256 BULLETIN OF THE BUREAU OF FISHERIES. 



The chief food of the Johnny darter is chironomid larvae, with oligochaetes forming the second 

 largest item. Forbes and Richardson (1908) stated that the food of the fish they examined consisted 

 of two-thirds chironomid larvae, 12 per cent small May flies, and 7 per cent gnat larvae. Hankinson 

 (1908) reported chiefly midge larvae, with some filamentous algae and Entomostraca. Reighard (1915) 

 found midge larvae and entomostracans. 

 Catostomus commersonii (Lac^pede). Common sucker, fine-scaled sucker. 



Station 24; July 2, 1915; number examined, 23. Length: Maximum, 24.3; minimum, 13; aver- 

 age, 19.9. Food: Chironomus lobiferus eggs, o.i; C. lobiferus larvae, 5.2; C. digitatus larvae, 5.6; C. 

 viridis larvae, 1.3; C. flavus larvae, 1.3; C. tentans larvae, 2.4; Cricotopus trifasciatus larvae, 41.3; C. 

 tentans pupae, 3.4; bug, +; midge, 0.3; ostracods, 17.5; Cyclops, 3.7; Cladoceran, 2.2; Bosmina, i.i; 

 Chydorus, 1.5; Eurycercus, +; oligochaetes, 13.5; rotifers, o.i; Closterium, +; Pediastrum, +; diatoms 

 aind desmids, +; Aphanothece, 0.1. 



Summary. — Food: Chironomid larvae, 55.9; chironomid pupae, 3.4; adult insects, 0.3; ostracods, 

 17.5; copepods, 3.7; cladocerans, 3.9; oligochaetes, 13.5; rotifers, i; Protozoa, +; algse, 0.1. 



Station 5; August 25; number examined, 6. Length: Maximum, 60; minimum, 38.5; average, 

 47.9. Food: Chironomus lobiferus larvae, 0.5; Probezzia glaber larvae, 0.8; ostracods, 12.3; Cyclops, 

 48.4; cladocerans, 0.3; oligochaetes, 7; Arcella, 0.1; Difflugia, 8.5; Closterium, 1.6; desmids and di- 

 atoms, 2.5; fine silt and debris, 16.9. 



Summary. — Food: Chironomid larvae, 1.3; ostracods, 12.3; copepods, 48.4; cladocerans, 0.3; oligo- 

 chaetes, 7; protozoans, 8.6; algse, 4.1; silt and debris, 16.9. 



Station 5; August 30; number examined, 3. Length: 58, 53.6, 44; average, 51.8. Food: Chiron- 

 omus lobiferus larvae, 4; Corethra adult, 2.3; Dytiscus, 2.3; mite, +; ostracods, 27; Cyclops, 14; 

 chydorid, 6.3; oligochaetes, 10; rotifers, 1.3; Arcella, 0.3; Difflugia, i; Closterium, 10.3; desmids and 

 diatoms, 14; silt and debris, 4.3. 



Summary. — Food: Chironomid larvae, 4; adult insects, 4.6; ostracods, 27; copepods, 14; cladoc- 

 erans, 6.3; oligochaetes, 10; rotifers, 1.3; protozoans, 1.3; algae, 24.3; silt and debris, 4.3. 



Station 5; September 2; number examined, i. Length: 44. Food: Enallagma eggs, 25; Cyclops, 

 56; Chydorus, i; oligochsetes, 10; rotifers, 1: Difflugia, i; desmids and diatoms, i; silt and ddbris, 5. 

 Grand summary. — Number examined, 34. Length: Maximum, 60; minimum, 13; average, 29.2. 

 Food: Insect eggs, 0.7; chironomid larvae, 40.6; chironomid pupae, 2.4; adult insects, 0.6; mites, 0.1; 

 ostracods, 16.8; copepods, 14.8; cladocerans, 3.6; oligochaetes, 11. 5; rotifers, 0.2; Protozoa, 1.3; algae, 

 3; silt and debris, 3.6. 



The common sucker when yoimg feeds mostly on chironomid larvae (40.6 per cent), entomostracans 

 (35.2 per cent), and oligochaetes (11.5 per cent). Tracy (1910) described the young as feeding on di- 

 atoms, desmids, and black-fly larvae; the adults on insects, worms, molluscs, young fishes, and fish eggs. 

 Reighard (1915) found that the young ate mostly cladocerans, 2,000 being found in one individual. 

 He told how the adults mouth over plants from one end to the other, and stated that they ate the eggs 

 of the log perch. Hankinson (1908) foimd the food of adults to consist of caddis-fly larvae and cases, 

 Sphaeridae, amphipods, insects, marl, midge larvae, and Daphnia. Baker (1916) reported his examina- 

 tions as follows: Mud and plant remains, 49 per cent; molluscs, 30 per cent; insecta, 21 per cent. 



The sucker is remarkable for the fineness of the food it is able to select. No other fish shows such 

 a high percentage of protozoans, unicellular algae, and rotifers in its food. 



Cottus ictalops (Rafinesque). Miller's thumb, common sculpin. 



Data/or 79/4 (Pearse, 1915). — All from station 11; number examined, 10. Average length, 45. 

 Food: May-fly nymphs, 66; chironomid larvae, 7.1; adult midge, 1.5; Hyalella, 13.5; ostracods, 0.5; 

 Cyclops, i-s; leech, 9; filamentous algse, 0.9. 



Station 14; July 9, 1915; nimiber examined, 2. Lengths: 21.7, 20.5. Food: Cricotopus adults, 

 7.5; Hyalella, 60; ostracods, 2.5; Cyclops, 10; chydorid, 2.5; oligochaetes, 10; filamentous algae, 7.5. 



Station 23; July 23; number examined, i. Length: 57.5. Food: Chironomus fulviventris larvae, 

 10; Diamesi waltii larvae, 10; Hyalella, 60; oligochaetes, 15; plant remains, 5. 



Station 19; August 18; number examined, i. Length: 31. Food: Chironomus lobiferus larvae, 40; 

 Hyalella, 60. 



Station 19; August 20; number examined, 2. Lengths: 33, 32.5. Food: Chironomus digitatus 

 larvae, 21.5; Hyalella, 75; sand, 3.5. 



