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CHARLES H GILBERT 

 CRUISE II - APRIL 1953 



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CHARLES H GILBERT 

 CRUISE 13- JUNE 1953 



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HUGH M SMITH 

 CRUISES 22-24 

 SEPT -NOV. 1953 



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With the exception of 

 Flight No. 2, on which eight 

 fish schools were sighted, the 

 results of the six flights were 

 very poor from the standpoint 

 of giving information on the 

 abundance and distribution of 

 skipjack in the Hawaiian area. 

 Although the flights were made 

 at different times of the year 

 and covered periods of rela- 

 tively heavy skipjack catches 

 by the commercial fleet as well 

 as the off-season months, the 

 aerial survey results did not 

 indicate such seasonal fluctua- 

 tions (table 10). On the con- 

 trary, the largest number (8) 

 of fish schools and bird flocks 

 seen was during the flight in 

 December 19^2, a month of low 

 skipjack catch in the Hawaiian 

 fishery. The flight made during June 1953, a month of good skipjack catches, resulted in the 

 sighting of only one bird flock. Furthermore, on all flights the number of flocks seen per 100 

 miles was far less than the number seen from our vessel scouting the sanne area simultaneously. 



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D, who sighted the least on 

 GILBERT 11 in Areas I and II, 

 sighted the most on GILBERT 

 1 3 in Area I. We believe that 

 the variations in the total num- 

 ber sighted indicate no difference 

 in effort, the differences being 

 due rather to a somewhat greater 

 than random variation in condi- 

 tions. This may well occur, 

 because groups of schools were 

 sometimes sighted in quick suc- 

 cession in a small area. We 

 conclude that these differences 

 between observers are not sig- 

 nificant and that the changes in 

 personnel did not affect our 

 results. 



EVALUATION OF 

 AIRPLANE SCOUTING 



AM 



HOUR 



PM 



Figure 6. --Diurnal variation in the frequency of sightings of 

 bird flocks on GILBERT cruises 11 and 13 and 

 SMITH cruises 22-24. 



It appears that our aerial scouting was greatly affected by weather and sea conditions. 

 For example, during Flight No. 2 the weather was excellent with superb visibility. The sea was 

 flat calm with only breeze patches in most areas. This flight resulted in the sighting of four 

 schools (three skipjack and one yellowfin) not associated with any birds and four other schools 

 attended by birds. Two of the flights (Flights 1 and 3) were nnade under generally adverse scout- 

 ing conditions, with occasional rain squalls, overcast skies, and poor visibility. The seas were 

 choppy with numerous white caps, making observations difficult. Flight No. 1 resulted in the 

 sighting of three flocks, while on Flight No. 3 only one flock was seen. Somewhat more dis- 

 couraging are the poor results of the last three flights (4, 5, and 6) which were made in typical, 

 that is generally good, weather with moderately choppy seas. Only eight flocks were seen on all 

 three flights. On these same three days the GILBERT was scouting and reported 31 flocks. 



