WEINSTEIN SHALLOW MARSH HABITATS AS PRLMARY NURSERIES 



more distinct seasonal presence in the Cape Fear 

 estuary, with young arriving in May and emigrat- 

 ing nearly completely from the estuary in late fall. 

 The more southerly distribution of this species 

 (Anderson 1957; Moore 1974; Richards and Cas- 

 tagna 19761, perhaps related to temperature tol- 

 erance, may be responsible for this pattern. 



Other winter-spawned species also were com- 

 mon in the Cape Fear. Flounders of the genus 

 Paralichthyf! were most abundant in March and 

 April when postlarvae first entered the marshes 

 (Figure 3. upper right). Brevnortia tyrannus 

 reached peak densities in April and May and were 

 fairly abundant throughout summer and early 

 fall, then they generally migrated out of the shal- 

 lows in October when temperatures decreased 

 markedly. The pooled data for the Atlantic men- 

 haden, however, do not indicate the large monthly 

 variation observed for catches of this species. In a 

 given creek, densities varied over more than an 

 order of magnitude between months, and peaks of 

 abundance were not coincident among marshes. 

 The only consistent pattern e.xhibited by the At- 

 lantic menhaden was their generally greater as- 

 sociation as postlarvae and early juveniles with 

 intermediate to lower salinities. Except for their 

 brief stay in brackish-water marshes as juveniles, 

 Atlantic menhaden did not seem to establish 

 long-term residency in any area, but instead 

 tended to range throughout the lower salinity por- 

 tions of the estuary, especially the river 

 mainstem. Their mode of feeding may have con- 

 tributed to this phenomenon (June and Chamber- 

 lain 1959; Jefferies 1975; Durbin and Durbin 

 1975). 



All three species of commercial shrimps (Figure 

 3, lower right) exhibited distinct seasonal pres- 

 ence: Penaeus aztecus was recruited to the marsh- 

 es as early as May, and white, P. setiferiis, and 

 pink, P. duorarum. shrimp were first captured in 

 July. For all three species, peak densities were 

 recorded during the month of first appearances, 

 and young adults emigrated from the shallow- 

 marshes during the fall, especially after October. 

 Callinectes sapid us (Figure 3, lower right) gener- 

 ally were abundant in all months, with a peak of 

 recruitment in November and December. Appar- 

 ently, the absence of early juveniles in January 

 and February 1977 catches reflected heavy mor- 

 tality or emigi'ation due to the extreme cold in 

 these months. 



Length-frequency data for abundant year 

 class fishes and brown shrimp indicated that most 



of these species resided in tidal creeks at relatively 

 small sizes and grew rapidly after April (Table 6). 

 The smaller increments of gi-owth occurring prior 

 to this month for winter-spawned species resulted 

 from the effects of low temperatures and the mask- 

 ing effect of continued recruitment through 

 March. Extended recruitment periods created a 

 similar "lag" in gi'owth for species spawned in 

 other sea.sons. 



Standing Crops at Peak Recruitment 



Patterns of distribution for selected species at 

 the peak of postlarval recruitment are shown in 

 Table 7; in all cases, more than 1 mo was averaged 

 since a plateau was indicated in the data. Catches 

 generally were lower at Baldhead Island stations 

 (including Shellbed Island) for most dominant 

 fishes, suggesting the inability of these marshes to 

 support as much juvenile production per unit area 

 as other Cape Fear marshes or perhaps indicating 

 greater predation pressure in this area. Leiosto- 

 mits xanthiiriis was relatively evenly distributed 

 although catches of this species and those oiMugU 

 cephalus and M. cureina were lower at Baldhead 

 Island; M. ciirema also was captured in reduced 

 numbers at low salinity sites. In addition, both 

 species of mullet were collected where the sub- 

 strate contained high levels of organic matter. 



Atlantic menhaden postlarvae and early juve- 

 niles ( 17-32 mm) predominated upriver at brack- 

 ish salinities and also were abundant in Walden 

 and Dutchman Creeks. Although salinity was rel- 

 atively low in Dutchman Creek in April (11.5 and 

 V2.6X,i at the rotenone and seine sites, respec- 

 tively) the high catch of menhaden in May at the 

 seine site (742 individuals/400 m^) occurred at a 

 time when salinity (35"/(mi) was at a yearly 

 maximum. Interestingly, the majority of these fish 

 were of a different age-class (probably yearlings, 

 50-109 mm) than were the postlarvae and early 

 juveniles that predominated in the April and May 

 collections at other stations. These individuals 

 may have already completed their early develop- 

 mental period in brackish waters (June and 

 Chamberlain 1959) and were moving freely 

 throughout the Cape Fear estuai'y. They also ap- 

 parently made forays into the Walden Creek sys- 

 tem, and in other months contributed to the patch- 

 iness at all stations described previously. 



Penaeid shrimp were an important component 

 of the marsh nekton community during the late 

 spring and summer months. Maximum densities 



347 



