403 



permanency of these new marshes is likely, except in spring seasons 

 of more than average water levels, to be a source of serious danger 

 to the fry before the fingerling stage is reached. In Danhole's field 

 the critical range of river levels for the young carp lies between 9.6 

 and 9.0 feet (Havana gage). At 9.6 feet this 600-acre tract is prac- 

 tically landlocked except for a single small opening- into the Crabtree 

 dredge ditch, toward the northeast corner of the field; and between 

 that level and 9.0 feet destruction of fry under six weeks old is known 

 to proceed on a large scale, as perhaps also some destruction of fry 

 still older. The stage of 9.6 feet was reached on May 17 in 191 1, and 

 great destruction resulted in the week following. The same level was 

 not reached till the last of June in 1910, when the greater age and 

 size of the fry seems to have permitted most if not all of them to 

 escape; but it should be noted here that the field observations of the 

 spring and summer of igio were broken off from June 3 to June 23, 

 and that our history of the fate of the fry that season is consequently 

 incomplete. 



A full list of dates follows, on which critical river levels for the 

 fry in Danhole's field were reached from 1900 to 191 1 inclusive. It 

 should be noted in this connection that at 9.6 feet the field is practically 

 landlocked, and that at 9.0 feet the destruction of fry by drying is 

 about completed. The unmarked years are those in which it is cer- 

 tain, on evidence of the observations of 1910 and 191 1, that more or 

 less extensive destruction of iry went on in such areas as Danhole's 

 field. The interrogation points indicate seasons in which the amount 

 of destruction that occurred is uncertain, depending very probably on 

 the date of spawning of the various broods and their size at the time 

 the critical level was reached. The years preceded by an asterisk are 

 those in which it is reasonably certain that the fry escaped, the num- 

 ber of these years being only three out of a total of twelve. 



Dates of Critical River Levels for Fry 



IN Danhole's Field, 1900-1911 



(Havana gage) 



