3.1. Blood glucose and plasma cortisol levels
Blood glucose was significantly higher in the PTNS group compared
to controls. In the PTS group glucose levels were not significantly different
than those of control fish (Fig. 1a). With respect to cortisol levels,
both PTNS and PTS had significantly higher plasma cortisol values
than the control group. Whereas cortisol values were highest in the
PTS group, there were no significant differences between PTS and
PTNS treatments (Fig. 1b).
3.2. Skin mucus bacterial counts
We first evaluated whether skin associated bacteria change prior
and after transport from the hatchery to Tingley Beach. Strikingly, the
numbers of culturable bacteria in both groups were significantly different
and stress caused a ~50-fold increase in total bacterial numbers
associated with the skin both in TSA and LB agar plates when no salt
was added (Fig. 2). In the presence of salt, bacterial numbers were still
significantly higher, but the fold increase was lower than that in the absence
of salt, about ~10-fold. No differences were found in the numbers
recovered on LB or TSA plates,
3.3. Scanning electron microscopy and light microscopy of rainbow trout
skin before and after stress
Stressed fish and other animals are known to secrete greater
amounts of mucus. We studied the skin of control and stressed trout
by scanning electron microscopy and confirmed these results. The general
morphology of the skin surface of control trout (Fig. 3a–b) differed
significantly fromthat of stressed trout in the PTS group (Fig. 3c–d) and
the PTNS group (Fig. 3e–f). The skin surface of control rainbowtrout had
an organized appearance characterized by polygonal-shaped epithelial
cells and the presence of some goblet cells showing discrete secretion
of mucus and few bacteria cells laying on the surface. In the PTS group