I'm currently eating herring in canola oil. I drain the oil. There's one walmart many miles away that has herring in tomato. I clean them out when passing. I'm not a big fan of sardines, but they are just as good for you. In the uk, it was mackerel in tomato sauce. I stay away from fish in high omega 6 oils and sauces with any of my 'bad' veg. Onion I can detect at minute levels... My blood pressure was causing concern when I was veggie, till about 8 years ago. It went down to athlete level after several years of fish therapy.