represents the inherent dissimilarity
between the two sites against which post-impact differences
are compared. If the difference between the control and Impact
site becomes significantly greater or lesser after the impact event
(i.e. CBefore −IBefore / = CAfter −IAfter), this is interpreted as an indication
that the impact event initiated the observed change. In our
study, we used replicate paired control and impact plots, with pairing
based on proximity (45–100m separation) and similarity in
mangrove forestry measures (Ellis and Bell, 2004b). This design
was intended to minimize pre-disturbance differences in fish abundance
and species composition.