Cox and Heintz: Electrical phase angle as a new method to measure fish condition 
483 
proteins, carbohydrates, and fats are lacking, which 
forces the use of stored nutrients to meet energetic 
demands (Moyle and Cech, 2004). Consistent with this 
use of stored nutrients are shifts in intra- and extra- 
cellular water, and findings by Finn et al. (1996) show 
that loss of body protein parallel a loss of intracellular 
water causing subsequent cell shrinkage and progres- 
sive cellular dehydration. As fish fasted, cells likely 
became more and more dehydrated and phase angles 
decreased. This has also been observed in humans with 
anorexia nervosa, where low phase angles reflect de- 
creased nourishment (Mika et al., 2004). As organisms 
continue to starve, phase angles continue to decrease 
as stored cofactors such as vitamins, which are needed 
for metabolic conversions, are depleted and cause a fur- 
ther decline in condition. Typical symptoms of vitamin 
deficiencies include muscle and cellular atrophy, poor 
growth, and anemia, all of which would lower phase an- 
gles. As phase angle changes with the nutritional status 
of laboratory-fasted fish, it is apparent that phase angle 
can be used to determine if a fish has been subjected to 
a food-limited scenario. 
When we compared hatchery fish to wild fish, we 
found that phase angle was lower in the wild fish, in- 
dicating that the condition of wild fish was lower. It 
can be assumed that food is not a limiting factor in 
hatchery fish, nor is there a need to forage. The oppo- 
site is true in wild fish, where food is usually limited 
and variable, and where there is almost always a need 
to forage. In the optimal foraging theory it is assumed 
that when food is limited, all energetic functions are 
not fulfilled and energy must be allocated to different 
different physiological parameters to maximize sur- 
vival of the animal (Molles, 2005). This conclusion is 
supported by Berg and Bremset (1998) who found that 
there are seasonal changes in the body composition of 
juvenile salmonids that are due to changing energy al- 
locations. In hatchery fish, foraging costs are reduced, 
risk of predation is minimized, and food is abundant. 
Furthermore, the weights and condition of wild foraging 
fish would naturally be more variable (as seen in these 
data) because both of these parameters are dictated by 
numerous variables. Any excess energy consumed by 
hatchery fish is allocated towards growth and storage 
and concurrently provides the fish with proper vita- 
mins and minerals to maximize growth. Phase angle 
was lower in wild fish where they may have had to use 
energy for foraging and storage. 
The lower phase angles observed in upstream adult 
salmon were due to their presumed diminished condi- 
tion resulting from consumption of endogenous energy 
stores and to increased extracellular water volume. Like 
