I brought this exact topic up to my father in law one time. I had told him that I wanted to keep a fish didn't matter what species, I just wanted one to throw on the grill. The first fish we caught was about a 8 lb laker, wich he promptly released and I said don't forget I want to keep one for the grill. Well to make a long story short I ended up keeping a 12lb king and I said to him. Yeah I guess the lakers are the ones that have all the bad stuff in them right? He said , "let me tell you something about the Bad fish in lake ontario, when they test a fish they throw them in a grinder, grind them from head to tail and test the results, anybody that knows anything about fishing or cleaning fish knows that when you filet a fish you are removing the backbone and that section of dark meat where most of the "bad" stuff is stored." I said yeah I guess that makes sense. To wich he replied, let me ask you a question, do you know or have anyone in your life that smokes and has been affected by cancer or other health issues, I said yes...and he said do you know or have you ever heard of anybody that has health issues because of consuming fish from Lake Ontario? I said no...and he said I rest my case...
Tom