Caldarone et al Nonlethal techniques for estimating responses of postsmolt Sa/mo sa/ar to food availability 
265 
Table 4 
Coefficients and Akaike’s second-order information criterion for small sample sizes (AIC c ) for the top 3 most parsimonious regres- 
sion models for proximate body composition (expressed as g and % wet weight) and growth rate of postsmolt Atlantic salmon 
( Salmo salar) reared at 12°C under 3 feeding regimens in order to obtain a range of nutritional condition and growth rates. 
tyW=wet weight (g); FL = fork length (cm); i? par =resistance in parallel (Q); Ac par =reactance in parallel (12); Z) = distance between 
bioelectric impedance detector electrodes (cm); R par conductor volume =D 2 /R par \ F=Fulton’s K (100 •WW/FL 3 )', capacitance (pF) is 
a measure of the electrical storage capacity of cells; impedance (Q) is a measure of the opposition to the flow of electrical current; 
R pa JD=R par standardized for D\ phase angle (°)=arctangent of Xc/R converted to degrees; AAICc= difference in AICc values with 
respect to the most parsimonious model. For all models PcO.OQOl. r 2 = coefficient of determination. 
Dependent variable n 
Model 
r 2 
AICc 
AAICc 
Total fat content (TF)( g) 60 
0.733 + 0.172HVW) - 0.696(FL) + 0.090 (R p JD) 
0.755 
-6.72 
0 
8.326 + 0.150( VFIV) - 0.755(FL) 
6.573 + 0.173GVW) - 0.648(FL) - 
0.742 
-5.71 
1.0 
54.90 )R par conductor volume) 
0.750 
-5.49 
1.2 
Carcass protein 65 
content (CP)(g) 
13.794 + 0.260(WWO - 0.825 (FL) - 4.453(F) 
28.269 + Q.285(WW) — 1.131(FL) - 0.002 (capacitance) - 
0.985 
-119.18 
0 
0.002 (impedance) - 6.62(F4 
0.986 
-117.97 
1.2 
2.261+0.2151 WW) - 0.234 (FL) - 0.0005(capacficmce) 
0.985 
-117.16 
2.0 
Total water 67 
-12.187 + 0.616( WW) + 1.109(FL) 
0.993 
-3.20 
0 
content (TWa Mg) 
-30.19 + 0.54KWW) + 2.002(FL) + 6.210(F) 
0.993 
-2.93 
0.3 
-7.791 + 603(WW) + 1.087(FL) - 0.055 (R p JD) 
0.993 
-2.35 
0.8 
Total fat concentration 60 
15.272 + 0.099( WW) - 0.842 (FL) 
0.326 
9.81 
0 
( TF% ) 
-1.568 + 0.28 (WW) + 5.70(F) 
0.324 
10.02 
0.2 
Carcass protein 65 
8.086 + 0.330IFL) + 7.910(F) 
32.185 + 0.044( WW) - 0.218 (FL) - 
0.318 
10.55 
0.7 
concentration (CP%) 
0.004 (capacitance) - 0.004 [impedance) 
27.318 + 0.026(WW) - 0.003 (capacitance) - 
0.503 
-83.17 
0 
0.004 (impedance) 
28.090 + 0.036( WW) + 0.041 (R pl , r /D) - 
0.483 
-82.96 
0.2 
0.004 (capacitance) - 0.005 {impedance) 
0.498 
-82.52 
0.6 
Total water 67 
86.901 - 0.044( WW) - 9.180(F) 
0.499 
20.00 
0 
concentration ( TWa % ) 
97.183 - 0.522(FL) - 12.553(F) 
0.496 
20.35 
0.3 
Instantaneous wet -weight 56 
based growth rate 
60.435 - 0.154IWW) - 1.310(FL) 
-0.6866 - 0.0016( WW ) + 0.0219(FL) + 
0 . 3882 ( R par conductor volume) + 
0.485 
21.86 
1.9 
(per day) 
0.0025 (R p JD) + 0.1931(F) 
-0.1087 + 0.0033(FL)-0.00003(capacfiance) 
0.481 
-582.29 
0 
+ 0.00374 (phase angle) + 0.0560(F) 
-0.2156 + 0.0034IFL) + 0.00003(impecfance) + 
0.453 
-581.85 
0.4 
0.0031 (phase angle) + 0.0578(F) 
0.444 
-580.98 
1.3 
group. However, when the whole data set was exam- 
ined, capacitance and fat concentration (range: 4-10%) 
were only somewhat correlated (coefficient of correlation 
[r] = 0.41, P<0.005). 
Isometric growth is assumed for Fulton’s K, and dif- 
ferences in the weight-length relation are interpreted 
as an indication of stored energy. Because the posts- 
molts were growing isometrically with little energy 
storage, Fulton’s K was unable to distinguish between 
fast and slow growers within the fed treatment, and K 
values of fed fish were significantly higher than those 
of fasted fish only on the final day of sampling (day 
23). Generally, Fulton’s K tends to have a long tempo- 
ral response (weeks to months) (Busacker et al., 1990). 
The relations among a fish’s wet weight, water weight, 
protein weight, and fat weight may explain this lag 
time. The wet weight of a fish is highly related to wa- 
ter weight (as was observed by Sutton et al. [2000] in 
Atlantic salmon parr), and water weight is much more 
strongly associated with protein weight than fat weight 
(20-40x more) (Breck, 2008). Therefore during the 
early stages of fasting, when fat stores are used first 
(Shulman and Love 1999, Jobling 2001), changes in a 
fish’s wet weight may be fairly subtle, but once a fish be- 
gins to use protein for energy, water loss (and thus wet 
weight loss) would accelerate. In our study, mean fat 
concentration in fasted fish decreased slightly with time 
while mean protein concentration remained constant. 
Within the fasted treatment there was a decreasing 
trend in mean K values, but owing to high variability 
