Abandoning the sekiyama (Murphy and Shomura 1955, Mann MS) and 

 shortening droppers reduced the cost of fabrication. Introducing the 

 wire mainline section reduced tangling and therefore the amount of 

 labor during hauling. Spacing branch lines 15 fathoms apart instead of 

 30 fathoms increased the catch more than it increased the labor. It is 

 equally clear that many development problems remain, e.g., reducing 

 the incidence of dropper failure and determining the optimum hook 

 spacing. 



SHARK DAMAGE TO TUNA CATCHES 



During the period the longline is in the water (5 to 10 hours) a 

 portion of the tuna catch is damaged by sharks. This damage, sum- 

 marized in table 5, suggests that commercial operators can expect 

 to lose about 20 percent of their catches when fishing in the central 

 equatorial Pacific. 



25 



