278 
Abstract — The relative value of 
pelagic habitat for three size classes of 
juvenile Pacific ocean perch (Sebastes 
alutus ) was investigated by compar- 
ing their abundance and condition 
in two areas of the Aleutian Islands. 
Diet, zooplankton biomass, and water 
column temperatures were examined 
as potential factors affecting observed 
differences. Juvenile Pacific ocean 
perch abundance and condition, and 
zooplankton biomass varied signifi- 
cantly between areas, whereas juve- 
nile Pacific ocean perch diet varied 
only by size class. Observed differ- 
ences in fish condition may have 
been due to the quantity or quality of 
pelagic prey items consumed. For the 
delineation of essential demersal fish 
habitat, important ecological features 
of the pelagic habitat must therefore 
be considered. 
Abundance, condition, and diet of juvenile 
Pacific ocean perch ( Sebastes alutus ) 
in the Aleutian Islands 
Jennifer L. Boldt (contact author ) 1 
Christopher N. Rooper 2 
Email address for contact author: Jennifer.Boldt@noaa.gov 
1 Joint Institute for the Study of the Atmosphere and Ocean 
School of Fishery and Aquatic Sciences 
University of Washington 
Box 355020 
Seattle, Washington 98195 
Present address: Alaska Fisheries Science Center 
National Marine Fisheries Service 
7600 Sand Point Way NE, Bldg. 4 
Seattle Washington 98115-0070 
2 Alaska Fisheries Science Center 
National Marine Fisheries Service 
7600 Sand Point Way NE, Bldg. 4, 
Seattle Washington 98115-0070 
Manuscript submitted 12 August 2008. 
Manuscript accepted 4 February 2009. 
Fish. Bull. 107:278-285. 
The views and opinions expressed 
or implied in this article are those 
of the author and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Studies defining essential fish habitat 
often focus on associations of marine 
fishes with seafloor characteristics 
(Neuman and Able, 1998; La Mesa et 
al., 2002). Although identifying these 
associations is necessary to define hab- 
itats used by fishes, it is also impor- 
tant to explore other factors that may 
affect fish survival. Pelagic production 
of food resources, such as zooplank- 
ton, may be a factor that affects the 
survival of demersal fish. Bottom-up 
control through variation in pelagic 
production, may in part explain the 
observations of large climate-change 
effects on demersal fishes, including 
rockfishes (Hollowed and Wooster, 
1992; Hollowed et al., 2001). 
Pacific ocean perch (Sebastes alu- 
tus', POP) are an important rock- 
fish species that migrate vertically 
off the seafloor and consume pelagic 
prey (Brodeur, 2001), thus providing 
a direct linkage between pelagic zoo- 
plankton and demersal fish produc- 
tion. In general, juvenile POP (defined 
as individuals <250 mm fork length 
[FL] based on their size at first ma- 
turity) are associated with high-re- 
lief structured habitats, such as rocky 
outcrops, boulder fields, deep-water 
sponges, and corals (Rooper and Boldt 
2005; Rooper et al., 2007). Little is 
known of the costs and benefits to 
juvenile POP of residing in different 
habitat types or the potential linkage 
between pelagic prey and demersal 
habitats. 
One measure of the relative value 
of different habitat types to juvenile 
POP may be fish condition. Fish diet, 
habitat, and water temperature are 
integrated into overall fish condi- 
tion, which may affect fish growth 
and subsequent survival (Paul, 1997; 
Boldt and Haldorson, 2004). The goal 
of this study was to examine the 
relative abundance and condition of 
three size classes of juvenile POP in 
two different areas of the Aleutian 
Islands. Fish occupying suboptimal 
habitats were expected to be in poor 
condition compared to those living in 
optimal habitats. Additionally, we ex- 
plored potential causes for observed 
differences in fish condition by exam- 
ining POP diet, prey availability, and 
water temperature observed in the 
different habitats. 
Methods and materials 
Study site 
Fieldwork for this study was conducted 
from 28 May to 9 June 2004, and from 
11 August to 23 August 2004, at two 
