FISIIKRY BULLETIN: VOL, 77, NO, 2 



tems (where deposition is greatest), this result 

 may have been expected. 



Thus, both spatial and seasonal programming 

 seem to play an integral role in habitat partition- 

 ing among ocean-spawned recruits utilizing Cape 

 Fear estuary primary nurseries. Whether or not 

 this partitioning results in enhanced survival of 

 otherwise competing species remains an area for 

 fruitful research. 



Communit) (Composition 



Each marsh community in the Cape Fear es- 

 tuary displayed several unique characteristics. In 

 addition to seasonal differences in species rich- 

 ness, abundance relationships varied among 

 marsh complexes (Tables 5, 8 1. Although some 

 species appeared in relatively low numbers, they 

 only occurred in certain areas or were much more 

 abundant in a specific marsh complex. The Atlan- 

 tic croaker, southern flounder, mosquitofish, and 

 the seasonal capture of freshwater species includ- 

 ing white catfish, Ictaliirus caliis. bluegill, golden 

 shiner, Noti'iiiigonuti crysoleucas, and largemouth 

 bass, Microptcrus! salmoidcs. were associated with 

 low salinity sites ( Walden, Hechtie, and Barnards 

 Creeks). More abundant members of these com- 

 munities also seemed to display a preference for 

 lower salinities including t idewater sil verside and 

 Oyear class Atlantic manhaden (see also Table 9). 



Two groups apparently set the high salinity 

 marshes apart from other areas. Several species, 

 usually associated with estuaries during the early 

 part of their life cycle, were restricted mainly to 

 the polyhaline zone. Pigfish. white mullet, red 

 drum, and southern blue crab were in this cate- 

 gory and along w-ith two permanent marsh resi- 

 dents. Atlantic silverside and striped killifish 

 were much more abundant or were only captured 

 at high salinities. 



The predominance of sandy areas near Bald- 

 head Island, in combination with higher salinity, 

 attracted several species — e.g.. the windowpane. 

 rough silverside, spotted whiff, Cithanchthys 

 niacrops, inshore lizardfish, and bighead sea rob- 

 in, Prionotiis tnbulus — were in this group. 



The proximity of the Baldhead Island marsh to 

 the ocean entrance also provided suitable condi- 

 tions for invasion by several stenohaline species 

 not usually associated with estuaries. Many of 

 these species were seasonal visitors to the area 

 and their general rarely suggests that the marsh 

 is not a primary nui-sery habitat. Young sergeant 



354 



major, Abudcfduf xuxatilis; great barracuda, 

 Sphyraena barracuda: Atlantic spadefish. Chae- 

 todipti-rus faher: lookdown, St'lc/ic roiuer; lane 

 snapper. Liitjaniis syna^ns; gag. and others are 

 seldom collected in marshes and, in fact, would 

 probably be classified as reef species. McHugh 

 ( 1967) has described these species as adventitious 

 invaders of the estuary. 



The majority of community dominants captured 

 in this study were transient in the marshes, being 

 resident for only part of their life cycle. The only 

 permanent residents which were dominant mem- 

 bers of the marsh community were mummichog. 

 striped killifish, and Atlantic silversides. Thus, 

 energy flow at higher trophic levels is predomi- 

 nantly through those species that utilize the 

 marsh nurseries in the first year of life. Although 

 larger individuals of these species probably make 

 feeding forays into the upper tidal creeks, their 

 importance in these areas is not known. 



Not surprisingly then, species richness was 

 greatest in areas (Baldhead Island and upriver) 

 influenced by the marine and freshwater biotas. It 

 IS tempting to relate higher species diversity to 

 more stable physicochemical conditions existing 

 at these sites, yet as indicated in Table 1. salinity 

 and temperature variations were generally simi- 

 lar at all stations. A more plausible explanation of 

 these phenomena may lie in what has been de- 

 scribed as an "edge effect" (Odum 1971). Thus. 

 Baldhead Island forms a mixing zone for es- 

 tuarine. shelf, and reef faunas as evidenced by the 

 seasonal invasion of the latter forms. Similarly, 

 Barnards and Hechtie Creeks are influenced by 

 fresh and brackish faunas at various times of the 

 year. 



It is a remarkable observation that if all the 

 transient members of the shallow marsh commu- 

 nity were removed, that the remaining, perma- 

 nent estuarine residents would form a community 

 distinguished by the paucity of its members (Em- 

 ery and Stevenson 19.57L The importance of the 

 link, or continuum, between the estuary and the 

 nearshore marine environment and the energy 

 transfers therein, is highlighted by this observa- 

 tion. It seems obvious that the functional integrity 

 of the estuarine eco.system is as much dependent 

 on the marine fish community as the members of 

 that community are dependent on the estuary for 

 part of their life cycle. Continued productivity, 

 within the estuary and marine environment for 

 certain species important to man may indeed, de- 

 pend on the continued health of this relationship. 



