Stream Fish Responses to Grazing Exclosures

Bayley, Peter B.; Li, Hiram W.

doi:10.1577/m05-165.1

Cited by 16 publications

(40 citation statements)

References 37 publications

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“…For example, trout responses may be more rapid following livestock removal relative to the negative impacts of grazing. Our results provide some support for this notion, given that stock exclusion and grazing studies differed considerably in their length (9.1 versus 22.9 years respectively; Table ), and several studies have shown short‐term (<5 years) responses at stock exclusion sites (Keller & Burnham, ; Stuber, ; Bayley & Li, ). However, more work is needed to explain why different responses were observed.…”

Section: Discussionmentioning

confidence: 89%

Do trout respond to riparian change? A meta‐analysis with implications for restoration and management

2017

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SUMMARY1. There are strong conceptual links between riparian zones and freshwater fish via riparian influences on water quality, habitat quality and availability, and trophic dynamics. Many of the world's riparian zones are, however, severely degraded, and the key functions they provide for fish are lost or compromised. In response to their ongoing degradation, extensive works are underway globally to restore the structure and function of riparian zones. Despite intense effort, we lack clear empirical evidence of how fishes respond to changes in riparian zones. 2. We conducted a systematic review and meta-analysis to explore how trout (specifically brook, brown, cutthroat, rainbow and steelhead), fish with globally important social, cultural, economic and ecological value, respond to key drivers of riparian alteration. We also identified where and with which species current research is being undertaken and examined the broad characteristics of different studies (e.g. location, focal species, length of study, study design) to better understand potential knowledge gaps in our understanding of how trout respond to changes in riparian zones. 3. ISI Web of Science and Google Scholar were searched for relevant peer-reviewed studies, and from an initial 6514 papers, 55 were included in the formal meta-analysis. From these, we extracted data to calculate response ratios comparing biological attributes at sites with altered riparian characteristics to suitable unmanipulated control sites. We used linear mixed effects models to assess general and species-specific trout responses to eight key 'drivers' of change in riparian condition. 4. Most studies were undertaken in North America using control-impact designs. We found little evidence for species-specific responses to riparian change, and surprisingly, many drivers deemed important in the literature (e.g. revegetation, managed canopy removal, grazing, and forestry clearing) did not consistently influence trout population-or individual-level metrics. Nonetheless, trout populations did respond positively to increasing woody debris and livestock exclusion (+87.7 and +66.6% respectively), and negatively to bushfire and afforestation (À67.4 and À88.2% respectively). We found some evidence that positive riparian changes may just attract fish (i.e. increased abundance or density) rather than enhance actual population production (i.e. individual size and growth). While this conclusion necessarily needs to be interpreted with caution, it does suggest that targeted research on the 'production versus attraction' hypothesis would be beneficial. 5. Several key drivers of riparian change, such as revegetation activities, have been the focus of only limited research. More generally, long-term data are lacking for most drivers. Both of these key information gaps limit our ability to predict the likely timing and trajectory of responses to riparian management. Robust monitoring programmes in areas with altered riparian zones -particularly using BACI designs to allow changes to be attribu...

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Section: Discussionmentioning

confidence: 89%

Do trout respond to riparian change? A meta‐analysis with implications for restoration and management

2017

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“…The high variability among sites within grazing systems suggests that larger‐scale processes also influenced fish populations and reduced local effects. Research evaluating effects of livestock exclosures on fish populations has produced inconsistent results (Platts, 1991; Sarr, 2002), probably because many were too small to provide the diverse habitats necessary for salmonids to complete their life history (Bayley & Li, 2008). WO exclosures were also small and difficult to find for our study and were often either located on small headwater streams or bounded on both ends by SLG, which may explain why results for invertebrates and fish under this grazing system were different than we predicted.…”

Section: Discussionmentioning

confidence: 99%

Grazing management influences the subsidy of terrestrial prey to trout in central Rocky Mountain streams (USA)

Saunders

Fausch

2012

Freshwater Biology

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Summary 1. Research in forest and grassland ecosystems indicates that terrestrial invertebrates that fall into streams can be an important prey resource for fish, providing about 50% of their annual energy and having strong effects on growth and abundance. However, the indirect effects of land uses like cattle grazing on this important prey subsidy for stream salmonids are unclear. 2. During summer 2007, we compared the effects of three commonly used grazing systems on terrestrial invertebrate inputs to streams in northern Colorado and their use by trout. Cattle graze individual pastures for about 120 days under traditional season‐long grazing (SLG), about 35–45 days under simple rotational grazing and 10–20 days under intensive rotational grazing in this region. We also compared these effects to a fourth group of sites grazed only by wildlife (i.e. no livestock use). 3. Overall, rotational grazing management (either simple or intensive), resulted in more riparian vegetation, greater inputs of terrestrial invertebrates, greater biomass of terrestrial invertebrate prey in trout diets, a higher input compared to trout metabolic demand and more trout biomass than SLG. However, these differences were frequently not statistically significant owing to high variability, especially for trout diets and biomass. 4. Despite the inherent variability, riparian vegetation and terrestrial invertebrates entering streams and in trout diets at sites managed for rotational grazing were similar to sites managed for wildlife grazing only. 5. These results indicate that rotational grazing systems can be effective for maintaining levels of terrestrial invertebrate subsidies to streams necessary to support robust trout populations. However, factors influencing the effect of riparian grazing on stream subsidies are both spatially variable and complex, owing to differences in microclimate, invertebrate and plant populations and the efforts of ranchers to tailor grazing systems to specific riparian pastures.

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“…). These degraded stream conditions typically reduce fish populations and aquatic community diversity (Bayley and Li ; Herbst et al. ).…”

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confidence: 99%

“…Riparian exclosures can result in increased woody and herbaceous vegetation growth, greater bank stability, narrower and deeper stream channels, and improved fish habitat (McDowell and Magilligan ). These changes to physical habitat along with changes in prey abundance, in turn, have been linked to increased abundance of juvenile salmonids in northeastern Oregon streams (Bayley and Li ). Others have shown terrestrial invertebrate inputs to streams not grazed by livestock to be greater than those in intensively grazed riparian pastures (Saunders and Fausch ).…”

mentioning

confidence: 99%

“…Unfortunately, not all exclosures have the desired influence on riparian vegetation and channel morphology (McDowell and Magilligan ). For example, small exclosure size has been cited as one reason why juvenile fish may respond to exclosures whereas large adults that require larger expanses of habitat beyond that exclosed often show no response (Bayley and Li ).…”

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confidence: 99%

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Response of Riparian Vegetation, Instream Habitat, and Aquatic Biota to Riparian Grazing Exclosures

Dauwalter

Fesenmyer

Miller

et al. 2018

N American J Fish Manag

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Improper riparian grazing can alter riparian vegetation and reduce streambank stability, negatively impacting aquatic habitat and biota. We evaluated differences in riparian and instream habitat, benthic macroinvertebrates, and fish inside versus outside seven riparian exclosures constructed from 1982 to 2005 in Idaho. The normalized difference vegetation index from Landsat imagery (1985 to 2015) showed significant increases in riparian vegetation productivity after some but not all exclosures were constructed. Field data collected in 2015 showed woody riparian vegetation to be more abundant, streambanks less altered, and stream channels narrower inside versus outside exclosures, as we expected. However, instream habitat, a benthic macroinvertebrate index, fish species richness, and adult salmonid density showed no response. Higher age‐0 salmonid densities were the only aquatic organism response observed. Broader watershed‐scale factors likely limited strong and consistent responses by aquatic biota to exclosures. We conclude that riparian exclosures have localized effects on stream systems, such as increased riparian vegetation, reduced streambank alteration, and improved channel stability, but may not always influence aquatic biota that commonly reflect larger watershed‐scale processes and conditions. Therefore, well‐maintained riparian exclosures should be used to eliminate livestock use in localized areas of stream corridors that are sensitive to disturbance. To improve stream health at the larger watershed scale that is relevant to most aquatic biota, exclosures should only be one of several grazing management tools implemented simultaneously to reduce the impacts of improper livestock grazing.

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Stream Fish Responses to Grazing Exclosures

Cited by 16 publications

References 37 publications

Do trout respond to riparian change? A meta‐analysis with implications for restoration and management

Do trout respond to riparian change? A meta‐analysis with implications for restoration and management

Grazing management influences the subsidy of terrestrial prey to trout in central Rocky Mountain streams (USA)

Response of Riparian Vegetation, Instream Habitat, and Aquatic Biota to Riparian Grazing Exclosures

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