Thermal refuge use and parasitism: Spatiotemporal variation in anchor worm and lamprey wounds on Klamath redband trout

Ortega, Jordan D.; Hahlbeck, Nicholas; Derrickson, Chris; Tinniswood, William; Levi, Taal; Armstrong, Jonathan

doi:10.1002/ecs2.4644

Cited by 3 publications

(1 citation statement)

References 81 publications

(109 reference statements)

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“…In northern California, thermal refuges have been shown to reduce exposure of juvenile coho salmon to the myxozoan parasite, Ceratonova shasta, because cooler areas have fewer parasitic spores and alleviate disease effects (Chiaramonte et al 2016). Cool-water refuges in the Klamath watershed have also been shown to reduce lamprey wounds on redband trout (Ortega et al 2023). Understanding thermal refuge dynamics in rivers that support coldwater fish is critical for conserving, restoring, and managing these ecosystems.…”

Section: Introductionmentioning

confidence: 99%

Restored off‐channel pond habitats create thermal regime diversity and refuges within a Mediterranean‐climate watershed

Moravek,

Soto,

Brashares

et al. 2024

Restoration Ecology

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Cool‐water habitats provide increasingly vital refuges for cold‐water fish living on the margins of their historical ranges; consequently, efforts to enhance or create cool‐water habitat are becoming a major focus of river restoration practices. However, the effectiveness of restoration projects for providing thermal refuge and creating diverse temperature regimes at the watershed scale remains unclear. In the Klamath River in northern California, the Karuk Tribe Fisheries Program, the Mid‐Klamath Watershed Council, and the U.S. Forest Service constructed a series of off‐channel ponds that recreate floodplain habitat and support juvenile coho salmon (Oncorhynchus kisutch) and steelhead (O. mykiss) along the Klamath River and its tributaries. We instrumented these ponds and applied multivariate autoregressive time series models of fine‐scale temperature data from ponds, tributaries, and the mainstem Klamath River to assess how off‐channel ponds contributed to thermal regime diversity and thermal refuge habitat in the Klamath riverscape. Our analysis demonstrated that ponds provide diverse thermal habitats that are significantly cooler than creek or mainstem river habitats, even during severe drought. Wavelet analysis of long‐term (10 years) temperature data indicated that thermal buffering (i.e. dampening of diel variation) increased over time but was disrupted by drought conditions in 2021. Our analysis demonstrates that in certain situations, human‐made off‐channel ponds can increase thermal diversity in modified riverscapes even during drought conditions, potentially benefiting floodplain‐dependent cold‐water species. Restoration actions that create and maintain thermal regime diversity and thermal refuges will become an essential tool to conserve biodiversity in climate‐sensitive watersheds.

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Section: Introductionmentioning

confidence: 99%

Restored off‐channel pond habitats create thermal regime diversity and refuges within a Mediterranean‐climate watershed

Moravek,

Soto,

Brashares

et al. 2024

Restoration Ecology

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Thermal refuge use and parasitism: Spatiotemporal variation in anchor worm and lamprey wounds on Klamath redband trout

Ortega,

Hahlbeck,

Derrickson

et al. 2023

Ecosphere

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Climate warming is increasing maximum temperatures during summer such that they more frequently exceed the thermal tolerances of ectotherms, particularly cold‐water fishes. One way that species can avoid thermal stress is by moving to thermal refuge habitats. Thermal refuges remain suitably cool during summer and are often complementary to foraging, spawning, and rearing habitats. Although the benefits associated with the thermal aspects of refuges are well studied, much less is known about potential costs associated with nonthermal aspects. For example, crowding of cold‐water fishes into seasonal refuge habitats could increase parasite loads and cause declines in fitness. We assessed lamprey and anchor worm parasitism in Upper Klamath Lake where adfluvial redband trout (Oncorhynchus mykiss newberrii) move to thermal refuge habitats during summer. We sampled trout in Upper Klamath Lake during spring and in adjacent thermal refuge habitats during summer. We also evaluated survival as a function of lamprey wounding using motion‐sensing radio tags. There was a fourfold decline in the number of lamprey wounds on trout upon the onset of thermal refuge use. In contrast, cases of severe anchor worm (≥20 sores) increased threefold during thermal refuge use. Survival in thermal refuge was not different for lamprey‐wounded trout than for trout that migrated to thermal refuge without lamprey wounds. We found that both parasites were absent in a lotic population of redband trout downstream that lacked access to thermal refuge. Thus, the effects of seasonal refuge use on parasite load varied depending on the parasite taxon considered and local habitat conditions, implying that managers will likely require empirical data for focal habitats and taxa to understand how parasitism affects thermal refuge use.

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Evidence of a temperature–oxygen squeeze within floodplain thermal refuge habitats

Barrett,

Gregory,

Armstrong

2024

Freshwater Biology

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Vertical heterogeneity in lakes and estuaries can present cold‐adapted fishes with a temperature–oxygen squeeze, such that the epilimnion is stressfully warm and the cooler hypolimnion is hypoxic, thereby restricting fishes to the metalimnion. In temperate floodplain rivers, patches of lentic habitat (e.g., alcoves) have the potential to provide thermal refuge for cold‐water fishes during summer, but little is known about whether these smaller habitat features present fish with temperature–oxygen constraints. In this study, we measured temperature and oxygen profiles in six cold‐water alcoves on the Willamette River floodplain (Oregon, U.S.A.) to characterise potential trade‐offs in temperature and oxygen for a cold‐water fish, coastal cutthroat trout (Oncorhynchus clarkii clarkii). To evaluate how fish responded to trade‐offs, we used synergistic methods (needle probe thermocouple, surgically implanted iButtons, and external temperature transmitting radio tags) to monitor fish body temperatures at different temporal scales and compare them to temperature–depth profiles. The cold‐water alcoves displayed a linear relationship between dissolved oxygen and temperature, where cooler temperatures came at the expense of reduced oxygen. Fish body temperatures were intermediate to temperatures recorded at the surface and bottom of the alcove. The span of depths selected by these fish represents less than 20% of the available vertical habitat in these alcoves. These results demonstrate that refuges formed by cool hyporheic upwelling can generate a temperature–oxygen squeeze where fish use only a subset of the refuge habitat feature. Oxygen constraints on thermal refuge use may be a blind spot for climate adaptation planning for cold‐water fishes, because dissolved oxygen data are limited compared to water temperature data, and many cool refuges are fed by subsurface flows which are potentially hypoxic.

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Thermal refuge use and parasitism: Spatiotemporal variation in anchor worm and lamprey wounds on Klamath redband trout

Cited by 3 publications

References 81 publications

Restored off‐channel pond habitats create thermal regime diversity and refuges within a Mediterranean‐climate watershed

Restored off‐channel pond habitats create thermal regime diversity and refuges within a Mediterranean‐climate watershed

Thermal refuge use and parasitism: Spatiotemporal variation in anchor worm and lamprey wounds on Klamath redband trout

Evidence of a temperature–oxygen squeeze within floodplain thermal refuge habitats

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