304 
Fishery Bulletin 95(2), 1997 
Table 2 
A summary of sightings of giant bluefin tuna during an aerial survey, 19 May-9 June 1995 over the Great Bahama Bank. 
Aircraft 
T/D 
Date 
Start 
time 
Total 
time (h) 
Est. time 
on Banks 
Total 
nmi 
Nmi. on 
banks 
Number 
of sights 
No. of 
bluefin 
Sight, per 
100 nmi 
Bluefin per 
100 nmi 
344Z 
rp* 
19 May 
9:14:0 
4.9 
3.4 
340 
230 
0 
0 
0.00 
0.00 
344Z 
T 
21 May 
9:15: 0 
3.7 
2.2 
249 
139 
0 
0 
0.00 
0.0 
270Q 
D 
22 May 
9:48: 0 
6.2 
4.7 
441 
331 
0 
0 
0.00 
0.0 
344Z 
T 
22 May 
9:47:15 
5.9 
4.4 
388 
278 
0 
0 
0.00 
0.0 
270Q 
D* 
23 May 
9:17:25 
6.6 
5.1 
424 
314 
0 
0 
0.00 
0.0 
344Z 
T 
23 May 
9:18:15 
6.5 
5.0 
440 
330 
0 
0 
0.00 
0.0 
270Q 
D 
25 May 
9:52:15 
6.1 
4.6 
438 
328 
0 
0 
0.00 
0.0 
344Z 
T 
25 May 
9:42:30 
6.4 
4.9 
406 
296 
0 
0 
0.00 
0.0 
270Q 
D 
26 May 
9:23:15 
3.6 
2.1 
268 
158 
0 
0 
0.00 
0.0 
344Z 
T* 
26 May 
9:23:45 
3.6 
2.1 
244 
134 
0 
0 
0.00 
0.0 
270Q 
T 
28 May 
9:46: 0 
7.5 
6.0 
540 
430 
1 
8 
0.23 
1.9 
344Z 
T 
29 May 
9: 9:15 
5.9 
4.4 
383 
273 
2 
9 
0.73 
3.3 
270Q 
D 
30 May 
9:21:45 
5.7 
4.2 
364 
254 
3 
37 
1.18 
14.6 
344Z 
T 
30 May 
9:20: 0 
5.7 
4.2 
372 
262 
1 
8 
0.38 
3.1 
270Q 
D 
31 May 
9:23:15 
5.6 
4.1 
345 
235 
3 
30 
1.27 
12.7 
344Z 
rp* 
31 May 
9:17:15 
5.7 
4.2 
374 
264 
6 
45 
2.27 
17.0 
270Q 
D 
1 June 
7:13: 0 
5.9 
4.4 
348 
238 
2 
81 
0.84 
34.1 
344Z 
T 
1 June 
7:13:30 
6.0 
4.5 
399 
289 
1 
100 
0.35 
34.7 
270Q 
D 
2 June 
8:51:15 
5.5 
4.0 
316 
206 
6 
93 
2.91 
45.2 
344Z 
T 
2 June 
8:44:30 
5.6 
4.1 
341 
231 
3 
32 
1.30 
13.8 
270Q 
D 
3 June 
9:11:30 
5.1 
3.6 
297 
187 
4 
84 
2.14 
44.9 
344Z 
T 
3 June 
9: 5:15 
5.2 
3.7 
298 
188 
6 
65 
3.19 
34.6 
270Q 
D* 
4 June 
9:54:15 
3.2 
1.7 
206 
96 
4 
90 
4.18 
94.0 
344Z 
rp** 
4 June 
9:53:15 
3.2 
1.7 
188 
78 
4 
96 
5.10 
122.4 
270Q 
D* 
7 June 
9: 8:15 
6.5 
5.0 
464 
354 
2 
29 
0.57 
8.2 
344Z 
T 
7 June 
9: 2:15 
7.1 
5.6 
445 
335 
3 
30 
0.90 
9.0 
270Q 
D* 
8 June 
9:34:30 
5.9 
4.4 
425 
315 
1 
1 
0.32 
0.3 
344Z 
T 
8 June 
9:38:15 
5.8 
4.3 
384 
274 
0 
0 
0.00 
0.0 
270Q 
D 
9 June 
9:54:15 
4.0 
2.5 
268 
158 
1 
1 
0.63 
0.6 
344Z 
T 
9 June 
9:54:15 
4.2 
2.6 
262 
152 
0 
0 
0.00 
0.0 
Totals 
162.9 
117.9 
10,656 
7,356 
53 
839 
Abbreviations: nmi=nautical miles; T=transect aircraft; D=discovery aircraft; *=Observer present. Great Bahama Bank mileage was estimated as 
total flight miles minus 110 (distance over land/Straits of Florida). Estimated time on Bank is total time minus 1.5 h. Transect aircraft mileage 
includes survey miles spent off transect. **=Transect abandoned due to squalls. 
dundant counts, a school of 100 fish recorded by 
Supercub 344Z and one of 80 fish recorded by Cessna 
270Q (Table 4) were judged to be the same, giving an 
adjusted estimated total count of 759 bluefin tuna. 
Bluefin tuna were most abundant adjacent to the 
region west of and between South Bimini and Castle 
Rock, with sighting concentrations near Victory and 
Gun Cays (Fig. 2A) similar to distributions described 
in the past by anglers (Farrington, 1939) and noted 
by Rivas (1954; 1978). 
The Cessna 270Q’s search area included broad search 
tracks extending to North Rock and west of Tuna Alley 
(Fig. 2B), but no bluefin tuna were sighted in these 
areas. In comparison with the 1970’s surveys, the two 
survey aircraft produced a 2-3 fold increase in effort 
hours but had only 33-45% of the number of observa- 
tion days in comparison with the 1974-76 surveys, 
which began almost three weeks earlier and ran 7-11 
days later in June (Table 5). In the 1974 and 1975 sur- 
veys, no bluefin tuna were observed after 11 June and 
2 June, respectively. Although it is possible that blue- 
fin tuna entered the region without being detected by 
recreational vessels, nevertheless, according to aerial 
and charter boat sightings, the 1995 migration period 
of about 20 days was considerably shorter than the pre- 
sumed 50 day migration period noted in the 1950’s and 
the 1970’s (Rivas, 1978). Although SPUE values are 
not strictly comparable in the present and 1974-76 sur- 
veys because of differences in survey protocols and plat- 
forms (Table 5), there are resemblances in the general 
appearance and behavior of giant bluefin tuna. 
In the present survey the majority of bluefin tuna 
(50 out of 53 sightings) were documented off transect; 
therefore the longitudinal transect along the Great 
