Recent fishing footprint of the high-seas bottom trawl fisheries on the Northwestern Hawaiian Ridge and Emperor Seamount Chain: A finer-scale approach to a large-scale issue
A standing data gap for management of high-seas seamounts of the Northwestern Hawaiian Ridge and Emperor Seamounts (ES-NHR) by the North Pacific Fisheries Commission is the footprint of fisheries activities on these seamounts. Using satellite AIS data and the algorithms of the publicly available Global Fishing Watch database, a spatial map of trawling in a 0.01-degree latitude by 0.01-degree longitude square grid was created to review the data available to map this footprint. From 2012 to 2018 much of the trawling effort for all countries focused on Koko, Yuryaku, Kammu, and Colahan Seamounts at depths between 400 m (summits) and the depth limit currently set by the North Pacific Fisheries Commission of 1500 m. Additional seamounts with fishing activity included Annei (North Koko), Kinmei, Jingu, and Suiko. The remaining ES-NHR seamount locations show no trawling in those years. Bottom contact fishing was predominately carried out by ships with flag states of Japan and Korea. To date there appears to be compliance with the recent small-scale closures on C–H seamount and Koko.
An additional source of data comes from scientific Autonomous Underwater Vehicle (AUV) surveys in 2014 and 2015 from three of these seamounts, in which scars from bottom contact gear are readily visible. These cover a smaller spatial area and depth range than the satellite data, but indicate the full footprint is not encompassed by the satellite data, suggesting either the fishing footprint is not fully captured by the AIS approach or that the footprint has shifted through time. AUV surveys also provide data on areas where abundant megafauna occur, which can provide candidate starting points for VME management efforts and further closures, similar to ones already in effect in the ES-NHR. The combination of satellite and AUV data provide a finer-scale fisheries footprint for this region that can aid in management of these sites.