Figure 1.— Station locations in North and South Santee Rivers, S.C. 



supplying Lakes Marion and Moultrie. About 23 km from the 

 ocean, the Santee River bifurcates to form the North and South 

 Santee Rivers. 



The Santee system has been classified by Kjerfve and Greer 

 (1978) as a partially mixed estuary' with weak-to-moderate salinity 

 stratification and gravitational circulation. However, this 

 classification is variable due to tidal fluctuations as well as varia- 

 tions in saltwater intrusion and freshwater discharge (Cummings 

 1970"; Stephens et al. 1975; Kjerfve 1976; Nelson 1976; Burrell 

 1977; Calder et al. 1977). The South Santee River receives less 

 freshwater drainage, with the result that saltwater intrusion is 

 greater than in the North Santee River. 



The two distributaries differ somewhat with regard to ba- 

 thymetry since the North Santee River is slightly deeper than the 

 South Santee River. Substrate in both rivers is very similar, 

 being predominately coarse to fine-grained sand and shell of 

 oceanic origin at the mouths, and hard mud and sand mix in the 

 intermediate reaches of the estuary, replaced by fine-grained 

 sand of inland origin in the upper estuary (Calder et al. 1977). 



Dissolved oxygen values fluctuate seasonally, being usually 

 9-14 mg/liter in winter and >4 mg/liter in summer (Cummings 

 footnote 3; Nelson 1976; Mathews"). 



MATERIALS AND METHODS 



Data Collection 



We sampled eight stations which were located in the channel 

 at 1,4, 7, and 1 1 river miles from the mouths of the North and 



t. winnings, T. R. 1970. A reconnaissance of the Santee River estuary. South 

 Carolina. A report prepared by United Stales Geological Survey, Water 

 Resources Division, Columbia, S.C. 96 p. 



*T. Mathews, Assistant Marine Scientist, South Carolina Marine Resources 

 Research Institute, Charleston. SC 29412. pers. commun. December 1979. 



South Santee Rivers (Fig. 1). Hereafter, we will refer to these 

 stations as NS01, NS04, NS07, and NS11 in the North Santee 

 River and SS01, SS04, SS07, and SS11 in the South Santee 

 River. Stations were sampled monthly over a 2-yr period from 

 January 1975 through December 1976, with the following excep- 

 tions which were not included in our analysis: SS11 was not 

 sampled in 1975; NS1 1 was sampled with a 5 m (16 ft) trawl in 

 May and July 1975; and NS07 was not successfully trawled in 

 May 1975. 



All collections were made with a 6 m (12 ft) semiballoon otter 

 trawl with 8 m headrope, composed of 2.5 cm (1 in) stretch 

 mesh throughout. A complete description of the trawl is given 

 by Shealy et al. (1974). Twenty-minute tows were made against 

 floodtide during daylight hours at a speed of 1.3 m/s (2.5 kn), 

 which resulted in a coverage of 1.5 ± 0.4 km during a tow. 



Bottom-water samples were collected with 6 liter capacity Van 

 Dorn bottles 0.3 m above the bottom at each station prior to 

 trawling. Water temperature was read from stem thermometers 

 mounted within the Van Dorn bottles. Salinity was measured in 

 the laboratory with a Beckman RS7B induction salinometer. 

 Dissolved oxygen was determined by the Winkler-Carpenter 

 method (Strickland and Parsons 1968). Turbidity was deter- 

 mined with a Hach Model 2100A turbidimeter. Specimens were 

 either processed in the field or preserved in 10% Formalin and 

 returned to the laboratory for identification, measuring, and 

 weighing. All specimens were weighed to the nearest 0. 1 g and 

 counted. We also recorded measurements (total length for 

 fishes, carapace width for crabs, and total length for shrimps) 

 for all species numbering <50 specimens per tow. At stations 

 where the trawl caught larger numbers of organisms, we sub- 

 sampled the catch as follows: If >50 to <250 individuals were 

 collected, then a minimum of 50 randomly selected specimens 

 were measured; if >250 to <500 individuals were caught, then 



