Ecology of Pelagic Amphipoda, I — Brusca 
TABLE 9 
Day and Night Depth Distributions for 
Hyperia galba 
DEPTH IN 
METERS 
TOTAL NO. 
SAMPLES 
NO. 
POSITIVE 
SAMPLES 
PER CENT 
POSITIVE 
Night 
0-50 
4 
0 
0 
50-100 
2 
1 
50 
100-200 
7 
2 
28 
200-300 
4 
4 
100 
300-400 
6 
3 
50 
400-500 
2 
1 
50 
500-600 
7 
1 
13 
600-700 
2 
0 
0 
700-800 
1 
0 
0 
800-900 
1 
0 
0 
900-1100 
3 
0 
0 
Day 
0-50 
2 
0 
0 
50-100 
2 
0 
0 
100-200 
2 
0 
0 
200-300 
4 
1 
25 
300-400 
4 
4 
100 
400-500 
5 
2 
40 
500-600 
5 
3 
60 
600-700 
4 
0 
0 
700-800 
3 
2 
75 
800-900 
4 
1 
25 
900-1100 
8 
6 
75 
individuals was noted in quantitative aliquots. 
The data suggest that Vibilia armata exists 
in a thick zone ranging from the surface to 
about 800 m at night and from 200 to 1100 m 
during the day. It is probable that the lower, 
daytime depth limit was greater than the sam- 
pling program of this study. Table 10 illus- 
trates the depth distributions. It appears that 
the entire population moves upward some 200 
m at night without actually concentrating near 
the surface. 
Vibilia viatrix Bovallius 
Vibilia calif ornica Holmes, 1908:490-492, 
figs. 1-2. 
Vibilia viatrix Stephensen, 1918:41-43, fig. 
13; Chevreux and Fage, 1925:385-386, fig. 
390; Pirlot, 1929:95-96; Barnard, K. H., 
1930:403; Pirlot, 1930:10-11; Barnard, K. H., 
1932:262-263; Shoemaker, 1945:234, Hur- 
ley, 1956:11. 
389 
TABLE 10 
Day and Night Depth Distributions for 
Vibilia armata 
DEPTH IN 
METERS 
TOTAL NO. 
SAMPLES 
NO. 
POSITIVE 
SAMPLES 
PER CENT 
POSITIVE 
Night 
0-50 
4 
3 
75 
50-100 
2 
2 
100 
100-200 
7 
5 
70 
200-300 
4 
3 
75 
300-400 
6 
5 
82 
400-500 
2 
2 
100 
500-600 
7 
2 
30 
600-700 
2 
2 
50 
700-800 
1 
1 
100 
800-900 
1 
0 
0 
900-1100 
3 
0 
0 
Day 
0-50 
2 
0 
0 
50-100 
2 
0 
0 
100-200 
2 
0 
0 
200-300 
4 
3 
75 
300-400 
4 
2 
50 
400-500 
5 
4 
80 
500-600 
5 
5 
100 
600-700 
4 
2 
50 
700-800 
3 
2 
66 
800-900 
4 
3 
75 
900-1100 
8 
7 
88 
Individuals of this species were taken in 53 
trawls ranging in depth from 10 to 1100 m. 
A total of 658 specimens was recovered from 
pint aliquots. A few individuals associated with 
salps were noted on the surface. 
Table 11 illustrates the day and night depth 
distributions. This species displayed a unique 
pattern of vertical migration: the upper por- 
tions of the population remained rather stable, 
while the deeper dwelling members rose at 
night, resulting in an absence of individuals 
at great depths during the dark hours. 
Family phronimidae 
Phronima sedentaria (Forskal) 
Phronima sedentaria Holmes, 1908:490; 
Stephensen, 1924:114-121, figs. 50-51, chart 
15; Chevreux and Fage, 1925:393-395, fig. 
396; Pirlot, 1929:110-112; Barnard, K. H., 
1930:422; Pirlot, 1930:12-14; Barnard, K. H., 
