Petersen -type tag was attached to the back of 

 the fish immediately below the dorsal fin. 

 When a shad was removed from the net, a 

 scale sample was taken and the fish was 

 weighed, measured, tagged, and released. A 

 total of 112 shad were tagged during the fish- 

 ing season. To ensure recovery of recaptured 

 tags, all fishermen who had been given log- 

 books were contacted several times during the 

 season and a reward of 50 cents was paid for 

 each tag returned. However, relatively few 

 tags were recovered, which tends to make our 

 estimate of population size subject to error. 



To estimate the size of run by means 

 of tag and recovery technique, the number of 

 shad tagged, the number of tags recovered, and 

 the total number of shad caught must be known. 

 Normally, data should be obtained from all 

 types of gear to make this estimate; however, 

 the lower fishery was closed to commercial 

 fishing on March 24, which was before the en- 

 tire run of shad had entered the river. There- 

 fore, the data from this fishery could not be 

 used. Also the scarcity of data response on 

 the part of the bow-net fishery made it im- 

 practical for use in the estimate. The catch 

 and tag recovery data from the remaining types 

 of gear were used to estimate population size. 

 To determine if there was a difference in the 

 tag recovery -catch ratio of the various types 

 of gear a chi -square test was made between 

 the total catch of female shad by each type of 

 gear and their respective tag recovery, as 

 follows: 



Number of Number of tags 

 female shad recovered 

 caught 



2 

 6 



3 

 1 



3,621 

 X 2 =3.6, P~0.30 



12 



This analysis indicates that there was 

 no significant difference in the tag recovery- 

 catch ratio of female fish regardless of the 

 type gear used; therefore, the data were used 

 to estimate the fish populan i Only female 



shad were used in the analysis because the 



gear from which tag samples were obtained 



was selective to female shad on the basis of 



size of fish caught (the gear caught only the 



large fish, most of which were females). The 



total catch by these gears was 6,117 shad (n) 



from which 12 tags were recovered (s). A 



total of 108z/ tags had been attached to fish in 



3/ 

 this area.—' 



The total population (N) available to the 

 upriver fishery was determined by the formula 



N = 



nt 



Solving this equation, it was found that 

 the population of the upriver fishery was 

 55,053 shad. Ninety -five percent confidence 

 limits were obtained for this estimate using a 

 formula (55) from Chapman (1948). Upper and 

 lower population estimates were calculated to 

 be 100,000 and 28, 000 shad, respectively. 



To determine the total number of shad 

 that entered the Edisto River, the catch made 

 in the lower fishery was added to the upper - 

 river population estimate . The number of shad 

 caught before entering the upriver fishery was 

 924; therefore our best estimate of the number 

 of shad entering the Edisto in 1955 was 56,000. 

 The total catch was 11,011 shad, the overall 

 fishing rate was calculated to be 20 percent, 

 and the spawning escapement was estimated to 

 be 45,000 shad. As previously stated, the 

 above estimates are based on few tag recover- 

 ies and therefore may be subject to large 

 error. 



Miscellaneous studies 



Scale samples from the commercial 

 catch were studied to determine age distribu- 

 tion and the number of times each fish had 

 spawned"'. No spawning marks were found on 



4/ Four of the original 112 tags were recap - 

 tured by the lower river fa ,; ii nets. 



5/ When a. shad spawns and returns to the 

 ocean it leaves a characteristic mark on its 

 scales which is termed a spawning scar or 

 mark 



