FISHERY BULLETIN VOL 77. NO 2 



by Marshall (1976) supported this observation, 

 even higher densities for total nekton were noted 

 in the studies of Turner and Johnson (1974) in 

 South Carolina tidal marshes. However, Marshall 

 cautioned that the efficiency and selectivity of 

 gear used to study various estuarine areas may, in 

 part, be responsible for some of the differences 

 seen among areas. Average densities in my study 

 for the same species listed by Marshall all ex- 

 ceeded 0.1 organism/m^ except for brown shrimp. 

 When seine data alone were considered for this 

 species, however, densities of 0.1/m- were re- 

 corded. 



The utilization of the marsh shallows does not, 

 however, hold for all postlarvae that inhabit the 

 Cape Fear region. Atlantic croaker, for example, 

 occurred primarily in the deeper water of the river 

 from the vicinity of the salt boundary through the 

 mesohaline zone. As postlarvae, this species was 

 noticeably absent in the downstream marshes and 

 densities generally were low at upstream stations. 

 The Atlantic croaker was not listed among the 10 

 most abundant species captured in each of two 

 marsh areas near Beaufort, N.C., by Marshall 

 (1976), nor was it among the 10 most abundant 

 species collected in six tidal creeks located near 

 Port Royal Sound, S.C. (Turner and Johnson 

 1974). In my study, only one specimen of the 

 1976-77 year class was collected before May, when 

 juveniles (27-35 mm) appeared at low salinity sta- 

 tions. In the early stages of recruitment for the 

 1977-78 year class, however, low densities of post- 

 larval and early juvenile croaker (9-19 mm) were 

 collected, principally at Hechtic and Barnards 

 Creeks. Haven (1957) and Wallace (1940) ob- 

 served a similar distribution in the Chesapeake 

 Bay, and for most Atlantic and Gulf coast es- 

 tuaries containing deeper channels, this relation- 

 ship seems to hold (Welsh and Breder 1923; 

 Suttkus 1955; Nelson 1969). However, the Atlan- 

 tic croaker also utilizes the marsh shallows exten- 

 sively in some of the (iulf states, including 

 Louisiana, Texas, and Mississippi (Herke 1971; 

 Parker 1971; Arnoldietal. 1974; Yakupzack et al. 

 1977). In the Cape Fear region, where there are 

 extensive marshes, the Atlantic croaker is simply 

 absent. Perhaps minimum temperatures during 

 winter recruitment in the Cape Fear and other 

 middle Atlantic coast estuaries are limiting for 

 this species (Joseph 19721. Another species that 

 seems to prefer open waters is the Atlantic 

 menhaden, which was captured in lower numbers 

 in the interior marshes than on the river shoals 



352 



and in the ship channel (Hodson see footnote 6). 

 Since postlarvae feed primarily on zooplankton 

 (Thayer et al. 1974) which are found in higher 

 concentrations out in the estuary (Jefferies 1975). 

 this preference for open waters is not surprising. 



These observations lead to conjecture as to the 

 mechanisms that may reduce potential competi- 

 tion among the early life stages of species with 

 similar food requirements (Thayer et al. 1974; 

 Kjelson et al. 1975). The results of recent studies 

 (May 1974; Thayer et al. 1974; Lasker 1975; 

 Houde 1977; Laurence 1977) suggested that food 

 supplies are potentially limiting in estuaries and 

 nearshore areas and that critical densities of food 

 items were required at several larval developmen- 

 tal stages. If species were undergoing diffuse com- 

 petition (MacArthur 1972), they might, therefore, 

 benefit from behavioral patterns that resulted in 

 temporal and/or spatial segregation on the nur- 

 sery grounds. There are apparently two major 

 nursery areas in the Cape Fear estuary: the in- 

 terior marshes, including the shallow marsh 

 fringe, and the river mainstem at the head of the 

 estuary. Related or potentially competitive 

 species, by utilizing either one of these zones, may 

 remain spatially segregated. 



Seasonal presence also may enhance survival of 

 many species; the data showed this clearly for 

 white and striped mullet and for penaeid shrimp 

 although local variables within each major nur- 

 sery zone also influenced patterns of distribution 

 for these groups. For example, white and pink 

 shrimp were recruited at similar times of the year, 

 yet they separated within the marsh zones on the 

 basis of salinity. White mullet were much more 

 abundant at high salinities in areas with sedi- 

 ments containing considerable quantities of or- 

 ganic matter; striped mullet were distributed 

 throughout the estuary although they, too, were 

 most abundant where sediments contained a high 

 level of organics. 



Salinity preferences for several dominant spe- 

 cies are treated statistically in Table 9. Although 

 consistent relationships appeared in the data, I 

 monthly values reflected local variations in fresh- I 

 water flow. In September, for example, heavy rain- I 

 fall in the vicinity of Dutchman Creek depressed 

 salinities 16"iiii below the previous collection date. 

 The resident population of white mullet appar- I 

 ently remained in the area and catches were high 

 (1,112 individuals 400 m'-^ at the rotenone sitei. 

 Along with lower catches for this species 

 elsewhere in the system, this observation suggests 



