Some food for thought.
The amount of fish in the ocean is countless. We just don't know how many are out there except for rough ideas at best.
The amount that contract diseases or parasites is unknown. Again we can only have a rougher guess based on out of how many fish caught have them and work up a percentage from the above number.
The mortality rate is another number out there somewhere in the ocean that we will never know for sure.
The repopulation rate is at best a guess.
Oh, and they have the biggest aquarium availabe to do whatever they want to in.
However take people out of this guestimate and the amount of fish species out there has the means to survive, even with odds that we would consider stagering, throughout disease, predators, and food shortages. Thats just the way I look at a very interesting question.