MANUAL OF FISH-CULTURE. 135 



Florida, about November 15, the season of greatest abiiudauce beiug 

 February aud March. lu the Savannah Eiver, Georgia, and the Edisto, 

 South Carolina, the run begins early in January aud ends the last of 

 March. In the North Carolina rivers these stages of the migration are 

 a little later. In the Potomac Eiver advance individuals appear late 

 in February, but the fish is most numerous in April. In the Delaware 

 Eiver the maximum run is about the 1st of May. It reaches the Hud- 

 son Eiver the last of March, and is found in the Connecticut toward 

 the end of April, is most abundant the last of May, and leaves the 

 stream late in July. In the Kennebec and Androscoggin rivers, Maine, 

 it is first taken m April aiid has left by the middle of July. In the St. 

 John Eiver, New Brunswick, it appears about the middle of May, and 

 in the Miramichi Eiver, New Brunswick, late in May. 



The main body of shad ascends the rivers when the temperature of 

 the water is from 56° to 60°, the numbers diminishing when the tem- 

 perature is over 66°. Successive schools enter the Potomac from 

 February to July, the males i^receding the females. Of 61,000 shad 

 comprising the first of the run received at Washington, D. C, from 

 March 19 to 21, 1897, 90 per cent were males. Toward the close of the 

 season males are extremely scarce. 



The movement of the shad up the rivers is not constant, but in 

 waves, causing a rise and fall in the catch. In some of the rivers the 

 fishermen claim that a fairly well-defined run occurs late in the season, 

 consisting of a somewliat different fish, known as "May shad." 



The erection of impassable dams along the rivers and streams was 

 probably the first thing to curtail the natural spawning-grounds of 

 these fish and to seriously check their natural increase. 



As shad enter the rivers only for the purpose of spawning, the 

 fisheries are necessarily prosecuted during the spawning season, and 

 often upon the favorite spawning-grounds. The increase of population 

 necessitates a larger supply of fish and requires the use of more 

 apparatus, and the number of shad that reach fresh water is therefore 

 greatly curtailed by assiduous fishing with all kinds of contrivances in 

 the estuaries and in the mouths and lower parts of rivers. Under these 

 conditions of a restricted spawning area and increased netting shad 

 would soon be exterminated without artificial propagation ; or the fish- 

 ery, at least, would greatly diminish and become unprofitable. Such a 

 crisis was fast approaching in 1879, when the Fish Commission entered 

 upon systematic work in shad propagation. 



From their birth until their return to the rivers shad are preyed 

 upon incessantly by other fish, so that the larger portion of the young 

 do not survive their few months' sojourn in fresh water, and of those 

 which leave the rivers each season probably not one in one hundred 

 reaches maturity to deposit its eggs and contribute to the perpetuation 

 of its species. In the rivers striped bass, white perch, black bass, and 

 other predaceous fishes devour the young, and when they reach salt 

 water, sharks, horse-mackerel, kingfish, etc., undoubtedly destroy many 



