262 
Fishery Bulletin 1 10(2) 
Table 2 
Proximate body composition (% whole-body wet weight), capacitance, and % change in wet weight of Atlantic salmon ( Salmo 
sala r) postsmolts reared at 12°C under 3 feeding regimens (fed; fasted; fasted then refed). The refed group was fasted for 11 days 
and then fed. TF %= total fat concentration; TWa %= total water concentration; CP%=carcass protein concentration. Capacitance 
(pF) is a measure of the electrical storage capacity of cells. Percent change in wet weight was calculated by subtracting the initial 
wet weight of a fish on day 0 (fed and fasted treatments) or day 11 (fasted then refed treatment, day they were fed) from its wet 
weight on the day it was sacrificed, expressed as a percent of its initial wet weight. Asterisks (*) in the body composition columns 
indicate a significant difference from baseline values, and in the capacitance column they indicate a significant difference from 
day 3 fed values (Dunnett two-tailed t-test, P<0.05). Values are means with standard deviation (SD) in parentheses. Mean initial 
wet weight of all fish was 76.0 g (SD = 12.6, [no. of fish sampled=74|). NA=not available. n=number of fish sampled. 
Feeding regimen 
Sampling day 
n 
TF% 
TWa% 
CP% 
Capacitance 
% change in wet weight 
Baseline 
0 
5 
7.1 (1.1) 
73.2 (1.2) 
17.6(0.5) 
NA 
0 
Fed 
3 
4 
7.4 (1.8) 
73.9(1.5) 
17.0 (0.4) 
2275 (322) 
NA 
7 
4 
6.3 (1.4) 
74.1 (1.3) 
17.4 (0.7) 
2057 (66) 
1.2 (1.9) 
11 
4 
5.9 (0.9) 
74.9(1.3) 
16.9(0.7) 
2012 (333) 
9.0 (2.3) 
15 
4 
5.5 (0.8) 
74.9 (1.0) 
17.4 (0.4) 
2144 (150) 
15.5 (6.5) 
19 
4 
6.2 (1.1) 
73.8(1.3) 
17.8(0.3) 
2024 (113) 
25.9 (5.0) 
23 
4 
6.7 (2.0) 
73.9(2.6) 
17.6(0.7) 
2024 (126) 
20.7 (7.2) 
Fasted 
3 
4 
7.9 (1.2) 
72.6 (1.1) 
17.0 (1.0) 
2112 (268) 
NA 
7 
4 
6.4 (1.3) 
74.8 (1.6) 
16.6 (0.4) 
2042 (156) 
-2.7 (0.8) 
11 
4 
6.0 (1.0) 
74.5(1.2) 
16.9(0.2) 
1861 (180)* 
-4.2 (0.9) 
15 
4 
5.2 (0.6)* 
75.9 (1.1)* 
17.0 (1.0) 
1919 (152)* 
-4.6 (1.4) 
19 
3 
5.3 (1.6) 
75.8 (1.6)* 
17.3 (0.2) 
1988 (175) 
-7.3 (2.5) 
23 
4 
4.9 (1.1)* 
76.5(1.5)* 
16.2 (1.1) 
1744 (297)* 
-7.3 (2.5) 
Fasted, then refed 
15 
5 
6.5 (2.1) 
74.8 (2.8) 
17.3 (0.9) 
2005 (228) 
NA 
19 
5 
5.7 (0.8) 
75.7 (1.2) 
16.8 (0.7) 
1876 (151) 
4.0 (4.5) 
23 
5 
5.8 (0.8) 
74.7 (0.9) 
17.4 (0.7) 
1978 (136) 
17.5 (2.7) 
27 
7 
5.8 (0.8) 
75.1 (0.7) 
17.2 (0.5) 
1953 (74) 
15.5 (5.9) 
NC). Unless otherwise stated, the level of significance 
was set at P<0.05. 
Results 
General observations 
At the start of the experiment we observed frayed or 
eroded dorsal fins in -78% of the fish, and fraying of 
the pelvic fin in -12% of the fish. During the experi- 
ment there was no change in the frequency of these 
abnormalities and there were no mortalities; however, 
one severely emaciated, moribund fish was excluded 
from the data set. None of the fish had well developed 
gonads and therefore all were considered to be imma- 
ture. Because sex did not emerge as a significant factor 
in any of the statistical analyses, it was not included 
in the data set. 
Within two weeks after their transfer to seawater, 
the postsmolts were actively feeding and appeared to 
be acclimated to the seawater and their surroundings. 
On day 0, wet weight ranged from 43 to 132 g, and fork 
length from 18 to 23 cm; size distributions of fish were 
not significantly different between feeding treatments 
(fed mean=76 g, SD = 12; fasted mean = 75 g, SD = 13; 
fasted then refed mean = 80 g, SD = 4). 
On day 0 we encountered instability problems with 
our handmade probes, which were resolved by the end 
of the day. Because we were not completely confident in 
our BIA measurements that day, we have not included 
these initial BIA values in any of our analyses. Cur- 
rently, BIA needle-electrodes are not manufactured and 
must be made in-house. Standardized manufactured 
probes would be necessary if BIA is to be routinely 
used. 
Within-treatment effects 
Over the course of the experiment, changes in fish 
weight and body composition (%WW) were observed 
within a treatment. On the final day of the experiment, 
fish in the fed treatment had increased in weight by 
14-28%, whereas fasted fish had lost 5-10% of their 
weight (Table 2). Fish in the fasted, then refed treat- 
ment lost an average of 4% in weight during their 11 
days without food, and gained 10-21% after 16 days of 
refeeding. Within each of the 3 feeding treatments, CP% 
(Table 2) and CA% (not shown) remained fairly constant. 
Changes in TF% (decreasing) and TWa% (increasing) 
occurred in fasted fish only, and differences from base- 
line values became significant after 15 d of fasting (Table 
2). Within a treatment and sampling day, TF% was the 
most variable of the body components, averaging an 
