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Layer: Intensity (ID: 1)

Name: Intensity

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Type: Raster Layer

Geometry Type: null

Description: <DIV STYLE="text-align:Left;"><DIV><DIV><P><SPAN>This data layer depicts the relative intensity of fishing effort for commercial bottom trawling off the U.S. West Coast from 1 Jan 2002 to</SPAN><SPAN><SPAN>11 Jun 2006. Each of the three coastal states administers a commercial logbook program, for which records are uploaded to the Pacific Fisheries Information Network (PacFIN) regional database. Database records were utilized for commercial trips using limited entry </SPAN></SPAN><SPAN>bottom trawl gear types (e.g., "small" footrope, "large" </SPAN><SPAN><SPAN>footrope, flatfish, selective flatfish, and roller trawl) regardless of fishery sector. Records from the majority of state-managed trawl fisheries (e.g., pink shrimp, ridgeback prawn, sea urchin) are not included in PacFIN and thus are not represented. However, tows targeting California halibut while also participating in the federal trawl fishery are submitted to PacFIN and included in this data layer</SPAN></SPAN><SPAN><SPAN>.</SPAN></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 = 3 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>

Copyright Text: 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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Supported Query Formats: JSON, geoJSON, PBF

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Supports Statistics: false

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Use Standardized Queries: true

Supports Datum Transformation: true

Drawing Info: Advanced Query Capabilities:
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Type ID Field: null

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Supported Operations:   Query   Generate Renderer   Return Updates

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