THE SEA A FOOD RESERVOIR MOORE. 599 



point has been somewhat slowly arrived at in order that the reader 

 might approach the subject with an understanding of antecedent and 

 collateral conditions, and be in a better position to appreciate its 

 importance, and his responsibilities and opportunities. This is the 

 waste of large quantities of good, in many cases excellent, food fishes 

 caught unintentionally and thrown away in whole or in part for lack 

 of a market. 



Fishermen set their nets, or fish their gear of whatever kind used, 

 for one or several kinds of fish having a market value and reputa- 

 tion, but incidentally they catch quantities of other species collec- 

 tive^ known as " trash," which are either thrown away to become a 

 nuisance near the fishing grounds, or are used for inferior purposes, 

 such as the manufacture of oil and fertilizer. There are other sea 

 foods readily obtainable in great quantities that are not taken at all 

 merely through ignorance of their availability or qualities, and are 

 wasted in the sense that they are not utilized. 



The aggregate of this wasted and neglected food supply is enor- 

 mous, and it is probable that, if it were all used, the supply of sea 

 foods — including in that term fresh-water products — could be doubled 

 with little additional effort on the part of the fishermen. The Bureau 

 of Fisheries has given considerable attention to this subject and has 

 introduced some of these neglected foods into consumption. The ex- 

 ploitation of others is being taken up as rapidly as possible. 



One of the most abundant shellfishes of the North Atlantic and 

 Pacific coasts is the sea mussel {Mytilus edulis) and, as it feeds on 

 minute particles of vegetable matter, it, even more than the men- 

 haden, is a highly efficient agent in the recovery of land wastes car- 

 ried into the sea. Although the gills are quite different from those 

 of the menhaden, they also serve not only the purposes of respiration 

 but as filters, the pores of which are so fine that they can be seen 

 only on powerful magnification. The gills are clothed with innumer- 

 able little fleshy processes or cilia which, lashing rhythmically, by 

 their united action draw into the open mouth of the shell currents of 

 water which pass through the minute orifices and gain exit by an- 

 other channel. The little water-carried plants and particles of vege- 

 table detritus which compose the mussel's food, although individually 

 too small to fall within the range of unaided vision, are too large to 

 pass through the pores, and become trapped in the mucous coating of 

 the gills and pass in a steady stream into the mouth, and thence into 

 a long alimentary canal in which they are digested. 



From experiments conducted with oysters, which have somewhat 

 similar gills, it is probable that, to get its daily meal, a mussel 3 or 4 

 inches in length filters from 25 to 50 gallons of water each 24 hours, 

 between 2,000 and 4,000 times its own bulk. 



