50 BULLETIN OF THE BUREAU OF FISHERIES 



of some size, which, as Doctor Neal tells us, grow to 4 to 7 inches in length 

 by July. However, during this same month other females caught along the coast 

 of Maine are found to contain embryos in very early stages of development, from 

 the formation of the germ ring to a length of about 4 mm. By September the 

 embryos of the older generation range from 7 to 11 inches in length, some of 

 them being almost ready to be born, while those of the younger generation (any 

 given female contains only embryos of one or of the other generation, never of 

 both) have grown to an average of about 17 mm. Probably the older generation 

 is born in October and November, while the younger one winters in the uterus 

 of the mother, to be born in spring. Fall-bearing females are then fertilized 

 again, the development of the next set of eggs commencing in the early 

 winter, while spring-bearers are fertilized in early summer, which corroborates 

 11 months as the known period of gestation (p. 49). This would also explain the 

 fact that dogfish smaller than a foot in length are never reported in the Gulf of 

 Maine, for the young are produced during the season when there are very few 

 dogs on this coast, these few probably being immature. In short, the inner parts 

 of the Gulf of Maine probably do not serve as a nursery for the dogfish, plentiful 

 though this fish is there in summer, but the young are born somewhere offshore 

 and probably while the parents are in deep water. It seems, however, that this 

 seasonal schedule does not apply west of Cape Cod, for Latham^* records a great 

 abundance of very young ones taken in the traps in Long Island Sound in August, 

 showing that one generation is produced there in midsummer. Dogfish only 1 foot 

 long, hence new born, have been found in the stomach of a goosefish at Woods 

 Hole in July (p. 527). 



Commercial value. — With the dogfish so destructive to fish and to gear, and with 

 so many of them caught both by lines and by otter trawls during more than half 

 the year, it is no wonder that serious efforts have been made to utilize them on a 

 large scale — to make them marketable and a source of revenue instead of a dead 

 loss. Since this matter has been the subject of discussion elsewhere we need point 

 out only that the dog is a far better food fish when fresh than is generally appre- 

 ciated, and that it would offer a tremendous supply of cheap food were a satisfac- 

 tory method of canning it to be worked out. Dogfish have also been used in the 

 manufacture of fertilizer, and enough dogfish livers are brought into New England 

 fishing ports to yield almost 10,000 gallons of oil annually, which is combined and 

 sold with cod-liver oil. Up to the present, however, dogfish have not been of 

 sufhcient value to compensate for a hundredth part of the damage they do and 

 most of those caught are thrown back into the sea.^' 



'8 Copeia, Oct. 16, 1921, No. 99, p. 72. 



3" For further discussion of the damage done by dogfish and of their commercial possibilities, see the following: " Report 

 upon the damage done by dogfish in the fisheries of Massachusetts," Annual Report, Commissioners of Fisheries and Game 

 [of Massachusetts] for 1905 (1906), pp. 97-169; "Aquatic products in arts and industries," by Charles H. Stevenson. Report 

 of the Commissioner, U. S. Commission of Fish and Fisheries, Part XXVIII, 1902 (1904), pp. 228-229; Field, 1907, pp. 12-18, 

 40-19; "Sea mussels and dogfish as food," by Irving A. Field. Proceedings of the Fourth International Fishery Congress. In 

 Bulletin. U. S. Bureau of Fisheries, Vol. XXVIII. 1908 (1910), pp. 243-257; and Mavor, 1921, pp. 125-135. 



