"Kezuriko" are gleanings of powder which is left over after dried fishes (such as a dried bonito, dried blue mackerel, and dried sardines) are chipped off to produce "kezuribushi" (shaved pieces).
Basically, kezuriko consists of several kinds of dried fish powder, but occasionally, it comes from a single dried fish.
Kezuriko is mainly used as a topping, sprinkled over "okonomiyaki" (a savory pancake with various ingredients) or "yakisoba" (fried noodles) instead of "katsuobushi" (shaved pieces of a dried bonito). Occasionally, it is put into the dough of okonomiyaki instead of soup stock.
Around Shizuoka City, there exists an odd use of kezuriko and dried green seaweed, that is, sprinkling them on "oden" (a Japanese dish containing all kinds of ingredients cooked in a special broth of soy, sugar, sake and so on).