6 
Fishery Bulletin 107(1 ) 
Table 4 
Angles of gliding and upswimming, distances (cm), and horizontal speeds over ground (cm/s) of individual bluefish ( Pomatomus 
saltatrix), January 1996, during the activity study. Angles of glides are in degrees below horizontal; angles of upswimming are 
in degrees above horizontal. Dashes indicate that no observations were available. 
Angle 
of glide 
Distance of 
glide (cm) 
Horizontal 
speed (cm/s) 
Angle of 
upswimming 
Distance of 
upswimming (cm) 
Horizontal 
speed (cm/s) 
6.3 
45 
22.1 
12.4 
125 
30.5 
7.1 
94 
32.2 
2.2 
93 
31.8 
10.7 
228 
20.6 
7.9 
44 
18.0 
11.5 
43 
21.8 
7.3 
60 
20.3 
13.2 
103 
34.7 
6.3 
103 
25.7 
15.3 
50 
24.6 
29.4 
172 
28.7 
15.3 
25 
26.0 
22.6 
94 
27.9 
17.5 
126 
19.7 
6.8 
58 
21.0 
18.2 
78 
25.3 
26.7 
194 
23.8 
18.2 
— 
— 
5.5 
125 
20.5 
18.3 
91 
22.8 
18.6 
89 
20.6 
18.5 
141 
27.2 
7.5 
50 
24.6 
18.9 
87 
29.0 
13.0 
66 
20.0 
19.5 
93 
30.4 
15.3 
85 
39.3 
19.8 
131 
21.1 
10.5 
119 
28.4 
19.9 
80 
— 
3.7 
162 
— 
20.0 
64 
20.7 
2.8 
97 
31.7 
20.4 
94 
— 
1.6 
210 
— 
20.8 
155 
21.7 
13.9 
43 
21.8 
21.3 
172 
23.7 
10.8 
90 
17.0 
21.9 
82 
19.9 
24.4 
107 
47.3 
23.6 
130 
24.9 
4.4 
98 
24.1 
Figure 3 
Swimming speeds (cm/s), with standard deviations (SD), from the 7 
hours before and after midday and 7 hr before and after midnight for 
bluefish (Pomatomus saltatrix), 10 Sept. 1995-28 June 1996 (/i = 25 
weeks). 
December and January, glides occurred 
during as many as 14 hr/d, even during 
daylight. During the greatest frequency 
of occurrence of the behavior in Janu- 
ary, the proportion of fish gliding was 
also greatest, up to 14%. 
Angles of descent during gliding 
ranged from 13-26° from the horizon- 
tal, and angles of ascent ranged from 
2-29° (Table 4). The average angle 
of descent for all fish was 17.9° and 
for ascent by those that followed the 
undulating path of the school was 
12.2°. The average speed of descent 
was 24.9 cm/s and of ascent was 26.3 
cm/s. Using the gliding model of Weihs 
(1973), we diagrammed the path of a 
bluefish selected from Table 4. It glided 
at angle d=19.8 0 for a distance a x =131 
cm and ascended at angle (3=10.5° for 
a distance a 2 =119 cm, a total distance 
of 250 cm. If it had actively swum, the 
horizontal distance would have been 
240 cm. 
Body roll angles were not measured 
in 1995-96, but in 2007 bluefish averaged 47° from 
vertical while gliding (n = 33, maximum 65°). The glide 
angle a averaged 19.7° (n= 23) in 2007. 
During periods when gliding was rare, bluefish 
sometimes moved very slowly at night in a swimming 
mode that can be called “milling.” The orderly spac- 
