I have pointed out for years, that when sewage and other costs are taken into account, that fish farms are a negative on the economy. My estimate, for sewage in BC, is $10.4 Billion that we, taxpayers, absorb.
I did a lot of research into sewage around the world before being willing to believe my own estimate. Here is one of my articles that details the negative effects on BC's economy from fish farms: http://fishfarmnews.blogspot.ca/2014/03/fish-farm-sewage-dfo-expansions-cost.html.
Look at the Index in October 2014 for past articles on sewage, or cruise 2015 for my articles on sewage cost in BC, as well as low or negative job effects and so on. For an article of mine that details the lopsided revenue picture, with wild fish revenue towering over farmed fish: http://fishfarmnews.blogspot.ca/2015/05/salmonfishing-revenue-towers-over.html.
Here is an article that gives you more references to follow up on the negative costs of fish farming on the economy. It is vastly negative in BC, on sewage cost alone. And the BC Stats article that compares the fishing sectors, noted that all of aquaculture is worth only $61.9 M to the economy while the commercial, processing and sport sector are more than $600 M economic effect, fully 90% of all activity surrounding the fish resource. (For the BC Stats Report: http://fishfarmnews.blogspot.ca/2013/02/sport-fishing-how-we-tack-up-feb-6-2013.html).