The sewage on the bottom of the ocean in Norway from fish farms is the equivalent of 17 million people: http://www.nrk.no/trondelag/far-torsk-som-har-beitet-pa-avforing-1.12638144.
As the population of Norway is only 8 Million people, that means fish farms put more sewage on the bottom of the ocean than 213% of the people in Norway, more than twice as much.
Looked at another way, Norway's human population would have to grow 9 million people more to equal the sewage under the fish farms.
But there is another way of looking at this. Sewage includes all the sewage released into the water column plus the remainder that ends up on the bottom. A way to calculate a conservative estimate is, at the accepted equivalent of 10 fish equal the sewage of 1 human, a conservative 1000 farms, and a conservative 500,000 fish per farm. The calculation is: 1000 X 500,000/10 = 50,000,000 humans.
In other words, the conservative estimate of the total sewage load from all the fish farms in Norway, is the equivalent of 50 million people, some 625% more than there are right now.
Note the article references 'researchers' who are not concerned. My response is: are they conflicted with fish farms? The fishermen say that fish eat the sewage and are so foul they would not eat them, or catch them to sell at market to humans.
Little wonder why those citizens who have to live with fish farms overwhelmingly reject them. You will recall the 110,000 British Columbians who signed a petition to stop expansion of fish farms in BC and get the farms out of the water. See: http://alexandramorton.typepad.com/alexandra_morton/2015/05/on-may-8-2010-i-helped-lead-the-final-steps-of-the-get-out-migration-a-6-day-walk-down-vancouver-island-to-victoria-th.html.