quality of the lines. Finally, those fish lost during the hauling have been 

 counted as part of the catch. 



After these adjustments were made, the analysis was confined to a 

 detailed examination of the catch and the bait return, and the relationships of 

 these two varlates with various methods of bait preservation, baiting methods, 

 kinds of bait, and environmental conditions. In soma Instances the catches were 

 separated and analyzed by tuna species rather than for the total catch, e.g.. In 

 the experiment on kind of bait, a separation was necessary to detect any bait 

 preference by the different tuna species. 



SOAKING TIME 



As mentioned earlier, the experiments discussed in this paper were 

 designed to control the factor of soaking time by alternating the varlates by 

 baskets or groups of baskets. The importance of time was recognized on earlier 

 longllne cruises, when it was observed that fewer baits were retrieved on the 

 baskets that soaked longer. Actually this was to be expected, because the soaking 

 time of the last basket of gear hauled may differ from the first by as much as 5 

 hours . 



The results of the bait data of Manning cruise 11 (January-March 1952) 

 are presented as an example to show the relationship of sardine bait returns with 

 soaking time and to justify the experimental design used in the various experi- 

 ments. This cruise was selected because only single-hooked sardines were used, 

 simplifying the description. It is realized that varying results may be obtained 

 with other types of bait and with different baiting methods, and therefore the 

 results from the Manning cruise 11 data should be considered as solely descriptive 

 of that cruise. 



Two Important effects of soaking time to be examined were: (1) whether 

 there were any differences In the levels of the 27 station regressions of bait 

 return with soaking time, and (8) whether there were significant differences 

 among the slopes of the 27 regression lines. It was thought that differences in 

 the levels of the 27 regression lines were highly probable, since the fishing 

 stations on that cruise covered a very wide area extending from 155°W. to 180° 

 longitude and from 8°N. to 8°S. latitude. Fishing over such a wide area involved 

 varying fish abundance and different environmental conditions (Murphy and Shomura 

 1953b). As expected, the results Indicated significant differences (F = 8.43, 

 P<0.01) among the levels of the 27 station regressions of bait return with soak- 

 ing time (table 1). These differences in the levels of the station regression 

 lines do not appear to have affected their slopes as Indicated in the test for 

 differences among regression lines (table 2). An average regression line was then 

 calculated to represent the 27 station regression lines (table 26, fig. 2). It 

 is clear from the slope of this line that experiments, to be meaningful, must 

 control soaking time. As stated earlier, this was accomplished by alternating 

 the varlates by baskets or groups of baskets. 



TREATMENT OF BAIT 



During early POFI cruises the bait was placed in a box of rock salt for 

 a few days prior to use to increase the firmness of the flesh and to prevent bac- 

 terial decomposition. The Hawaiian longllne fishermen from whom this practice 

 was adopted find it necessary because of the lack of mechanical refrigeration on 

 their vessels (June 1950). Salting entails considerable effort in placing bait 

 individually in the box of rock salt and this handling of bait in the soft, thawed- 

 out condition Increases the number of broken baits. Consequently, experiments 

 were carried out on cruises 12 and 15 of the Manning to discover a better way of 

 treating the bait. The three methods tested were (I) dry salting, (2) brining, 

 and (3) tmtreated bait. 



