One of five people on this planet depends on fish as the primary source of protien. Total fish production was estimated at around 160 million tons per year, worth about 70-80 billion. With the population increase and higher standards of living, demand will increase substantially. Fishing is central to the livelihoods and food security of many communities, indeed etnire countries and regions.
As with many of the twenty burning global issues, the cost of tackling this one could be very modest on a global scale.