Lutcavage et at: Aerial survey of Thunnus thynnus in the Straits of Florida 
305 
Table 3 
Transect of the giant bluefin tuna aerial survey, 19 May-9 June 1995 over Great Bahama Bank. 
Date 
Start time 
End time 
Trackline 
nmi 
Sighting 
Bluefin 
tuna 
Sightings per 
100 nmi 
Bluefin tuna per 
100 nmi 
19 May 
10:51:0 
11:50:0 s 
0 
0 
0 
0 
19 May 
12:35:0 
13:15:0 s 
0 
0 
0 
0 
21 May' 
11:07:30 
12:09:15 
72 
0 
0 
0 
0 
22 May 
11:28:0 
12:42:45 
80 
0 
0 
0 
0 
22 May 
13:33:0 
14:50:45 
75 
0 
0 
0 
0 
23 May 
10:57:15 
12:11:0 
77 
0 
0 
0 
0 
25 May 
11:44:0 
12:46:0 
71 
0 
0 
0 
0 
25 May 
13:40:15 
14:43:15 
70 
0 
0 
0 
0 
26 May 
11:06:30 
12:05:45 
71 
0 
0 
0 
0 
28 May 
11:46:45 
12:47:29 
80 
0 
0 
0 
0 
29 May 
11:06:45 
12:15:14 
74 
1 
1 
1.3 
1 
29 May 
13:04:29 
04:15:00 
74 
1 
1 
1.3 
1 
30 May 
11:06:30 
12:11:15 
71 
0 
0 
0 
0 
30 May 
13:05:0 
14:10:30 
71 
0 
0 
0 
0 
31 May 
11:11:30 
12:10:45 
69 
1 
1 
1.46 
1 
31 May 
13:07:15 
14:07:15 
69 
0 
0 
0 
0 
1 June 
09:06:15 
10:06:0 
68 
1 
100 
1.47 
147 
1 June 
10:59:45 
11:58:15 
66 
0 
0 
0 
0 
2 June 
11:13:0 
12:08:30 
68 
0 
0 
0 
0 
3 June 
11:24:45 
12:22:45 
69 
0 
0 
0 
0 
4 June 2 
7 June 
11:28:50 
12:52:45 
95 
0 
0 
0 
0 
7 June 
13:19:15 
13:46:15 
28 
1 
6 
3.54 
21 
8 June 
11:25:0 
12:31:0 
70 
0 
0 
0 
0 
8 June 
13:25:0 
14:40:30 
78 
0 
0 
0 
0 
9 June 
11:45:0 
13:09:15 
84 
0 
0 
0 
0 
Totals 
1,650 
5 
109 
1 Trackline altered to avoid local storm squalls. 
2 Transect abandoned because of squalls. All transects, except that flown on 28 May, were conducted by Supercub 344Z. 
3 We experienced GPS problems on 19 May 1995; therefore times were estimated, not actual. 
Bahama Bank and Tuna Alley may be less effective 
than other survey methods. On days when fish were 
present on the banks, general sightings per search 
mile (i.e. schools or bluefin tuna per nmi of spotter 
pilot search effort) were within the same order of mag- 
nitude for the Cessna 270Q and the Supercub 344Z 
(which spent nearly half its search time off transect). 
In general, the schooling behavior of bluefin tuna 
travelling adjacent to the Great Bahama Bank dif- 
fered substantially from what we have observed in 
the Gulf of Maine aerial surveys (Lutcavage and 
Kraus, 1995). On the Great Bahama Bank, giant 
bluefin tuna were much less tightly aggregated and 
did not exhibit cartwheeling and milling formations 
or smashing behaviors that indicate feeding, al- 
though they are said to “smash” on rare occasion far- 
ther offshore (Mather et al., 1995). In contrast with 
prolonged surface “shows” and the appearance of 
densely packed schools in New England, the Great 
Bahama Bank schools spent very little time at the 
surface, making it difficult for pilots to photograph 
the school in entirety. As in previous surveys, schools 
were most readily detected and successfully photo- 
graphed while swimming over white sand in shal- 
low water. Photographs of schools in the deeper blue 
water usually depicted only a few fish visible at the 
surface. Because of the lack of color contrast between 
the tuna and the water and because of their deeper 
position in the water column, these schools were more 
difficult to detect and photograph, but experienced 
spotters use several cues including color contrast and 
surface disturbance to identify bluefin tuna. 
Singles and loosely aggregated groups swam 
steadily north at an estimated speed of 6-8 knots, 
similar to speeds reported by Mather et al. (1995), 
with the exception of one school, which we followed 
for 36 minutes in the air (Fig. 3). As two fishing boats 
approached from opposite sides, the school of ten fish 
changed spatial conformation several times, turned 
west, and disappeared into deeper water. 
