Lower Missouri River and Yellowstone River Pallid Sturgeon Study, 1994-1995 Report

Liebelt, James

A total of 23 pallid sturgeon ranging in weight from 8.8 to 32.0 kg and an average of 18.8 kg were captured by drift netting in teh Missouri and Yellowstone rivers during 1994 and 1995. Mean fork length was 1405 mm and ranged from 1222-1613 mm. Ten were recaptures from previous years and 13 were "new" fish. No pallid X shovelnose sturgeon hybrids were suspected based on character index measurements. Shovelnose sturgeon were the most abundant species captured during both years and were found in all sections sampled in both rivers. A total of 1,121 were netted and tagged. Mean for length and weight were 589 mm and 883 gms, respectively. A total of 36 recaptures were netted and 63.9% were caught within 5 miles of the original capture site in both rivers. Larval fish sampling in the Missouri River above the Yellowstone River confluence during 1994 collected four sturgeon and three paddlefish larvae and no sturgeon/paddlefish eggs. In 1995, 22 sturgeon and 63 paddlefish larvae and 31 sturgeon/paddlefish eggs were collected, primarily in the Missouri River below the confluence and in the lower 15 miles of the Yellowston River. Beach seining in both rivers captured 30 fish species in 1994 and 25 species in 1995. Flathead chub were the most abundant species caught in both years. Sicklefin chub and sturgeon vchub were also seined in both years. A trawl was used in 1995 to sample deep, main channel habitat in both rivers. Ten fish species were captured with sicklefin and sturgeon chubs comprising 65.2% of the total fish caught. Four mesolarval sturgeon (44-50 mm) were collected in the Missouri River above the confluence at river mile 1589.5. Aquatic macroinvertebrates were collected in both rivers during both years. Seven orders of insects, representing 30 families, were identified. Ephemeroptera and Trichoptera were the most common orders found.