616 



Fishery Bulletin 100(3) 



New Jersey 

 1989-1990 



North Carolina 

 1989-1990 



15 25 35 45 55 65 75 85 95 105 115 125 



Estimated age (days) 



Figure 5 



Percentage distribution of estimated age (5-d intervals) for larval 

 Atlantic menhaden (Brevoortia tyrannus) recruited to Fivers 

 Island, North Carolina, and Little Sheepshead Creek, New Jersey, 

 in 1989-90, 1990-91, and 1992-93. 



for Atlantic menhaden spawning suggested by Stegmann 

 et al. (1999), there were no water temperatures above 

 12°C in the MAB in December through March (Fig. 9) 

 during the three years of our study. 



Two differing hypotheses could explain the occurrence 

 of menhaden larvae recruiting to the New Jersey estuary 

 in winter and spring. One is that larvae spawned in the 

 MAB in October or November remain in the MAB until 

 they move into estuaries in the spring. This hypothesis 

 would require a retention mechanism to keep larvae on 

 the continental shelf over the winter in water <10°C. No 

 such mechanism is likely as field and modeling studies 

 indicate persistent southwestward transport (Pietrafesa et 

 al., 1994; Churchill and Berger, 1998; Werner et al., 1999). 

 If larvae overwintered on the continental shelf, they would 

 be about 150-210 d old when they recruited to the estuary 

 5-7 months after spawning. No Atlantic menhaden this old 

 were found in any of the samples, or from any other studies 



(Warlen, 1994; Rice et al., 1999), and underaging of larval 

 otoliths in our study did not appear to be a problem. 



An alternative but more feasible hypothesis for the ob- 

 served winter-spawned larvae collected in New Jersey from 

 December to the end of the recruitment season (May-June) 

 is that they were spawned in the SAB and were transported 

 northward to the MAB. We used the density-weighted, back- 

 calculated spawning date distributions of larvae collected 

 in New Jersey that were spawned from November to April 

 as the best estimator of the percentage of the total recnaits 

 that were spawned in the SAB. If we use the portion of lar- 

 vae spawned December or later as the most conservative es- 

 timator, then the contribution of larvae from the SAB, of all 

 New Jersey recruits, was 87% in 1989-90, 47% in 1990-91, 

 and 10% in 1992-93. If larvae spawned November or later 

 are considered to be from the SAB where there was spawn- 

 ing, then the estimate (87%) is the same for 1989-90 but 

 increases to 55% in 1990-91 and to 23% in 1992-93. 



