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BULLETIN OF THE BUREAU OP FISHERIES 



deposit from 20,000 to upwards of 40,000 eggs, averaging about 30,000. In sexually 

 mature herrings, just before spawning commences, the genital organs are so large 

 as to make up about one-fifth the total weight of the fish. The period of incubation 

 is governed by temperature — European students tell us that it requires as long as 

 40 days at 38.3° F., 15 days at 44° to 46° F., and 11 days at 50° to 51° F., while 

 experiments on the Massachusetts coast by the U. S. Bureau of Fisheries gave 10 to 

 12 days in the temperature prevailing there in autumn. Ten to fifteen days might 

 be stated as an average for the Gulf of Maine. 



Fig. 41.— Eggs of the herring (Clwpea harengus) attached to seaweed. After Ehrenbaum 



Spawning grounds in the Gulf of Maine. — Herring spawn all along the shores of 

 the Gulf of Maine wherever the bottom is suitable, from Grand Manan on the east 

 to Cape Cod on the west, as well as along the western shores of Nova Scotia, as, 

 for instance, about the Trinity Ledges (an important breeding ground), though 

 whether as universally there we have not been able to learn. Probably the most 

 productive spawning ground within the limits of the Gulf is at the mouth of the 

 Bay of Fundy, particularly about Grand Manan. At present, according to Hunts- 

 man, herring spawn only locally, e. g., at Minas Basin, in the inner part of the bay. 



