the 10-day pre-collection period was 

 21.6 cm recorded in June 1973 (Fig- 

 ure 2). Lower peaks of 13.2 and 

 19.3 cm were recorded in September 

 and October 1972, respectively. In 

 June 1974, 6.1 cm of rain occurred 

 and in September 1974, 8.1 cm of 

 rain were recorded. 



Salinity ranges and means for 

 each station were: Station 38-2, 0.2- 

 31.6 ppt, x= 12.8 ppt; Station 

 200-2, 0.2-35.2 ppt, x = 24_^4 ppt; 

 Station 44-2, 0.0-18.3 ppt, x = 7.7 

 ppt; Station 54.3, 0.1-17.1 ppt, X = 

 7.9 ppt. Salinity was negatively 

 correlated with local rainfall at 

 Stations 38-2, 200-2, 44-2, and 54-3 

 (r = -0.45, -0.73, -0.53, and -0.51, 

 respectively, p£ 0.01). 



Streamflow and salinity patterns 

 for Stations 38-2 and 200-2 are given 

 in Figure 3. Streamflow for the Nue- 

 ces River (Station 38-2) had its 

 first major increase in June 1973 to 

 23,960 cfs (670.9 m /sec), followed 

 by a decrease to 6,007 cfs (168.2m / 

 sec) in July and 4,596 cfs (128.7 

 m /sec) in September. The highest 

 inflow for Station 38.2 was 99,930 

 cfs (2798.0 m /sec) which occurred 

 in October 1973. The salinity de- 

 creased to 3.6 ppt in June 1973 and 

 reached a low of 0.4 ppt in October 

 and November 1973. Although the in- 

 flow decreased to 2,868 cfs (80.3 

 m /sec) in December 1973 the salin- 

 ity was still low at 1.3 ppt. An- 

 other influx of fresh water was re- 

 corded on the Nueces River in August 

 and September 1974 (28,471 cfs 

 (^97.2 ni /sec) and 64,210 cfs (1797.9 

 m /sec), respectively. For August 

 1974 salinity decreased to 0.4 ppt 

 and in September 1974 salinity was 

 0.2 ppt. Streamflow had a negative 

 correlation with salinity for Station 

 38-2 (r = -0.47, p < 0.005). 



In June 1973 the inflow for Oso 

 Creek (Station 2QO-2) increased to 

 2,944 cfs (82.4 m /sec) with a cor- 

 responding decrease in salinity to 

 8.2 ppt. (Figure 3). Streamflow 

 dropped in July and August to 134 cfs 

 (3.8 m /sec) and 92 cfs (2.6 m /sec) , 

 respectively, and salinity increased 

 to 23.3 ppt and 24.2 ppt, respec- 

 tively. Major inflows of 5,511 cfs 

 (154.3 m /sec) with corresponding sa- 

 linities of 0.2 ppt and 3.6 ppt, oc- 

 curred in September and October 1973. 

 Although flow increased in June and 

 September 1974 to 905 cfs (25.3 

 m /sec) and 304 cfs (8.3 m /sec), 

 respectively, no decrease in salinity 

 was measured. Streamflow was nega- 

 tively correlated with salinity at 

 Station 200-2 (r = -0.77, p 10.005). 



The Aransas River-Chiltipin 

 Creek drainage (Station 44-2) and 

 the Mission River (Station 54.3) had 

 inflow and salinity patterns similar 

 to each other (Figure 4) . Major 

 streamflow increases occurred from 

 June through October 1973, in May 

 and June 1974, and in September 1974. 

 Both Station 44-2 (r = -0.50, 

 p £0.005) and Station 54.3 (r = 

 -0.49, p £0.005) had negative corre- 

 lations between streamflow and sali- 

 nity. 



To determine effects of fresh- 

 water inflow on zooplankton popula- 

 tions, species were first catego- 

 rized to be estuarine or freshwater 

 species. A list of the dominant zoo- 

 plankton is given in Table 1. Those 

 species with an asterisk are con- 

 sidered to be freshwater organisms. 



The effect of streamflow on 

 standing crops (total number of in- 

 dividuals/m ) of estuarine and fresh- 

 water zooplankton at Station 38-2 is 

 shown in Figure 5. Standing crops of 



457 



