Branchiopod and Malacostracan Crustaceans 
21 
Table 6. Seasonal abundance of Hyalella azteca at sites where collected. Data 
are expressed as percentage of such stations at which its occurrence 
was common or uncommon. Data from 1982 and 1983 have been 
combined. 
Common 
Uncommon 
Number of Stations 
Dec-Jan 
45.6 
54.3 
23 
Mar-May 
83.3 
16.7 
12 
June 
88.7 
11.3 
62 
July 
67.8 
32.1 
28 
Aug 
41.3 
58.7 
46 
Nov 
60.6 
39.4 
33 
Table 7. Sex ratios and percentages of females of Hyalella azteca and Crangonyx 
r. richmondensis that were ovigerous, by month. Data from 1982 and 
1983 have been combined. N = number of sexed individuals; Total N - 
total number of sexed individuals plus unsexed juveniles. 
Male: Female 
% Ovig. 
N 
Total N 
H. azteca 
Jan 
0.71 
5.1 
101 
101 
Mar 
0.49 
69.8 
264 
264 
May 
0.50 
72.9 
248 
248 
Jun 
0.46 
52.7 
1650 
1650 
Jul 
0.57 
52.6 
359 
359 
Aug 
0.67 
52.0 
633 
633 
Sep 
0.92 
68.6 
129 
129 
Nov 
0.61 
18.0 
477 
477 
Dec 
0.82 
3.5 
260 
260 
C. r. 
richmondensis 
Jan 
0.97 
16.9 
116 
122 
Mar 
12.00 
0.0 
13 
13 
May 
1.14 
28.6 
15 
15 
Jun 
0.67 
0.0 
5 
87 
Jul 
0 
0 
Aug 
0.00 
0.0 
2 
13 
Sep 
0.0 
0 
1 
Nov 
0.79 
5.3 
68 
69 
Dec 
0.86 
4.5 
80 
82 
