614 



Fishery Bulletin 100(3) 



larval catches in some periods in New Jersey are associ- 

 ated with low water temperatures. There were no larvae 

 caught in December^anuary of 1989-90 and 1990-91 

 and in February-March 1993 when water temperatures 

 remained between 1.0 and 5.0°C (Fig. 3). In contrast, re- 

 cruitment in North Carolina began in November and was 

 continuous until ending in April or May (Fig. 2). Water 

 temperature in North Carolina was warmer than in New 

 Jersey and only twice dropped below 6°C (Fig. 3). In all 

 three years in North Carolina, recruitment was character- 

 ized by a late season peak that occurred in March or April 

 (Fig. 2). Predominant recruitment in New Jersey occurred 

 either early (1992-93), late (1989-90) or with peaks early 

 and late in the season (1990-91). 



Larval age and size 



Menhaden lai-vae entered both estuaries after development 

 in the ocean. Most larvae were >1 month old and > 17 mm 

 long and there were no recently hatched specimens. How- 

 ever, the age and size of larvae entering the two estuaries 

 differed within and between sites. The weekly mean age 

 of Atlantic menhaden larvae collected in North Carolina 

 increased linearly from early in the season to about the 

 end of March in each year (Fig. 4). The weekly mean age 

 over this period increased by a factor of 2-3x. In two years 

 (1990, 1993) the mean age declined after March to levels 

 approximating those early in the recruitment season. 

 Larvae collected in the North Carolina estuary during 

 peak recruitment were also the older (and larger) larvae. 

 In New Jersey, although there was a general increase in 

 larval age between October and December, there was no 

 late season decline in mean age as we observed for North 

 Carolina larvae. Larvae collected in New Jersey were gen- 

 erally younger than those collected in North Carolina for 

 each of the three years (Fig. 5). The overall mean age of 

 larvae collected in North Carolina for 1989-90, 1990-91, 

 and 1992-93 were 60.7, 58.6, and 69.3 d as compared to 

 54.3, 52.7, and 50.9 d for New Jersey, respectively. The size 

 of larvae showed seasonal trends similar to those for larval 

 ages in each of the years, i.e. larval length increased and 

 then decreased through time in North Carolina, whereas 

 in New Jersey it increased but did not decline (Fig. 6). 

 Larvae recruited in North Carolina were generally similar 

 in size but were on average larger (24.9, 25.4, and 25.8 mm) 

 than larvae recruited in New Jersey (22.2, 21.3, and 22.1 

 mm) in all three years (Figs. 6 and 7). 



Growth of larvae 



Larvae collected in North Carolina were generally older 

 and larger and grew faster than larvae in New Jersey (Fig. 

 8). Population growth curves were significantly different 

 between sampling locations in all years (Table 1). The pre- 

 dicted overall average growth rate from hatching to 65 d 

 for larvae recruited in North Carolina was similar among 

 years (0.35 mnVd for 1989-90, 0.36 mm/d for 1990-91, and 

 0.35 mm/d for 1992-93). Corresponding rates for larvae 

 recruited to New Jersey were 0.30 mm/d for 1989-90, 

 0.31mm/d for 1990-91, and 0.32 mm/d for 1992-93. 



Larval birthdates 



Back-calculated spawning dates varied between years in 

 both locations but were most variable in New Jersey (Fig. 

 2). In New Jersey in the 1989-90 season there were two 

 distinct groups of larvae. About 13'7f of the larvae were 

 spawned early (September-October), then none to the 

 middle of December, and the remaining larvae (87%) were 

 spawned thereafter to the end of March. Larvae captured 

 in North Carolina were spawned from the week ending 

 21 October 1989 continuously through the week ending 3 

 March 1990 and overlapped the later spawning dates for 

 New Jersey larvae. Larvae spawned in March recruited to 

 New Jersey but virtually none recruited to North Carolina. 



In the 1990-91 season, spawning dates of larvae collected 

 in New Jersey (7 months) totally overlapped those collected 

 in North Carolina (4 months) (Fig. 2). About 45% of the New 

 Jersey larvae were spawned early (through week ending 27 

 October 1990) and the balance was distributed over the last 

 five months with a mode in the week ending 23 February 

 1991. As in 1989-90, March-spawned larvae recruited to 

 New Jersey but not to North Carolina. The highest frequen- 

 cy of spawning dates of larvae caught in North Carolina 

 occurred from mid-January to the end of the season and 

 peaked during the week ending 26 January 1991. 



The spawning date distributions in 1992-93 were dif- 

 ferent from those in the previous two sampling seasons. 

 About 77% of the New Jersey larvae were spawned by 

 the end of October An additional 18'7( of the total larvae 

 entering the estuary were spawned in November to mid- 

 December and only about 5% of the total were spawned 

 in March-April. Larvae recruited to North Carolina had 

 been spawned from October to April but there was no dis- 

 tinct mode as observed in the other two years. Late season 

 spawning (March-April) contributed larvae to both New 

 Jersey (=5% of total) and North Carolina (=13% of total). In 

 both earlier years there were no April-spawned larvae and 

 March-spawned larvae were only found in New Jersey. 



Discussion 



Atlantic menhaden larvae recruited to the New Jersey 

 estuary probably originate from two sources: locally 

 (MAB) and from the SAB. Evidence of local spawning is 

 seen in the larvae recruited to the New Jersey estuary 

 from October through early December (Fig. 2). These 

 larvae probably originated from local (i.e. New Jersey) 

 spawning as adults begin their southward migration out 

 of the MAB area in about November of each year (Higham 

 and Nicholson, 1964). Schools of spawning-size adults 

 (200 mm-i-) are captured in the commercial fishery in the 

 fall and early winter as they riTove south along the coast 

 from Maryland to North Carolina (Smith-*). Spawning in 

 the SAB produces larvae, some of which are transported 

 northward and contribute recruits to New Jersey later in 



^ Smith, J. W. 1996. Personal commun. Center for Coastal 

 Fisheries and Habitat Research, National Ocean Service, 

 NOAA, 101 Pivers Island Rd., Beaufort, NC. 



