Age Determination and Rate of Growth in Polyodon spathula, by Means of the Growth Rings of the Otoliths and Dentary Bone

In recent years, papers have appeared on various phases of the life history of Polyodon, but little has been reported on anything pertaining to their age. Stockard (1907) made a study of the habits of Polyodon in Louisiana, Mississippi, and Arkansas, while in search of information concerning their spawning habits. He failed to discover their spawning places, however. In his table of measurements, of 15 specimens from 30 to 69 inches, he mentions two specimens with eggs, one 63 inches and one 69 inches in length. Barbour (1911) described a small specimen 35 mm. in length. Danforth (1911) described a 74 mm. specimen. The smallest specimens now known were collected by Thompson (1933) near Grand Tower, Illinois, on the Mississippi River. These seven specimens were seined from a sandbar and were from 17 mm. to 20 mm. in length. Thompson (1934), in his paper on the relative growth of Polyodon, gives some very interesting tables showing the relation of the rostrum to the body in different periods, varying in total length from 17 mm. to 2159 mm.