484 
Fishery Bulletin 107(4) 
Hatchery Wild 
Fish origin 
Figure 5 
Notched boxplots of phase angles and means (*) from 
brook trout ( Salvelinus fontinalis) from a hatchery 
(n = 21) and from the wild (n = 35). Notches extend to 
±1.58 interquartile rang e/Vn and represent roughly 95% 
confidence intervals. Open circle (O) represents outlier 
determined by a Grubbs test. 
the fasted fish in the laboratory studies, anadromous 
salmon fast as they migrate upstream to spawn and 
must rely on stored fat and protein as energy sources 
during their journey. Jonsson et al. (1997) found that 
during upstream migrations, percent somatic and vis- 
ceral lipid content can decrease from 12% to 2%, and 
11% to 1%, respectively, and total stored energy losses 
can total 60%. Both cellular degradation and extracel- 
lular hydration would result in decreasing phase angles 
from the dorsal tissue. 
Lower phase angles were observed in the ventral 
musculature, confirming that phase angle measures are 
location-specific. Phase angles calculated from ventral 
tissue revealed that ventral tissues do not degrade at 
the same rate as dorsal musculature. Conservation of 
the cell integrity in the musculature surrounding the 
gonads is consistent with observations that gonad qual- 
ity is conserved during migration. Jonsson et al. (1997) 
found that although migrating salmon experience a 
marked decrease in energy content of somatic and vis- 
ceral tissues during upstream migration and spawning, 
energy content in ventral gonadal tissue remained high 
throughout migration. It is noteworthy that phase angle 
was sensitive enough to indicate tissue-specific differ- 
ences in condition and therefore could have potential 
use in quantifying reproductive readiness. 
The sensitivity of phase angle to nutritional status 
was further indicated among Pacific herring between 
March and April. Whereas mass-specific energy content 
increased by approximately 5% between March and 
April, phase angle increased by 50%. Multiple studies 
on Pacific herring indicate reductions in energy and 
lipid content, and growth rates during over-wintering 
(Arrhenius and Hansson, 1996; Pangle et al., 2004). 
As energy stores become diminished from lack of food, 
physiological condition of the fish declines in a manner 
similar to the aforementioned “starving” fish. Vollenwei- 
der (2005) found that diminished mass-specific energy 
content in Pacific herring rebounded after spring algal 
blooms. This rebound occurs after spawning and likely 
reflects the reallocation of energy from gonad matura- 
tion to somatic growth and the replenishment of energy 
