Barbieri et al.: Maturity, spawning, and ovarian cycle of Micropogonias undulatus 



675 



(Fig. 3). However, the capture of developing females 

 (stage 2) from May through August and regressing 

 females (stage 6) from September through Decem- 

 ber indicates that spawning initiation and cessation 

 were not synchronous among individuals. Although 

 the population spawned over a six-month interval 

 (July-December), individuals apparently spawned 

 over a shorter period. Most females appeared to 

 spawn for 3^1 months as indicated by the large per- 

 centages of fully developed (stage 3) ovaries from 

 August through November. 



The pattern of gonad development in males pro- 

 vided further evidence of an extended spawning sea- 

 son for Atlantic croaker. Mean and maximum GSI 

 values increased sharply during July and August, 

 and remained relatively high until November or De- 

 cember, depending on the year (Fig. 4). In addition, 

 males with very large testes and free-running milt 

 were common during August-September in collec- 

 tions from all locations and sampling gears, indicat- 

 ing intense male spawning during this period. 



Spawning of Atlantic croaker occurred in the estu- 

 ary as well as in coastal oceanic waters. Females with 

 hydra ted oocytes (gonad stages 4 and 5), indicative 

 of imminent spawning, were collected in the lower 

 York and James rivers {n=8 in 1990; n=3 in 1991; 

 Fig. 3) and from coastal waters off Virginia and North 

 Carolina (rc = l in 1990; n=3 in 1991; Fig. 3). Collec- 

 tions of spawning fish (gonad stages 3-5) in Chesa- 

 peake Bay during the period July-October («=649 

 in 1990; n=277 in 1991; Fig. 3) and from offshore 

 waters during November-December in=39 in 1990; 

 n=ll in 1991; Fig. 3) suggest spawning continues 

 offshore and south as Atlantic croaker migrate from 

 the estuary. However, the presence during Septem- 

 ber-October of regressing and resting females in 

 Chesapeake Bay (n=39 in 1990; «=24 in 1991; Fig. 

 3 ) indicates that some individuals may complete their 

 spawning in estuarine waters. 



Although gravid and running-ripe females were 

 collected during most of the spawning season (Au- 

 gust-November, Fig. 3), they were present in very 

 low numbers. During both years of sampling only 

 seven gravid and eight running-ripe females were 

 collected. In Chesapeake Bay, despite the large num- 

 ber of poundnet and haul-seine collections (1,422 

 mature females processed), gravid or running-ripe 

 females were obtained only from gill nets and mainly 

 from collections from the lower James River (six 

 gravid and four running-ripe females). Daily gillnet 

 collections in the lower York River during August- 

 October 1990 and July-October 1991 (456 mature 

 females processed) showed only one running- ripe and 

 one partially spent female, i.e. a fully developed fe- 

 male that had fresh left-over hydrated oocytes in the 



I 



1 



2 3 4 5 6 7 



Feb 



2 3 4 5 8 7 



2 3 4 5 8 7 



n 



I 



Aug 



2 3 4 5 8 7 



I 



Sep 



2 3 4 5 6 7 



Apr 



2 3 4 5 



L 



2 3 4 5 6 7 



May 



Ju 



2 3 4 5 6 7 



LJ 



2 3 4 5 6 7 



2 3 4 5 6 7 



I 



It 



u 



234567 234567 



Gonad stage 



Figure 3 



Percentage of gonad maturity stages by month 

 for mature female Atlantic croaker, Micro- 

 pogonias undulatus, in the Chesapeake Bay 

 and adjacent coastal waters. Black bars=1990 

 data; open bars=1991 data. Gonad stages are 

 (2) developing; (3) fully developed; (4) gravid; 

 (5) running-ripe; (6) regressing; and (7) rest- 

 ing. Monthly sample sizes are presented in 

 Table 2. Samples from April to October are 

 from Chesapeake Bay; samples from Novem- 

 ber to March are from coastal waters off Vir- 

 ginia and North Carolina. 



ovarian lumen indicating recent spawning but that 

 still had a large number of advanced yolked oocytes 

 and could potentially spawn again. Offshore collec- 

 tions during November-December of 1990 and 1991 



