The power analysis for penguin responses to fishing around Dassen and Robben
islands has been completed. Response variables considered are chick condition,
active nest proportion, fledging success, chick growth, foraging path length, and
foraging trip duration. Although complete results are given here only for the first
two of these variables, overall there are clear indications regarding the residual
variances associated with these variables. Those variances are now estimable for
Dassen and Robben islands with sufficient reliability to allow a decision on whether
an experimental closure programme could yield definitive conclusions regarding
the impact of fishing close to island colonies on penguin demographics within a
realistic time span. Thus the purpose of the feasibility study has been achieved and
the study can be concluded, with the island closure experiment commenced for
these two islands. Definitive results from the experiment can be expected for both
islands with about 2–4 years’ additional data
