15 



the spawning ponds, their size depending upon: (1) geographi- 

 cal location, spawning taking place earlier in southern waiters; 

 (2) time of spawning, eggs from the first run hatching almost 

 two months earlier than those of the last; (3) temperature, 

 abundance of food supply, size of spawning ponds, and length 

 of time before the return to salt water. Their subsequent 

 rate of growth is largely a matter of conjecture, since they are 

 not seen again until they return as adult fish to the parent 

 stream for spawning. 



Food. — In salt water, the food of the alewife and other her- 

 ring consists mostly of small plankton forms, such as diatoms, 

 algse, small crustaceans, and other minute animals and plants. 

 Instances have been cited where alewives have risen to the 

 artificial fly, and where they have been taken with small eels 

 as bait; but, as a rule, in passing to the spawning grounds 

 alewives take little or no food. The young feed on the fresh- 

 water plankton forms so abundant in the spawning ponds, and 

 with increasing size enlarge the scope of their dietary. 



Enemies. — Among the natural enemies which attack both 

 young and adult are man, predacious fish, birds, disease, pollu- 

 tion and changes in environment. As soon as the eggs are de- 

 posited the uphill struggle for existence begins. , Following the 

 spawning alewives come a procession of white and yellow perch, 

 suckers and minnows, eagerly devouring the ripe spawn, — a 

 procedure which occurs in every pond inhabited by these 

 species. Individually, suckers appear the most destructive, 

 yellow perch next and white perch the least. 



As the young alewives increase in size they serve as food for 

 the larger fresh-water fishes such as perch, bass and pickerel, 

 and when they descend to the ocean their arrival is often an- 

 ticipated by numerous salt-water species which lie in wait at 

 the mouths of the coastal rivers. In the fall of 1915, in Aga- 

 wam River, a school of white perch was observed eagerly feed- 

 ing upon young alewives as they descended the stream. The 

 loss from birds such as herons, terns and other fish-eating 

 species is an indeterminable but probably a negligible factor. 



Both the young and old fish are susceptible to bacterial and 

 parasitic diseases, concerning which little is known at the pres- 

 ent time. The older fish have a lowered vitality after spawn- 



