Determining resource intake of a nonnative fish highlights potential predatory and competitive interactions

Hedden, Skyler C.; Gido, Keith B.; Hedden, Crosby K.; Pennock, Casey A.; Duran, B. R.; Hines, Brian A.; Gilbert, Eliza I.; McKinstry, Mark C.; Durst, Scott L.; Franssen, Nathan R.

doi:10.1007/s10530-022-02777-8

Cited by 8 publications

(14 citation statements)

References 63 publications

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“…Overpeck & Udall, 2020) and potential habitat degradation from encroaching riparian vegetation (e.g., Scott et al, 2018). For in- are the primary predatory threat (Hedden et al, 2020;Hedden et al, 2022). We observed no correlation between potential nonnative competitors or non-native predators (San Juan only) and native fishes.…”

Section: Encroachment Of Riparian Vegetation Following Reductions In ...mentioning

confidence: 61%

“…For example, smallmouth bass are expanding in the White River since being detected in 2008 (Smith et al, 2020), and while efforts that quantify their abundance began in 2012, the timing of their arrival also corresponds directly with declines in flow. Conversely, smallmouth bass are not established in the San Juan River, and channel catfish are the primary predatory threat (Hedden et al, 2020; Hedden et al, 2022). We observed no correlation between potential non‐native competitors or non‐native predators (San Juan only) and native fishes.…”

Section: Discussionmentioning

confidence: 99%

“…This result could also reflect a compensatory recruitment response to removal of adult channel catfish on the San Juan River, whereby removal of adults reduces predation pressure or frees up resources for juvenile fish (Pennock et al, 2018). Substantial effort and funding go towards non‐native fish removal programmes in the CRB (e.g., Franssen et al, 2014; Mueller, 2005), but the effects of non‐native species on native fish population dynamics relative to other confounding factors (e.g., reductions in flow) are not clear, at least in the San Juan or White River (Gido & Propst, 2012; Franssen et al, 2014; Hedden et al, 2022; this study).…”

Section: Discussionmentioning

confidence: 99%

“…y-axes scales vary among panels and are on a log 10 -scale. Length of sampling period (x-axes) differs among rivers fish population dynamics relative to other confounding factors (e.g., reductions in flow) are not clear, at least in the San Juan or White River(Gido & Propst, 2012;Franssen et al, 2014;Hedden et al, 2022; this study).Increased aridity and concomitant reductions in catchment runoff due to climate change will make it more difficult to meet e-flow standards unless they are given higher priority in the future. The evidence of declining catchment runoff and increasing aridity in the CRB is unequivocal (Milly & Dunne, 2020; Overpeck & Udall, 2020; Udall & Overpeck, 2017).…”

mentioning

confidence: 87%

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Failure to achieve recommended environmental flows coincides with declining fish populations: Long‐term trends in regulated and unregulated rivers

et al. 2022

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Dams can be operated to mimic components of the natural flow regime to minimise impacts on downstream ecosystems. However, infrastructure, societal needs, water management, and catchment runoff constrain which and when flow regime attributes can be mimicked. We compared fish assemblage responses, including native and non‐native species, over 2 decades of managed environmental flows to those in a river retaining a relatively unaltered flow regime. Both of these arid‐land rivers are within the overallocated Colorado River basin and have experienced declines in catchment runoff over the past 20 years. We predicted that fish–flow relationships would be conserved across time and between managed and unmanaged rivers. Declines in flow in both rivers coincided with declines in some native fishes, and more native and non‐native fish species exhibited declines in the managed river than in the unmanaged river. Our ability to detect previously documented native fish–flow relationships diminished in the managed river system because established environmental flow targets were not met due to water management, but we detected these fish–flow relationships in the unmanaged river. Our results suggest declining catchment runoff and increased consumptive water use could reduce the effectiveness of environmental flows that have lower priority in most years.

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Section: Encroachment Of Riparian Vegetation Following Reductions In ...mentioning

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 87%

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Failure to achieve recommended environmental flows coincides with declining fish populations: Long‐term trends in regulated and unregulated rivers

et al. 2022

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“…However, the current adult population is relatively small, likely because survival rates of stocked fish are low (Clark et al, 2018). A significant contribution to these low survival rates seems unlikely to be driven by non‐native fish predation as neither Colorado pikeminnow nor more common native fishes responded positively to intensive non‐native fish removal (Franssen et al, 2014); possibly because the most abundant large‐bodied non‐native fish, channel catfish ( Ictalurus punctatus ), is not highly piscivorous (Hedden et al, 2021; Hedden et al, 2022; Pennock et al, 2021). In addition, attempts to mimic a more natural hydrograph have been hampered by the increased aridity in the San Juan River Basin (Pennock et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Changes to the trophic structure of a desert fish community following river regulation and species turnover: Implications for an endangered top predator

Gilbert

Franssen

2023

River Research & Apps

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A poor understanding of factors leading to species decline can result in inefficient or ineffective species restoration. Endangered Colorado pikeminnow (Ptychocheilus lucius) was nearly extirpated from the San Juan River, NM, USA and recent efforts to reestablish the species via hatchery augmentation of juveniles has yet to reach the target number of adults in the system. To assess how changes to the river's food web could be limiting reestablishment of this top predator, we used stable isotope (δ13C and δ15N) signatures of the fish community pre‐ (museum specimens) and post river regulation with coincident extirpations and invasions. Following river regulation, four of five community‐wide trophic structure metrics that quantify overall resource use were reduced and species turnover likely had little effect per se. For species sampled in both time periods, shared trophic resources generally increased (mean niche overlap = +35.7%). Additionally, Colorado pikeminnow experienced the largest decrease in niche breadth (−72%) and diet mixing models suggested a shift from piscivory towards insectivory in contemporary collections. Our results suggest an overall reduction in basal resource availability after river regulation. We propose increased reliance on similar resources may be limiting fish prey for Colorado pikeminnow, ultimately contributing to the slow and limited reestablishment in the San Juan River. This study adds to the growing body of knowledge provided by museum specimens and stable isotope analyses to identify food‐web dynamics that are a departure from historical conditions, which can provide novel information critical to imperiled species management in modified systems.

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Translocation in a fragmented river provides demographic benefits for imperiled fishes

Pennock,

Healy,

Bogaard

et al. 2024

Ecosphere

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Fragmentation isolates individuals and restricts access to valuable habitat with severe consequences for populations, such as reduced gene flow, disruption of recolonization dynamics, reduced resiliency to disturbance, and changes in aquatic community structure. Translocations to mitigate the effects of fragmentation and habitat loss are common, but few are rigorously evaluated, particularly for fishes. Over six years, we translocated 1215 individuals of four species of imperiled fish isolated below a barrier on the San Juan River, Utah, USA, that restricts access to upstream habitat. We used re‐encounter data (both passive integrated transponder tag and telemetry detections and physical recaptures) collected between 2016 and 2023, to inform a spatially explicit multistate mark–recapture model that estimated survival and transition probabilities of translocated and non‐translocated individuals, both below and above the barrier. Individuals of all four species moved large (>200 km) distances upstream following translocation, with the maximum upstream encounter distance varying by species. Results from the multistate mark–recapture model suggested translocated fish survived at a higher rate compared with non‐translocated fish below the barrier for three of the four species. Above the barrier, translocated individuals survived at similar rates as non‐translocated fish for bluehead sucker (Catostomus discobolus) and flannelmouth sucker (Catostomus latipinnis), while survival rates of translocated endangered Colorado pikeminnow (Ptychocheilus lucius; mean, 95% CI: 0.75, 0.55–0.88) and endangered razorback sucker (Xyrauchen texanus; 0.86, 0.75–0.92) were higher relative to non‐translocated individuals (Colorado pikeminnow: 0.52, 0.51–0.54; razorback sucker: 0.75, 0.74–0.75). Transition probabilities from above the barrier to below the barrier were generally low for three of the four species (all upper 95% CI ≤ 0.23), but they were substantially higher for razorback sucker. Our results suggest translocation to mitigate fragmentation and habitat loss can have demographic benefits for large‐river fish species by allowing movements necessary to complete their life history in heterogeneous riverscapes. Further, given the costs or delays in providing engineered fish passage structures or in achieving dam removal, we suggest translocations may provide an alternative conservation strategy in fragmented river systems.

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Determining resource intake of a nonnative fish highlights potential predatory and competitive interactions

Cited by 8 publications

References 63 publications

Failure to achieve recommended environmental flows coincides with declining fish populations: Long‐term trends in regulated and unregulated rivers

Failure to achieve recommended environmental flows coincides with declining fish populations: Long‐term trends in regulated and unregulated rivers

Changes to the trophic structure of a desert fish community following river regulation and species turnover: Implications for an endangered top predator

Translocation in a fragmented river provides demographic benefits for imperiled fishes

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