Identification of Representative Seamount Areas in the Offshore Pacific Bioregion, Canada

The Offshore Pacific Bioregion (OPB) is a dense cluster of ecologically and biologically significant areas, most of which are underwater mountain ranges known as seamounts. Seamounts support a range of ecosystems, depending on a suite of physical and biological characteristics. The Fisheries and Oceans (DFO) Science Branch was asked to develop an ecological assessment to identify representative seamount areas to detect changes within the OPB (i.e., areas that capture examples that reasonably reflect the full range of ecosystems present at the scale of assessment). The focus of the assessment is an Area of Interest (AOI) in anticipation of a proposed Large-Scale Marine Protected Area. Historically little is known about the variety of ecosystems and species supported by the OPB seamounts. Before 2017, research on the OPB seamounts was limited to information from the relatively small fisheries and rare scientific surveys. Since then, the Deep Sea Ecology program (DFO Pacific Region) has led three intensive seamount surveys. Herein we identify and describe representative seamount areas primarily using models, classification systems, habitat level surrogates, and ground-truthing with the new survey data. We also identify new seamounts, new seamount classes, natural seamount boundaries, the ecological uniqueness and ecosystem functions provided by each seamount, species found on seamounts, existing knowledge, and anticipated environmental changes. There are 62 seamounts in the OPB, 47 of which are in the AOI, and dozens that are newly discovered and unnamed. We found that depth- and nutrient-related seamount characteristics are often indicative of enhanced ecological characteristics, where seamounts with shallower summits and higher potential flux of particulate organic carbon support regionally unique or rare species or habitats, higher biomass, higher biological diversity, and more ecosystem functions. Shallower, more productive seamounts are also more likely to have pre-existing data, have attracted previous research, and are more likely to suffer anthropogenic impacts, now and in the future (e.g., fishing and climate change). The evaluation herein determined all seamounts provide rare shallow offshore ecosystems and support ecologically important species (e.g., cold water corals and sponges). However, Union, Dellwood, and Explorer seamounts are unique or rare within the AOI (and the OPB). The establishment of the proposed Marine Protected Areas (MPAs) will significantly enhance the representativity of offshore ecosystems and species within conservation areas. Together with the existing SGaan Kinghlas-Bowie Marine Protected Area, all regional seamount classes will be protected within conservation areas—with only a few examples of notably different seamounts occurring outside of a conservation area (e.g., SAUP 5494 and Tuzo Wilson). SK-B, Union, Dellwood, and Explorer seamounts are also identified as good candidates for representative seamount areas (i.e., reference sites) to detect changes. The ecological assessments within this Research Document are intended to support ongoing adaptive ecosystem management, to be re-examined as questions that arise regarding management and monitoring.

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