Confluence configuration of river networks controls spatial patterns in fish communities

Boddy, Nixie C.; Booker, D. J.; McIntosh, Angus R.

doi:10.1007/s10980-018-0763-4

Cited by 23 publications

(17 citation statements)

References 51 publications

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“…Moreover, effects of confluences on stream fish assemblages extend approximately two reaches upstream, so sampling two reaches in each direction from the confluence was sufficient to represent changes in fish assemblages associated with confluence‐related habitat diversity (Boddy et al., 2020). Each sampling reach was single‐pass electrofished in an upstream direction without stopnets; the results of this method correlate well with more intensive quantitative techniques in these systems, for both Galaxiidae ( r 2 = 0.99) and Salmonidae ( r 2 = 0.82) abundance (Boddy et al., 2019). Fish caught were identified to species, and size classes recorded based on fork length.…”

Section: Methodsmentioning

confidence: 75%

“…braided rivers; Figures 2 and 3). In these systems, RDI scores also reflect variations stream habitat, including characteristics such as water temperature and substrate size, associated with the flood disturbance differences, but variations in flooding were not associated with changes in land use characteristics that might confound the comparison (Boddy et al., 2019). Furthermore, because the occurrence of flooding events in New Zealand is aseasonal and driven by the unpredictable maritime climate (Tonkin et al., 2017), bed‐moving disturbances occurred throughout the year in disturbed branches and our sampling was spread throughout the fieldwork‐able times of the year.…”

Section: Methodsmentioning

confidence: 99%

“…The low heterogeneity category consisted of either confluences between two stable streams, or confluences between two streams with disturbed flow regimes (Figure 2a). Where possible, we sampled confluences between third‐order mainstems and second‐order tributaries to control for the effects of stream size (see Boddy et al., 2019 for physical descriptions).…”

Section: Methodsmentioning

confidence: 99%

“…Because floods are a major form of disturbance to rivers (Hart & Finelli, 1999; Bunn & Arthington, 2002; Poff & Zimmerman, 2010), variation in flood disturbance regimes should be a primary source of coarse‐scale differences between river branches. For example, disturbance due to flooding that affects the physical characteristics of river beds can explain nearly fifty percent of the among‐site variation in physical characteristics of river confluences in New Zealand (Boddy et al., 2019). Thus coarse‐scale variability in physical disturbance from flooding may be a key factor determining composition and stability of assemblages at coarse scales.…”

Section: Introductionmentioning

confidence: 99%

“…the tributary and mainstem branches of a confluence have either similar (low heterogeneity) or different (high heterogeneity) flow disturbance regimes. Because differences in the spatial layout of habitats in stream branches joining at confluences influence stream fish abundance and assemblage composition (Boddy et al., 2019), spatial dissimilarity in flow disturbance regimes around confluences could influence aspects of community stability.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Could spatial heterogeneity in flow disturbance drive temporal stability of native–invasive species co‐occurrence in riverscapes?

Boddy

McIntosh

2021

Freshwater Biology

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Spatial heterogeneity of abiotic influences like disturbance in riverscapes could play an important role in dispersal‐aided community stability. We tested if higher spatial variability in conditions around river confluences caused by different flood disturbance regimes in branches could possibly influence the stability of a fish assemblage dominated by strong negative interactions between non‐native trout and native galaxiid fishes. We used field surveys to evaluate the effects of disturbance‐driven differences between river branches on fish densities and temporal variation in the relative abundance of galaxiids. Three repeated electrofishing surveys were conducted in two reaches of all branches of eight confluences in Canterbury, New Zealand. We found the differences in flood disturbance regimes between the two stream branches joining at a confluence were associated with higher mean fish abundance and more temporal stability in the relative abundance of native fish. Conversely, when flood disturbance conditions in the two streams joining were similar, resulting in a homogeneous confluence, fish abundance was lower and temporal variability was higher. For homogeneous confluences, strong interactions between native galaxiids and invasive trout probably produced lower fish densities where rivers with low flow disturbance met, whereas when two highly flow‐disturbed rivers met, environmental harshness probably lowered fish densities. By comparison, enhanced galaxiid temporal stability at confluences containing both disturbed and stable river branches probably reflected the combined effects of refugia from trout predation in disturbed branches and refugia from flooding in stable branches. Overall, these results are likely to reflect the combined effects of population‐specific responses to physical heterogeneity and spatially variable interspecific interactions. They may mean that river network configuration, and confluences especially, could influence community stability through a habitat portfolio effect. Furthermore, it will be worth investigating further whether preservation or restoration of differences in flow disturbance conditions in riverscapes encourages higher ecosystem resilience in the face of global change.

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Section: Methodsmentioning

confidence: 75%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Could spatial heterogeneity in flow disturbance drive temporal stability of native–invasive species co‐occurrence in riverscapes?

Boddy

McIntosh

2021

Freshwater Biology

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Quantifying the contributions of tributaries to large‐river fish populations through mark‐recapture modeling

Healy,

Smith

2024

N American J Fish Manag

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Tributaries may play a vital role in maintaining populations of large river fishes, although the specific contributions of tributaries toward recruitment of river‐wide populations are not often understood. Tributaries may experience fewer cumulative anthropogenic impacts relative to mainstem rivers and may offer more natural conditions supportive of native fish populations, which may provide opportunities for fish population restoration. Thus, an improved understanding of tributary‐mainstem population dynamics may inform targeted conservation actions for spatially structured populations of large‐river fishes. Colorado River tributaries in the Grand Canyon, Arizona, USA are a focus of imperiled Humpback Chub Gila cypha conservation, which includes translocations to enhance population redundancy and to expand the overall population. However, the fate of fish dispersed to the mainstem has not been thoroughly quantified. Using open population mark‐recapture models, we quantified the relative contribution of three groups of Humpback Chub, including fish of confirmed tributary origin that were either translocated or produced in situ, and others presumed to be Colorado River mainstem origin fish, to three mainstem populations. Our specific study objectives were to 1) estimate Colorado River abundances of tributary and mainstem‐origin fish over time, 2) compare relative group‐specific contributions to three mainstem populations, and 3) compare group‐specific survival rates of Humpback Chub in the Colorado River and in a tributary where a recent translocation has occurred. Tributaries contributed 26% and 43% of the overall abundance in two tributary inflow reach populations, and zero in a third, which we attributed to uncharacteristically low tributary survival immediately following translocation. In the mainstem, survival of tributary‐origin fish was higher compared to mainstem‐origin fish, suggesting an advantage of tributary residence. Our contrasting results from three different tributary inflow populations highlight the potential role for tributaries in sustaining large‐river fish populations, which may have important implications for long‐term maintenance of river metapopulations.

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Watersheds and stream networks viewed longitudinally: Example insights from novel spatial portrayals of watershed characteristics

Raulerson

Sytsma

Webster

et al. 2023

River Research & Apps

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Longitudinal depictions of watershed structure and characteristics, including topography, stream networks, wetlands, ground water levels, and land use, can provide watershed knowledge and understanding unavailable from standard plan view maps. Three case studies provide examples of knowledge gained by applying longitudinal views of stream networks, watershed hydrologic behavior, and land use distributions. Longitudinal views of mountain stream networks show extreme variability in the slope-area relationships of low Strahler order streams, large discontinuities in drainage area (large parts of drainage area space are absent in networks), and large variations in network curvature. Longitudinal views of a groundwater-dominated headwater watershed increase the inference available from limited groundwater observations and clearly reveal how groundwater connections affect the permanence of surface water features and the distribution of vadose zone storage in the landscape. Plotting land uses longitudinally illuminates and allows a quantitative analysis of how land uses are distributed relative to topographic position. Viewing watersheds and stream networks longitudinally can provide new insights into watershed forms and processes and motivate new questions and research.

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Confluence configuration of river networks controls spatial patterns in fish communities

Cited by 23 publications

References 51 publications

Could spatial heterogeneity in flow disturbance drive temporal stability of native–invasive species co‐occurrence in riverscapes?

Could spatial heterogeneity in flow disturbance drive temporal stability of native–invasive species co‐occurrence in riverscapes?

Quantifying the contributions of tributaries to large‐river fish populations through mark‐recapture modeling

Watersheds and stream networks viewed longitudinally: Example insights from novel spatial portrayals of watershed characteristics

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