Boldt and Rooper: Abundance, condition, and diet of Sebostes o/utus 
279 
168°0'CTW 
170WW 
ALASKA: 
Gulf 
of 
Alaska 
Umnak 
Island 
Samalga 
Island 
1 70°0'0“W 
i69 e o , o n w 
Islands 
of Four 
Mountains 
Samalga 
Pass 
80 
Kilometers 
Figure 1 
Map of the study area in the Aleutian Islands, Alaska. Study sites were located 
near the Islands of Four Mountains, north of Samalga Island (N), and south of 
Samalga Island (S). At both sites, juvenile Pacific ocean perch ( Sebostes alutus ) were 
collected with a bottom trawl, zooplankton were collected with a ring net, and water 
column temperature profiles were recorded with a conductivity, temperature, depth 
recorder. 
sites near Samalga Pass in the Aleutian Islands (Fig. 1). 
One site was located on the south (S) side and one on 
the north (N) side of Samalga Island (Fig. 1). Two sta- 
tions were sampled at each of the two sites in August 
and two stations were sampled at the N site in June. 
All the stations were located at depths from 117 to 
146 m in high relief habitat (boulder fields) inhabited 
by juvenile POP. 
Juvenile POP abundance and size classes 
Juvenile POP (<250 mm FL) were collected during day- 
light hours with a standard NMFS poly Nor’eastern 
bottom trawl. A net (with average net width of 16.5 m) 
was towed at a target speed of 3 knots over distances 
of 0. 4-1.0 km. The catch per unit of effort (CPUE in 
number of juvenile POP per hectare) at each site was 
calculated by using the area swept. Juvenile POP were 
measured for fork length and frozen for laboratory analy- 
ses. Temperature was measured twice daily at each site 
with a SeaBird CTD (conductivity, temperature, depth 
recorder, Sea-Bird Electronics, Inc., Bellevue, WA) to 
obtain temperature-depth profiles. 
In the laboratory, juvenile POP were thawed, mea- 
sured, weighed, and dissected. Fish stomachs were 
weighed full and empty, and stomach contents were 
preserved in 10% buffered formalin for later diet analy- 
ses. Length frequencies of juvenile POP were plotted 
and natural breakpoints were used to divide the fish 
into three size categories (<160 mm FL, 160-210 mm 
FL, and >210 mm FL). Diet and fish condition were 
analyzed by these size categories and by site. 
Juvenile POP condition 
Fish condition was assessed by using log-transformed 
length-wet-weight regression residuals (indicator of 
somatic growth and hereafter referred to as wet-weight 
residuals; n = 226) and log-transformed length-dry- 
weight regression residuals (indicator of energy stor- 
age and hereafter referred to as dry-weight residuals; 
n=226). Also, the energy content of dried fish (n=226) 
was determined with a Parr 1425 Semimicro bomb 
calorimeter (Parr Instrument Company, Moline, IL). If 
available, at least 10 fish of each size category per site 
were dried in a 60°F drying oven or in a freeze dryer 
until a stable weight was reached. To test for differences 
in dry weights between the drying methods, thirty ran- 
domly chosen fish were individually ground and divided 
in half; one half of each fish was dried in the drying oven 
