STREAM FLOW REGIME, TEMPERATURE AND CLIMATE CHANGE: THE LOSS OF FISH HABITAT (original) (raw)
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Effect of climate change on brown trout thermal habitat shifts along the river continuum
Proceedings 10th International Symposium on Ecohydraulics, 2014
Water temperature is a central issue in freshwater ecology because it influences on physical, chemical and biological processes and, therefore, on organisms that live all the time or part of this in water. Therefore, climate change might drive the availability of suitable habitat for many fish species including brown trout. This paper deals with the mechanics of the effects of Climate Change on thermal performance in two streams in the centre of the Iberian Peninsula (Duero basin) and its consequences on brown trout (Salmo trutta) distribution. Water temperature data were collected by means of 11 thermographs located along the altitudinal gradient of the trout range in the streams. Trout abundance was studied using electrofishing samplings conducted at 37 sites. A high resolution spatio-temporal model was developed to reconstruct the temperature regime of the streams in the past and to simulate its behaviour in the future, using air temperature as the independent variable. The thermal behaviour simulations of the streams were based on the most recent climate change scenarios used in the 5th Assessment Report of the Intergovernmental Panel on Climate Change. According to observations in this study, climate warming might drive a retraction up to 56% of the current brown trout thermal habitat in the studied streams.
2015
This paper addresses the determination of the realized thermal niche and the effects of climate change on the range distribution of two brown trout populations inhabiting two streams in the Duero River basin (Iberian Peninsula) at the edge of the natural distribution area of this species. For reaching these goals, new methodological developments were applied to improve reliability of forecasts. Water temperature data were collected using 11 thermographs located along the altitudinal gradient, and they were used to model the relationship between stream temperature and air temperature along the river continuum. Trout abundance was studied using electrofishing at 37 sites to determine the current distribution. The RCP4.5 and RCP8.5 change scenarios adopted by the International Panel of Climate Change for its Fifth Assessment Report were used for simulations and local downscaling in this study. We found more reliable results using the daily mean stream temperature than maximum daily temperature and their respective seven days moving-average to determine the distribution thresholds. Thereby, the observed limits of the summer distribution of brown trout were linked to thresholds between 18.1 °C and 18.7 °C. These temperatures characterise a realised thermal niche narrower than the physiological thermal range. In the most unfavourable climate change scenario, the thermal habitat loss of brown trout increased to 38% (Cega stream) and 11% (Pirón stream) in the upstream direction at the end of the century; however, at the Cega stream, the range reduction could reach 56% due to the effect of a “warm-window” opening in the piedmont reach. This article is protected by copyright. All rights reserved.
Climate changes affect aquatic ecosystems by altering temperatures and precipitation patterns, and the rear edges of the distributions of cold-water species are especially sensitive to these effects. The main goal of this study was to predict in detail how changes in air temperature and precipitation will affect streamflow, the thermal habitat of a cold-water fish (the brown trout, Salmo trutta), and the syn-ergistic relationships among these variables at the rear edge of the natural distribution of brown trout. Thirty-one sites in 14 mountain rivers and streams were studied in central Spain. Models of streamflow were built for several of these sites using M5 model trees, and a non-linear regression method was used to estimate stream temperatures. Nine global climate models simulations for Representative Concentration Pathways RCP4.5 and RCP8.5 scenarios were downscaled to the local level. Significant reductions in streamflow were predicted to occur in all of the basins (max. −49 %) by the year 2099, and seasonal differences were noted between the basins. The stream temperature models showed relationships between the model parameters, geology and hydrologic responses. Temperature was sensitive to streamflow in one set of streams, and summer reductions in streamflow contributed to additional stream temperature increases (max. 3.6 • C), although the sites that are most dependent on deep aquifers will likely resist warming to a greater degree. The predicted increases in water temperatures were as high as 4.0 • C. Temperature and streamflow changes will cause a shift in the rear edge of the distribution of this species. However, geology will affect the extent of this shift. Approaches like the one used herein have proven to be useful in planning the prevention and mitigation of the negative effects of climate change by differentiating areas based on the risk level and viability of fish populations.
Effects of Future Climate Change on a River Habitat in an Italian Alpine Catchment
The impact of prospective climate change on the hydrological and ecological status of the mountain stretch of the Serio river (ca. 300 km 2) in the Northern Italian Alps was investigated. A hydrological model was used to mimic theflow regime, and experimental suitability curves were used to assess weighted usable area (WUA) for brown trout (Salmo trutta) in different stages (adult, young, and spawning), and four macroinvertebrates families (Leuctridae, Heptageniidae, Limnephilidae, and Limoniidae). Discharge-WUA curves were obtained using instream flow incremental methodology/physical habitat simulation system (IFIM-PHABSIM), and a seasonal WUA assessment was carried out. The future (until 2100) hydrological cycle was projected using outputs from two general circulation models from Assessment Report 5 of the Intergovernmental Panel on Climate Change (IPCC). The results display a potential for a large flow decrease yearly, until −60% at 2050 and −56% at 2090. Spring melt peaks will be largely dampened, with the largest projected decrease of −60% in 2050 and −66% in 2090. Also fall flows will be largely smoothed, down to −70% for 2050 and −56% for 2090. To quantify habitat quality, a specific quantile WUA 20% , was used and exceeded presently for 292 days in a year, and the percentage of critical days n c% when WUA < WUA 20%. Adult trouts will have decreasing n c% yearly (from 20% now to down to 13% in 2090), increasing in winter and spring and decreasing in fall. Young trouts will have decreasing n c% yearly (from 20% now to down to 2% in 2040 and 2090), but increasing in winter. Spawning, occurring in winter, will have lower n c% (from 16% now, to down to 8% in 2090). Macroinvertebrate families will have constant n c% yearly, unless for Leuctridae (from 20% now to up to 38% in 2050), and noticeable decrease of n c% in winter for Leuctridae until 2090, increase in spring and summer, and decrease in fall for all families until 2090. Correlation analysis of the WUA against weather and hydrological variables displayed that temperature is the most influencing variable, decreasing habitat suitability for all species in fall, and increasing suitability in spring, unless for young trouts.
2021
This study assessed the impact of climate change on monthly streamflow in the Verde River Basin, located in the Grande River Basin headwater. For this purpose, the SWAT and VIC hydrological models were used to simulate the monthly streamflow under RCP4.5 and RCP8.5 scenarios, obtained by Regional Climate Models Eta-HadGEM2-ES, Eta-CanESM2 and Eta-MIROC5 in the baseline period (1961-2005) and three time-slice (2011-2040, 2041-2070, and 2071-2099) inputs. At the end of the century, the Eta-HadGEM2-ES showed larger decrease of precipitation in both radiative scenarios, with an annual reduction of 17.4 (RCP4.5) and 32.3% (RCP8.5), while the Eta-CanESM2 indicated major warming, with an annual increase of 4.7 and 10.2°C under RCP4.5 and RCP8.5, respectively. As well as precipitation changes, the Eta-HadGEM2-ES also showed greater impacts on streamflow under RCP4.5 for the first time-slice (2011-2040), with an annual decrease of 58.0% for both hydrological models, and for the RCP8.5 scenario by the end the century (2071-2099), with an annual reduction of 54.0 (VIC model) and 56.8% (SWAT model). Regarding monthly streamflow, the Eta-HadGEM2-ES and Eta-CanESM2 inputs indicated decrease under the RCP8.5 scenario by the end the century, varying from 7.2 to 66.3 % (VIC model) and 37.0 to 64.7% (SWAT model). In general, Eta-MIROC5 presented the opposite in terms of direction in the simulations with both hydrological models at the end of the century. Combined effects of climate models, hydrological model structures and scenarios of climate change should be considered in assessments of uncertainties of climate change impacts.