by the results of the statistical analyses (see 

 Table 4). All tests indicated no significant dif- 

 ferences between shad and nehu at the 0.05 

 probability level. 



Alternation of both shad and nehu on the same 

 school.— Results of experimental fishing during 

 cruises 105, 106, and 108 are summarized in 

 Table 5. The basic catch data for these three 

 cruises are given in Table 6. These results 

 also show shad compared favorably with nehu 

 as live bait. Analysis of the skipjack tuna catch 

 per minute showed no significant difference be- 

 tween either shad or nehu as bait (see Table 4). 

 Additional statistical tests were not made be- 



cause further stratification of the data would 

 have considerably reduced the sample size. 

 Information on the amount of shad and nehu 

 chummed at each station was not collected be- 

 cause this would have required temporarily 

 suspending chumming at the end of each period 

 with the result that the school of skipjack tuna 

 probably would have sounded and fishing ended. 



Number of skipjack tuna in the fishing area. — E sti- 



mates of the concentration of skipjack tuna in 

 the fishing area near the hooks are given in 

 Table 7. Mean values for cruises 108, 109, 

 and 110 ranged from 1.7 skipjack tuna per 

 photograph with nehu during cruise 108 to 5.0 



Table 4. — Summary of analyses made to compare the effectiveness of threadfin shad with nehu as a live 

 bait during Charles H. Gilbert cruises 105, 106, 108, 109, and 110. All tests indicated no signifi- 

 cant differences between shad and nehu at the 0.05 probability level. 



Cruise no. 



Statistic compared, 

 shad versus nehu 



Analysis used 



Value 

 calculated 



Probability 



of 

 occurrence 



109, 110 



105, 106, 108 



Skipjack tuna catch per 

 minute 



Skipjack tuna <4.5 kg, 

 catch per minute 



Skipjack tuna >4.5 kg, 

 catch per minute 



Number of skipjack tuna 

 caught per school 



Duration of fishing per 

 school 



Total weight of skipjack 

 tuna caught per school 



Skipjack tuna catch per 

 minute 



Mann-Whitney U-test 



do. 



do. 



do. 



do. 



do. 



Wilcoxon matched-pairs, 

 signed-ranks test 



>0.10 

 >0.10 

 >0.42 

 >0.10 

 >0.10 

 >0.05 

 >0.05 



Table 5. — Summary of experimental fishing for skipjack tuna with both threadfin shad and nehu alter- 

 nated as bait on the same school during Charles H. Gilbert cruises 105, 106, and 108. 



Item 



Shad 



Nehu 



Number of schools first chummed with 



Number of schools responding to first bait chummed 



Percent of schools responding to first bait chummed 



Number of schools fished with both baits 



Total number of fishing periods for each bait 



Average number of skipjack tuna caught per minute (4 men fishing) 



Number of skipjack tuna caught 



Total weight (kg) of skipjack tuna caught 



Average number of skipjack tuna caught per school 



Average total weight (kg) of skipjack tuna caught per school 



Average catch per minute of skipjack tuna <4.5 kg 



Average catch per minute of skipjack tuna >4.5 kg 



'One school was first chummed with shad, but did not respond until nehu was chummed. 



