VARIATION IN VERTEBRAL NUMBERS OF JUVENILE 

 ATLANTIC MENHADEN 



By Doyle F. Sutherland 



ABSTRACT 



Juvenile Atlantic menhaden (Brevoortia tyrannus), collected in 45 estuaries along 

 the Atlantic coast of the United States, were examined for vertebral numbers. Analy- 

 sis of variance of mean vertebral numbers of 17,024 fish in 182 samples from 4 

 successive year classes, 1956-59, indicated that two groups, or subpopulations, of 

 juveniles existed, one north and the other south of Long Island, N,Y. Sex, size, and 

 water temperature were considered in the interpretation of the data. 



INTRODUCTION 



Adult Atlantic menhaden {Brevoortia tyrannus) 

 occur along the Atlantic Coast of the United 

 States from central Maine to central Florida. 

 Larvae enter estuaries soon after the occur- 

 rence of eggs in nearby oceanic waters (Her- 

 man, 1959; Kuntz and Radcliffe, 1917; Perl- 

 mutter, 1939; Reintjes, 1961; Richards, 1959; 

 Wheatland, 1956). Juveniles are found in most 

 estuaries from Cape Cod, Mass,, to northern 

 Florida and only occasionally stray beyond 

 these geographic limits (Scattergood, Trefe- 

 then, and Coffin, 1951; Springer and Wood- 

 burn, 1960). They spend the first summer of 

 life in estuaries, emigrate to sea in the fall, 

 and appear in huge schools off the coast of 

 North Carolina in December and January. In 

 the following summer, they normally are the 

 main support of the commercial purse seine 

 fishery from Delaware to Florida (June, 1961; 

 June and Reintjes, 1959, 1960). 



Variations in abundance of juveniles and 

 adults, both within and between years, have 



Note.—Doyle F. Sutherland, Fishery Research Biolo- 

 gist, formerly stationed at the Bureau of Commercial 

 Fisheries Biological Laboratory, Beaufort, N.C., at 

 present is stationed at Weiser, Idaho. 



led to the question of whether this species is 

 homogeneous through its range, or is 

 composed of groups, each with its own bio- 

 logical characteristics and range. One ap- 

 proach to this problem is the comparison of 

 body structure of juveniles from different 

 estuarine nurseries, since those inhabiting 

 a given estuary are more likely to have orig- 

 inated from a nearby, rather than a distant 

 parent stock. Furthermore, the occurrence of 

 juveniles in a given estuary provides a known 

 starting point in the life cycle. 



From an analysis of selected meristic 

 characters, June (1958) found that juveniles 

 of the 1955 year class were separable into 

 two subpopulations, one occurring north and 

 the other south of Long Island, N.Y. The pur- 

 pose of the present study was to examine 4 

 successive year classes, 1956-59, to deter- 

 mine if the earlier findings were confirmed 

 or refuted on the basis of vertebral numbers. 



MATERIALS AND METHODS 



Juveniles, comprising 182 samples of 17,024 

 fish, were collected, mostly by beach seine, 

 from 45 estuaries along the Atlantic coast 

 from 1956 to 1959. A few collections were 



