Exploitation, Survival, Reproduction, and Habitat Use of Gravid Female Paddlefish in Ozark Lake, Arkansas River, Arkansas
Steven B. Donabauer, Joseph N. Stoeckel, and Jeffrey W. Quinn
Abstract.—We assessed potential impacts of harvest and proposed channel modifications on the paddlefish Polyodon spathula fishery of Ozark Lake, Arkansas River, Arkansas. Ultrasonic telemetry was used to determine commercial and recreational exploitation rates, survival, spawning locations, and habitat use of gravid female paddlefish. Monthly searches were conducted for 40 tagged fish and we recorded 862 locations in Ozark Lake from January 2004 through December 2005. Adjacent reservoirs (i.e., Pool 13 and Lake Dardanelle) were tracked periodically, but interpool movement was not detected. Commercial fishing exploitation was determined at a mandatory check station and was estimated to be 30% during a 5-d special season. Annual recreational snag-fishing exploitation estimates were 8% (2004) and 3% (2005). Survival was different between years and was much lower the year (2004) with a commercial fishing season. Kaplan-Meier staggered-design survival estimates (±95% confidence interval [CI]) for 2004, 2005, and 2004 through 2005 were 0.60 ± 0.19, 0.92 ± 0.11, and 0.55 ± 0.18, respectively. With commercial and recreational harvests omitted from the analysis, the estimated 2-year survival rate was 0.91 ± 0.13 (±95% CI), which corresponds to 5% annual natural mortality. Gravid females migrated a median distance of 33 and 32 km in the spring of 2004 and 2005 and likely spawned in the tailwater of James W. Trimble Lock and Dam from late March to early April. Successful paddlefish reproduction was verified by capture of 23 prolarvae. Paddlefish selected tributary mouth habitat in all seasons (59% of locations). Tailwater and inundated creek channel habitats were selected in spring and summer, respectively. A navigation project to deepen the channel from 2.7 to 3.7 m will impact approximately 50% of the tailwater spawning habitat. Channel modifications (i.e., dredging and dike construction) near the mouth of the Mulberry River may disturb an important tributary mouth habitat for paddlefish where 55% of all locations were recorded. Our study identified biologically important habitats that need conservation and indicates that commercial harvest was the primary source of mortality for gravid female paddlefish in Ozark Lake.