one thing that is certain is that farmed fish and in particular farmed salmon, organic or not (and imo using the term organic to describe farmed salmon of any kind is a betrayal of what the term organic means to me) is bad news. Fish farming is INCREDIBLY destructive to the environment. For every one ton of farmed salmon (including organic) produced up to 3 tons of wild fish (sand eels, juvenile fish of all species) have been killed to feed them.
Concentrating migratory fish like salmon in dense populations causes massive blooms of parasites which ravage wild fish and pollute our coastline.
Seatrout on the West coast of scotland have been driven close to extinction by fish farms.
Moving away from salmon, 'ranched' tuna is leading to the decimation of eastern atlantic tuna stocks. Farmed seabass causing most of the same problems as salmon. Wild seabass, unless line caught, is generally caught by a technique the uses two trawlers and kills vast numbers of dolphins.
Turbot, halibut, cod, bluefin tuna, monkfish and skate are all endangered.
So you need to buy line caught fish. And you have to choose sustainable fisheries. MCS helps. Choose fish that grow fast and breed young like mackerel, herring, sardines. At all costs avoid long lived slow maturing species like bluefin, cod, chilean seabass (a total disaster).
Do not eat farmed salmon. Organic or not and quite apart from the environment, it has to be a strong contender for the next BSC type scandal.
hth.