occur at stations upriver from NS04. Members of group F were 

 not found downestuary of station NS07. 



In the South Santee River, species in group G were considered 

 to be ubiquitous over all sites. The constancy of these species 

 ranged from high at stations SS04 and SS07 to moderate at SS01 

 and SSI 1; however, species in this group were not restricted to 

 any station location. Groups A, C, and D included species 

 which were associated with higher salinity areas in proximity to 

 the river mouth. Stenohaline marine species in these groups in- 

 cluded sheepshead, Archosargus probatocephalus; black sea 

 bass, Centropristis striata, butterfish, Peprilus triacanthus; and 

 Atlantic bumper, Chloroscombrus chrysurus. Group B species 

 were not consistently collected at any station location and 

 displayed low fidelity to stations SS04 and SS11. These species 

 are generally considered to be marine in origin and their penetra- 

 tion as far as SS11 is unusual. Species which were associated 

 with higher and intermediate salinities constituted group E. 

 These were found at all stations except SSI 1, but were not con- 

 sistently collected at any site. Group F contained the stenohaline 

 freshwater species, Ictaturus punctatus and /. furcatus, and the 

 anadromous species, blueback herring, Alosa aestivalis, which 

 were restricted to station SS11. 



Based on results of the two-way coincidence table (Fig. 3), it 

 was possible to distinguish four assemblages of fishes and 

 decapod Crustacea in both the North and South Santee Rivers. 

 The first assemblage consisted of euryhaline species which oc- 

 curred throughout both rivers and included the fishes Anchoa 

 mitchilli; Brevoortia tyrannus; Trinectes maculatus; 

 Micropogonias undulatus; Leiostomus xanthurus; Bairdiella 

 chrysoura; southern flounder, Paralichthys lethostigma; and /. 

 catus; and the decapods Penaeus setiferus, Caliinectes sapidus, 

 and Palaemonetes vulgaris, grass shrimp. Coastal marine 

 species, which may penetrate into the estuary for short periods 

 of time, constituted the second assemblage. Species in this 

 category included the fishes Centropristis striata; skilletfish, 

 Gobiesox strumosus; feather blenny, Hypsoblennius hentzi; 

 southern kingfish, Menticirrhus americanus; and pinfish, 

 Lagodon rhombiodes — and the decapods pink shrimp, Penaeus 

 duorarum, and humpback shrimp, Trachypenaeus constrictus. 

 The third assemblage consisted of species which can tolerate a 

 range of intermediate to low salinities. Rhithropanopeus har- 

 risii, mud crab, which occurs in both the North and South 

 Santee Rivers, was distributed in this manner. The fourth 

 assemblage was composed of the stenohaline freshwater species 

 Ictalurus punctatus, I. furcatus, and the anadromous species, 

 Alosa aestivalis. 



Although the formation of these categories is based on 

 distributional patterns formed from an actual collection of the 

 organisms, it remains an artificial attempt at forcing species into 

 designated groups based on their general affinities within the 

 estuary. Therefore, it is possible and certainly probable that 

 species will encounter others outside their group and may even 

 form peripheral associations. This is especially true of the 

 euryhaline species which are capable of widespread penetration 

 of the estuarine environment. 



Temporal and Spatial Distributions — Fishes 



Temporal and spatial distributions for four abundant species 

 of fishes — Micropogonias undulatus, Anchoa mitchilli, Ic- 

 talurus catus, Bairdiella chrysoura, and Trinectes maculatus — 

 are compared in Figures 4-6. A summary table of the distribu- 



tion and lengths for all species collected is available from the 

 authors. 



Micropogonias undulatus, Atlantic croaker. — The Atlantic 

 croaker was found throughout both rivers, although its presence 

 at stations varied over the 2-yr sampling period (Fig. 4A). In the 

 North Santee River, number and biomass of the Atlantic 

 croaker were greatest during spring 1976 at NS07. This is in 

 marked contrast to spring 1975 when none were collected at this 

 station or at NS11 further upriver. The absence of croaker at 

 these stations in 1975 may be attributed to the significant altera- 

 tion of physicochemical properties by the freshet in spring 1975. 

 A similar decrease in abundance was not noted in the South 

 Santee River, but failure to occupy SSI 1 during 1975 precludes a 

 true assessment of freshet effects far upriver. The apparent 

 absence of Atlantic croaker at upriver stations in the North 

 Santee River during fall 1976 cannot be readily attributed to any 

 hydrographic parameter but may reflect a lag in recruitment of 

 young fish during this period. 



Length-frequency distributions (not shown) indicated that 

 sizes of most Atlantic croaker available to our bottom trawls 

 were < 10 cm in both rivers during all seasons. The 

 predominance of smaller fish accounts for the low biomass 

 observed for Atlantic croaker. Young fish, 4-16 cm, were 

 prevalent in both rivers during fall and winter. A few larger fish 

 which ranged from 12 to 26 cm were also present, but their num- 

 bers were low, which could reflect gear avoidance, movement 

 away from the channel, or emigration from the estuary. Size of 

 young Atlantic croaker had increased to a mode of 8-9 cm by 

 summer and abundance had increased. Others (Haven 1957; 

 Hansen 1969; Hoese 1973; Shealy et al. 1974; Chao and Mu- 

 sick 1977) have noted that small Atlantic croakers are pres- 

 ent in different estuarine systems along the east coast through- 

 out much of the year. The abundance of young fish in the 

 Santee system is probably related to the long spawning season of 

 the Atlantic croaker (Chao and Musick 1977), which may be 

 more protracted in South Carolina waters than in temperate 

 northern estuaries, although our choice of sampling gear, biased 

 toward capture of smaller fish, is undoubtedly also a factor. 



Anchoa mitchilli, the bay anchovy. — Anchoa mitchilli was 

 found at all stations in both the North and South Santee Rivers 

 sometime during the 2-yr sampling period, but catches were 

 generally greater in the South Santee River (Fig. 4). Abundance 

 of A. mitchilli appeared to be lowest at low-salinity stations 

 located further upriver in both rivers. This decreased abundance 

 was especially noticeable in spring and summer. During these 

 seasons, bay anchovy were found at more seaward stations 

 within the estuary. This distributional pattern is similar to that 

 observed in the Edisto and Cooper Rivers, S.C. (Shealy et al. 

 1974), and York River, Va. (Markle 1976). 



Length-frequency distributions for A. mitchilli were strongly 

 bimodal with smaller (20-35 mm) and larger (50-75 mm) fish 

 cooccurring during most seasons (not shown). These data do 

 not indicate an influx of small fish into the population during a 

 particular season, such as summer (Hoese 1973; Shealy et al. 

 1974), but suggest that small fish are present in the Santee 

 system throughout the year. Multiple spawns (Hoese 1965) or a 

 protracted spawning season (Hildebrand and Cable 1930) best 

 explain the bimodality of frequencies observed for bay anchovy 

 in the Santee system. Similar findings were noted by Hoese 

 (1965), who believed that A. mitchilli spawns during all seasons 

 in Texas and probably is short-lived. In addition, Mansueti and 



