American alligators are predators of Paddlefish: An undocumented predator-prey linkage affecting Paddlefish population dynamics

Abstract

It has been suggested that adult Paddlefish Polyodon spathula have no natural predators with the exception of humans and few heterospecific freshwater fishes which tend to target only early life stages (i.e., larvae, age-0 juveniles). However, we photographically documented another natural predator, the American alligator. The predation event took place in a small waterbody (0.8 ha) over a 45-minute period during which the alligator frequently transported the Paddlefish onto land, and retracted back into the water. This is the second event of its kind documented in this small river system. From a capture-recapture study, we have identified over 100 fish in the pool, 50 of which were surgically implanted with an acoustic transmitter for continuous monitoring of emigration. However, two have unexplainably disappeared, presumably from predation. Given the two known alligator mortality events, and two potential additional events suggested by transmitter disappearance, we presume adult Paddlefish predation may be more common than previously thought. Although adult Paddlefish were thought to have no natural predators, this newly documented predator-prey linkage provides support that alligator predation on Paddlefish may occur more frequently in southeastern waterbodies than previously believed, particularly when Paddlefish are in high abundance or in relatively small systems such as ours.