When wandering in the seafood section of a Japanese market last week, I came across these little fish and was struck by how nice it feels to be able to eat a whole animal in one bite: head, bones, fins, and all. You can't say that for most land animals we eat, unless you count tiny birds and insects.
(The majority of what we talk about on Nasty Bits is, by default, mammalian for the variety of organs and cuts we eat from pigs and ruminants. The viscera from seafood is more difficult to obtain and more limited in scope, with a few notable exceptions. See this piece for musings on milt.)
Their Japanese name is shishamo (meaning, "Willow Leaf Fish") and they are a type of smelt. That is, from any number of small, silvery fish generally used as bait, but which are really very good to eat on their own. (See here for another type of smelt fish that you are likely to come across at Chinese markets.)
In order to want to cook and eat shishamo, you really have to like fish eggs. There is no flesh to speak of and given the size of the fish, no bones to contend with. It's as if the fish are mere vessels for their reproductive matter. When deep-fried in a thin dusting of flour and salt, their bodies are like little ice cream cones of crispy skin encasing a tender nub of cooked caviar.
Mild in taste with a pleasantly grainy texture, the eggs are a fine palate for a sauce of your choosing. I like a light ponzu or tempura-style dipping sauce so as not to overwhelm the taste of the fish eggs. But they would be very good with a mustard sauce, a green herby sauce with parsley, minced garlic, and lemon, or just plain vinegar. Fry 'em up in a matter of minutes, and you have finger food that's pregnant with flavor.