Document Type
Poster
Journal/Book Title/Conference
Utah Annual American Fisheries Society
Publisher
Utah State University
Publication Date
2-10-2025
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Abstract
Freshwater fish have experienced the highest extinction among all North American vertebrates, with interactions with introduced species among the leading factors of freshwater fish declines. In Utah Lake, effective hatchery stocking efforts have allowed the spawning abundance of threatened June sucker (Chasmistes liorus) to increase substantially over the past decade. Yet, recruitment of wild-spawned individuals remains very limited. A recent survivorship study of June sucker found individuals < 300mm experienced exceptionally poor survival, indicating a recruitment bottleneck persists despite significant recovery efforts. Current recovery efforts of Utah Lake have broadly targeted habitat improvement; However, prior studies have shown that large predation pressures by nonnatives have achieved recruitment bottlenecks in closely related species, suggesting predation could be limiting recovery efforts. Therefore, failure to address these pressures, if present, would result in overall recovery failure. Furthermore, predator management has focused on targeting Invasive Northern Pike (Esox Lucius) for potential impacts on June sucker. However, the impacts of more abundant nonnative piscivores remain largely unspecified.
Here, we use a simulation approach based on empirical data to examine the relative predation pressure on June sucker of different lengths from individual piscivore species as well as the piscivore community as a whole. We generated a distribution of the lengths of prey consumed by the piscivore community by (1) randomly selecting a piscivore species based on the observed relative abundance in catch data, (2) randomly selecting a piscivore length based on length-at-age from literature-derived estimates and age composition, and (3) randomly selecting prey lengths based on predator-specific quantile regressions of observed fish prey lengths as a function of predator length. We repeated the simulation 10,000 times to achieve a representative model.
We found the overall distribution of prey items consumed was unimodal and right-skewed with a median prey length of 74mm (95% simulation interval: 13 – 238 mm) and a maximum prey length of 535mm. The third quartile (120mm) was roughly the same length as that of June Suckers at their first annulus (111mm), suggesting that most predation on June sucker is occurring during their first year. Abundant mesopredators, Channel catfish, White bass, and Black bullhead drove the vast majority of predation pressure, consuming > 98% of prey items consumed, while high trophic level predators accounted for the remaining < 2%. Together, these results suggest substantial predation pressure on age-0 June sucker, particularly from Channel Catfish and White Bass, may explain the limited recruitment of wild June sucker despite the steadily increasing abundance of spawning adults. Thus, predation on juvenile June Suckers presents a significant barrier to the establishment of a self-sustaining June Sucker population in Utah Lake.
Recommended Citation
Garner, Austin; Landom, Kevin; Fadlovich, Rae; and Walsworth, Timothy E., "Modeling Vulnerability of Juvenile June Sucker to the Piscivore Community in Utah Lake" (2025). Watershed Sciences Student Research. Paper 56.
https://digitalcommons.usu.edu/wats_stures/56
