well, MM, Baseline backround radiation emmisions are the precise level we have evolved to survive in. coal plant radio emmisions, which are much more than nuclear plant emmissions, per capita and in gross total, are in addition to our natural background levels. source makes little difference to their effect.
catching wild life is fine as long as the demand is relatively small. but as our population grows and we put more demand on the natural ecosystem, it declines rapidly. a pack of wolves survives very well until they take the last deer, or buffalo then how long do they last?
I think aquaculture can be fine as long as we dont exploit other resources which pollute, to excess. much like we currently do with all forms of energy and mineral resources. it produces farmed fish stocks but at a greater cost. the return is poor.
Thats where your fond Unicorn power comes ito play. things like wind, solar, geothermal, energy recapture, are all better forms of making energy. plus better design on conumption to make them more efficient and reclaim much of the inherent waste energy. there is a whole lot we can do to get more from each kilowatt of power we produce and expend.
I like growing corals, and raising fish. but i also see my current system is an energy hog. to do it better, natural light green houses heated and cooled geothermally, with transparrent glass PV roofs for power to run pumps would be a better method. rather than buying power from the grid which produces on average 2 pounds of CO2 for each kilowatt of electricity produced. We have a long ways we can go to do it better . only limited by our imagination and ingenuity.
a new article today makes a new discovery on how depleting fish stocks might also be depleting the alkalinity of the oceans.
http://www.nature.com/news/2009/090115/full/news.2009.30.html
seems they help replenish some of the carbonate. so , one more thing to worry about.