About 71 percent of the planet is water and not land. Additionally, although there is United Nations sanctioned Law of the Sea, to a large scale, and once away fromclearly demarcated coastal waters, the ocean is seen more as being held in common by all peoples, and subsequently suffers from the "tragedy of the commons", which simply means that when we all are perceived to have equal rights to something, that certain people and industries will have a strong tendency to take more, especially those that are bigger or have more sophisticated techniques and equipment, because their attitude can simply be broken down into one of "better that I get it, rather than someone else" , because ultimately the whole exercise is seen as a zero-sum game. This means that in certain parts of our vast ocean that fishing stocks have become depleted, or have become negatively impacted for various reasons, to the long-term detriment of the fishing industry, the aqua-environment, and the balance of these in general.
Through the years, mankind has become master of his own food supply, to which, the days of hunting down food as a necessity or a way of life, has been replaced as merely something to do as sport. For instance, today, if you want cattle or poultry products, you aren't going to go to the trouble of targeting those animals in the wild, instead you are going to raise them up under a typically very specific, master plan, which in the course of events, includes: growth hormones, supplements, antibiotics, cages, fences, tagging, artificial lighting, and overall efficiency which didn't exist even a couple of generations ago. From a consumer standpoint, we are the beneficiaries of beef and poultry products that are mass produced because they cost us a lot less money in the pocketbook as well as being easier to procure because of these efficiencies.
Havinghad such great success in production of food products based on land-based animals, mankind has taken the next step to master the sea-based fish world as well, so that the harvesting principles previously created for animals are now being used to handle salmon, tilapia, shrimp, trout, cod, and other species of fish. This means that, once again, the consumer is the beneficiary of this efficiency, and this is the basic reason why you are able to find easily within your grocery stores or restaurants a plentiful selection of fish and shrimp at very reasonable pricing. Fish farming or aqua-farming is not meant to replace the fishing of lakes and oceans by commercial or indigenous people but as a necessary supplement to it, so that the oceans and lakes can begin to recover from having been over-fished for so long.
While there has been justified criticism about fish farming in the sense that fish spawned from many of these farms are much more likely to have a higher concentration of antibiotics and pesticides as well as being typically of a lower nutritional value as a comparable wild-caught fish, this isn't unusual given the circumstances of spawning fish in such a manner as to maximize their growth and yield with all this to be accomplished within a given time frame. This means, that the FDA must be about its "P's and Q's" in helping to assure that the American public consumes fish that is both safe and within the appropriate guidelines for its consumption.