Ecology of Pelagic Amphipoda, II — Brusca 
453 
TABLE 7 
Seasonal Variation in the Percentages of Mature Females Carrying Ova (O) and Young 
(Y), Mean Size of Females (MSf) and Males (MSm), Size Range of Females (SRf) 
and Males (SRm), and the Female/Male Ratio (f/m) of Hyperia galba 
SEASON 
O 
Y 
MSf (mm) 
MSm (mm) 
SRf (mm) 
SRm (mm) 
f/m 
Summer 
0% 
45% 
9 
12 
8-12.5 
11-13 
4.5/1 
Fall 
10% 
17% 
9 
11.5 
6-19.5 
9-15 
4.6/1 
Winter 
50% 
18% 
10.5 
10.5 
7.5-12.5 
6-15 
1.5/1 
Spring 
98% 
0% 
9 
11.5 
8.5-10 
8.5-17 
1.5/1 
tive information. Egg production was highest 
in the summer months, and the highest inci- 
dence of young in the brood pouches was in 
the spring. The abundance of males does not 
appear to correlate with the presence of ova. 
Young were released from the parents by sum- 
mer, but their entrance into the mature popula- 
tion was not reflected in the size data until fall, 
at which time there was an extension of the 
lower limit of the size ranges for both males 
and females. This suggestion is also supported 
by an increase in population density from an 
average of 3 individuals per trawl hour in the 
summer to 10 per trawl hour during the fall 
months. There appears to be about a three- 
months’ lag between the release of young from 
the brood pouches and their entrance into the 
catchable population. The whereabouts of the 
newborn amphipods is unknown. Analyses of 
local plankton samples taken during the sus- 
pected time of release offered no positive in- 
formation. 
Family vibiliidae 
Vibilia armata Bovallius 
A total of 2,742 individuals was sorted from 
pint aliquots. Some of the reproductive data 
for this species are difficult to interpret. 
Stephensen (1918) reported on collections 
from the Mediterranean in which he found 
breeding females in January and February and 
from June through September and young at all 
times of the year. In this present study no 
ovigerous females were noted during the winter 
and only a low percentage was recorded for the 
rest of the year (Table 8). The presence of 
young in the brood pouches suggests that the 
release from the parents took place in the late 
spring and early summer, at which time an ex- 
tension of the lower limit of the size range and 
a drop in mean size were noted. The popula- 
tion density, however, did not show a signifi- 
cant increase until early fall. 
Vibilia viatrix Bovallius 
In all 658 individuals were recorded from 
the sorting of pint aliquots. Stephensen (1918) 
reported specimens of V. viatrix in breeding 
condition during March and October in the 
North Atlantic. The information gathered in 
this present study is given in Table 9. 
Ovigerous females were most abundant in 
the fall and a high percentage was carrying 
young by winter. Apparently juveniles were re- 
leased from the brood pouches during the 
TABLE 8 
Seasonal Variation in the Percentages of Mature Individuals Carrying Ova (O) and 
Young (Y), Mean Size (MS), Size Range (SR), and Average Number per Trawl 
Hour (n/th) for Vibilia armata 
SEASON 
O 
Y 
MS(mm) 
SR(mm) 
n/th 
Summer 
3% 
10% 
6.5 
3-10 
14 
Fall 
8% 
35% 
7.5 
6-10 
251 
Winter 
0% 
45% 
7 
6-9 
71 
Spring 
8% 
51% 
8.5 
6-10 
30 
