RESULTS 



Physicochemical Parameters 



Bottom-water temperatures were very similar among all sta- 

 tions with mean temperatures lowest but most variable in Feb- 

 ruary and warmest in July, August, and September. Yearly 

 average temperatures were lowest in 1976 and 1977 (Table 1). 



Salinities measured monthly were highly variable at all sta- 

 tions; nonetheless, average salinities were sufficiently different 

 between stations (Table 1) to justify classification of sites ac- 

 cording to the Venice system (Anonymous 1958). Station 

 C001 was classified as limnetic because salinity did not 

 exceed 0.5°/oo throughout the year it was sampled. Salinities at 

 stations C002 and C003 ranged from 0.4 to 18.0%o, and 

 these stations were characterized as limnetic-mesohaline. We 

 classified station C004 as limnetic-polyhaline based on the 

 salinity range of 0.67-26.2%o. Stations J001 (7.5-27.7°/oo) 

 and J003 (19. 4-33. 3°/ oo) had the highest salinities and were 

 classified as mesopolyhaline and polyeuhaline, respectively. 

 Average salinity varied also with season, being lowest in spring 

 and highest in fall (Table 1). 



Average dissolved oxygen concentrations were greatest at all 

 stations in January and February and lowest in summer. No 

 relation was apparent between dissolved oxygen concentra- 

 tions and station or depth. The lowest average concentration 

 measured in the Cooper River was 4.9 mg/ 1. 



Although we did not specifically determine sediment char- 

 acteristics for our fixed stations in the Cooper River-Charles- 

 ton Harbor system, Mathews and Shealy (1978) reported the 

 general bottom type to be as follows: C001 (hard-mud), C002 

 (sand), C003 (shell and sand), C004 (mud-shell-sand), J001 

 (mud and sand), and J003 (shell and mud). 



Table 1. — Average water temperatures and salinities in the Charles- 

 ton Harbor-Cooper River estuarine system, S.C., 1973-77. 









Environmental factors 







Avg. temp. 



Avg. salinity 



Parameters 







CO 



(°/oo) 



Year (all stations) 









1973 







22.1 



12.0 



1974 







20.2 



14.1 



1975 







21.1 



14.5 



1976 







19.9 



15.7 



1977 







19.8 



15.7 



Station (all 



years, 



1973-77) 







J003 







20.9 



27.6 



J001 







20.7 



19.2 



COM 







19.8 



12.6 



C003 







20.9 



5.4 



C002 







20.5 



1.8 



COM 







18.6 



0.07 



Season (all 



stations, 1973-77) 







Fall 







19.1 



15.6 



Winter 







11.7 



14.5 



Spring 







21.7 



13.7 



Summer 







28.4 



14.9 



Community Composition and Richness 



A total of 101 species of fishes was collected from the 

 Cooper River-Charleston Harbor system during the 1973-1977 

 sampling period (Table 2). Length, bottom salinity, and tem- 



perature ranges, along with relative abundance of all species 

 collected, are available upon request from the authors. Ten 

 species accounted for 90% of the total number and 7 1 % of the 

 total biomass of fishes collected in this estuarine system: Star 

 drum, Stellifer lanceolatus; bay anchovy, Anchoa mitchilli; 

 Atlantic croaker, Micropogonias undulatus; Atlantic 

 menhaden, Brevoortia tyrannus; spot, Leiostomus xanthurus; 

 blackcheek tonguefish, Symphurus plagiusa; silver perch, 

 Bairdiella chrysoura; weakfish, Cynoscion regalis; spotted 

 hake, Urophycis regia; and hogchoker, Trinectes maculatus. 

 Stellifer lanceolatus was the most abundant fish collected each 

 year of the study, except in 1977 when Brevoortia tyrannus 

 was most abundant. 



During the 5-yr sampling period, we collected 44 decapod 

 crustacean species (Table 3). Decapods dominated the fishes: 

 numerically but not in biomass. The numerical dominance was 

 due to large numbers of white shrimp, Penaeus setiferus, col- 

 lected in the Cooper River-Charleston Harbor system. This 

 species constituted 83% of the total number and 69% of the 

 total biomass of decapod crustaceans. Penaeus setiferus was 

 numerically dominant during each of the 5 yr of our study, 

 except in 1977 when P. aztecus was most abundant. These two 

 penaeid shrimps, together with seabob, Xiphopenaeus kroyeri, 

 and blue crab, Callinectes sapidus, composed about 96% by 

 number and 97% by weight of total decapod fauna collected 

 from the Cooper River-Charleston Harbor estuarine system. 



Average numbers of species collected were greatest in 1976 

 at the higher salinity stations C004, J003, and J001 (Table 4), 

 whereas species richness decreased along the transect of sta- 

 tions upriver. Mean numbers of individuals were greatest at 

 the higher salinity stations (C004, J003, J001). In addition, 

 more individuals were collected in 1975-76 than in 1973-74 and 

 1977 (Table 5). The fewest individuals were collected in 1977, 

 probably because of prolonged periods of extremely low water 

 temperatures during January and February 1977. 



Normal classification analysis showed that collections were 

 not distinctly grouped according to their location along the 

 salinity gradient. During all seasons, collections from stations 

 classified as limnetic and/or mesohaline were faunistically 

 least similar to those from high-salinity sites, but overlap oc- 

 curred in classification of collections in the mesopolyhaline 

 and polyeuhaline range. Because groups broadly overlapped 

 by stations and were not clearly separated by cluster analysis 

 according to salinity regimes within the estuary, we compared 

 collections from our fixed stations, rather than site groups as 

 determined from cluster analysis, with the species groups listed 

 in Table 6. In this way, seasonal comparisons among stations 

 were facilitated by direct cross-referencing against the species 

 assemblages at each station. 



During all seasons, collections from higher salinity stations 

 J003 and J001 were characterized by stenohaline marine 

 species. These included black sea bass, Centropristis striata; 

 searobins (Prionotus spp.); striped cusk-eel, Ophidion 

 marginatum; lady crab, Ovalipes ocellatus; seabob, 

 Xiphopenaeus kroyeri; swimming crabs (Portunus spp.); and 

 hermit crabs, Pagurus longicarpus and Clibanarius vittatus. 

 In fall, stenohaline marine species (Group B) displayed only 

 moderate to low constancy and fidelity for collections at 

 stations J003 and J001 (Fig. 2), while in winter, many of the 

 same species and other marine transient species were still 

 infrequently encountered but highly faithful to collections 

 from station J003 (Fig. 2). Stenohaline marine species, which 



