manner. Upon arrival on the fishing grounds, 

 scouting commenced for bird flocks, which 

 usually signify the presence of skipjack tuna 

 schools. When approaching a fish school, the 

 bait supplies were readied and the chummer, 

 fishermen, and observers took their places. 

 As the vessel crossed the head of the school, 

 the chummer began broadcasting the bait until 

 the school was brought to the stern and fishing 

 started. If the attempt was unsuccessful, the 

 ship would then return for another "pass" and 

 the process was repeated. Several passes were 

 usually made on each school until either the 

 school was successfully fished or until it be- 

 came obvious the school was not going to re- 

 spond and was abandoned. 



The first sign that fishing would probably be 

 successful was a surface break or splash made 

 by the skipjack tuna feeding on bait near the 

 stern of the vessel. When this occurred, the 

 vessel would slow to fishing speed (ca. 2 knots), 

 the fishermen would enter the racks, and water 

 sprays would be turned on and directed to the 

 sea surface just behind the vessel. Water 

 sprays are used by the commercial skipjack 

 tuna fishermen in Hawaii in order to improve 

 the catch rate (Yuen, 1969). Two scientific 



observers helped coordinate the experiment 

 and recorded data. One observer, stationed on 

 the afterdeck near the chummer, recorded the 

 number of skipjack tuna caught and the time 

 that each bait species was used during fishing. 

 He was in communication by telephone with the 

 second observer, who was stationed in an 

 underwater observation chamber located on the 



Table 1. — Dates of experimental fishing and num- 

 ber of skipjack tuna schools fished aboard the 

 Charles H. Gilbert. 



Figure 3. — Underwater observation chamber used for 



iitfish and skipjack tuna. 



