Identification of Vulnerable Marine Ecosystems on seamounts in the North Pacific Fisheries Commission Convention Area using visual surveys and distribution models

Abstract

The North Pacific Fisheries Commission’s (NPFC) Scientific Committee is required to develop a process to identify Vulnerable Marine Ecosystems (VMEs) and areas where VMEs are likely to occur. NPFC recently adopted i) a methodology to identify VMEs based on visual data; and ii) a framework that identifies predictive models as one means to identify likely VMEs (i.e., areas where VMEs are likely to occur above an identified threshold). To identify observed VMEs on Cobb Seamount between 400 m and 1,200 m deep, a threshold methodology was employed based on the United Nations Food and Agriculture Organization's (the FAO) criterion of structural complexity. A VME indicator density threshold was estimated based on visual data from Cobb Seamount. This resulted in Canada identifying five VME areas on Cobb Seamount with a combined area of 508 m2 (representing 5% of the area surveyed). The locations of likely VMEs in the broader Cobb-Eickelberg seamount chain, in the depth range from 400 m to 1,200 m, were predicted using spatial modelling of VME indicator density with selected environmental parameters. Likely VMEs were predicted to be present on seven seamounts and one ridge in the Cobb-Eickelberg seamount chain. A total of 99 km2 (representing 10% of the modelled area) was identified as likely VMEs, with Cobb Seamount having the largest total area (27.5 km2). Multiple sources of uncertainty were identified including: limited available data; the representativeness of Cobb Seamount and extrapolation to nearby seamounts that may have different environmental characteristics; areas outside the depth range remain that were unassessed; the impact of pre-existing fishery damage on the modeling and results; the exclusion of potential VME indicator taxa; limiting the assessment to only one of five FAO VME criteria; and the selection and resolution of modelled environmental variables. An important implication of these sources of uncertainty is that the identified VMEs and likely VME areas are expected to be a subset of the full VME extent in this seamount range, considering VMEs and likely VMEs outside the 400 to 1,200 m depth range have yet to be evaluated. Future research to advance Canada’s identification of VMEs in the NPFC Convention Area could include: additional visual surveys designed for VME identification; further analysis of the VME indicator density threshold and methodology; investigation of other approaches to identify VMEs and likely VMEs based on the other four FAO VME criteria; and ground truthing of predictive models of the location of likely VMEs throughout the Cobb-Eickelberg seamount chain.