Duffy-Anderson et al.: Stage-specific vertical distribution of Pleuronectes quadrituberculatus eggs 
165 
Table 2 
Results of staging Alaska plaice (Pleuronectes quadrituberculatus) eggs and the percentage of eggs in each developmental stage 
bin by gear type (early: stages 1-12; middle: stages 13-15; late: stages 16-23). The late stage was subdivided into three cat- 
egories (early late: stages 16-18; middle late: stages 19-21; and late late: stages 22-23). Stages were adapted from Blood et al. 
(1994) and two developmental stages were added for this study. MOCNESS=multiple opening and closing net and environmental 
sampling system. 
Percentage of 
Number of eggs/stage 
total eggs/stage Neuston net 
MOCNESS 
Developmental 
(neuston net 
(neuston net (percentage of 
(percentage of 
stage 
and MOCNESS) 
and MOCNESS) eggs collected) 
eggs collected) 
Early 
1 
0 
0 
2 
0 
0 
3 
0 
0 
4 
0 
0 
5 
3 
0.14 
6 
7 
0.32 
7 
20 
0.92 
8 
2 
0.09 
9 
20 
0.92 
10 
7 
0.32 
11 
14 
0.64 
12 
10 
0.46 
Total 8.1 
0.5 
Middle 
13 
10 
0.46 
14 
23 
1.06 
15 
51 
2.35 
Total 8.4 
0.4 
Early late 
16 
58 
2.67 
17 
158 
7.27 
18 
67 
3.08 
Total 23.0 
5.2 
Middle late 
19 
209 
9.61 
20 
230 
10.58 
21 
285 
13.11 
Total 30.2 
35.7 
Late late 
22 
727 
33.44 
23 
272 
12.51 
Total 30.3 
58.2 
in the middle stages of development (stages 13-15). 
Among late-stage eggs in 2003, the densities of egg 
abundances were depressed in the near surface waters 
(0-10 m) and significantly so for ML and LL stages 
(Table 3). In general however, most eggs were collected 
from above the mixed layer (<30 m). In 2005, a different 
pattern emerged; late-stage eggs consistently occurred 
at shallower depths than did earlier stages (Fig. 3), 
and the majority were collected in near-surface waters. 
Statistical examination revealed that more eggs were 
collected from depths 0-10 m and 10-20 m than in any 
of the deeper depths. 
Considered collectively, approximately 34% of the 
catch in the two years occurred in the top 10 m of the 
water column, 24% occurred between 10 and 20 m, 18% 
between 20 and 30 m, 11% between 30 and 40 m, 8% 
between 40 and 50 m, and 5% between 50 and 60 m 
depth. 
Discussion 
This is the first study to describe stage-dependent verti- 
cal and horizontal distribution of Alaska plaice eggs. Our 
data indicate that spawning occurs offshore of the 40-m 
isobath, and likely near-bottom, confirming hypotheses 
outlined in Bailey et al. (2003). Eggs occur throughout 
the water column, but many eggs occur in the upper 
water column (<30 m depth). The vast majority of eggs 
collected in the present study were in the later stages 
of development, and we estimate that the majority of 
spawning occurred a few weeks before collection. Maxi- 
