Nowhere to swim: interspecific responses of prairie stream fishes in isolated pools during severe drought

Reale

2020

Freshwater Biology

Section: Introductionmentioning

confidence: 99%

“…These management actions can be costly and labour intensive, and are not always possible every year. Lennox et al (2019) identified eight key research questions to improve the conservation of freshwater fishes through understanding how freshwater fishes respond to drought.…”

Section: Introductionmentioning

confidence: 99%

No quarter: Lack of refuge during flow intermittency results in catastrophic mortality of an imperiled minnow

Reale

2020

Freshwater Biology

“…During periods of river drying, Rio Grande silvery minnow are forced into isolated pools [37]. Compared to other intermittent streams in the American Great Plains region [15,40] and around the world [41], isolated pools in the MRG are shallow (<0.6 m) and short-lived, with only a small percentage persisting > 4 days [37]. Globally, isolated pools can last for weeks to years and allow the persistence of fishes and other organisms [42][43][44].…”

Section: Methodsmentioning

confidence: 99%

“…Some stream temperatures are projected to exceed the thermal critical maxima for many fishes [9], which may lead to temperature-dependent mortality, population declines, or other sublethal effects [10][11][12]. Exposure to intermittent habitats and elevated water temperatures can reshape fish assemblages [13,14], which may result in shifts towards more homogenous assemblages dominated by extremophile species [15]. Understanding the long-term consequences of drought on fish communities, including the effects of water temperature and streamflow intermittency, will likely be an ever-increasing challenge for native fish conservation [16,17].…”

Section: Introductionmentioning

confidence: 99%

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Fish Rescue during Streamflow Intermittency May Not Be Effective for Conservation of Rio Grande Silvery Minnow

Diver

Reale

2020

Water

Streamflow intermittency can reshape fish assemblages and present challenges to recovery of imperiled species. During streamflow intermittency, fish can be subjected to a variety of stressors, including exposure to crowding, high water temperatures, and low dissolved oxygen, resulting in sublethal effects or mortality. Rescue of fishes is often used as a conservation tool to mitigate the negative impacts of streamflow intermittency. The effectiveness of such actions is rarely evaluated. Here, we use multi-year water quality data collected from isolated pools during rescue of Rio Grande silvery minnow Hybognathus amarus, an endangered minnow. We examined seasonal and diel water quality patterns to determine if fishes are exposed to sublethal and critical water temperatures or dissolved oxygen concentrations during streamflow intermittency. Further, we determined survival of rescued Rio Grande silvery minnow for 3–5 weeks post-rescue. We found that isolated pool temperatures were much warmer (>40 °C in some pools) compared to upstream perennial flows, and had larger diel fluctuations, >10 °C compared to ~5 °C, and many pools had critically low dissolved oxygen concentrations. Survival of fish rescued from isolated pools during warmer months was <10%. Reactive conservation actions such as fish rescue are often costly, and in the case of Rio Grande silvery minnow, likely ineffective. Effective conservation of fishes threatened by streamflow intermittency should focus on restoring natural flow regimes that restore the natural processes under which fishes evolved.

Effects of flow recession regime on stranding of Rio Grande silvery minnow suggests that conservation actions must overcome evolutionary traps

Gonzales

Thomas

et al. 2022

Aquatic Conservation

1. Flow intermittence is a major disturbance for riverine fishes. Many species of fishes that evolved in naturally intermittent streams have specialized adaptations to survive drought such as movement to refuge habitats. Conservation of fishes in river systems with highly altered flow regimes requires understanding of how individuals and populations respond to flow intermittence.2. Here, flow was manipulated in two 16-km segments of the Rio Grande, New Mexico, to determine whether managed flow recession could reduce stranding imperilled Rio Grande silvery minnow in isolated pools.3. Slower flow recessions did not decrease stranding in isolated pools over the range tested. Flow recession rate appeared to have an adverse impact on stranding; fewer fish were stranded under faster recession rates, but complex interactions were evident. Fish were stranded throughout both segments regardless of flow recession rate.4. No evidence of a synchronized movement response was observed. Instead, many Rio Grande silvery minnows were probably trapped within proximal habitats, which dry completely and function as evolutionary traps, rather than moving to areas of perennial flow. Use of proximal habitats during streamflow intermittence has implications for management of the species and mitigation of mortality, including managed flow recession rates, and position and function of refuge habitats.5. Effective mitigation for flow intermittence and stranding in streams with highly modified flow regimes will depend on the life history and behavioural response of the species. For Rio Grande silvery minnow, facilitating adaptive behaviour would require creating refuge areas that increase fish survival for weeks to months, as reducing the attractiveness of the traps is likely to be impossible given lack of a synchronized movement response to declining flows. Mismatching life-history strategies, behaviour, and scale of conservation actions may result in ineffective