The article is filled with mistakes and misunderstandings or maybe this guy eats in really terrible places:
Spanish people weren't buying "fake olive oil" when poisoned. This was canola oil, was advertised as canola oil, and everybody in Spain can spot the difference among the wine and cider or between the cheapest olive oil and other vegetable oils. All this paragraph is false, including the “No one is checking, Olmsted writes".
Not, Your salmon is most probably true salmon, because to use fake salmon is a mess when the true species is breeded in farms since decades, is relatively cheap, can be found easily in your market, and its origin can be tracked easily by the tag.
There is only an "acceptable" substitute to salmon available, and is rainbow trout feeded with carothenes; smaller and more expensive to produce for farmers than true salmon. This is like to say that your coke bottle is probably faked because in the restaurant somebody could refill it with other thing of equal value or more expensive.
Yes, I must admit that milk is basically a cheap imitation currently, and there is a lot of things that must improve in tracking fisheries and marine species, but spreading fears and saying that nobody is surveying this is not correct. You have the NOAA for example, blatantly ignored in the article.