When hunters in California wanted more ducks to hunt, they created Ducks Unlimited. Soon they were up to their eyebrows in ducks.
If fishermen want fish to fish, they should make fish. This is not unrealistic.
Already, relatively low tech offshore fish farms show great potential to produce huge numbers of fish, not just for the table, but to increase the wild stocks.
Little more than a ring of pontoons descending a net into the water, with a tug-like boat controlling the lot. Fish are introduced from a hatchery, then fed at intervals, letting the ocean keep the area clean and oxygenated.
If done in a very large scale, such aqua-farms could feed countries. But they are so relatively inexpensive to run, that some could be run just to “raise and release” fish once they had reached a good size. Not just food fish, but exotic fish as well.
Granted, any predators in the area would feast, and fishermen would be encouraged to leave such artificial schools alone for a while. But done intelligently, it could radically increase the natural bounty of fish.
A profusion of fish would negate the need for destructive fishing habits, such as drift nets. It would encourage fishermen to be more like farmers. A more reliable harvest is a big selling point.
Atoll islands, even artificial islands, could be used to make fish farms over dozens of square miles, producing thousands of tons of fish. And placing such aquaculture far away from major coastlines prevents a lot of pollution and other harmful effects.
Japan alone consumes 10 million metric tons of fish a year. If much of their need was met with aquaculture, just about everyone would benefit.
1st problem...no one owns the sea.