areas. Although spawning occurs over several 

 months for both species, the principal spawning 

 months are December- January for spot and October- 

 December for Atlantic croaker. Some Atlantic 

 croaker were collected each month until mid-April; 

 spot were caught through March. 



Preflexion larvae, indicative of recent spawning, 

 were present generally during the first half of each 

 season at many offshore stations and at a lesser num- 

 ber of inshore stations, but the size variation of larvae 

 between the two areas suggests that the primary 

 spawning area was offshore (Figs. 2, 3). The 1972-73 

 data show that small, recently hatched larvae were 

 more predominant offshore than inshore and that lar- 

 vae generally were progressively larger as they 

 moved into the estuary, as was also found by Warlen 

 (1982). Size increased with passage of time as the lar- 

 vae moved from the major offshore spawning area, 

 through the transitory inshore area, to the estuarine 

 nursery area. 



With some exceptions, larvae were more abundant 

 offshore than inshore. During the 1972-73 season, as 

 larvae moved to inshore waters, their numbers (avail- 

 able to our gear) usually showed a marked decline, 

 probably the result of natural mortality, predation, 

 and the ability to avoid capture because of their in- 

 creased mobility at a larger size. In the estuary, 

 availability again increased as numbers built up in a 

 much smaller area (Table 4). 



UJ 



< 



> 



DC 

 < 



ZONES 



FIGURE 2. — Mean length and relative abundance of spot larvae 

 collected October 1972-March 1973 in Onslow Bay and Newport 

 River estuary, N.C. Sampling stations are grouped according to 

 offshore distance and water depth: Zone 0, Newport River estuary; 

 zones 1-3, inshore to ocean; zones 4-6, offshore to ocean. The mean 

 length (mm) scale is 0- 1 for each month. Some plots extend into ad- 

 jacent months when a point exceeds 10 mm (i.e., the first point plot- 

 ted in February is 14 mm). 



o 



UJ 



< 



UJ 



5 



1973 

 JAN 



UJ 

 < 



> 



rr 

 < 



ZONES 



Figure 3. — Mean length and relative abundance of Atlantic croaker 

 larvae collected October 1972-March 197 3 in Onslow Bay and New- 

 port River estuary, N.C. Sampling stations are grouped according 

 to offshore distance and water depth: Zone 0, Newport River es- 

 tuary; zones 1-3, inshore to ocean; zones 4-6, offshore to ocean. 

 Some plots extend into adjacent months as in Figure 2. 



TABLE 4. — Estimated numbers and percentages of spot and 

 croaker larvae (adjusted by standard haul factor) collected in On- 

 slow Bay and Newport River estuary, N.C, October-April 1972-73 

 and 1973-74. 



Area 



1972-73 



1973-74 



We were unable to relate the mean length and rela- 

 tive abundance of spot and Atlantic croaker larvae to 

 different sampling areas for the 1973-74 season, to 

 the same degree as for the 1972-73 season, because 

 of the low availability of larvae. 



The conclusions derived from our Onslow Bay 

 study show a general offshore-to-inshore gradient for 

 spot and Atlantic croaker larvae. This gradient for 

 both mean numbers and size of larvae appears to be a 

 function of distance from shore and time of year. 



Generally, protracted spawning occurs offshore, 

 and larvae of these two species continue to grow as 



411 



