26o 



BULLETIN OF THE BUREAU OP FISHERIES. 



The data summarized in Table 5 cover a somewhat longer period of time than that 

 including the catches in Green Lake. It might have been longer, for fishing in Lake 

 Mendota was carried on from March 29 to September 29, 1919; but the general results 

 do not differ markedly from those already published for this lake (Pearse and Achten- 

 berg, 1920), and therefore only the period necessary to make adequate comparisons 

 with Green Lake is listed. The summary shows clearly that perch were abundant in 

 deep water in June and that they gradually migrated to higher levels as that region of 

 the lake lost its oxygen. This migration offers a striking contrast to the conditions in 

 Green Lake, where there is oxygen at all depths during the summer and where the 

 common deep-water fishes (ciscoes) remain in the depths of the lake. 



Table 6 gives a summary of catches in Lake Mendota from August 13 to September 

 4, grouped to show the total catches at different depths. 



Table 6. — Summ.'\ry of Gill-Net Catches in Lake Mendota, 



PER Hour. 



1919, Giving Depth and Catch 



Footing the total catch per hour for all species caught in Lake Mendota the results 

 are: Perch, 4.71; carp, 0.14; white bass, 0.05; cisco, 0.04; largemouth black bass, 0.03; 

 rock bass, 0.02; sucker, 0.02; bluegill, o.oi; crappie, o.oi; pickerel, o.oi; wall-eyed pike, 

 o.oi; gar, -|- ; crayfish, 0.05. Most of the fishes were not caught below 10 m., the only 

 exceptions being the carp, cisco, and perch. 



The perch is by far the most abundant fish large enough to be caught in gill nets at 

 all depths in Lake Mendota. The comparative number of fishes for the two lakes 

 judged by catches per hour in gill nets, is shown in Table 7. 



