Fishery Bulletin 91(1), 1993 



15 22 29 6 13 20 27 



10 17 24 31 



14 21 28 6 13 



Figure 5 



Percentage distribution of the number of larval spot Leiostomus xanthurus 

 of back-calculated birthweeks recruited to the Newport River estuary, No- 

 vember 1987 to May 1988. 



Age and length of birthweek cohorts Larvae from 

 the beginning and end of the spawning period reached 

 the estuary at younger mean ages than those from the 

 middle period (Fig. 3). Larvae from birthweek cohorts 

 were recruited to the estuary over periods ranging from 

 2 to 10 weeks, with an average of 7 weeks for the main 

 spawning period (Table 1). In all but four cohorts (25 

 October, 22 November, 6 December, and 3 January), at 

 least 50% of the larvae from the cohort reached the 

 estuary during a single week (Table 1 ). 



The SL of larvae reaching the estuary (Table 2) 

 follows a similar pattern to age. Except in one instance 

 (3 February), the first two and the last five cohorts to 

 reach the estuary had a mean SL <13.9mm. In the 

 middle period, the weekly mean SL of larvae was gen- 

 erally larger. The difference between the smallest and 

 largest mean SL of larvae of any one birthweek cohort 

 throughout the recruitment period varied from 0.3 to 

 11.7 mm. This was generally related to the total time 

 during which a cohort recruited to the estuary. 



Abundance of birthweek cohorts Several birthweek 

 cohorts contributed substantially to more than one of 

 the recruitment peaks. Three cohorts (13, 20, 27 De- 

 cember) contributed at least 50% of their respective 

 total recruits to the large influx of larvae that occurred 

 on 23 March (Table 1). The high densities of larvae 

 (Fig. 2, Table 1) captured on 10 and 24 February, 23 

 March, and 13 April were collections to which some 

 birthweek cohorts contributed >50% of their total re- 

 cruitment (e.g., 1 and 8 November cohorts to catch of 

 13 April ). 



Oceanic abundance and age/size 

 distribution of larvae 



Abundance of larvae The highest densi- 

 ties of spot larvae collected offshore during 

 January and February generally occurred 

 in waters >30m (Fig. 6). Densities there 

 ranged from 24 to 68 larvae/100 m ', but di- 

 minished toward the coast and further off- 

 shore toward the shelf break. In areas 

 within 40 km of the coast at depths <30m, 

 densities were <5 larvae/100 m ! . Except for 

 two larvae collected off Beaufort Inlet in 

 January (Fig. 6A), no larvae were collected 

 within 10 km of the coast. Larval densities 

 in the estuary at Pivers Island were always 

 higher than at any oceanic station <30m 

 deep within 40 km of the coast. 



Spot larvae were collected at two of seven 

 stations sampled east and north of Onslow 

 Bay during January (Fig. 6A). In February, 

 spot larvae were collected at all but one of 

 these stations (Fig. 6B). Densities were rela- 

 tively low except at the station nearest Onslow Bay. 



Age and length distribution of larvae Ages of 351 

 spot larvae caught during oceanic sampling ranged 

 from 9 to 69 d. Youngest larvae occurred farthest off- 

 shore, over the outer continental shelf and within the 

 Gulf Stream (Fig. 7A,B). Age of larvae varied inversely 

 with distance from shore along the Beaufort Inlet 

 transect in January and February and the Oregon In- 

 let transect in February (Table 3, Fig. 7A,B). The mean 

 age of larvae in Onslow Bay during February seems to 

 increase toward shore from a dispersion center on the 

 outer continental shelf south of Beaufort Inlet. Older 

 larvae radiate to the north and west in Onslow Bay 

 (Fig. 7B). Larvae in the transect across the continen- 

 tal shelf off Oregon Inlet (Fig. 7B) may have a general 

 spawning area in common with larvae collected in 

 Onslow Bay. 



The length of larvae also varied inversely with dis- 

 tance from shore (Table 3, Fig. 7C,D). Smallest larvae 

 were found on the outer continental shelf and over the 

 continental shelf break. The mean size of larvae was 

 3.4mmSL (range 2. 1-10. lmm) in January and 

 6.2mmSL (range 2.5-12.7 mm) in February. 



Spawning time Spot larvae collected off North Caro- 

 lina were spawned over the period 8 November to 17 

 January (Fig. 8). As many as six cohorts were found in 

 any one sample and the overall mean number of co- 

 horts per sample was three. In 19 of 33 stations, >50% 

 of the larvae were from one cohort, and in six stations 

 >50% were from two consecutive cohorts. The remain- 



