Miller et a!.: Distribution, abundance, and growth o\ Micropogonias undulatus 



111 



enter nursery areas during the spring and sum- 

 mer This second cohort (between 10 and 45 mm) 

 was observed in June 1998 and 1999 during our 

 study and in May or August (20-30 mm) in the 

 York River of the Chesapeake Bay (Chao and Mu- 

 sick, 1977). Similarly, a second mode was usually 

 apparent from April through August during three 

 years in North Carolina creeks and bays (Ross, 

 1988), and in May in Georgia (Dahlberg, 1972). 

 In South Carolina, a second smaller cohort began 

 appearing in March and subsequently became the 

 dominant mode in June and July (Bearden, 1964). 

 In addition, the larger-size individuals that have 

 appeared during the fall months simultaneously 

 with the ingressing fall cohort during our study 

 and in the Chesapeake Bay (Haven, 1957; Chao 

 and Musick, 1977), may be individuals of this 

 late-arriving second cohort that did not enter the 

 Chesapeake and Delaware bays until fall. 



These late arrivals to nursery areas in the 

 Chesapeake and Delaware bays may be individu- 

 als that were spawned close to or south of Cape 

 Hatteras in late winter because there is no evi- 

 dence of spawning in late winter or spring north 

 of Cape Hatteras in the MAB. Atlantic croaker 

 larvae were caught only from August to Janu- 

 ary 1977-1987 over the continental shelf in the 

 MAB and while entering estuaries in central New 

 Jersey (Able and Fahay, 1998), or from November 

 to February in coastal Virginia (Cowan and Bird- 

 song, 1985). In contrast, just south of Cape Hat- 

 teras, larvae as small as 5.2 mm SL were present 

 in collections made from October through mid- 

 April within and offshore of the Newport River 

 estuary in North Carolina in both 1972-73 and 

 1973-74 (Lewis and Judy, 1983). Small larvae 

 also were collected in the same estuary from November 

 through mid-April in 1985-1986 (Warlen and Burke, 1990) 

 and 1991-92 (Hettler et al., 1997) and in the Cape Fear es- 

 tuary from mid-March to Mid-April in 1978 (Weinstein et 

 al., 1980). Together, these studies indicate that late winter 

 spawning occurs and suggests that it takes place south of 

 Cape Hatteras. Analysis of otolith microstructure of lai^val 

 and juvenile Atlantic croaker from the MAB indicates that 

 later spawned larvae and juveniles have slower growth 

 rates (Warlen, 1982; Nixon and Jones, 1997), which may 

 account for the much smaller size of the later-arriving 

 cohort when it enters the Chesapeake and Delaware bays 

 during the late spring and early summer. 



Ross (1988) suggested that there may be two groups of 

 Atlantic croaker that overlap and mix in North Carolina. 

 The first group, occurring from North Carolina southward 

 through the northern Gulf of Mexico, with a tendency to- 

 ward high mortality, lower longevity, early maturation, re- 

 sults from winter spawning (White and Chittenden, 1977; 

 Barger, 1985) and mostly spring recruitment to estuaries. 

 The second group ranges from North Carolina to about New 

 Jersey and may exhibit lower mortality, higher longevity, 

 greater size at age, late summer-fall spawning, mostly fall 

 recruitment, and greater size at maturity (Wallace, 1940; 



• Upper bay sites 

 ' ' Lower bay sites 



May Jun Jul Aug 



May Jun Jul Aug 



Date 



Figure 10 



Linear regressions and goodness-of-fit measures of the monthly 

 median total lengths of young-of-the-year Atlantic croaker (Micropo- 

 gonias undulatus) caught at the upper bay (open circles) and lower 

 bay (black circles) marsh sites and regions of Delaware Bay from 

 May to August in 1997 and 1998 (see Table 3). The coefficient of 

 determination is shown in the upper left for the upper bay regression 

 lines and in the lower right for the lower bay. There is no regression 

 for the lower bay because sample sizes in this region during June 

 and July of 1997 were too small. 



Morse, 1980; Barbieri et al., 1994a). However, the group 

 of larger, older Atlantic croaker observed by Ross (1988) 

 apparently has been absent in Chesapeake Bay in recent 

 years (Barbieri et al., 1994b). Lankford et al. (1999) did not 

 find statistically significant genetic differences between fall- 

 spawned YOY Atlantic croaker from north of Cape Hatteras 

 and spring-spawned YOY from south of Cape Hatteras, but 

 YOY from the Gulf of Mexico were genetically discrete from 

 those from the Atlantic coast. This lack of marked genetic 

 differences north and south of Cape Hatteras is not sur- 

 prising if there is southward migration of adults from the 

 MAB during winter as has been suggested (Haven, 1957). 

 Although, spawning and recruitment to nursery areas does 

 appear to occur later in the South Atlantic Bight (Bearden, 

 1964) and in the Gulf of Mexico (Pearson, 1929; Suttkus, 

 1955; Hansen, 1969), more research is needed to determine 

 if there are significant biological differences between adults 

 in these two areas and if the late arriving YOY in the north 

 originate from spawning at or south of Cape Hatteras. 



Habitat use 



Young-of-the-year Atlantic croaker in this study used the 

 entire range of marsh creek habitats, i.e. small intertidal 



