Updated impact assessment framework to estimate the cumulative footprint and impact on VME taxa of bottom longline fisheries in the CCAMLR Area

ABSTRACT Since 2008 New Zealand has been developing an impact assessment framework to estimate the likely impacts of bottom longline fishing on Vulnerable Marine Ecosystems (VMEs), as required by Conservation Measure 22-06. The most recent iteration of the impact assessment (Sharp 2010) was recommended in 2010 by WG-SAM (paragraph 4.16) and WG-EMM (paragraph 3.20) as the basis by which Members submitting new and exploratory fishery notifications should estimate impacts on VMEs associated with their proposed bottom fishing activities, as well as the basis by which WG-FSA might complete cumulative impact assessments for all gear types combined at the scale of entire fisheries. Both WG-SAM and WG-EMM gave specific guidance as to how the framework might best be applied. This paper updates the impact assessment taking account of the specific recommendations of WG-SAM and WG-EMM 2010 and incorporating new information arising from WG-EMM 10/33, including the choice of improved input distributions representing key variables driving the impact simulation and the use of alternate assumptions in which lateral movement frequency is negatively correlated with depth. Impact estimates are summarized separately for each of 17 benthic bioregions defined in Sharp et al. (2010), and displayed as frequency distributions of fine-scale pixels experiencing different levels of impact, as advised by WG-SAM 2010 (paragraph 4.18). We conclude that the relationship between depth and lateral line movement is highly uncertain, but it is likely that improved understanding of this relationship will yield impact estimates that are slightly higher for shallow habitats on the shelf relative to previous estimates, and substantially lower for deep habitats. Overall estimates of impact remain low within all bioregions.