Not to a level that could feed the entire country, surely.
The numbers look pretty insane, you can raise many tons of fish in relatively small volumes of water (several hundred kg of fish per year per cubic meter). You just gotta build the ponds/tanks/cages, and the infrastructure to filter the water, supply the oxygen and deliver the feed.
Barring some planetary-scale cataclysm, most of Europe and the US are at no real risk of starving. There are other countries that are at a real risk, but the map doesn't make a clear distinction between "red as a matter of convenience" and "red because they physically can't do it".
Then we will lack whatever was produced on the place where you those new ponds with huge amount of fish.
Most of the richer countries/trade unions have a large meat surplus that could be easily shifted to something else, too.
Obviously nations do have limited surface area and creating new agricultural areas for them would be to the detriment of forests and "nature"
Farmed fish are often fed on fish meal from the ocean - e.g. fish meal made from species that are not eaten by people. Between 5% and 10% of ocean fishing is used for such aquaculture.
Same same as the cattle example in Ireland being fed on imported animal feed.
You can provide the right mix of proteins and fats from algal and insect sources, so this shouldn't be a barrier to increased adoption of fish farming.
(Scaling wastewater and disease management are perhaps greater challenges, but ought not to be intractable either)