is a rather versatile feeder, with the chief constituents of its food, insects (35 

 per cent), entomostracans (31.3 per cent), and vegetation (13.6 per cent). Forbes and Richardson 

 (igo8) found that Wolflfia and unicellular algae formed three-fourths of the food of this species, insects 

 and crustaceans making up the rest. Hankinson (1908) reported entomostracans, algae, mites, midge 

 larvae, snails, and insects. 



III. FOODS UTILIZED BY FISHES. 



DIFFERENT SPECIES OF FISHES HAVE DIFFERENT FOOD HABITS. 



Table i shows the different kinds of food eaten by the shore fishes of lakes. If 

 more complete information is desired it may be obtained from the preceding section, 

 where the food of the fishes in each catch is given in considerable detail. 



Most fishes are not indiscriminate feeders, but select specific things from the avail- 

 able food supply. A good illustration of this point is furnished by the fishes caught to- 

 gether at station 18, July 3, 191 5. The foods taken by each of these fish are shown in 

 Table 3, and it will be noted that the different species were about the same average size. 

 The black bass is the most versatile, having taken 21 different items of food, the blue- 

 gill comes next with 16, the shiner has 14, and the top minnow 11. Each fish has taken 

 a different item in the largest quantity — i. e., the black bass, 25 per cent Enallagma 

 antennatum nymphs; the top minnow, 49 per cent Hyalella; the bluegill, 47 per cent 

 Eurycercus; and the shiner, 42.6 per cent Daphnia longispina hyalina. All the fishes had 

 eaten Eurycercus, which must have been abundant, and two had taken Hyalella. The 

 other two items taken in largest amount {Daphnia hyalina and Enallagma antennatum) 

 were each eaten by only a single species. In Table 4 (which resembles Table 3) three of 

 the species have eaten more fish than any other kind of food, but the fourth has taken 

 none. Table 2 shows the Johnny darter feeding largely on chironomid larvae and oligo- 



