384 
Fishery Bulletin 108(4) 
( Brachionus plicatilis) enriched with Algamac 2000 
(Aquafauna, Hawthorne, CA; Park et al., 2006) and mi- 
croparticulate dry food (Otohime A, Marubeni Nisshin 
Feed Co., Tokyo). Rotifers were supplied at densities of 
4 prey/mL twice daily and dry food was provided 2-3 
times per day. 
At periodic intervals, a subsample of 10 larvae was 
removed from each tank to determine the mean size 
of larvae in the tank. For the 2007 experiments, six 
samples were drawn at 7-d intervals (starting on day 
0). For the 2008 experiments, all tanks were sam- 
pled on days 0, 10, 23, and 36. Sampled larvae were 
individually photographed under magnification and 
measured from calibrated digital photographs using 
ImagePro® (Media Cybernetics, Bethesda, MD) soft- 
ware. The morphometries used in these analyses were 
standard length (L s ) and body depth of the myotome 
at the anus CD). 
Dry weight of individual larvae was calculated us- 
ing a two-step model with L s and D developed from an 
independent collection of similar size Pacific cod larvae 
reared in the laboratory under identical conditions. 
These fish were individually photographed and dried on 
preweighed foil at 68°C for at least 24 hours before de- 
termination of dry mass (to 1.0 pg) with a microbalance. 
Fourty-four fish with L s of 5 to 11 mm were sampled 
periodically over the first 45 dah. First, the body depth 
deviation (D Dev ) was calculated for each fish, reflecting 
variance in “condition” from the equation 
D Dev = D - 0.0873-e°- 2164 L s. (1) 
Individual dry mass (M D mg) was calculated from D Dev 
and L s from the equation 
M d = 0.0204-e° 3734 ' L s + (0.9685- D Dev - 0.1113). (2) 
These equations explained 97.8% of the variation in dry 
mass of fish in the sample. 
Growth rates were calculated for each replicate tank 
from the increase in mean size of fish in measured sub- 
samples. Growth in length (g L , mm/d) and mass (g M , /d) 
were calculated from linear regression of mean length 
and ln-transformed mass against sampling date. 
Postflexion larvae 
Growth rates of postflexion larvae were measured in 
a separate experiment applying similar procedures. 
Experiments were established with fish 50 dah, reared 
at 8°C under conditions similar to those described above 
for preflexion larval experiments. Given the variation in 
body size among cultured fish, each fish was assigned 
to one of three size categories on the basis of visual 
estimation. This sorting by size was done to minimize 
the potential for intracohort cannibalism frequently 
observed in larval and juvenile gadids (Folkvord and 
Ottera, 1993, Sogard and Olla, 1994). One group of 
35-40 larvae from each size category was assigned to 
each temperature treatment (2°, 4°, 8°, 11°C). In addi- 
tion, a sample of 15-20 fish from each size category was 
sacrificed to determine initial size distributions. 
After establishment of experimental groups (day 0), 
temperatures were adjusted to target temperatures at 
a rate of 2°C per day. Larvae were offered particulate 
food three to four times per day, supplemented with 
enriched rotifers twice per day (first 20 d only). As fish 
grew, larger size particulate food (up to 620 pm) was 
included in daily feedings. A subsample (7-10 fish) was 
drawn from the 8°C and 11°C treatments on day 18 
and from the 2°C and 4°C treatments on day 24. The 
experiments were ended and all surviving larvae were 
measured on day 32 for the 8°C and 11°C treatments 
and on day 45 for the 2°C and 4°C treatments. Lengths 
(L s and L T ) of all sampled larvae were measured with 
digital calipers under a dissecting microscope and wet 
masses (M w ) were measured with a microbalance. Dry 
mass (M d ) of each larvae was determined after 48 hours 
in a drying oven at 50°C. 
Growth rates were calculated from the increase in 
mean size of fish in measured subsamples. Growth in 
length (g L , mm/d) and mass (g M , /d) were calculated 
from linear regression of mean length and ln-trans- 
formed mass against sampling date. 
Postsettlement juveniles 
Age-0 Pacific cod were captured from Kodiak Island 
juvenile nurseries in July 2008 with a 36-m beach seine. 
Fish were maintained for at least 48 hours at the AFSC 
Kodiak Laboratory in ambient seawater before shipment 
to the AFSC’s laboratory in Newport, Oregon. Fish were 
shipped overnight in insulated containers filled with sea- 
water and oxygen. Before use in laboratory experiments, 
fish were maintained in 1-m diameter round tanks with 
flow-through seawater maintained at 8-10°C. Fish were 
fed thawed krill and commercially available pellets on 
alternating days. 
The experiment was initiated by assigning fish-size 
categories based on visual estimation and stocking fish 
into experimental tanks. One tank of each size catego- 
ry (n= 3) was assigned to each temperature treatment 
{n= 4; 12 tanks total). After establishment of experimen- 
tal groups, temperatures were adjusted to treatment 
temperatures (2°, 5°, 8°, and 11°C) and fish were accli- 
mated to the treatment temperature for 10 days. 
Experimental tanks were 66x45.7 cm, filled to a 
depth of 23.2 cm. During the experiment fish were fed 
thawed krill to apparent satiation once per day. In ad- 
dition, a gelatinized combination of squid, krill, her- 
ring, commercial fish food, amino acid supplements, and 
vitamins was provided three times per week. Lights 
were maintained on a 12:12 h light:dark photoperiod 
for all experiments. Tanks were checked twice daily 
for mortalities, and dead fish were removed, weighed, 
and measured. 
Growth rates were estimated by measuring (L T to 1 
mm) all fish in the experiment three times at 10-d in- 
tervals. To minimize stress to small fish from repeated 
handling, wet masses were measured only at the end 
