67 



(1) Ripe Fish. — The principal obstacle in artificial hatching 

 is obtaining ripe fish for stripping. It is impracticable to obtain 

 the fish in their journey up stream, since the ratio of males to 

 females is large, and practically all the eggs are "green" at this 

 time. 



Holding the alewives in pockets until ripe on their way up 

 stream offers a possible solution of this difficulty. Tests at 

 East Sandwich indicate that confinement in small pools is un- 

 satisfactory, as the eggs did not ripen and the fish eventually 

 died from fungus. Fifty alewives taken at the Bournedale 

 Stream between May 18 and 21, 1920, were held in a pool 8 

 by 50 feet in size, with wooden sides and sand bottom, in 1 

 foot of water, flowing 2,000 gallons per hour. The water came 

 from a pond where alewives spawned naturally, and was of the 

 same character as in the. stream up which they normally ran. 

 By June 9 all were dead, and no eggs had ripened. 



Seining the fish on the spawning grounds seemed the logical 

 method of approach. The ratio of male and female necessitates 

 handling large numbers of superfluous males, as well as many 

 unripe females. However, with labor and patience a sufficient 

 quantity of eggs may be secured. 



(2) Protection of Spawn. — The possibility of protecting the 

 spawn from the depredations of other fish by screening the 

 spawning beds was considered, but the uncertainty of when 

 and where the spawning would take place, and the fact that 

 the fish which prey upon the eggs follow in schools close behind 

 the alewives, rendered this idea impracticable. 



(3) Hatching. — ^Yhen seined the fish are stripped by the 

 usual method. After fertilization, owing to their adherent 

 nature, the eggs mass together, but this may be obviated by 

 constant stirring and by changing the water every five minutes 

 until they "harden." Hatching takes place at 72° F. in forty- 

 eight to ninety-six hours in open MacDonald hatching jars. 

 The eggs at first adhere to each other, but later they separate. 

 The fry, which have the appearance of fine transparent threads 

 attached to a relatively large yolk sac, can be held only for a 

 short time in tanks before planting. 



(4) Planting. — The advantage of artificial hatching over 

 natural spawning is the protection of the egg from the inroads 



