University of Cape Town
FISHERIES_2020_OCT_SWG-PEL_103.pdf (362.48 kB)

A proposal for a basis to consider future island closures, taking account especially of the current results from the island closure experiment

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posted on 2021-02-05, 10:45 authored by Doug ButterworthDoug Butterworth
This document provides proposals for a basis to consider future island closures, first taking account of the results to date for estimates of the impact of closure parameter δ from the island closure experiment obtained using the 2016 Panel algorithm. A pragmatic approach is adopted, given difficulties arising from outstanding matters of interpretation of the input data, which require further discussion. In essence, based only on the indications (which currently remain unclear) of whether or not biologically meaningful effects of closure on the penguin populations concerned have been demonstrated, suggestions are made to open Dassen island, to increase the relative frequency of closures at Robben island, and to maintain the current experimental closure schedule at St Croix and Bird islands with a possible increase in closure frequency at the former and decrease at the latter. In this situation, with important aspects of uncertainty still remaining concerning whether and to what extent closures might benefit penguins, final decisions will need to be based on trade-offs. These need to be quantified to the extent possible; they relate to the potential benefits to the penguins and the losses to the fishing industry in terms of financial returns and employment under different future closure proposals. The PWG will need to provide a summary of those benefits and losses, and some suggestions are made in that regard. Furthermore, continuation of the experiment in some form so as to better estimate closure impact parameter values obviously requires continuation of monitoring of at least some of the penguin response variables considered to date at all four islands; hence, plans to do so need to be confirmed.



Department of Mathematics and Applied Mathematics, University of Cape Town