Did you know that fish markets have often been the sources of some of marine biology's greatest discoveries? In one case, a coelacanth -- a type of fish long thought to have been extinct for millions of years -- was found salted in a third-world market.

Most of us think of a fish market as a place to find saltwater fish, but the fact is that freshwater species are becoming more common. Tilapia, salmon, and catfish are very common, since all three are easy to farm, but there are freshwater fisheries in some large lakes, too.

While fish markets tend to focus on the fish themselves, some vendors may be able to help you with other related items, from books to seasonings to recipes and tips. Keep a sharp eye out for them, and don't hesitate to ask if you don't see any.