94 American Fisheries Society 



Its subsequent growth is somewhat a matter of conjecture. Adult 

 fish range from 7 to 12.5 inches, the majority, presumably three 

 and four year olds, running from 10 to 12 inches. 



In late summer schools of various sized alewives are found in 

 the spawning ponds, depending upon the following factors: 



(1) Geographical location, spawning taking place earlier in 

 southern waters. 



(2) Time of spawning, eggs from the first run hatching two 

 months earlier than the last. 



(3) Temperature, abundance of food supply, and size of 

 spawning ponds. 



Food. — The food of the adult alewife consists mostly of the 

 plankton forms, such as diatoms, algae, and small crustaceans. 

 Instances have been cited where alewives have risen to the arti- 

 ficial fly, and also have been taken with young eels as bait. 



Enemies. — Among the enemies of the young and adult may be 

 mentioned fish, birds, disease and man. 



Migration. — The history of the alewife in the interval between 

 its descent to the ocean and its return as a mature fish is as yet 

 unknown. We are better acquainted with the freshwater part of 

 its life cycle. Governed primarily by temperature, the fish 

 approach the coast at a definite period in the spring, appearing 

 first in the rivers of the Middle South as early as March, and in 

 Canada in May. In Massachusetts they usually are noticed 

 toward the last of March or the first of April. After spawning, the 

 adult fish return to salt water in a lean, emaciated condition. 

 Whether these fish spawn again has not been determined. 



Parent Stream Theory. — From observations in handling local 

 alewife fisheries, the "Parent Stream Theory" has been evolved. 

 Briefly, the theory is that the young alewives descending from a 

 particular pond and stream will return as adult fish to the same 

 stream for spawning, thus establishing a continuous chain. There 

 are good reasons for us to consider this theory favorably. Practical 

 demonstration has shown that fisheries have been created in 

 streams which had no alewives by the simple expedient of placing 

 mature spawning alewives in the headwaters. The offspring 

 returned as adult fish, to the same spawning grounds, thus estab- 

 lishing a fishery. Similarly, depleted fisheries have been re-estab- 



