For those looking for more scientific reading on the risks spreading pathogens for farmed fish to wild populations:
 
Norway has the largest salmon-farming industry in the world, an industry that is still growing, and in recent years production of marine species like Atlantic cod has also increased. At the same time, Norway has the world's largest wild stock of Atlantic salmon and has fjord systems and ocean areas rich in wild marine fish species which form the basis of a large fishing industry. As the aquaculture industry grows and diversifies, there is concern about the potential effects of pathogens spreading from farmed fish to wild populations