Biotic and abiotic factors affecting the distribution of Paddlefish Polyodon Spathula in William “Bill” Dannelly Reservoir and the Cahaba River, Alabama.

Abstract

Paddlefish Polyodon spathula river section use, and summer backwater use (where zooplankton is thought to be abundant) vary seasonally. I quantified Paddlefish habitat use in Dannelly Reservoir, Alabama, which includes the confluence with the Cahaba River. I considered three longitudinal reservoir sections based on channelization and available backwater habitat, and tagged, and tracked 63 Paddlefish using both active and passive telemetry. In addition, I collected seasonal zooplankton samples across the system to quantify food availability. Zooplankton density did not differ between mainstem and backwater sites but was significantly lowest in the Cahaba River. Paddlefish detection upstream was associated with lower temperatures and higher water levels and likely represents an area critical for Paddlefish spawning. The midstream section was used year-round. The downstream section and backwaters were primarily used late spring/early fall, and backwater detections were negatively associated with food availability. I also observed limited emigration by Paddlefish from the reservoir.