266 
Fishery Bulletin 110(2) 
Table 5 
Pearson product-moment correlations (r) between (A) proximate body composition (g) or (B) wet-weight-based proximate body 
composition or instantaneous wet-weight-based growth rate of Atlantic salmon ( Salma salar) post-smolts, and wet weight, bioelec- 
trical impedance analysis (BIA) measures and Fulton’s K. i? par =resistance in parallel; Xc par = reactance in parallel; D = distance 
between BIA detector electrodes; R par and Xc par conductor volume =D 2 /R pgr and D 2 lXc par , respectively; phase angle (“^arctan- 
gent of Xc/R converted to degrees; capacitance is a measure of the electrical storage capacity of cells; impedance is a measure 
of the opposition to the flow of electrical current; Fulton’s A=(100»wet weight/fork length 3 ). Boldface type highlights highest 
correlation between body composition or growth rate, and wet weight, BIA measures, and Fulton’s K. * P<0.050, ** P<0.005, *** 
P<G.Q001. ,v= number of fish sampled. 
A 
Variable 
WW 
CP 
TF 
TWa 
n 
69 
66 
61 
68 
Wet weight ( WW ) 
1 
0.99*** 
0.84*** 
0.99*** 
Carcass protein content (CP) 
0.99*** 
1 
0.84*** 
0.98*** 
Total fat content ( TF ) 
0.84*** 
0.74*** 
1 
0.78*** 
Total water content ( TWa ) 
0.99*** 
0.98*** 
0.78*** 
1 
R par conductor volume 
0.92*** 
0.91*** 
0.71*** 
0.93*** 
Xc par conductor volume 
0.94*** 
0.93*** 
Q ^4*** 
0.95*** 
Phase angle 
0.62*** 
0.60*** 
0.53*** 
0.62*** 
Capacitance 
0.56*** 
0.54*** 
0.54*** 
0.54*** 
Impedance 
-0.58*** 
-0.57*** 
-0.54*** 
-0.57*** 
Fulton’s K 
0.28* 
0.31* 
0.46** 
0.24* 
B 
Variable 
WW 
CP% 
TF% 
TWa% 
Growth rate 
n 
69 
66 
61 
68 
56 
Wet weight (WW) 
1 
0.66** 
0.48*** 
-0.57*** 
0.53*** 
Carcass protein concentration ( CP % ) 
0.66*** 
1 
0.32* 
-0.44** 
0.38* 
Total fat concentration (TF%) 
0.48*** 
0.32* 
1 
-0.93*** 
0.09 
Total water concentration ( TWa% ) 
-0.57*** 
-0.44** 
-0.93*** 
1 
-0.23 
Rpar'® 
0.92*** 
0.58*** 
0.34* 
-0.44** 
0.50*** 
Xc par /D 
0.94*** 
0.60*** 
0.38** 
-0.48*** 
0.51*** 
Phase angle 
0.62*** 
0.44** 
0.37** 
-0.46** 
0.37* 
Capacitance 
0.56*** 
0.39** 
0.41** 
-0.51*** 
0.22 
Impedance 
-0.58*** 
-0.45** 
-0.41** 
0.53*** 
-0.22 
Fulton’s K 
0.28* 
0.31* 
0.47** 
-0.57*** 
0.32** 
within a single day’s sample, the values were not signif- 
icantly different from day 0 (Fig. IB). Contrary to our 
findings, Wilkinson et al. (2006) observed significantly 
lower mean K in 14-month-old Atlantic salmon smolts 
after 15 days of fasting (when compared to continually 
fed fish values), and significantly higher mean K 7 
days after being refed (when compared to continually 
fasted fish values). By the end of our experiment (16 
days after refeeding), K values for refed vs. fasted fish 
were not significantly different. Differences in metabolic 
rate or initial fat content may explain the dissimilarity 
in response time of A" values to fasting and refeeding 
observed between these studies. 
A significant correlation between K and total fat 
(r=0.74) was observed during an 13-day study of food- 
deprived juvenile steelhead trout ( Oncorhynchus mykiss ) 
(total fat range 0.4 to 3.6g) (Hanson et al., 2010). K 
and total fat were less correlated in our study (r = 0.46) 
which encompassed a larger range of total fat values 
(1.8— 12. 7g). In our postsmolt Atlantic salmon, K values 
were not highly correlated with body composition (g or 
%WW) or growth rate (all r< | 0.6 1 ) 
Estimates of conductor volume 
Equations based on conductor volume have been devel- 
oped to predict water-, fat- and protein-content of five 
species of fish (Cox and Hartman, 2005; Pothoven et ah, 
2008; Hanson et ah, 2010). For simple cylindrical shapes, 
when R is measured at a constant temperature and fre- 
quency, a conductor volume (V) calculated with Ohm’s 
law ( V=pL 2 / R) should approximate a physical volume 
(Lukaski et ah, 1985). Both Cox and Hartman (2005) 
(brook trout) and Hanson et al. (2010) (juvenile steel- 
head) observed strong linear relations between conductor 
volume (r 2 >0.95) and total water and protein content in 
their fish. The relation of total fat to conductor volume 
was equally high in the brook trout (r 2 =0.96; Cox and 
