Switching to greener energy would be my first choice too, and it looks very hopeful that we will be doing so soon. However, we are also depleting the ocean fish by overfishing and pollution. Spending some resources in producing a better environment for supporting the larger ocean fish seems good. Granted there are always secondary unplanned effects of any action we may take but artificial upwelling to produce increased phytoplankton seems initially to be a good idea as far as I can see but I'm no expert in this.