128 



BULLETIN OF THE BUREAU OF FISHERIES. 



Page. 

 Enemies and parasites — Continued. 

 Active enemies — Continued. 



Other gastropods 217 



21S 

 218 

 219 

 219 

 219 

 219 



Fishes 



Birds 



Mammals . . 

 Passive enemies 



Eelgrass .... 



Algae 



Invertebrates ... 220 



Parasites 220 



Polydora ciliata 220 



Haplosporidium mytilovum, n. sp. . 220 



Uses and commercial value 222 



Chemical composition and nutritive value . . 224 



Pa?e. 



Seasonal changes in structure and food value 225 



When mussels are unfit for food 227 



Mussels and typhoid fever 227 



Ptomaines 228 



Peculiar poisons 229 



Sources of poison 230 



Chemistry of mussel poison 232 



Conclusion 234 



Cultivation of mussels 234 



Duration of mussel beds 240 



Efforts to develop a mussel industry in the 



United States 241 



Summary, conclusions, and recommenda- 

 tions 245 



Bibliography 247 



INTRODUCTION. 



The object of this report is to present as completely as possible the facts known 

 concerning the biology and economic importance of the sea mussel Mytilus edulis 

 Linn, and the possibilities of developing a mussel fishery in the United States. In a 

 previous paper (Field, 191 1) the food value of the sea mussel was demonstrated to be 

 equal to or greater than that of any other commercial shell-fish on our coast, and the 

 mussel beds of our eastern and western coasts were shown to constitute one of our 

 great undeveloped marine food resources. The importance of this sea mussel as a 

 valuable source of food supply was considered so great that a more exhaustive study of 

 the life history, distribution, and the commercial possibilities of utilizing the species 

 was considered advisable. The results of this investigation show the possibility of 

 adding to our food supplies millions of pounds of wholesome flesh food annually. 



The material entering into this report is based upon the review of an extensive 

 literature verified and supplemented by a series of investigations carried on during 

 seven summers for the United States Bureau of Fisheries at its biological station at 

 Woods Hole, Mass., and by a reconnaissance of the mussel beds on a limited portion of 

 the north Atlantic coast. A considerable portion of the work was done in the biological 

 laboratories of Clark University. 



SYSTEMATIC AND ECONOMIC RELATIONS OF MOLLUSKS. 



The term mussel, as generally used, applies to either of two groups of bivalve mol- 

 lusks one of which is restricted to salt and brackish waters, the other to a fresh-water 

 habitat. 



The marine species belong to the genus Mytilus and other allied genera of the 

 family Mytilidae. On our eastern coast there are five species of this family represent- 

 ing three genera, the most important of which is the common sea mussel, Mytilus edulis 

 (fig. 100, opp. p. 128), which ranges from the Arctic Ocean to Cape Hatteras. The horse 

 mussel, Modiolus modiolus, is next in importance, ranging from the Arctic Ocean to New 

 Jersey. Mytilus hamatus, the hooked mussel, is found from Chesapeake Bay south- 

 ward and on the Gulf coast. Modiolus demissus (Modio/a plicalula), the plicated mus- 

 sel, is a shallow water form found from Maine to Georgia. Modiolarm nigra is a north- 

 ern form which inhabits the deeper waters from the Arctic Ocean to Cape Hatteras. 



