Formerly, whitebait were considered to be the young of the shad; and
only of late years has the misnamed fish taken its proper position. It
appears that Mr. Yarrell, the able naturalist, was one morning in March
struck with the early appearance of whitebait in a fishmonger's shop in
St. James's; and knowing that shads, which they were supposed to be, did
not make their appearance till much later (May), he took up the matter,
and persevered in a course of investigation, which lasted from March to
August, 1828. The specific distinction between the two fishes, on which
Mr. Yarrell relies as of the greatest value, is the difference of their
anatomical character; and especially in the number of vertebræ, or small
bones, extending from the back-bone. "The number of vertebræ in the
shad," he states, "of whatever size the specimen may be, is invariably
fifty-five, while the number in the whitebait is uniformly fifty-six;
even in a fish of two inches, with the assistance of a lens, their exact
number may be distinctly made out."
------------------