ANCOVA revealed a significant linkbetween fish body size and three
parameters of the biochemical blood profile, i.e. total proteins, ALT, and
potassium. The sampling period directly affected 6 from 12 of the biochemical parameters analyzed (Table 2) (in addition, the effect of sampling period on glucose concentration was close to being significant:
p = 0.055).A significanteffectof fishgroupwasfoundfor totalproteins
concentration, glucose concentration, activities of ALT and AST enzymes, cholesterol and phosphorus. In addition, a significant effect of
sampling period–fish group interaction on the activities of both enzymes was found (Table 2). A significantly higher level of total proteins
was found in gibel carp when compared to common carp and hybrids
(p b 0.01). The ALT activity of hybrids achieved lower values than
those measured in gibel carp and common carp, and this was evidenced
in both samplingperiods (Fig. 2A); however, using the post hoc test, the
difference was significant only between gibel carp and hybrids (p =
0.039). Taking both periods together, the AST of hybrids reached intermediate values between gibel carp and common carp (Tukey post hoc
test, p b 0.001 and p = 0.05 respectively). However, when a significant
sampling period effect was taken into account, hybrids exhibited intermediate AST activity in autumn and lower AST activity in spring when
compared to parental species (Fig. 2B). Concerning glucose concentration,cholesterolandphosphorus,intermediatevalueswerefoundinhybrids when compared to pure species (Fig. 3A–C). When these
biochemical parameters were compared within sampling periods, we
found significant differences between common carp and gibel carp
(Tukey post hoc test, p b 0.05). Significant differences (p b 0.05) between gibel carp and hybrids were more often evidenced than significant differences between common carp and hybrids.