Fishes of the Western North Atlantic 383 



smallest specimens, about 22—25 "^"^ ^o"S> rather certainly identified as this species, 

 were taken at Key West, Florida, on August 25, 191 9, but they are not in good con- 

 dition, having been partly dried. Although they cannot be used for obtaining propor- 

 tions, it is evident from these and others that the proportionate depth of the body in 

 examples under 25 mm is much less than in those 100 mm and more. In fact, those 

 up to 75 mm long generally are notably more slender than adults, though there is 

 much individual variation at all sizes. 



The chief distinctive marks in the smallest young at hand are the projecting 

 lower jaw; the long shallow cheek; the shallow concavity in the margin of the opercle 

 in front of the pectoral fin; the positions of the fins, which correspond to those of the 

 adult; and the number of dorsal and anal rays, which already can be counted with a 

 fair degree of accuracy. The last ray of the dorsal becomes prolonged much earlier in 

 some individuals than in others; for example, it already is somewhat produced in a 

 specimen 30 mm TL from Mustang Island, Texas, but in others up to 37 mm long 

 from Beaufort there is no sign of prolongation. Ventral scutes can be accurately counted 

 when the fish attain a length of about 30 mm, and even earlier in some examples. The 

 gill rakers, as shown in the Description, increase in number with age and growth. 



The color of the young is rather variable. The smallest ones have a silvery lateral 

 band (dark in some lots of specimens, presumably due to preservative used) that 

 increases in width with age and merges with the generally silvery color of the side in 

 some specimens only 35—40 mm long; but it remains visible in others up to a length 

 of 50 mm or so. In some young, as in some adults, the shoulder spot is absent whereas 

 it is quite evident in others at a length of 35 mm. Occasionally there are smaller dark 

 spots within the lateral band behind the shoulder spots; these may or may not disappear 

 when the lateral band merges with the silvery color of the side. The black peritoneum 

 is often visible through the body wall in the young. 



Little is known about the rate of growth. A few measurements made at Beaufort 

 indicate that the fish attain a length of about 35—60 mm at the age of one year and 

 90— 1 20 mm by the end of their second summer. Sexual maturity, at least in some 

 individuals, is reached at a length of only 1 50 mm. 



Spawning. At Beaufort, North Carolina, spawning takes place during May and 

 June, as determined from the gonads of adult fish. 



Migrations and Habitat. These Thread Herring often school, but solitary examples 

 were frequently taken at Beaufort, North Carolina, and on the Atlantic coast of Panama. 

 They hold more closely to salt water than menhaden and some other Clupeidae and are 

 not known to migrate inshore to spawn. They are essentially tropical and subtropical 

 fish, and although they stray northward to Cape Cod, they generally are not numerous 

 north of North Carolina. In North Carolina, where they usually are abundant during 

 the summer, they are taken from May through September. 



Food. These fish, like most of their relatives, feed largely on small organisms, 

 which they strain from the water with the numerous close-set gill rakers. Copepods 

 constituted the chief food of specimens from Chesapeake Bay {5g: loi). However, 



