FISHES OF THE GULF OF MAINE 



115 



Gulf in its utilization of the planktonic vegetable 

 pasture. Menhaden feed, as Peck described, by 

 swimming with the mouth open and the gill 

 openings spread. We have often seen specimens 

 in the aquarium at Woods Hole doing this. 31 And 

 we have watched small ones in Chesapeake Bay, 

 swimming downward as they feed, then turning 

 upward, to break the surface with their snouts, 

 still with open mouths. 



The mouth and pharyngeal sieve act exactly 

 as a tow net, retaining whatever is large enough 

 to enmesh, with no voluntary selection of particu- 

 lar plankton units. The prey thus captured (as 

 appears from the stomach contents) includes small 

 annelid worms, various minute Crustacea, schizo- 

 pod and decapod larvae, and rotifers, but these 

 are greatly outnumbered as a rule by the sundry 

 unicellular plants, particularly by diatoms and 

 by peridinians. And the food eaten at a given 

 locality parallels the general plankton content of 

 the water, except that none of the larger animals 

 appear in the stomachs of the fish on the one 

 hand, nor the very smallest organisms (infusoria, 

 and certain others such as the coccolithophorids) 

 on the other. The menhaden, in short, parallels 

 the whalebone whales, the basking shark, and 

 the giant devil rays in its mode of feeding, except 

 that its diet is finer because its filter is closer 

 meshed. 



Peck has calculated from observations 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 whic'.i these fish congregate. The abundance 

 of microscopic plants in the water of bays and 

 estuaries, and along the coast has often been 

 invoked to explain the concentration of menhaden 

 close to shore. 



Enemies. — No wonder the fat oily menhaden, 

 swimming in schools of closely ranked individuals, 

 helpless to protect itself, is the prey of every pre- 

 daceous animal. Whales and porpoises devour 

 them in large numbers; sharks are often seen fol- 

 lowing the pogy schools; pollock, cod, silver hake, 

 and swordfish all take their toll in the Gulf of 



31 Apparently Ehrenbaum (as quoted by Bullen, Jour., Mar. Biol. Assoc. 

 United Kingdom, vol. 9, 1910-13, pp. 394-403) was not acquainted with the 

 habits of menhaden when he wrote to the effect that no fish eat plankton 

 indiscriminately, or swim about habitually with open mouth when feeding. 



Maine, as do weakfish south of Cape Cod. Tuna 

 also 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. 384). Not only 

 do these pirates devour millions of menhaden every 

 summer, but they kill far more than they eat. 

 Besides the toll taken by these natural enemies, 

 menhaden often strand in myriads in shoal water, 

 either in their attempt to escape then enemies or 

 for other reasons, to perish and pollute the air for 

 weeks with the stench of their decaying carcasses. 



Breeding and growth. — Very little is known about 

 the breeding habits of the menhaden, except that 

 it spawns at sea and that the chief production of 

 eggs takes place south of our limits. According to 

 observations at Woods Hole, 32 the main body of 

 the fish off southern New England spawn in June, 

 continuing through July and August; even into 

 October as in 1915, when the Grampus collected 

 eggs and larvae in Nantucket Sound and westward 

 from Martha's Vineyard in that month. And re- 

 ports of spent fish in the Gulf of Maine in July 

 and August, with others approaching maturity, 

 BUggesI that the menhaden is a summer spawner 

 there also. We have found no eggs in our tow- 

 nel tings north of Cape Cod (young fry were taken 

 in abundance in Casco Bay in October 1900), prob- 

 jil.lv because our work there was carried on during 

 a series of poor menhaden seasons. From Chesa- 

 peake Hay southward the spawning season appears 

 to be late in the autumn, and in early winter. 



Menhaden eggs are buoyant and resemble those 

 of the European pilchard (Clupea pUchardus), bul 

 are easily distinguished from the eggs of any other 

 Gulf of Maine fish by their large size (1.5 to 1.8 

 mm. in diameter), broad perivitelline space, small 

 oil globule (0.15 to 0.17 mm.), and very long em- 

 bryo. Incubation is rapid (less than 48 hours), as 

 Welsh found by experiment. The newly hatched 

 larvae are 4.5 mm. in length, growing to 5.7 mm. 

 in 4 days after hatching. The dorsal and caudal 

 fins first become visible at a length of 9 mm.; at 

 23 mm. all the fins are well developed; scales are 

 present at 33 mm.; and at 41 mm. the fry show 

 most of the characters of the adult, except that 

 their eyes are much larger, proportionately. The 

 youngest larvae much resemble young herring, but 

 the fins are formed, the tail becomes forked, and 



u By Kuntz and Radcliile. Bull. U. S. Bur. Fish., vol. 35, 1918, p. 119, who 

 describe the eggs and larvae. 



