Of all fish-roe products, caviar, specifically sturgeon caviar, is the most famous (and most expensive) but other types of roe can be delicious, too.
What is it? All fish produce eggs, known as roe - and many types are considered delicacies. Some are eaten after minimal or no processing, while the production of others is time consuming and labour intensive. In Taiwan and Italy, for instance, whole sacs of roe (usually mullet, although other fish are used) are salted, dried and pressed. They're then grated or used in thin shavings. Caviar also takes a lot of work: the eggs are removed from the sacs; rinsed and have any connective tissue discarded; sorted by size, colour and quality; and salted, before being packed into tins.
What else? Caviar - without the name of a fish preceeding it - describes only sturgeon roe. The depleted wild sturgeon population in places where caviar is traditionally produced (such as Iran and Russia) has led other countries to experiment with 'farmed' caviar, whereby the sturgeon are raised in special tanks. A method whereby the roe sacs are surgically removed from live fish, rather than after having killed them, has also been tried. Some caviar is produced on the mainland.
How to use: it depends on the type of roe. Good-quality sturgeon caviar is best appreciated on its
own so the subtleties of flavour and texture are obvious. It's often served with blini (small buckwheat pancakes) or small boiled potatoes, with sour cream, chopped hard-boiled egg and minced chives or shallots. Caviar from other types of fish is less expensive so it can be enjoyed in larger quantities. Sake-marinated salmon caviar (ikura) is delicious when spread in a thick layer over a bowl of rice. If it's really fresh ikura, the eggs will pop crisply in the mouth.
Tarama - a salted roe popular in Greece - is made into taramasalata by mixing it with breadcrumbs (or mashed potatoes), lemon juice, olive oil and garlic.