Fishes of the Western North Atlantic 355 



tion is offshore and inshore." No doubt temperature is an important factor in the 

 movements of the fish; it certainly affects the supply of plankton upon which they 

 feed. In years when inshore runs fail, it is even probable that the fish remain so far 

 offshore that they are beyond the usual range of the fishing vessels. In slight con- 

 firmation of this theory, I recall that one autumn, when the usual inshore runs failed 

 at Beaufort, a progressive operator, upon my suggestion, induced one of his boat 

 captains to go farther offshore than usual in search of a catch. Fish, indeed, were 

 found, at a considerable distance offshore, apparently too far off for practical fishing 

 with the crews and schooners available. 



Food. Menhaden feed on small organisms strained from the water by their numer- 

 ous long, slender, close-set gill rakers, which form an effective strainer. While feeding, 

 the fish generally swim near the surface and often "break water"; they whirl around, 

 sound a short distance, come out of the whirl, and swim up and straight ahead at a 

 considerable speed for a rather short distance. During this time the mouth is wide 

 open and the gill covers are lifted, thus making it possible for a fish to filter a great 

 amount of water with minimum effort. The food that is ingested depends in large 

 measure upon the organisms that are present where the fish are feeding. Even a 

 considerable amount of mud and general debris is often swallowed. Included in the 

 stomach contents examined by various investigators were: numerous small crustaceans, 

 especially copepods; small annelid worms; rotifers; and unicellular plants, particularly 

 diatoms and peridinians. The plant organisms, as a rule, constitute the chief food. 



This species has a very thick-walled stomach, and a long intestine, as is usual among 

 fish that feed on vegetable matter. Among 64 fish taken at Beaufort, ranging between 

 65—214 mm, the intestinal tract increased more or less proportionately with the length 

 of the fish; generally it remained between 400 and 450 "/o of the standard length, 

 according to A. Bascom Hardcastle (unpublished data). 



Enemies. Most predatory animals associated with the sea feed on Atlantic Men- 

 haden — an easy prey because of their habit of schooling. Their fiercest enemy prob- 

 ably is the bluefish {Pomatomus)^ which, it is said, kills many more than it eats. Among 

 the other fish that feed on them extensively are the cod, pollock, hakes, weakfish, 

 swordfish, tuna, dolphin, amberjacks, and sharks. Whales and porpoises, as well as 

 birds, also devour many of them. 



Parasites. Atlantic Menhaden so often have a large crustacean parasite in the 

 mouth that they are sometimes referred to as "bugfish." It is said that in some schools 

 nearly every fish has a parasite in its mouth. This "bug," an isopod listed as Olencira 

 praegustator (Latrobe) (J07 : 231), has a robust body, generally fully half an inch long 

 and occasionally approaching an inch in length. Sometimes the mouth of the fish is 

 deformed because of its presence ;''thus the amount of water screened for food must be 

 considerably reduced in fish so infected. 



37. According to Rose {tio: 104, 105), the recent investigations by the U. S. Fish and Wildlife Service make it likely 

 that the north-south migrations of the Menhaden are more regular and extensive than Dr. Hildebrand supposed. 

 — H. B. B. 



23* 



