Revised impact assessment framework to estimate the cumulative footprint and impact on VME taxa of New Zealand bottom longline fisheries in the Ross Sea region

In 2008-2009 New Zealand developed an impact assessment framework to estimate the likely impacts of bottom longline fishing on vulnerable benthic invertebrate taxa, termed Vulnerable Marine Ecosystems (VMEs), consistent with the requirements of Conservation Measure 22-06 (Bottom fishing in the Convention area). The impact assessment framework was subsequently endorsed within CCAMLR for routine application by Members submitting notifications of their intent to participate in new or exploratory fisheries using bottom fishing gear (SC-CAMLR XXVIII, paragraph 4.247 v–vii), and was applied to estimate the cumulative historical bottom fishing footprint of all fisheries in the CCAMLR area. The Scientific Committee called for additional work to address remaining uncertainties about the nature and extent of bottom fishing impacts on potential VMEs (SC-CAMLR-XXVIII paragraph 4.251). The purpose of this paper is: i) to estimate impacts on VMEs per unit effort using a simulation approach with explicit incorporation of uncertainties in the input assumptions; ii) to examine the application of the impact assessment framework at different spatial scales, and implications for the validity of the underlying structural assumptions of the assessment framework; and iii) to express impact estimates in a spatially explicit manner with reference to areas of distinct environmental characteristics arising from a benthic bioregionalisation of the Ross Sea region (Sharp et al. 2010). We conclude that bottom fishing impacts on VME taxa in the Ross Sea are low.