I recall reading an article, maybe two or so years ago, about a sustainable aquaculture co-op being developed in Maine. It was pretty interesting. Instead of a monoculture they use a system of raising several different types of seafood in a given area, much like the symbiotic relationship that exists in nature. So it's using kelp, various bivalves, fish, etc, all the way down the water column. Apparently, if done properly, it can be rather cost effective because the inputs are so low. Also, because the inputs are low, it has little environmental impact.
The problem, of course, is scaling up so that this method of aquaculture becomes the dominant way seafood protein is raised, rather than the devastating death trawlers that scrape wide swaths of the ocean floor and toss away any "bi-catch" that they don't think is commercially viable.
FWIW, my wife and I switched to a mostly plant-based diet about eight months ago. We are not the zealous vegan types, and we never tell other people how to eat. We do on rare occasion eat fish, eggs, and dairy. We weren't really big beef or pork eaters before, but did eat chicken. Because we didn't eat all that much animal protein overall, the change wasn't really that difficult. I would encourage anyone on the fence to take a few baby steps towards plant-based eating. Unlike the zealots, I don't think people need to go full-on vegan; just cutting back a bit on the animal products is great for heath and for the environment. And, if you stay away from the over-processed vegan meat substitutes (which really aren't that healthy anyway), it's been our experience that it's cheaper. Meat is expensive these days! As an added bonus, we save all of our veggie scraps in a freezer bag and when it's full I boil up a big pot of veggie stock and toss it into quart freezer containers. Perfect for soups, stews, sauces, etc.
