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The main purpose of this data layer is to help inform the National Marine Fisheries Service Biological Opinion on Continuing Operation of the Pacific Coast... |
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The main purpose of this data layer is to help inform the National Marine Fisheries Service Biological Opinion on Continuing Operation of the Pacific Coast... |
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Fishery Resource Analysis and Monitoring Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration
Pacific States Marine Fisheries Commission |
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5000 |
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[] |
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<DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>This data layer depicts the relative intensity of fishing effort for shoreside processed commercial midwater rockfish off the U.S. West Coast from 1 Jan 2016 to 31 Dec 2017. Records of at-sea processed midwater trawl tows were compiled from observer records from the West Coast Groundfish Observer Program (WCGOP) and the electronic monitoring program coordinated by the Pacific States Marine Fisheries Commission (PSMFC). </SPAN></P><P><SPAN>The intensity layer is a raster layer with cell values representing the total length of all lines intersecting a standardized area. To calculate this metric, we applied a line density algorithm in ArcGIS geographical information system software (Environmental System Research Institute, Incorporated, Redlands, California). The line density algorithm calculates density within a circular search area (radius = 5 km) centered at a grid cell (size 500 m x 500 m). The value (units: km/km</SPAN><SPAN><SPAN>2</SPAN></SPAN><SPAN>) for each raster cell is the quotient of total line portions intersecting the circular area per cell area. Since density outputs are highly sensitive to the specified radius and cell size, the absolute values are less important than the relative nature of them. The benefit of this output over depicting lines themselves is that the density output better identifies areas where fishing effort is concentrated, while still ensuring confidentiality of individual fishing locations. The initial density output was more spatially extensive than the one shown in the figures, because it included cells with density values calculated from tows made by less than three vessels. Those "confidential" cells were removed for the final published data layer. Density parameters were chosen in order to minimize data exclusion (due to confidentiality mandates) while still providing a fairly high spatial resolution (500 x 500 m).</SPAN></P><P><SPAN><SPAN>This spatial summary of fishing effort was developed from lines connecting gear set and retrieval points. It is recognized that fishing events, particularly for mobile gears, rarely follow straight-line paths; however, this was the most readily available information. This summary is not intended to quantify total impact of fishing on either benthic or pelagic habitats.</SPAN></SPAN></P></DIV></DIV></DIV> |
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| title:
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Relative Intensity of Shoreside Processed Commercial Midwater Rockfish-Targeting Trawling off the U.S. West Coast (1 Jan 2016 – 31 Dec 2017) |
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["Northeast Pacific Ocean","California Current Large Marine Ecosystem","marine","groundfish","fishing","fishing effort"] |
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en-US |
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150000000 |
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