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Surface ocean currents are driven by global wind patterns. As these currents pull along the surface, this creates a 'gap' that is replaced by deep ocean water. This process is known as upwelling.

This map shows the major upwelling zones in red. When water comes from the deep it is nutrient-rich, providing the basis for more ocean life.

Thinking about the previous maps, how can ocean currents explain the locations of commercially-important fisheries?

Exclusive Economic Zones (EEZs) are the areas of the ocean that nation states can commercially exploit. This map shows their global extent. Typically these areas, stretching for 200 nautical miles (370 km) cover the shallow seas above the continental shelf. Countries marked in a darker blue have applied for their EEZs to follow the continental shelf rather than be limited by the 200 nautical mile rule.