FISHES OF THREE WISCONSIN LAKES 29 



FOOD OF THE FISHES 



The methods used in determining the food of the fishes were 

 the same as those described in previous papers (Pearse, 1918; 

 Pearse and Achtenberg, 1920). All fishes were examined while 

 fresh. The contents of the alimentary canal were stripped out 

 on a glass plate; the entire canal was then slit open from end to 

 end and the lining scraped to remove adhering food and para- 

 sites. The glass plate was then placed under a binocular and the 

 food mass was slowly teased across the field with needles. The 

 volume of each constituent was estimated. When necessary 

 the food was also examined with a compound microscope. 



In the following discussion all lengths of fishes are given in 

 millimeters and do not include the tail fin. The numbers after 

 foods indicate per cent of total volume; + means an amount 

 less than .1 per cent. 



FOOD or FISHES IN LAKE PEPIN 



Amia caha Linnaeus, dogfish 



A female 578 mm. long, taken in a commercial seine on July 

 1, contained no food. 



Anguilla chrysypa Rafinesque, eel 



A single specimen was caught in a slew connected with the 

 lower end of Lake Pepin, on a trot-line, July 7. It measured 

 810 mm. in length and had eaten nothing but crayfishes. 



Aphredoderus say anus (Gilliams), pirate-perch 



Five specimens caught at the outlet of the lake July 9 in a 

 minnow seine furnished the following data: Length: 26-32; 

 average 30. Food: chironomid larvae 80; Cyclops 20. Four 

 specimens contained no food. 



Aplodinotus grunniens Rafinesque, sheepshead 



Six adults from various sources were examined, June 28 to 

 July 13. Length: 198-456; average 289. Food: fish 4; chirono- 

 mid larvae 3.8; caddis-fly larvae 14; mayfly nymphs 9; Corethra 

 pupae .2; Hyalella 1; unidentified amphipods 1.2; Leptodora 

 15.6; Daphnia 13.6; ostracods .2; snails 12; Sphaeridae 6; young 

 clams 19. The largest specimen contained no food. 



