Ecology of Pelagic Amphipoda, II — Brusca 
455 
TABLE 11 
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 Average Number per Trawl Hour (n/th) for Paraphronima gracilus 
season 
O 
Y 
MSf (mm) 
MSm (mm) 
SRf (mm) 
SRm (mm) 
n/th 
Summer 
8% 
50% 
13.5 
10.5 
9-16.5 
10-14 
8 
Fall 
43% 
47% 
10 
10.5 
9.5-13 
10-11 
33 
Winter 
24% 
55% 
11 
10.5 
10-12 
10-11 
18 
Spring 
2% 
75% 
11 
11 
10-12 
10-12 
20 
TABLE 12 
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 Average Number per Trawl Hour (n/th) for Paraphronima. crassipes 
season 
O 
Y 
MSf (mm) 
MSm (mm) 
SRf (mm) 
SRm (mm) 
n/th 
Summer 
7% 
50% 
20 
16.5 
14-28 
13.5-23 
16 
Fall 
49% 
49% 
19 
18.5 
13-26.5 
14-23 
40 
Winter 
24% 
56% 
22 
20 
20-28 
18-22 
52 
Spring 
2% 
75% 
24 
18.5 
13.5-31 
13-24 
41 
abundant in the summer. The female/male 
ratio was relatively low at the suggested time 
of ova production (2/1), and there was an 
increase in the average number per trawl hour 
from 8 per trawl hour in the summer to 33 per 
trawl hour in the fall, indicating the release 
of young into the mature population. There 
was also a drop in the mean size of the female 
population during the fall, but other size data 
offer no correlations. 
Paraphronima crassipes Claus 
A total of 922 individuals were recovered 
from pint aliquots. Hurley (1956) reported 
specimens collected in local waters during July 
and August to be carrying ova or young in their 
brood pouches. Table 12 gives the reproductive 
information regarding P. crassipes gathered in 
this present study. 
The highest percentage of females with ova 
was noted in the fall, followed by a high inci- 
dence of young in the brood pouches in the 
winter and spring. Apparently young were re- 
leased from most of the females in the summer 
and fall, during which time there was a drop 
in mean size and, by fall, an increase in the 
population density. The ratio of females/males 
was lowest during the fall (1/1), correspond- 
ing with the production of eggs. 
CONCLUSIONS 
During this study certain general trends were 
noted regarding the reproductive activity of the 
total amphipod population. As illustrated in 
Table 13, the highest production of ova occurred 
during the summer and fall months, with de- 
velopment of young continuing throughout the 
following spring and summer. Most species re- 
leased their young into the adult population by 
early fall, as indicated by the percentages listed 
in Table 13 along with the increase in the total 
amphipod population density. 
It can be seen that, although the above men- 
tioned trends are observed, precise analyses of 
the activities of individual species are complex 
and difficult to make. A sampling program de- 
TABLE 13 
Seasonal Variation in the Percentages of 
Mature Females with Ova (O) and 
Young (Y) in the Brood Pouches, and the 
Number per Trawl Hour (n/th) for the 
Total Amphipod Population 
SEASON 
O 
Y 
n/th 
Summer 
24% 
40% 
49 
Fall 
20% 
32% 
135 
Winter 
10% 
35% 
50 
Spring 
14% 
43% 
40 
