TABLE 2. — Movement patterns of individual tagged striped bass during spring 

 1980 in the Savannah River, Ga., as compared with a pretide gate study 

 (Dudley et al. 1977). Fish observed more than once in a given section on a given 

 day are counted as one observation. 



'This river section was not used in calculating totals or percents since it was not used in the pre- 

 tide gate study. 

 2 These fish exhibited unusual movement patterns which may have been caused by tagging. 



remained in river segment H from 22 April until 9 

 May. These fish continued to move about in that seg- 

 ment and later left. Only one other fish in our earlier 

 study (Dudley et al. 1977) entered that area. 



Eighty-seven percent of our observations of striped 

 bass were in river segments A and D during the 1 980 

 spawning season. None were found in segment B, 

 although in our previous study (Dudley et al. 1977) 

 32% of our observations of fish were in that segment. 

 The distribution of our observations among river 

 segments in 1980 differed significantly (P = 0.005) 

 from that found in 1973, 1974, and 1975 (Dudley et 

 al. 1977). The difference is due to the increased use 

 by 1980 of segment D by striped bass, and a de- 

 creased use of segment B. In 1 980, with the tide gate in 

 operation, striped bass were more likely to be found 

 further upstream in Back River. 



Five striped bass (Fl, F3, F4, F5, F6) tagged 

 priortothe startofthe 1980 spawning season gave an 

 indication of the first arrival of the fish on the spawn- 

 ing grounds. Although gill nets set in upper Back 

 River captured some smaller striped bass as early as 

 mid-February, our tagged fish did not enter upper 

 Back River until late March. Four of our five fish first 

 entered this area between 21 March and 14 April 

 when the river temperature was between 17° and 

 18°C. The other fish (F6) did not enter this area until 

 22 April after residing in segments C and G. 



Each of the 12 tagged fish (all except fish F2) left the 

 spawning area between 11 April and 9 May. The 

 mean date of departure was 26 April (± 1 d), similar 



to the mean date of departure (25 April ±5 d) found 

 in our earlier work. As expected, the fish moved up- 

 stream after spawning. Four of the six striped bass 

 carrying radio transmitters were subsequently found 

 as far upstream as km 301, even though only one in- 

 complete search of the river was made in late May 

 (Table 1). 



Discussion 



The Savannah tide gate has caused significant 

 alterations in both flow and salinity regimes. Our 

 data regarding the location of adult striped bass dur- 

 ing the spawning season showed that these fish are 

 found farther upstream when the gate is in operation. 

 This observation is consistent with that of an earlier 

 study (Dudley and Black footnote 1) that striped bass 

 eggs occur farther upstream when the tide gate is 

 operating. Thus the tide gate apparently causes an 

 upstream shift in striped bass spawning. This shift 

 possibly reflects an alteration in salinity patterns. 

 Savannah River striped bass spawn in freshwater 

 and would thus move farther upstream to avoid in- 

 creased salinity. The overall effect on spawning 

 success from this upstream shift is probably minimal, 

 although in combination with altered flow patterns 

 its ultimate effect on striped bass eggs and larvae 

 is unclear. 



Our data concerning movements at other times of 

 the year supplement earlier finds (Dudley et al. 

 1977). Savannah River striped bass are primarily 



424 



