Larval Fish Abundance in the Benthic and Surface Drift of the Missouri River

Authors

Ryan L. Ruskamp, University of Nebraska-LincolnFollow

First Advisor

Mark A. Pegg

Date of this Version

4-2022

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Masters of Science

Major: Natural Resource Sciences

Under the supervision of Professor Mark A. Pegg

Lincoln, Nebraska, April 2022

Comments

Copyright © 2022, Ryan L. Ruskamp Ryan L. Ruskamp

Abstract

Knowledge of the larval fish community of the Missouri River is one of the biggest gaps in fisheries research. The Nebraska Game and Parks Commission has sampled the drift of the Missouri River for many years (1983-2015), but these data have not been compiled into a unified assessment. Therefore, the objectives of this study were to: 1) quantify temporal and spatial aspects of larval fish community composition (richness) and structure (abundance) of the surface drift, 2) quantify associations of larval fish communities of the drift to different discharges of the Missouri River, 3) quantify the larval benthic drift community, and 4) document evidence of natural spawning and fertilization success by Pallid Sturgeon Scaphirhynchus albus through capture of free embryos entering the drifting phase in the Nebraska portion of the Lower Missouri River.

For the surface drift portion of this thesis, there were nine sites from four segments used for these analysis. The greatest overall abundance occurred in 2000 (2.036 fish/m³, SE=0.122), with Sciaenidae, (N = 155,400) being the most abundant. There were either no significant trends or declining trends in relative abundance over time for all sites and families except for Clupeidae at St. Helena. When comparing segments, similar results were noted with only three segment/family combinations yielding a positive trend (Catostomidae (Segment 1), Cyprinidae (Segment 3), and Percidae (Segment 3)). Analysis of similarity (ANOSIM) found Segment 1 was dissimilar from Segment 2, Segment 3, and Segment 4. Post hoc similarity percentage (SIMPER) analysis displayed that abundances of Sciaenidae across the segments was the reason for this difference. Annual discharge did not influence fish communities of the surface larval drift.

The benthic fish community was sampled primarily at Nebraska City, NE (rkm 907.6), with limited sampling at Niobrara, NE. The most abundant family sampled in the benthic drift was Sciaenidae from the Nebraska City Site in 2015 (n=88) (0.008 fish/m³, SE+0.0027). One wild Pallid Sturgeon free embryo was captured on May 28, 2014

Sampling the larval fish drift provides insights on the overall health and productivity of the system and by assessing trends in the larval fish abundance of the drift annual variations and changes in recruitment can be detected.

Advisor: Mark A. Pegg