I think it is about time the human race gave up hunting and gathering for sea life and start fish farming. Even the Romans had in-shore netted area where fish stocks may be kept and grown.
We should be building very large tanks inland where monocultures of fish could be gown, fed with food crops specially grown in local greenhouses.
The fish would need to be specially bred and selected to thrive in this environment.
We could have river fish in fresh water tanks and sea fish in brine tanks. The tanks would be totally enclosed so that it would have its own air and water supply. The tanks would be stocked with disease and parasite free fish or other sea creatures to be used as food for the human community.
Chris