Fishes of the Western Nortli Atlantic 337 



theory") was confirmed when the progeny of gravid adults planted in depopulated 

 streams returned to these rivers three years after hatching (j6: rio). This incident 

 is also cited in a subsequent paragraph as a successful method of restocking streams. 

 But a much more intensive study of this interesting question is needed before any 

 categorical statement can be made as to how generally the parent stream theory applies 

 in the case of the Graybacks {1$: 103). 



As in the case of bluebacks and shad, relatively little is known about the home 

 of Graybacks in the sea. The capture of 1 8 adult Graybacks 70 odd miles off Barnegat, 

 New Jersey, on March 5, 1931 {14.: 327), suggests that the home may be some distance 

 offshore. Since these adults were taken in March, they may have been en route to some 

 nearby stream, hence it should not be assumed that the fish actually were taken from their 

 usual abode in the sea. It has been surmised for some time that the Graybacks, as well 

 as blueback herring and American shad, live quite a distance offshore from the rivers of 

 their origin and that their migrations consist of inshore and offshore movements. This 

 theory finds slight support in the discovery that different races spawn in different 

 river systems. However, further study is needed. 



The young, often with bluebacks and American shad of similar age, have been 

 seen descending as early as June 15 in the more southerly streams fringing the Gulf 

 of Maine. Successive companies of fry move out of the places where they were hatched, 

 run down with the current throughout the summer and are at sea by autumn. In the 

 Potomac, which the fish cannot ascend beyond Little Falls, the young remain abundant 

 in the vicinity of Washington, D. C. Here they may be taken in the same seine hauls 

 with bluebacks and American shad until October, when the main seaward migration 

 takes place; however, some young remain in the river until November and a few 

 linger until December. Most of the young apparently pass directly through Chesapeake 

 Bay and out to sea, but some stop to spend their first winter in the deeper parts of the 

 Bay, a few seem to remain for their second winter, and very few apparently stay there 

 for their third winter. 



The fish in the freshwater lakes endeavor to carry out the same spawning migra- 

 tion as those that inhabit the Atlantic coast, for the fish enter the shallow parts of 

 the lakes and ascend the tributary streams to spawn. 



Food. The food of the young while in fresh water apparently consists principally 

 of diatoms, copepods, and ostracods. After they enter salt water, their chief diet seems 

 to be shrimps and fish. Young 50—70 mm long, taken in fresh water, had fed principally 

 on copepods and ostracods; and larger young, 83—178 mm long, caught in Chesapeake 

 Bay, had continued to feed on copepods, though the larger ones had ingested prin- 

 cipally mysids and fish {^g : 90). Copepods, shrimps, and young squid were listed as 

 the food of the young by Sumner, et a/. {12 J: 72). Bigelow and Welsh (16: 1 10) have 

 described their chief food as copepods, amphipods, shrimps, and appendicularians, small 

 fish (such as herring, eel, launce, and cunner) as well as fish eggs and young of their 

 own. Alewives often contain diatoms, even when adult. It is conceivable that diatoms 

 could be screened from the water by the rather numerous, close-set gill rakers of adults. 



