Differences in Na+ influx rates (Jin) and copper accumulation
between “stressed” and “unstressed” fish were evaluated using an
unpaired Student’s t-test, while individual and group efflux rates
(Jout) were evaluated using a two-way analysis of variance (ANOVA)
using stress status (Day 1 or Day 2) and hour as the two factors.
Opercular frequency was evaluated with a two-way repeated
measures ANOVA, with post hoc Holm–Sidak pairwise multiple
comparisons used to assess differences across time points. Mean
efflux rates were related to opercular frequency using simple linear
regression. Copper absorption values were log transformed and
efflux rates for individuals were square root transformed in order
to achieve equal variances. All statistical analyses were conducted
using SigmaStat, with a significance level of p < 0.05.