Seasonal Variation in Sampling Indices for Fish Populations Collected From the Missouri River Below Fort Randall Dam, South Dakota

Seasonal influences on sampling data have been documented for many sport fishes in lentic environments. To determine if similar influences occur with native riverine species in lotic systems, I selected two study sites within the riverine reach of Lewis and Clark Reservoir, South Dakota. Gill nets and electrofishing were used to collect relative abundance, weight, and length data for river carpsucker Carpiodes carpio, shorthead redhorse Moxostoma macro/epidotum, shovelnose sturgeon Scaphirhynchus platorynchus, channel catfish lctalurus punctatus, freshwater drumAplodinotus grunniens, bigmouth buffalo lctiobus cyprinellus, smallmouth buffalo lctiobus bubalus, and sauger Stizostedion canadense. Sampling data were used to calculate relative species composition, size structure, relative weights (Wr), and catch per unit effort (CPUE). These indices were then assessed for seasonal trends. Seasonal fluctuations were apparent in relative species composition, size structure, Wr, and CPUE. Relative species composition varied monthly within sites and also between sites for shorthead redhorse, river carpsucker, shovelnose sturgeon, sauger, and channel catfish. Freshwater drum and smallmouth buffalo were not abundant at either site, making seasonal pattern detection difficult. Within-site variations in size structure generally were not significant for any species analyzed. However, the median length of fishes tended to be higher at the upper site during early sample months and higher at the lower site during the later sample months, suggesting a migratory pattern for adult fish. Channel catfish, shorthead redhorse, shovelnose sturgeon, and river carpsucker all exhibited significant monthly variation in mean Wr values during at least one sample year. However, no consistent patterns in seasonal variation for mean Wr values were obvious. In general, Wr values for all species tended to be highest early in the year followed by a steady decline to a seasonal low during the later sample months. Shorthead redhorse, river carpsucker, and sauger CPUE followed a similar bimodal pattern of spring and fall peaks, with lower CPUE during summer. Catch per unit effort of shovelnose sturgeon was highest in the fall at the lower site with no differences found at the upper site. Channel catfish CPUE was highest at the upper site during the early sample months and decreased through the later sample months. At the lower site, channel catfish CPUE was lowest during the early sample months and increased through the later months. Thus, seasonal patterns in common sampling indices were evident for native riverine fishes in the Missouri River below Fort Randall Dam. Fishery biologists working in similar lotic environments must consider seasonal changes in sampling data when making population and community assessments.

Name thesis:degree_name

Master of Science (MS)

Level thesis:degree_level

Thesis - University Access Only

Discipline thesis:degree_discipline

Wildlife and Fisheries Science

Year

2000

Author dc:creator

• Jordan, George R.

Contributors dc:contributor

• David W. Willis

• Natural Resources and Conservation

Statement dc:rights

• Copyright © 2000 George R. Jordan. All rights reserved.

Language dc:language

en

Repository record dc:identifier

https://openprairie.sdstate.edu/etd/489

OAI identifier oai:identifier

oai:openprairie.sdstate.edu:etd-1489