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Fishery Bulletin 100(3) 



major spawning grounds (Higham and Nicholson, 1964). 

 The larvae are recruited to estuaries in North Carolina 

 (Lewis and Mann, 1971; Warlen and Burke, 1990; Hettler 

 and Barker, 1993; Warlen, 1994). For the purposes of this 

 article, we define estuarine recruitment as the ingress or 

 immigration of larvae to the estuary from the ocean. 



A variety of field and laboratory observations suggest 

 that spawning is not likely to occur at the temperatures 

 found from late fall through spring in the MAB. Field 

 observations in Naragansett Bay, Rhode Island (GovoniM, 

 have indicated that peak densities of Atlantic menhaden 

 eggs are found at 18-20°C and very few eggs are found 

 at temperatures below 16°C. Kendall and Reintjes (1975) 

 found Atlantic menhaden eggs at only one of 92 stations 

 during one (9 November-14 December) of three late fall- 

 winter cruises in the MAB. A summary of the Marine 

 Monitoring Assessment and Prediction (MARMAP) col- 

 lections, for November-April of the 1979-87 surveys in 

 the MAB west of longitude 72°W from Montauk Point, 

 New York, to Cape Hatteras, North Carolina, showed late- 

 stage eggs in only 25 of 2247 plankton hauls (Berrien and 

 Sibunka, 1999). Except in one haul in January near Cape 

 Hatteras, all other Atlantic menhaden eggs found in this 

 MAB survey were collected in November. Atlantic menha- 

 den eggs were collected in Onslow Bay, North Carolina, 

 in December 1992 only at temperatures of 17-23. 5°C, and 

 most were found at about 22°C (Peters'-). During South 

 Atlantic recruitment experiment studies (SABRE), eggs 

 were found between the Gulf Stream and mid-shelf fronts 

 (17-23°C) in Onslow Bay (Checkley et al., 1999). Reduced 

 temperatures (14.8-15.7°C) appeared to diminish the abil- 

 ity to induce spawning of Atlantic menhaden in the labora- 

 tory (Fitzhugh and Hettler, 1995) as compared to tempera- 

 tures >17°C. Even if spawning can occur at temperatures 

 <15°C, there must be successful hatching and larval 

 development to ensure larval survival. At 16°C, early 

 larval growth in dry weight was about one-half that at 

 20°C (Powell, 1993). Therefore, we concluded that opti- 

 mum temperature for hatching and larval survival and 

 growth is probably >16°C. 



From the above findings, we concluded that late-fall to 

 early-spring water temperatures in the MAB are unsuit- 

 ably low for Atlantic menhaden spawning. Water tempera- 

 tures in the MAB to at least 300 km offshore are usually 

 7-14°C from mid-November through April (Benway et al., 

 1993a, 1993b). However, Atlantic menhaden larvae, prob- 

 ably spawned during that period, recruit to New Jersey es- 

 tuaries from winter to spring (Witting et al., 1999). These 

 two facts suggest a warmer water (i.e. southern) origin of 

 the wintertime larval Atlantic menhaden recruits in New 

 Jersey and prompted us to ask whether larval transport 

 from the SAB could explain this occurrence. To test this 

 hypothesis, we examined synoptic collections of larval At- 



' Govoni, J. J. 1996. Personal commun. Center for Coastal 

 Fisheries and Habitat Research, National Ocean Service, 

 NOAA, 101 Fivers Island Rd., Beaufort, NC 28516. 



^ Peters, D. S. 1996. Personal commun. Center for Coastal 

 Fisheries and Habitat Research. National Ocean Service, 

 NOAA, 101 Pivers Island Rd., Beaufort, NC 28516. 



lantic menhaden recruiting to estuaries in North Carolina 

 and in New Jersey from fall to spring. We determined the 

 duration of recruitment, age and size, relative abundance, 

 spawning season, and relative contribution of cohorts of 

 larvae spawned in a given calendar week to the estuarine 

 recruitment of Atlantic menhaden larvae to an estuary in 

 each area. These data were used to estimate the percent- 

 age of larval Atlantic menhaden collected in the New Jer- 

 sey estuary that may have originated in the SAB. 



Methods 



Larval occurrence and abundance 



Sampling for larval Atlantic menhaden was conducted in 

 North Carolina and New Jersey as these larvae recruited 

 to the estuaries from the Atlantic Ocean. In North Caro- 

 lina, larvae were collected at a station adjacent to Pivers 

 Island in the lower Newport River estuary about 2 km 

 inside Beaufort Inlet (Fig. 1). Nighttime sampling was 

 conducted weekly at mid-flood tide during the expected 

 recruitment period in three seasons (15 November 1989-2 

 May 1990, 14 November 1990-24 April 1991, and 19 

 November 1992-11 May 1993). Initial seasonal sampling 

 was based on previous years' collections (Lewis and Mann, 

 1971; Warlen, 1994) that showed that Atlantic menhaden 

 larval recruitment usually began no earlier than mid- 

 November. End-of-year sampling terminated when larval 

 density dropped to zero. Larvae were collected in four 

 consecutive sets of a 1x2 m neuston net with 947-pm 

 mesh fished (most sets 5-7 minutes long) just under the 

 surface from a bridge platform. A flow meter was attached 

 to the net to estimate the amount of water filtered. Details 

 of the sampling protocol are given in Warlen (1994). Ich- 

 thyoplankton samples were preserved in 95% ethanol and 

 diluted so that the final concentration was at least 70% 

 ethanol. Catches were standardized as the number of 

 larvae/100 m-^ of water filtered. The mean of the density 

 data for the four net sets on a given night was used as the 

 density estimate of Atlantic menhaden larvae recruiting 

 during the flood tide. 



In New Jersey, gear type and sampling effort were 

 similar in concept but differed in some details (Witting 

 et al., 1999). Ichthyoplankton were collected with a 1-m 

 diameter ( 1-mm mesh) plankton net fitted with a flow me- 

 ter The net was fished during nighttime flood tides from 

 a bridge spanning Little Sheepshead Creek about 3 km 

 upstream from the mouth that is approximately 2.5 km 

 inside Little Egg Inlet (Fig. 1). Water depth at this bridge 

 and the Pivers Island bridge was approximately 4 m. 

 Sampling was conducted over the same years as in North 

 Carolina, and sampling was conducted year round in New 

 Jersey. A mean larval density (number larvae/100 m-* wa- 

 ter fished) was calculated from all samples on each night 

 ( five surface and five bottom sets in 1989-90, three surface 

 and three bottom sets in 1990-91, three mid-water sets 

 in 1992-93) and was used to estimate Atlantic menhaden 

 larval recruitment during the flood tide. Each net set last- 

 ed 0.5 hour Current speeds were generally 25-50 cm/s. 



