FISHES OF THE GULF OF MAINE 123 



fish are spawned. Sexual maturity is apparently attained in the season following the 

 third winter, and a few of the older fish that he examined showed as many as^_9 to 10 

 winter rings on the scales. 



When the menhaden first arrive on our coasts in spring they are thin, but they 

 put on fat so rapidly that while the average yield of oil per 1,000 Gulf of Maine 

 fish was about 12 gallons for the whole summer season of 1894, it rose to 14J-4 gallons 

 for Boston Harbor fish in August and to 16 or IS gallons in September. It is 

 generally accepted, furthermore, that fish taken on the New England coast always 

 average larger and fatter than those caught farther south. 



Food. — The menhaden, formerly thought to subsist on mud, is now known to 

 feed chiefly on microscopic plants, particularly diatoms, and on the smallest Crus- 

 tacea. 28 These it sifts out of the water with a straining apparatus in the shape 

 of successive layers of pectinated gill rakers as efficient as our finest nets. Men- 

 haden feed, as Peck described, by swimming with the mouth open and the gill 

 openings spread, and we have often seen specimens in the aquarium at Woods 

 Hole doing this. 29 The mouth and pharyngeal sieve act exactly as a tow net, 

 retaining whatever is large enough to enmesh with no voluntary selection of par- 

 ticular plankton units. The prey thus captured, as appears from the stomach 

 contents, includes small annelids, various minute Crustacea, schizopod and decapod 

 larvae, rotifers, etc., but as a rule these are greatly outnumbered by the sundry 

 unicellular plants, particularly by diatoms and peridinians. At a given locality 

 the food eaten parallels the general plankton content of the water, except that 

 none of the larger animals, on the one hand, nor the very smallest organisms (that 

 is, certain infusoria), on the other, appear in the stomachs of the fish. The men- 

 haden, in short, parallels the whalebone whales in its mode of feeding, except that 

 its diet is finer because its filter is closer meshed. Peck has calculated from obser- 

 vations on the living fish that an adult menhaden is capable of filtering between 

 6 and 7 gallons (about 24 to 28 liters) of water per minute, and while the fish do 

 not feed continuously this will give some measure of the tremendous amount of 

 water sifted and of plankton required to maintain the hordes in which these fish 

 appear. The abundance of microscopic plants in the water of bays, estuaries, etc., 

 has often been invoked to explain the concentration of menhaden close to the shore. 



Enemies. — No wonder the menhaden, fat and oily, swimming as it does in 

 great schools of closely ranked individuals and helpless to protect itself, is the 

 prey of every predaceous animal that swims, and that the havoc wreaked on it by 

 other fish has often been described. Whales and porpoises devour them in large 

 numbers; sharks are usually seen following the pogy schools; pollock, cod, silver 

 hake, and swordfish all take their toll in the Gulf of Maine, as do weakfish and 

 bluefish south of Cape Cod. Tuna, or "horse mackerel," kill great numbers, but 

 the worst enemy of all is the bluefish, and this is true even in the Gulf of Maine 

 during periods when both bluefish and menhaden are plentiful there (p. 239). Not 

 only do these pirates devour millions of menhaden every summer but they kill far 



M For a detailed account of the food and of the branchial sieve of the menhaden, see Peck (Bulletin, United States Fish Com- 

 mission, Vol. XIII, 1893 (1S94), pp. 113-124, pis. 1-8. Washington). 



" Apparently Ehrenbaurn (as quoted by Bullen, Journal, Marine Biological Association of the United Kingdom, Vol. 

 IX, 1910-13, pp. 394-403. Plymouth) was not acquainted with the habits of the menhaden when he wrote to the effect that no 

 fish eat plankton indiscriminately or habitually swim about with open mouth when feeding. 



