y'all canned tunas are doing it wrong, canned sardines/smoked herring is a few cents more and much tastier. I seem to remember reading sardines don't collect mercury....something about tuna being special in some way.
I eat sardines, too. But like tuna, there are many, many varieties, and the labels don't always tell you what you're getting. My comments here apply primarily to labeling in the USA. There are many different species of fish that fall into the category of sardines, and they are not required to identify the species on the label. Sometimes the label has useful information and sometimes it does not.
I can show you tins of sardines imported from Spain and Portugal that go for as much as $10 or $20 in the USA. But you won't find that in a typical grocery store like Kroger or Wal Mart.
At Kroger or Wal Mart, you'll find low to medium grade sardines packed in water, soybean oil, olive oil, and other stuff like mustard sauce, tomato sauce, and Louisiana hot sauce.
Sardines packed in water are very low quality fish, and they often have a strong, fishy flavor. Sardines in soybean oil are a bit better, even if they are the same fish, because the oil soaks into the fish and improves the flavor. Sardines in olive oil are the best.
Sardines in water or soybean oil go for as little as $1 or $2 per can. Better quality sardines in olive oil run about $4 a can. These are prices in the midwest USA.
The stuff they pack in tomato sauce, mustard sauce and hot sauce is just garbage in my view. Those heavy sauces mask the flavor of really low quality fish.
Interesting facts:
In the USA,
sprats are a type of sardine. Thus under US labeling regs, all sprats are sardines, but not all sardines are sprats.
All sardines (including sprats) are a subset of herring, and this is true under the definitions used by all countries. Thus all sardines are herring, but not all herring are sardines.