162 
Stage-specific vertical distribution of Alaska plaice 
( Pleuronectes quadrituberculatus ) eggs 
in tSie eastern Bering Sea 
Kathryn L. Mier 
Email address for contact author Janet.Duffy-Anderson@noaa.gov 
Resource Assessment and Conservation Engineering Division 
Recruitment Processes Program 
Alaska Fisheries Science Center 
National Marine Fisheries Service 
National Oceanic and Atmospheric Administration 
7600 Sand Point Way NE 
Seattle, Washington 98115-6349 
Abstract — The stage-specific distri- 
bution of Alaska plaice (Pleuronectes 
quadrituberculatus ) eggs in the south- 
eastern Bering Sea was examined 
with collections made in mid-May in 
2002, 2003, 2005, and 2006. Eggs in 
the early stages of development were 
found primarily offshore of the 40 -m 
isobath. Eggs in the middle and late 
stages of development were found 
inshore and offshore of the 40-m iso- 
bath. There was some evidence that 
early-stage eggs occur deeper in the 
water column than late-stage eggs, 
although year-to-year variability in 
that trend was observed. Most eggs 
were in the later stages of develop- 
ment; therefore the majority of spawn- 
ing is estimated to have occurred a 
few weeks before collection — probably 
April — and may be highly synchro- 
nized among local spawning areas. 
Results indicate that sampling with 
continuous underway fish egg collec- 
tors (CUFES) should be supplemented 
with sampling of the entire water 
column to ensure adequate samples 
of all egg stages of Alaska plaice. Data 
presented offer new information on 
the stage-dependent horizontal and 
vertical distribution of Alaska plaice 
eggs in the Bering Sea and provide 
further evidence that the early life 
history stages of this species are vul- 
nerable to near-surface variations in 
hydrographical conditions and climate 
forcing. 
Manuscript submitted 6 July 2010. 
Manuscript accepted 19 January 2011. 
Fish. Bull 109:162-169 (2011). 
The views and opinions expressed 
or implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National Marine 
Fisheries Service, NOAA. 
Janet T. Duffy-Anderson (contact author) 
Deborah M. Blood 
Knowledge of the vertical distribu- 
tions of fish eggs and larvae is impor- 
tant to understanding how wind and 
currents may affect early life stages. 
The eggs of several pleuronectid spe- 
cies in the North Pacific are positively 
buoyant (Pearcy, 1962; Bailey et ah, 
2005). Retention of pelagic eggs at 
the top of the water column exposes 
them to wind mixing that ensures 
an adequate oxygen supply for the 
developing egg, but also increases 
susceptibility of the eggs to stochastic 
wind events and adverse advection. 
Consistent baroclinic flows below the 
wind-mixed layer facilitate retention 
of developing eggs, but also could 
expose eggs to anoxia and increased 
predation. Vertical position often 
changes with development, and stage- 
dependent ascension can occur slowly 
throughout the developmental period, 
or quickly once eggs reach a critical 
stage. 
Alaska plaice (Pleu?'otiectes quadri- 
tuberculatus) is one of the major shal- 
low water flatfishes in the Bering Sea; 
however, there is not a significant 
fishery for the species. Alaska plaice 
are primarily harvested as bycatch in 
fisheries targeting other, more lucra- 
tive groundfishes, and a large por- 
tion of the Alaska plaice biomass is 
discarded. Adult Alaska plaice spawn 
in spring over the middle Bering Sea 
shelf at depths of 50-100 m, and egg 
and larval stages are pelagic (Bailey 
et al., 2003). Previous work (Duffy- 
Anderson et al., 2010) has shown that 
Alaska plaice larvae occur in the up- 
per 20 m of the water column, but 
vertical patterns of egg distribution 
have not been determined. 
The continuous underway fish egg 
sampler (CUFES; Checkley et al., 
1997) is a tested collection system 
used in sampling near-surface eggs 
from a fixed depth (3 m) and has the 
advantage of being able to sample 
eggs in adverse weather conditions 
when tows with nets are not possi- 
ble (Checkley et al., 2000; Lo et al., 
2001). The CUFES has been used in 
other regions to sample and estimate 
the densities of marine fish eggs in 
the water column (Dopolo et al., 
2005; Pepin et al., 2005). Accurate 
derivation of depth-integrated egg 
densities from near-surface estimates 
requires a complete understanding 
of patterns of vertical egg distribu- 
tion with depth and development, but 
this information is not available for a 
number of fish species in the Bering 
Sea, including Alaska plaice. 
The goals of the present study were 
1) to determine the developmental 
stage of Alaska plaice eggs collected 
from depth-discrete tows conducted in 
the eastern Bering Sea; 2) to exam- 
ine the vertical distribution of staged 
eggs; and 3) to determine whether the 
CUFES could be a suitable sampler of 
Alaska plaice eggs in the Bering Sea. 
