Current aquaculture tech could provide 100 times current seafood consumption
UCLA researchers found that over 11,400,000 km2 are potentially suitable for fish and over 1,500,000 km2 could be developed for bivalves. Both fish and bivalve aquaculture showed expansive potential across the globe, including both tropical and temperate countries. However, as would be predicted by metabolic theory, many of the areas with the highest GPI were located in warm, tropical regions. The total potential production is considerable: if all areas designated as suitable in this analysis were developed (assuming no further economic, environmental or social constraints), they estimate that approximately 15 billion tonnes of finfish could be grown every year—over 100 times the current global seafood consumption.
Overpopulation is a myth.
For God's sake, no it's not. That's like saying "rain is a myth" when it's sunny.
If I breed mice in a room but limit their resources and there are eventually 2,000 mice literally jampacked in the room, eating each other, dying on top of each other, starving to death, would you say "overpopulation is a myth?"
Overpopulation is framed by the amount of consumable resources + the number of consumers. If there are too many consumers and/or too few resources, there is overpopulation. That's no fucking myth, that's basic objective fact.
The solution to overpopulation is twofold, and you're generally on the money for one when you mention this Cornucopian ideal.
You either reduce the number of consumers or increase the amount of consumables. You either reduce the number of mice in that room or you increase their living space and amount of food and water. Cornucopians, from what I can tell, aim for the latter.