"Whitebait are young fish; in Europe the term applies to young herring, but in other parts of the world it is used for similar fish of other species. Whitebait are tender and edible. The entire fish is eaten including head, fins and gut but typically each 'bait' is only 25-50 mm in length and about 3 mm in cross section."

According to Wikipedia, smelts are up to 20cms in length.