290 
Fishery Bulletin 114(3) 
Table 1 
Sampling schedule for postsmolt Atlantic salmon (Salmo salar) reared in the laboratory at 12“C under 3 feeding regimens 
(fed; fasted; fasted then refed) in order to determine the response time to varyhing food availability. Condition indices ob- 
tained by nonlethal sampling techniques (RNA/DNA; RNA/protein; DNA/protein; IGFl) and wet-weight-based growth rate 
were determined for each fish. The refed group was fasted for 11 days and then fed for 16 days. Numbers listed are number 
of fish sampled. 
Sampling day and feeding regimen 
Day 0 
Day 3 
Day 7 
Day 11 
Baseline 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Length, weight 
5 
24 
24 
22 
4 
4 
0 
4 
4 
0 
4 
4 
22 
Muscle plugs 
for nucleic acid 
and protein 
5 
0 
24 
0 
4 
4 
0 
4 
4 
0 
4 
4 
22 
Blood sample for 
IGFl measurement 
5 
0 
24 
0 
4 
4 
0 
4 
4 
0 
4 
4 
22 
Day 15 
Day 19 
Day 23 
Day 27 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Fed 
Fasted 
Refed 
Length, weight 
4 
4 
5 
4 
4 
5 
4 
4 
5 
0 
0 
7 
Muscle plugs for 
nucleic acid 
and protein 
4 
4 
5 
4 
4 
5 
4 
4 
5 
0 
0 
7 
Blood sample for 
IGFl measurement 
4 
4 
5 
4 
4 
5 
4 
4 
5 
0 
0 
7 
was recorded. Additionally, 2 muscle plugs and a blood 
sample were obtained from fish assigned to the fasting 
treatment in order to track individual response times 
to fasting. Fish in the group of refed postsmolts were 
again weighed and measured and then sampled on day 
11 to obtain individual baseline fasting values before 
fish were refed. Total time needed for the biochemical 
sampling was less than 1 minute per fish. From day 3 
onward, 5 fish from the fasted and fed treatments were 
sampled and sacrificed every 4 days for 20 days. From 
day 15 onward, 5 fish from the refed treatment were 
sampled and sacrificed every 4 days until day 27 when 
7 fish were sacrificed (Table 1). Final wet weight, FL, 
2 muscle plugs for biochemical analysis, and a blood 
sample for IGFl determination were obtained from all 
sacrificed fish. All fish were also sampled for bioelec- 
trical impedance analysis (BIA) indices and proximate 
body composition (see Caldarone et al., 2012). All as- 
pects of this experiment were conducted in accordance 
with guidelines established by the Institutional Animal 
Care and Use Committee (lACUC) at the University of 
Rhode Island 
Sampling protocol and biochemical analyses 
IGFl Blood samples (0.3 mL) for IGFl analysis were 
obtained from the caudal vein using a sterile heparin- 
ized syringe (23-gax25-mm needle). Samples were im- 
mediately transferred to a microfuge vial, stored on 
wet ice for < 0.5 hour, and centrifuged at 5000xg for 
5 minutes. Plasma was removed by pipet, transferred 
to a 1.5 mL microfuge vial and stored at -SO^C until 
further analysis. Samples were analyzed at the Na- 
tional Marine Fisheries Service, Northwest Fisheries 
Science Center by using an immunoassay to measure 
the concentration of IGFl. Briefly, IGFl was isolated 
from plasma by acid-ethanol extraction, and measured 
by TRF immunoassay by using a modification of the 
methods described by Small and Peterson (2005). Each 
sample was analyzed in duplicate, and samples with 
low (<30%) or high (> 85%) binding, as well as those 
with a coefficient of variation exceeding 10%, were re- 
analyzed or excluded. IGFl values are reported as ng/ 
mL plasma. 
Nucleic acids and protein A 2-mm diameter biopsy 
punch (MacLean et al., 2008) was used to remove 2 
muscle samples for analysis of nucleic acids and pro- 
tein. Samples were taken from the epaxial muscle be- 
tween the lateral line and dorsal fin. Each muscle plug 
was immediately placed in a microfuge vial, stored on 
wet ice for <0.5 hour and then transferred to -80°C 
until analysis. Nucleic acid levels were measured by 
using a 2-enzyme (RNase, DNase) ethidium bromide 
fluorometric microplate method. On the day of analy- 
sis, each muscle plug was transferred to a cold glass 
slide and any fat layer, skin, or blood was removed. 
The top 2 mm of the muscle plug was transferred to 
