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Fishery Bulletin 107(4) 
for dorsal measures, and 10.30° and 11.15°, respectively, 
for ventral measures (Fig. 6). Phase angle also decreased 
during winter months in Pacific herring collected from 
Sitka Sound (LME, P<0.003, df=225). Phase angle 
decreased from 12° to 10° from January to March (Fig. 
7), whereas mass-specific energy content declined from 
7.15 kJ/g to 4.79 kJ/g. Phase angle increased to 15° in 
April, and mass specific energy increased to 5.02 kJ/g. 
| B 
Figure 3 
Notched boxplots and means (*) of phase angles measured weekly for 
4 weeks from (A) small (<100 mm) and (B) large (100 mm) rainbow 
trout (Oncorhynchus mykiss) that were fed ad libitum (white boxes, 
n = 12) or fasted (gray boxes, n = ll). Notches extend to ±1.58 inter- 
quartile range/vfi and represent roughly 95% confidence intervals. 
Open circles (O) represent outliers determined by a Grubbs test. 
Phase angle and water balance 
in postmortem fish 
Phase angles over time in postmortem 
fish reflected changes in cell integrity and 
subsequent water movement from intra- to 
extracellular spaces, reflected by the two 
components ( R and Xc) which are used to 
calculate phase angle. In all three dead fish, 
slopes were initially positive reflecting an 
increase in Xc and a concomitant increase 
in R. Within 12 hours of death, this process 
reversed and slopes became negative as 
phase angle decreased (Fig. 8). There was 
not enough evidence to indicate that slopes 
were different between fish (LR [likelihood 
ratio]=110.7, P<0.001, slope=-4.2). 
Discussion 
In this study, in both laboratory and field 
settings, phase angle was used to compare 
the relative nutritional condition of salmo- 
nids and clupeids in fresh and saltwater 
while each was in a different condition. In 
each case where fish were expected to be 
in poor condition, phase angle was lower 
than in fish in good condition. The range of 
phase angle values was also greater in the 
larger rainbow trout than in the smaller 
rainbow trout. Phase angle reflects changes 
in condition by directly measuring the R 
and Xc of the body tissue, and more specifi- 
cally, the ratio of these two values directly 
represents changes in intra- and extracel- 
lular water distributions (i.e., intracellular 
dehydration and extracellular hydration) 
(Schwenk et al., 2000b). Water distribution 
(namely, the movement from intra- to extra- 
cellular spaces) can be attributed to use of 
energy stores as indicated by the herring 
study in field study 3. In humans, phase 
angle can reflect loss of body protein during 
starvation as well as presence of infection, 
both of which decrease the condition of the 
organism (Plank et al., 1998; Schwenk et 
al., 2000a). Changes in phase angle in fish 
are therefore likely to reflect the general 
health of fish in addition to their nutritional 
status. Consequently, phase angle should be 
considered a reliable independent marker of 
fish condition. 
Phase angle changes with nutrient levels 
in fish. When fish fast, nutrient inputs of 
