308 
Fishery Bulletin 95(2), 1 997 
the highest range of values given in the length his- 
togram of fish captured previously in the Bahamas 
from 1939 to 1966 (Mather et al., 1995). Rivas (1976) 
noted that the mean length of Bahama bluefin tuna 
increased by 20-25 cm over a 20-yr period dating 
back to the 1950’s. Bluefin tuna documented in New 
England aerial surveys spanned a much broader 
range of size classes and include small medium ( 145- 
178 cm SFL, 61<107 kg), large medium ( 178-196 cm, 
107<141 kg), and a broader range within the giant 
bluefin tuna size class (>196 cm, >141 kg). 
As in previous Bahamas surveys, the majority of 
sightings occurred under conditions of strong winds, 
but 121 out of 839 (759 adjusted total) bluefin tuna 
were sighted under calm or variable wind conditions. 
Experienced tuna guides emphasized that bluefin 
tuna do not appear on the Bank until winds are of 
sufficient strength from the southern sector or when 
Table 5 
Comparison of giant bluefin tuna aerial surveys conducted in the Straits of Florida and the Great Bahama Bank region. 
1974 7 
1975' 
1976 7 
1995 
Survey dates 
9 May-16 June 
1 May-16 June 
2 May-20 June 
19 May-9 June 
Survey type 
1-mi transect 
across Tuna Alley 
1-mi transect 
across Tuna Alley 
1-mi transect 
across Tuna Alley 
70-nmi transect 
and discovery fits. 
Aircraft used 
not given 
not given 
not given 
2, single engine 
Time of day (h) 
11:00-13:00 
12:00-14:00 
09:30-14:00 
11:00-13:00 
Total observation days 
37 
46 
42 
17 
Total survey hours 
37.7 
48.6 
51.6 
117.9 
Date of first sighting 
9 May 
1 May 
6 May 
28 May 
Date of last sighting 
11 June 
2 June 
15 June 
9 June 
Total bluefin 
3,125 
368 
1,120 
839 
1 1974-76 surveys are taken from Rivas, 1978. 
