Spatiotemporal Plasticity in Reproductive Readiness and Recruitment of Ichthyoplankton of Invasive Silver Carp along a Western Invasion Front

Authors

Jessi L. Urichich, University of Nebraska-LincolnFollow

First Advisor

Jonathan J. Spurgeon

Committee Members

Mark Pegg, Kirk Steffensen, Sarah A. Sonsthagen, Rich Holland

Date of this Version

8-2024

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 Master of Science

Major: Natural Resource Sciences

Under the supervision of Professor Jonathan J. Spurgeon

Lincoln, Nebraska, August 2024

Comments

Copyright 2024, Jessi L. Urichich. Used by permission

Abstract

Individuals of invasive species at the edge of their invasion distribution may exhibit enhanced reproductive capacity and phenotypic plasticity leading to accelerated range expansion. Environmental conditions in highly fluctuating environments at distribution edges may either promote or hinder such reproductive readiness and phenotypic plasticity. Dynamic habitat conditions and periodic disturbances experienced in prairie streams, such as drought (e.g., low-flow, high water temperatures), may potentially reduce suitable spawning environments and ichthyoplankton recruitment of invasive Silver Carp, potentially slowing range expansion or enabling management strategies that reduce abundance in the absence of a reproducing population. Female Silver Carp batch fecundity, Gonadosomatic Index (GSI), reproductive phases, and the recruitment of ichthyoplankton were assessed across the lower Platte River basin and the Missouri River upstream of the Platte River confluence in 2022 and 2023 during a regional drought. Of the 348 female Silver Carp analyzed, reproductive readiness was higher at the distribution edge in the lower Platte River basin than at the core range in the Missouri River. Of the 105 Silver Carp ichthyoplankton collected, maximum catch occurred in the Missouri River in 2022 and in a Platte River tributary in 2023, whereas the majority were located near the core range both years. Female Silver Carp were spawning capable and exhibited evidence of prior spawning (e.g., post-ovulatory follicles) at every site and season, suggesting an extended spawning season into the fall. These results indicate that Silver Carp are established in the lower Platte River and exhibit trait variation that may enhance reproductive readiness and recruitment in response to highly heterogenous environments experienced in prairie streams. Focusing removal efforts on the highly fecund individuals found at distribution edges in early spring may restrict further reproduction, dispersal, and environmental adaptation in prairie streams.

Advisor: Jonathan J. Spurgeon