Q: I have wondered for years why it is that you can easily buy sardines in cans but it's all but impossible to find them fresh. Why is that? Also, while you're at it, can you tell me how they get those guys into a can, all jammed in like, well, sardines?
A: OK. I'll give it to you straight. There are no sardines. It's all a big lie!
The word ''sardine" does not strictly refer to any particular species of fish (it's a bit like getting scrod in Boston). There is a standards body, called the ''Codex Alimentarius Commission," which allows each country to decide on its own definition of ''sardine," and there are 21 possible candidates.
The French and Portuguese tend to go for young pilchards, while in Norway sprats and immature herrings are used most often.
It will come as little surprise that the French insist that the term ''sardine" should be reserved for ''Sardinia pilchardus" -- which, of course, is the pilchard fish they favor -- though they have yet to persuade the commission to change its standard.
In the United States, the Bureau of Fisheries has declared that any fish in the clupeid family can be a sardine. This includes small herring, brisling, and sprats in addition to pilchards. Those of you out there who like anchovies will be happy to know that these are not allowed to be called sardines.
Sardines, regardless of their species, are canned before cooking. The can is filled with steam and heated in order to cook the fish, tilted so that fish fluids can flow out, and then pumped with whatever oils, spices, etc. are desired. The can is then sealed, cleaned, labeled, and shipped to wherever you buy your so-called sardines.
Dr. Knowledge answers your questions about science each week. E-mail questions to email@example.com or write Dr. Knowledge, c/o The Boston Globe, PO Box 55819, Boston, MA 02205-5819. Include your initials and hometown.