Aquatic animals are more efficient sources of protein due to physics: buoyancy allows them to devote less energy to building bones that can support their weight, the water takes care of that for them. That is why you can get absolutely insane calories yields from aquaculture.
Not everyone likes fish. So, lets genetically engineer some aquatic cattle. More meat per animal, and since you’re starting with a ruminant anyway, they can still be fed a variety of feed. Best of both worlds.
Or go the other direction and develop a ruminant fish.
I'm super keen on starting my own sea can vertical farm. I've had technical success with my small aquaponics setup and want to expand operations. I'm curious about operating costs, zoning, and building permits.