The success of fishing in relation to the time 

 of day followed a pattern similar to that seen 

 for sightings relative to time of day (table 13 

 and fig. 13). Following a rapid increase in 

 fishing success from daybreak to a peak at 

 0901-1000 and a dip at 1001-1100, there were 

 two other peaks--one at 1201-1300 and another 

 at 1401-1500. 



There is also evidence that the vessels caught 

 a large proportion of the day's catch, by weight, 

 usually after 1200 (table 15). Dividing the day's 

 total catch aboard each vessel by schools and 

 by time of day, we found that usually the ves- 

 sels had only 11 percent of the day's catch 

 aboard by 0900, had less than half — 37 percent — ■ 

 of the day's catch aboard by noon, then aver- 

 aged 31 percent of the day's catch in both the 

 third (1201-1500) and fourth (after 1501) quar- 

 ters of the fishing day. 



Cloud cover and wave height. --Fishing ves- 

 sels usually operate under various weather 

 conditions. Data collected at the time of fish- 

 ing revealed that the vessels operated on days 

 that were cloudless, cloudy, overcast, and 

 rainy, and in seas varying from calm to very 

 rough. We were, however, interested primari- 

 ly in learning whether cloud cover or wave 

 height had any effect on the biting behavior of 

 skipjack tuna. Imamura (1949) reported that 

 Japanese skipjack tuna fishermen experienced 

 better fishing on cloudy days, but Yuen (1959) 

 found that weather had no significant effect on 

 biting behavior of skipjack tuna found in Ha- 

 waiian waters. 



For June-August 1967, we found that for 

 nearly 50 percent of the schools chummed, 

 cloud cover at the time of fishing was three- 

 tenths or less (table 16). Dividing the data into 

 categories of schools with and without catches, 

 we tested the probability of success in fishing 

 relative to cloud cover and found that the 

 r atios--success to failure--did not vary by 

 more than chance ( X^= 10.60; d.f. = 9; p > 0.25). 

 We concluded that very cloudy, overcast, or 

 rainy days probably affected fishing only by 

 reducing the fishermen's chances of sighting 

 schools. 



Table 15. — Percentage of the day's total catch 

 aboard the vessels in the first (by 0900) , 

 second (0901-1200) , third (1201-1500) , and 

 fourth (after 1501) quarters of the fishing 

 day for seven Hawaiian skipjack tuna fishing 

 vessels, June-August 1967 



Vessels 



Quarters of the fishing day 



First 



Second 



Third 



Fourth 



Percent Percent Percent Percent 



C 

 D 

 E 

 F 

 G 

 All 

 Cumulative 



3.3 

 15.5 

 17.0 

 9.2 

 7.1 

 7.2 

 16.4 

 10.8 

 10.8 



31. 

 15. 

 20. 

 24. 

 41. 

 40. 

 10. 

 26. 

 37. 



42.4 

 35.4 

 23.7 

 35.2 

 28.5 

 33.3 

 21.0 

 31.4 

 68.6 



22.8 

 33.8 

 39.1 

 30.7 

 22.8 

 18.6 

 52.3 

 31.4 

 100.0 



Table 16. — Number and percentage of 619 schools with catches and 443 schools without 

 catches, fished by seven Hawaiian skipjack tuna fishing vessels and tabulated by 

 cloud cover at the time of fishing, June-August 1967 



Cloud cover 



Schools 



With catches 



Without catches 



Total 





Number 



Percent 



Number 



Percent 



Number 



Percent 



Cloudless 



23 



3.7 



31 



7.0 



54 



5.1 



1/10 or less 



128 



20.7 



91 



20.5 



219 



20.6 



2/10 and 3/10 



146 



23.6 



89 



20.1 



235 



22.1 



4/10 



83 



13.4 



67 



15.1 



150 



14.1 



5/10 



63 



10.2 



49 



11.1 



112 



10.5 



6/10 



60 



9.7 



28 



6.3 



88 



8.3 



7/10 and 8/10 



42 



6.8 



35 



7.9 



77 



7.3 



9/10 and 9/10 plus 



39 



6.3 



28 



6.3 



67 



6.3 



10/10 



23 



3.7 



17 



3.8 



40 



3.8 



Rain 



12 



1.9 



8 



1.8 



20 



1.9 



20 



