Tuna fishing has grown into an eight-billion dollar industry.
And over four million tonnes of tuna are caught worldwide each year, a four-fold increase in as many decades. Almost two-thirds of the catch now comes from the Pacific. In the Atlantic, yellowfin catches have been shrinking since 1990. Now a similar decline has begun in the Pacific. Tuna need to swim constantly to keep water flowing over their gills, otherwise they can't breathe.