Relative Position of Coded Wire Tags in Paddlefish Rostrums

Paddlefish Polyodon spathula were tagged with 2-mm-long coded wire tags (CWTs) inserted 2 mm into the distal end of the rostrum to determine if the relative position of CWTs changed as the rostrum grew. Thirty fish were randomly selected weekly for measurements of body length (anterior edge of eye to tail fork), rostrum length (anterior eye to distal end of the rostrum), and relative position of the tag (determined from X rays). Mean body length of tagged paddlefish increased from 79 mm on 30 June 1995 to 183 mm on 10 August 1995. Mean relative position of the tag (length from tag to tip of rostrum/rostrum length) varied from 9.7% of total rostrum length on 30 June 1995 to 18.6% on 3 August 1995. We believe that the change in relative position of CWTs is a function of rostrum growth rate, and the change would probably be highest in age-0 paddlefish and decline as age increases.