Rostrum Size of Paddlefish (Polyodon spathula)(Acipenseriformes: Polyodontidae) from the Mississippi Delta
Paddlefish rostra vary in size and shape suggesting existence of multiple morphotypes. Measurements for 118 adult paddlefish from a Mississippi delta river indicate that the rostrum becomes shorter, narrower, and straighter as a fish grows. Negative allometric growth of rostra, and high variation within size classes, may obscure existence of distinctive rostral morphotypes.Abstract

Rostral dimensions of paddlefish. (A) Variation in relative rostrum length with size of fish, n = 118. (B) Variation in relative rostrum breadth with size of fish. (C) Variation in anterior expansion of rostrum with size of fish. (D) Relative rostrum length and anterior expansion of rostrum for fish 630–680 mm EFL, n = 30