Fishes of the Western North Atlantic 301 



and must find their own food. If food is found and if other conditions are favorable for 

 survival, then the spawning season is a successful one. The success or failure of a spawn- 

 ing season in a river is usually evident from the size of subsequent catches when the 

 fish hatched in a given year return later to spawn in the same stream. The comparatively 

 large fluctuations in catches over a period of years no doubt result in large part from 

 the measure of success of the particular spawnings from which the fish composing the 

 catches were derived. 



Spawning and Migrations. American Shad spawn in fresh water. Some spawn 

 as soon as they arrive from the sea while others do not spawn until they reach the 

 upper tributaries of rivers. Virtually all spawning, in this species as in many others, 

 takes place in the evening between five and ten o'clock. While spawning, the fish are 

 paired, swimming close together side by side. Since no nests are made, the eggs fall 

 loosely in the water, and doubtless many are smothered when they fall on muddy bot- 

 tom. An individual returns to spawn year after year. 



The water temperature governs the date when mature American Shad approach 

 the mouths of the rivers to spawn, about 50-55° being required. Accordingly, they 

 appear off the Florida coast (St. Johns River) in November, to remain until March, 

 in the sounds along the Carolina coast in February and March, in the Chesapeake 

 Bay area in March and April, and farther north in May and June. But the precise 

 date of arrival at any particular locality along the coast may vary by a couple of weeks 

 from year to year, depending on the variation from year to year in the vernal warming 

 of the water. 



In large rivers, they run far upstream if their passage is not blocked. Thus they 

 still run up 375 miles (or did recently) in the St. Johns River in Florida, 300 miles in 

 the Altamaha in Georgia, about 200 miles in the St. John in New Brunswick, and at 

 least 200 miles in the St. Lawrence {122 '. 11; 12'j: 129, 130). American Shad as- 

 cending the estuary of the St. Lawrence may travel as much as 25-50 miles in 24 

 hours (J27: 129). 



The spent fish, very thin after spawning, begin their return journey to the sea 

 immediately afterward; i.e. in March to May in the southern part of the range and 

 in June to August in the northern part. But the young fry (product of that season's 

 spawning) remain in the parent stream until autumn, when the temperature falls to 

 60° or lower. In the Chesapeake Bay region, their migration out into salt water takes 

 place principally in October and November; but it is not until late November or De- 

 cember that all of them are in salt water. 



Southward from Cape Cod the spent fish vanish upon re-entering salt water. While 

 a few young fry in the Chesapeake Bay area spend their first winter in the deeper 

 parts of the Bay, those from the Hudson may linger nearby for an entire year, for 

 catches of 6- to 8-inch fish in Gravesend Bay in autumn have been reported (5: 208). 

 The larger sizes of immature fish vanish as completely from the southern part of the 

 coast as do the spent fish, until they reappear there for their first spawning. 



Spent fish up to ten pounds and averaging about five pounds have been reported 



