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Fishery Bulletin 107(4) 
angles reflect circuits that consist of equal amounts 
of capacitive reactance and resistance (Meeuwsen et 
al., 2001). Lower phase angles appear to be consistent 
with low reactance and either cell death or a break- 
down in the selective permeability of the cell membrane 
(Schwenk et al., 2000a, 2000b). Higher phase angles are 
consistent with high reactance and large quantities of 
intact cell membranes and body cell mass (Abu Khaled 
et al., 1988; Foster and Lukaski, 1996). The use of phase 
angle as a human health indicator is becoming more 
common in medical fields (Dejmek and Miyawaki, 2002; 
Damez et al., 2007). Even when other anthropometric 
evaluation methods such as body mass index (BMI) and 
skin-fold tests are not accurate or sensitive to tissue 
change, phase angle has been found to be accurate. 
Furthermore, phase angle is considered to be a possible 
global marker of health and evaluation of cell membrane 
function, and consequently serves as a prognostic tool 
for human disease (Barbosa-Silva and Barros, 2005). 
We demonstrate that phase angle can be used to mea- 
sure the nutritional condition of fish under laboratory 
and field conditions. Our objective was to determine 
whether fish known to have decreasing nutritional sta- 
tus have lower phase angles than those fish with high 
nutritional status. We made these measurements on 
six species of fish: brook trout ( Salvelinus fontinalis), 
rainbow trout ( Oncorhynchus mykiss), Chinook salmon 
(O. tshawytscha), chum salmon (Q. keta ), pink salmon 
(O. gorbuscha), and Pacific herring ( Clupea pallasii) 
under laboratory conditions and on fish collected from 
the field. In addition, we examined postmortem changes 
in phase angle in fish to illustrate how phase angle 
reflects membrane integrity and water balance. 
Materials and methods 
We tested the hypothesis that phase angle changes with 
the nutritional status of fish by conducting three labo- 
ratory experiments and three field studies using live or 
freshly killed fish. Throughout this study, we assume 
that malnourished, over-wintering, and migrating anad- 
romous fish are in diminished nutritional condition 
compared to their nourished, prewinter, and premigra- 
tory counterparts. This assumption has been thoroughly 
evaluated in the literature where condition declines have 
been found to be synonymous with depletion of stored 
fat, protein, and carbohydrates (Adams et al., 1982; 
Weatherup and McCracken, 1999). We also monitored 
phase angle in postmortem adult salmon to measure how 
phase angle changes in response to cell degradation and 
water movements from intra- to extracellular spaces. In 
all cases, phase angles were calculated from impedance 
measures ( R and Xc ) of fish that were sampled accord- 
ing to the methods in Cox and Hartman (2005). In this 
study, two sets of needle electrodes (stainless 28 gauge, 
Grass Telefactor, West Warwick, R.I.) each consisting of 
a signal and detecting electrode were inserted to a depth 
of 1 cm. One set was placed towards the caudle peduncle 
and the second set was placed in the nape region of the 
fish. Variables that could introduce error in R and Xc 
measures (e.g. varying the depth and gauge of needles, 
placement of fish on different conductive surfaces) were 
standardized to negate any bias, whereas temperature 
and time effects are explained experimentally. 
Temperature and time 
To test for significant effects of temperature on imped- 
ance measurements from dead fish, regression analysis 
was used to test whether slopes and intercepts differed 
from zero on regressions of temperature and response 
measures (phase angles). Three adult pink salmon 
(520-550 mm fork length) were killed and connected 
to a BIA Quantum-II Desktop System (RJL Systems, 
Point Heron, MI) using standard needle electrodes and 
orientations as described by Cox and Hartman (2005). 
The Quantum-II was set to record impedance every five 
minutes for 12 hours. An ibutton thermometer (Maxim 
Integrated Products Inc., Sunnyvale, CA) was placed 3 
cm inside the dorsal musculature of the fish and was set 
to record temperatures every 5 minutes. Both impedance 
measurements and thermometers were synchronized 
before the experiment. Each fish was brought directly 
from the water, killed, and placed on a 4-inch wire stand 
(to allow air flow around the fish) in the empty freezer 
compartment of a standard freezer. Initial fish tempera- 
tures were equal to ambient water temperature of 8°C. 
After 12 hours, the fish was removed from the freezer 
and impedance measures and temperature data were 
downloaded onto a computer. For regression analysis, 
only impedance measures taken when the fish tempera- 
ture was between 0°C and 8°C were used. Impedance 
measures of R and Xc were used to calculate phase angle 
measures. Significance tests to test for nonzero slopes 
were done on each fish by using a standardized major 
axis (SMA) test and between fish by using the Bartlett- 
corrected likelihood ratio (LR) test for differences in the 
slopes. An analysis of covariance was used to test effects 
of temperature and individual fish on phase angle. 
We examined the effect of time after death on re- 
sponse measures (phase angles) to determine time 
effects on phase angle. Juvenile coho salmon (/j = 30, 
mean=10 g, standard deviation [SD] = 2.72) from the 
Sheldon Jackson Hatchery, Sitka, AK, were killed and 
groups of six fish were randomly placed in plastic bags 
and placed on ice. At 0-, 3-, 6-, 9-, and 12-hour inter- 
vals, a bag was removed and six fish were measured for 
length, weight, and impedance. Impedance measures 
followed standardized procedures found in Cox and 
Hartman (2005). Impedance measures were then used 
to calculate phase angle. Linear-effects mixed models 
were used to test for effects of time on phase angles. 
Laboratory study 1 : fasted and fed brook trout 
To determine the effects of malnutrition on phase angle 
in brook trout in fresh water, phase angle was repeatedly 
measured in fed and fasted juvenile brook trout over 
a period of nine weeks (December 2002-March 2003). 
