Fishery Bulletin 91(1). 1993 



the percentage age composition and den- 

 sity of larvae. 



The seasonal differences in age and size 

 of larvae at estuarine recruitment (Fig. 

 3) suggest that spawning may have been 

 nearer the coast at the beginning and 



end of the spawning season. As adult spot emigrate 

 from the estuary to offshore waters in fall, at a time of 

 decreasing photoperiod and water temperature (Mer- 

 cer 1989), they probably seek suitable water tempera- 

 tures for spawning ( 17.5-25°C) (Hettler & Powell 1981). 

 This temperature range is present over much of the 

 North Carolina continental shelf water (Stefansson et 

 al. 1971) in the early months of spawning. During later 

 spawning (mid-December to February), nearshore wa- 

 ters are cooler and well mixed and water above 17.5°C 

 is generally restricted to areas on the outer continen- 

 tal shelf (Stefansson et al. 1971, Atkinson 1985). Also, 

 in winter the extent of this potential spawning area 

 may be influenced by the Gulf Stream and its occa- 

 sional wave-like perturbations (cyclonic meanders and 

 filaments) along its western edge which can intrude 

 onto the continental shelf. It is known that average surface-water 

 temperatures on the outer continental shelf are moderated by the 

 Gulf Stream (Atkinson 1985). The winter (January and February) 

 distribution patterns of age and size of spot larvae in Onslow Bay, 

 with the youngest, smallest larvae occurring only furthest offshore, 

 support the idea that spawning may occur some 90 km offshore. 

 Spawning that occurs further offshore as the spawning season 

 progresses has been suggested for spot (Lewis & Judy 1983, Warlen 

 & Chester 1985) and Atlantic croaker Micropogonias undulatus 

 (Warlen 1982). Norcross & Austin (1988) also suggested that the 

 area of warm water encountered upon migration of Atlantic croaker 

 from Chesapeake Bay onto the continental shelf determines spawn- 

 ing location. 



Differences in age at estuarine recruitment may also be due to 

 differences in transport rate that result from the degree to which 

 favorable currents facilitate more rapid transport of larvae toward 

 shore. Different transport rates and spawning distances from shore 

 could also act in concert to produce the observed differences in age 

 and size at recruitment. Although some of the physical processes 

 that could affect larval transport have been discussed (Checkley et 

 al. 1988, Miller 1988, Pietrafesa & Janowitz 1988), precise larval- 

 fish transport mechanisms still remain unknown. 



The higher abundance of spot larvae in water deeper than 30 m 

 may be a function of spawning location and subsequent larval trans- 

 port toward shore. The reduced abundance observed inshore of the 

 30 m isobath may reflect fewer numbers of larvae present or their 

 reduced vulnerability to capture by bongo nets. Mortality will also 

 reduce larval abundance over time. Kjelson et al. (1976) and Miller 

 et al. (1984) suggest that spot larvae offshore are more pelagic but 

 that inshore they are more benthic-oriented. Spot larvae caught 

 from shore to the 30 m isobath were 40-61 d old and 8.2-12.1 mm SL, 

 and correspond to the early stages of the transformation period 

 (Govoni 1980 and 1987, Powell & Gordy 1980) when spot begin to be 

 more benthic. 



Larval spot are recruited from offshore spawning areas to estuar- 

 ies bordering Onslow Bay. Fish of the same ages also are found 

 along the offshore to onshore Oregon Inlet transect (Figs. 6,7). This 

 data and the fact that larval spot were found in and near the Gulf 



