402 



THE fry's STRUGGIvE FOR EXISTENCE FROM HATCHING TO 



fingerung stage 



1. Natural enemies. — Large numbers of gar, bass, and pickerel 

 (grass pike) frequent the marshes used by carp for spawning grounds 

 and themselves spawn there. The pickerel are in the fingerling stage 

 by the time the carp are Yi to Va. inch long. The bass and gar spawn 

 at about the same time as the carp, in general, but the large size of 

 the mouth of these species and their well-known predaceous tendency, 

 doubtless make them destructive enemies of at least the later-spawned 

 carp fry. 



2. High temperatures on the spawning grounds. — By May 22, 

 191 1, water temperatures in the marshes and overflowed flats about 

 Havana had reached 86° Fahr. ; but some fry were found still alive 

 at that time in drying-up holes in Danhole's field, in water registering 

 92°, as likewise in small puddles left from the drying-up of Beck's 

 ponds, July i, 1910. 



3. Landlocking and drying up of spazmiing grounds before fry are 

 old enough to escape. — Large numbers of fry perished from these 

 causes in May, 191 1, (Danhole's field,) and in June and July, 1910, 

 (Beck's ponds). To what extent their instincts protect young carp of 

 proper age from the danger of falling water is not altogether certain. 

 The bottom- and vegetation-loving habit of the fry, from hatching to 

 the fingerling stage, is probably always a source of danger. That 

 great numbers of them fail to take care of themselves when 4 to 6 

 weeks old and from ^•^ to ^■^ inch long, is apparently proven by the 

 observations made in Danhole's field in May, 191 1. The slightly 

 greater age of the fry when first critical levels were reached in the 

 last week of June, 19 10, was proba1)ly the only thing that prevented 

 even greater destruction then. 



There are also indications of a general nature that conditions in 

 the lakes and sloughs about Ha\'ana, and perhaps at other points along 

 the river, are now less favorable to the development and maturity of 

 carp fry than they were previous to the opening of the Chicago Drain- 

 age Canal in igoo. Previous to 1900 there was much vegetation in 

 what is now open water. The shallower lakes then offered excellent 

 opportunities for spawning, many of them over considerable areas 

 well away from shore, and in all cases with deeper water always with- 

 in easy reach. Now in most of the lakes the vegetation is reduced to 

 a narrow zone along portions of the shores, and the newly formed 

 marshes due to the temporary overflow of the old lake-banks ofTer 

 the most extensive and suitable territory available in April and May 

 for spawning purposes ; but the flatness and shallowness and im- 



