Global Fisheries Data
Global fish catch data is first classified into fishing methods, associated with point locations, converted to a raster grid, then adjusted by primary productivity of the surrounding are. This technique gives us a ratio of fish catch to productivity - a useful measure of fishing pressure for each method.
The fish catch data was aggregated by 5 different fishing methods:
- Palagic, high bycatch
- Palagic, low bycatch
- Demersal, destructive
- Demersal, non-destructive, high bycatch
- Demersal, non-destructive, low bycatch
Each catch rate is associated with a particular point location. It is then rasterized and normalized by primary productivity to give an indicator of global fishing pressure.
- Export the the point locations table to dbf files
- Add XY data in ArcMap to convert the location table into a point dataset. Save as shapefile.
- select for each catch type and export a seperate dbf
- join each dbf to the cell locations (SEQ from the point layer -> CELL from the catch data) and output the 5 joined shapefiles.
- Rasterize each of the joined shapefiles using the catch rate column (CR) for the value.
- Resample the fisheries data to the same cellsize and extent and the productivty data
- Grid algebra to adjust for productivity. The focalmean ensures that local variations in production are not as important as the average productivity of the general area.
fishprod1 = (C:/WorkSpace/Global_Fisheries_NEW/resamp_rasters/fish1 * 907184.74) div
fishprod2 = (C:/WorkSpace/Global_Fisheries_NEW/resamp_rasters/fish2 * 907184.74) div
fishprod3 = (C:/WorkSpace/Global_Fisheries_NEW/resamp_rasters/fish3 * 907184.74) div
fishprod4 = (C:/WorkSpace/Global_Fisheries_NEW/resamp_rasters/fish4 * 907184.74) div
fishprod5 = (C:/WorkSpace/Global_Fisheries_NEW/resamp_rasters/fish5 * 907184.74) div
The unit conversion factor ensures that the output grids ensure that the units are tons of fish catch per tons of carbon production annually.
units on fish catch: millions of tons fish / km^2 * 1km^2/ 1,000,000 m^2 = tons fish/ m^2
units on procuctivity: grams Carbon/ m^2 * 1 ton carbon/ 907184.74 g carbon = tons carbon / 907184.74 m^2
fish catch / productivity : tons fish / m^2 * 907184.74 m^2 / tons carbon = tons fish / tons carbon