By subtracting the catch from the best 

 estimate of population size (35,508 - 20,096) 

 the estimated escapement from the commercial 

 fishery was 15,412 shad or 43 percent of the 

 total run . 



Standardization of effort 



To determine the fishing effort of the 1954 

 Ogeechee River shad fishery, 100 yards of 

 gill net was chosen as a unit of gear . One unit 

 of gear fished for I day was termed 1 unit of 

 effort or 1 net-day. Total units of effort fished, 

 catch, and catch per unit of effort for each 

 type of gear are given in table 2 . 



To obtain total fishing effort, the effort of 

 the various types of gear must be combined. 

 It can be seen (table 2) that the catch per unit 

 of effort differs between types of gear. This 

 may be attributable to a difference in fishing 

 efficiency of each type of gear. 



The fishing efficiency of the various types 

 of gear can be determined by use of a method 

 described by Fredin (1954) . A comparison of 

 the fishing power of the various types of gear 

 will make standardization of fishing effort 

 possible. Fishing power can be defined as the 

 ability of I unit of gear (100 yards of gill net) 

 to capture a certain fraction of the fish present 

 in 1 day's fishing. This function will be desig- 

 nated as p and can be considered to be constant 

 within a season and between seasons, provided 

 (l)there is no alteration in the design or opera- 

 tion of fishing gear which would change its 

 efficiency, (2) the fishing effort is uniform 

 throughout the season, and (3) the migration 

 pattern of shad within the river is the same 

 each year. 



The method used to determine gear effic- 

 iency is dependent upon whether (1) the fishing 

 gears fish the same area or (2) the fishing 

 gears fish different areas. In the first in- 

 stance the fishing efficiency of each type of 

 gear can be determined by comparing their 

 catch -per -unit -of -effort values (Fredin, 1954) 

 and in the second instance it can be determined 

 by comparing their fishing power (Talbot, 1954). 

 The coastal drift nets and Kings Ferry set nets 

 each fish a specific area in the river, while 



the upper set nets and upper drift nets fish the 

 same area . To determine the efficiency of the 

 gears fished on the Ogeechee River, both of 

 the foregoing methods must be used. 



The catches per unit of effort of the upper 

 set nets and upper drift nets, which fish the 

 same area, were 10.7 and 17.6 respectively 

 (table 2) . Compared with upper drift nets, 

 upper set nets were 60 times as efficient. 

 If upper-set-net effort is converted with upper- 

 drift -net effort (407 multiplied by 0.60) the 

 total units of effort of the upper nets is then 

 352 net-days. The efforts of the upper set and 

 drift nets were combined, and henceforth these 

 gears will be termed "combined upper nets . 

 We now have three classifications of gear 

 (coastal drift nets. Kings Ferry set nets, and 

 combined upper nets), each fishing a different 

 area of the river. The fishing effort exerted 

 by each of these gears in net-days is as follows: 

 Coastal drift nets, 455; King Ferry set nets, 

 353; and combined upper nets, 352 . 



Talbot (1954), using the formula q" = E/N 

 from Fredin (1954) shows a method for deter- 

 mining the fishing power (p) of gear fished in 

 separate areas of a river. Fishing effort (net- 

 days) is represented by n where q equals that 

 fraction of the population escaping one net -day's 

 fishing; E equals escapement from each type of 

 gear; and N equals total number of fish avail- 

 able to each type of gear . 



From the tagging experiment we estimated 

 that the total run was 35,508 shad. Hence, 

 that number of shad was available to the coast- 

 al drift net fishery. The number of net -days 

 fished was 455. the catch was 9,490 shad 

 (table 2), and the escapement from these nets 

 was 26,018 (35,508 - 9,490), thus. 



455 26,016 



from which q = . 99932 



35,508 

 and p -- 00068 . 



The number of fish escaping the coastal 

 drift net fishery and therefore available to 

 Kings Ferry set nets was 26,018. In 353 net- 

 days, the latter nets caught 4,359 fish (table 2) 

 and the escapement from these nets was 21,659. 

 In this case, q'^^^ ; 21^659^ ^^^^ ^j^.^,j^ 



q z 0.99948, and p^;S°.b?)052 . 



6 



