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Fishery Bulletin 92(2). 1994 



the longest time periods. However, 70% or more of 

 any cohort were usually recruited in <3 consecutive 

 weeks. In each recruitment year, those birthweek co- 

 horts with the greatest numbers of individuals con- 

 tributed most to the estuarine recruitment mode (Fig. 

 7). Also, within the larval catch of any given week, 

 from one to 10 birthweek cohorts were represented 

 (Fig. 7). 



Discussion 



Relatively large schools of larger-sized Atlantic men- 

 haden, migrating from New England and mid-Atlan- 

 tic states, along with local (North Carolina at least) 

 Atlantic menhaden emigrating from estuaries, spawn 

 off the southeast Atlantic states. The area from Cape 

 Hatteras to about northern Florida is thought to be 

 the major spawning location for this species (Higham 

 and Nicholson, 1964; Reintjes, 1969; Nelson et al., 

 1977; Judy and Lewis, 1983; Lewis et al., 1987). Al- 

 though the previous studies suggested that Atlantic 

 menhaden spawn in the fall and winter off the south- 

 east Atlantic states, none were able to estimate 

 within season spawning intensity. The present study, 

 which utilized samples collected throughout the re- 

 cruitment year, estimated within season spawning 

 intensity based on survivors entering an estuary. 

 However, without any knowledge of egg production 

 and the survival of cohorts between offshore spawn- 

 ing and estuarine recruitment, it was not possible to 

 know how closely the estimates of the birthdate dis- 

 tributions represented the actual seasonal egg pro- 

 duction. 



In each year, the Atlantic menhaden spawning sea- 

 son was protracted. This long spawning season might 



indicate a "bet hedging" strategy 

 (Lambert and Ware, 1984) where 

 eggs are released continuously over 

 the spawning season to ensure some 

 reproduction during the most favor- 

 able periods for survival. Based on 

 the birthdate distributions of larvae 

 that recruit to the estuary, the most 

 favorable period each year appears 

 to be for those fish spawned in a rela- 

 tively short period between early 

 December and mid-to-late January. 

 For all seven years, it was within this 

 major spawning period that the week 

 of peak spawning occurred. Larvae 

 from this major spawning period are 

 probably progeny of the large men- 

 haden schools migrating southward 

 from the New England and mid-At- 

 lantic states. These schools, which contain many fish 

 of spawning age (3+ years), are harvested from about 

 late November to late January during the North 

 Carolina fall purse seine fishery (Smith et al., 1987). 

 Larvae spawned earlier (October-November), may 

 originate from adults inhabiting North Carolina 

 coastal waters and estuaries in the summer or from 

 early fall adult immigrants to North Carolina wa- 

 ters (Wilkens and Lewis, 1971). Larvae spawned late 

 (February-March) may have been spawned further 

 south and immigrated to the estuary late in the sea- 

 son or were the offspring from northward migrating 

 adults in early spring. This late spawned group con- 

 tributed the younger, smaller larvae observed at the 

 end of the recruitment year (Figs. 4 and 5). 



Spawning locations, and routes and rates of trans- 

 port probably account for the variation in age of lar- 

 vae recruited to the estuary. While the precise loca- 

 tions of menhaden spawning are not known, the gen- 

 eral area is thought to be on the mid- to outer-conti- 

 nental shelf off North Carolina (Checkley et al., 

 1988; Warlen, 1992). However, accounts of the oc- 

 currence of eggs are limited (Reintjes, 1969; Judy 

 and Lewis, 1983) and no records of actual spawning 

 events exist. Although some early season spawning 

 may occur closer to shore, the largest contribution of 

 recruited larvae to the estuary is later in the season, 

 probably from the warm, plankton rich areas closer 

 to the Gulf Stream. Water temperatures are gener- 

 ally >18°C (Govoni, 1993), even in winter. These 

 warm temperatures are due, in part, to intrusions of 

 warm surface water onto the middle continental shelf 

 (Atkinson, 1985). Frequent upwelling events 

 (Pietrafesa et al., 1985) stimulate primary produc- 

 tivity by providing nutrients (Atkinson, 1985; Yoder, 

 1985) for phytoplankton growth (Yoder et al., 1983) 



