Document Type

Dissertation - Open Access

Award Date

2026

Degree Name

Doctor of Philosophy (PhD)

Department / School

Natural Resource Management

First Advisor

Steve Chipps

Second Advisor

Alison A. Coulter

Abstract

Riverine systems are highly dynamic, and changes in flow conditions can impact the population dynamics of fishes. Increased flows from historical averages in eastern South Dakota rivers have likely impacted fish populations. The goals of this study were to 1) better understand the changes in resource use by Blue Suckers Cycleptus elongatus through retrospective eye lens stable isotope analysis, 2) determine the effects of record flooding in the James River on complex woody habitat and Flathead Catfish Pylodictis olivaris population structure, and 3) assess the influence of river discharge and temperature on Channel Catfish Ictalurus punctatus and Flathead Catfish condition and growth in the Big Sioux River and James River. Blue Sucker population-level eye lens stable isotope trends increased by ~3‰ for δ13C as eye lens diameter increased above 2 mm, whereas δ15N values were consistent (within ~1‰) across the range of lens diameters. Juvenile eye lens δ13C values decreased as river discharge increased, likely indicating increased floodplain feeding, while δ15N values exhibited little change. Record flooding in 2019 caused the total number and visible area of woody habitat complexes to decline by 35% and 64% in the James River. Population density of Flathead Catfish (>305 mm) in post-flood years was consistent with the pre-flood estimate. Conversely, size structure increased after 2018 with each subsequent sample from 2022-2024, indicating a potential lack of recruitment. Channel Catfish relative weights were positively related to river discharge, whereas Flathead Catfish condition was not influenced by environmental variables. The interaction between temperature and discharge was important for growth in catfish populations. River discharge was positively related to growth and had a much greater impact than temperature, particularly in the James River. Overall, results of this study indicate that increased river discharge, including flood events, can have mixed effects on fish populations. Changes in available habitat as a result of flooding can influence recruitment either positively or negatively, and variable water levels can impact condition and growth. Results of this study provide insight that can inform how projected increased precipitation and river flows under future climate change will impact fishes in eastern South Dakota rivers.

Publisher

South Dakota State University

Download

Share

COinS
 

Rights Statement

In Copyright