Far smaller fishing footprint than previously believed

A new and more accurate study reveals that about 4% of the ocean area experiences fishing each year, a far smaller estimate than previous studies that relied on very large grid sizes. Two recent studies estimated that fishing takes place in 55% of the ocean and 90% of the ocean each year. But these estimates divide the ocean into 0.5°×0.5° grid cells, which are ~3100 km² in size at the equator, and assume each cell is fished if a single fishing location is recorded in the entire cell. The higher estimate additionally assumes that catches occur in areas inhabited by a fished species, not just in fished locations, potentially placing actual fishing locations into multiple grid cells. Now, researchers using the same dataset have examined what happens if the estimates are recomputed using high resolution data, to get a more accurate estimate of the ocean area fished. When the grid cells are reduced to 0.1°×0.1°, only 27% of the ocean area is fished; and when the grid cells are 0.01°×0.01°, then only 4% of the ocean area is fished. Furthermore, even for the tiniest grid cells they examined, half of the grid cells could not have been fully covered by fishing even if fishing uniformly covered the grid cells. The authors also showed that large areas where fishing is banned in Alaska appear to be completely fished when using 0.5°×0.5° grid cells, but are not fished when using fine resolution 0.01°×0.01° cells. The results overturn the main tenet of one of the original papers, that the area footprint of fishing is larger than the footprint of agriculture; instead, the opposite is true. The new results appear in Science magazine, and were authored by an international group of scientists headed by SAFS postdoc Ricardo Amoroso.

Using smaller grid cells results in a much more accurate estimate of fishing footprint. Shown here are estimates for Alaska and southern South America. Fishing is banned in the red area in Alaska, but appears to be fully fished when using large grid cells.
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