Abstract. — Larval Atlantic 

 menhaden, Brevoortia tyrannus, 

 were collected weekly during their 

 expected recruitment (November- 

 April) to the estuary near Beaufort, 

 North Carolina, over seven con- 

 secutive years beginning 1985-86. 

 The larval density in nighttime 

 quantitative samples was calcu- 

 lated and ages determined from 

 otolith microstructure. Back-calcu- 

 lated birthdates and larval abun- 

 dance data were used to estimate 

 the relative contribution of weekly 

 age cohorts to seasonal recruitment 

 of larvae. Summaries of these data 

 were measures of the spawning dis- 

 tributions. Larvae were recruited 

 to the estuary from mid-November 

 through April, with about 86% col- 

 lected during February-April. In 

 all years, age and size of larvae in- 

 creased linearly throughout re- 

 cruitment until the end of March 

 and then declined. The mean age 

 of recruited larvae over all years 

 was 61 days and the mean stan- 

 dard length was 24.6 mm. Atlantic 

 menhaden spawning season was 

 protracted, lasting 4-6 months. In 

 every spawning season, a dominant 

 birthweek mode in either Decem- 

 ber or January contributed from 

 25-43% of the total recruits. More 

 than 76% of all spawning occurred 

 in the December- January period. 

 Individual birthweek cohorts re- 

 cruited to the estuary over periods 

 from one week to several months. 

 Cohorts that usually contributed 

 the greatest number of individuals 

 to estuarine recruitment usually 

 recruited over longer periods. At- 

 lantic menhaden have apparently 

 selected a spawning season and lo- 

 cation that ensures transport of 

 larvae across the southeast United 

 States continental shelf and arrival 

 of most larvae during a time when 

 conditions are conducive to optimal 

 survival in the estuary. 



Spawning time and recruitment 

 dynamics of larval Atlantic 

 menhaden, Brevoortia tyrannus, 

 into a North Carolina estuary 



Stanley M. Warlen 



Beaufort Laboratory, Southeast Fisheries Science Center 



National Marine Fisheries Service, NOAA 



101 Pivers Island Road, Beaufort, North Carolina 28516-9722 



Manuscript accepted 20 October 1993 

 Fishery Bulletin 92:420-433 (1994) 



420 



The Atlantic menhaden, Brevoortia 

 tyrannus, is a commercially impor- 

 tant clupeid that ranges on the east 

 coast of the United States from the 

 Gulf of Maine to the central coast 

 of Florida. Tagging studies have 

 shown that this species makes ex- 

 tensive seasonal, migrations north- 

 ward along the coast in spring and 

 southward in fall and winter 

 (Dryfoos et al., 1973; Nicholson, 

 1978). Most of the population is 

 thought to overwinter in the area 

 between Cape Hatteras, North 

 Carolina, and northern Florida 

 (Ahrenholz et al., 1987). Spatial and 

 temporal trends in Atlantic menha- 

 den spawning have been suggested 

 by studies on the distribution of 

 eggs and larvae (Reintjes, 1961; 

 Kendall and Reintjes, 1975; Judy 

 and Lewis, 1983) and studies on 

 ovarian maturity and fecundity 

 (Higham and Nicholson, 1964; 

 Lewis et al., 1987). Those studies 

 show that spawning occurs off New 

 England from late spring to early 

 summer and again in early fall, off 

 the mid-Atlantic states in spring 

 and fall and off the southeastern 

 states from October to March. Maxi- 

 mum numbers of menhaden prob- 

 ably spawn in winter in offshore 

 waters south of Cape Hatteras 

 (Reintjes, 1969; Judy and Lewis, 

 1983) and waters off the North 

 Carolina coast may be one of the 

 major spawning grounds for Atlan- 



tic menhaden (Higham and Nichol- 

 son, 1964). 



Plankton collections taken off 

 North and South Carolina suggest 

 that Atlantic menhaden may con- 

 tinuously spawn from late fall to 

 early spring. Collections taken in 

 the vicinity of Beaufort, North Caro- 

 lina, from 1955 to 1961 (unpubl. 

 data, National Marine Fisheries 

 Service, Beaufort Laboratory, cited 

 by Higham and Nicholson, 1964) 

 showed larvae in samples beginning 

 in November or early December and 

 continuously thereafter until mid- 

 April. Subsequent work supported 

 these estimates of the timing of es- 

 tuarine immigration of menhaden 

 larvae. Lewis and Mann (1971) 

 sampled larval menhaden semi- 

 monthly as the fish recruited to the 

 estuary near Beaufort Inlet in the 

 fall/winter 1966-67 and 1967-68 

 seasons, to estimate relative in- 

 dexes of abundance. Densities of 

 menhaden larvae recruited to estu- 

 aries were reported for North Caro- 

 lina (Hettler and Chester, 1990; 

 Warlen and Burke, 1990) and South 

 Carolina (Allen and Barker, 1990). 



Examination of otolith micro- 

 structure to count daily growth in- 

 crements has made possible reason- 

 ably accurate estimates of the age 

 and growth of the early life history 

 stages of fishes. Age at estuarine 

 recruitment can be tracked within 

 and among seasons or years. Age at 



