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Projected impacts of climate change on stream salmonids with implications for resilience-based management

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The sustainability of freshwater fisheries is increasingly affected by climate warming, habitat alteration, invasive species, and other drivers of global change. The State of Michigan, USA, contains ecologically, socioeconomically valuable coldwater stream salmonid fisheries that are highly susceptible to these ecological alterations. Thus, there is a need for future management approaches that promote resilient stream ecosystems that absorb change amidst disturbances. Fisheries professionals in Michigan are responding to this need by designing a comprehensive management plan for stream brook charr (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss) populations. To assist in developing such a plan, we used stream-specific regression models to forecast thermal habitat suitability in streams throughout Michigan from 2006–2056 under different predicted climate change scenarios. As baseflow index (i.e., relative groundwater input) increased, stream thermal sensitivity (i.e., relative susceptibility to temperature change) decreased. Thus, the magnitude of temperature warming and frequency of thermal habitat degradation were lowest in streams with the highest baseflow indices. Thermal habitats were most suitable in rainbow trout streams as this species has a wider temperature range for growth (12.0–22.5°C) compared to brook charr (11.0–20.5°C) and brown trout (12.0–20.0°C). Our study promotes resilience-based salmonid management by providing a methodology for stream temperature and thermal habitat suitability prediction. Fisheries professionals can use this approach to protect coldwater habitats and drivers of stream cooling and ultimately conserve resilient salmonid populations amidst global change.
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Projected impacts of climate change on stream
salmonids with implications for resilience-based
management
Andrew K. Carlson
1
, William W. Taylor
1
, Kelsey M. Schlee
1
, Troy G. Zorn
2
, Dana M. Infante
1
1
Department of Fisheries and Wildlife, Center for Systems Integration and Sustainability, Michigan State University, East Lansing, MI 48824, USA
2
Michigan Department of Natural Resources, Marquette Fisheries Research Station, Marquette, MI 49855, USA
Accepted for publication November 16, 2015
Abstract The sustainability of freshwater fisheries is increasingly affected by climate warming, habitat alteration,
invasive species and other drivers of global change. The State of Michigan, USA, contains ecologically,
socioeconomically valuable coldwater stream salmonid fisheries that are highly susceptible to these ecological
alterations. Thus, there is a need for future management approaches that promote resilient stream ecosystems that
absorb change amidst disturbances. Fisheries professionals in Michigan are responding to this need by designing a
comprehensive management plan for stream brook charr (Salvelinus fontinalis), brown trout (Salmo trutta) and
rainbow trout (Oncorhynchus mykiss) populations. To assist in developing such a plan, we used stream-specific
regression models to forecast thermal habitat suitability in streams throughout Michigan from 2006 to 2056 under
different predicted climate change scenarios. As baseflow index (i.e., relative groundwater input) increased, stream
thermal sensitivity (i.e., relative susceptibility to temperature change) decreased. Thus, the magnitude of temperature
warming and frequency of thermal habitat degradation were lowest in streams with the highest baseflow indices.
Thermal habitats were most suitable in rainbow trout streams as this species has a wider temperature range for
growth (12.022.5 °C) compared to brook charr (11.020.5 °C) and brown trout (12.020.0 °C). Our study
promotes resilience-based salmonid management by providing a methodology for stream temperature and thermal
habitat suitability prediction. Fisheries professionals can use this approach to protect coldwater habitats and drivers
of stream cooling and ultimately conserve resilient salmonid populations amidst global change.
Key words: brook charr; brown trout; rainbow trout; Michigan; temperature; resilience
Introduction
As climate warming, habitat fragmentation, invasive
species and other drivers of global change alter aqua-
tic ecosystems throughout the world, managing fish-
eries for resilience has become an important
conservation framework (Hansen et al. 2015). Resili-
ence is the capacity of a system to absorb distur-
bances and retain its structure and function (Holling
1973). Managing aquatic ecosystems for resilience is
particularly important when they contain species that
are sensitive to ecological stressors. For instance,
with relatively low thermal tolerance thresholds
(Raleigh 1982a,b; Raleigh et al. 1986), salmonid
fishes may experience reductions in growth and sur-
vival due to temperature elevation caused by climate
change. Thus, managing these species and their
ecosystems for thermal resilience is an important
task. Collaboration among scientists, managers, poli-
cymakers and public stakeholders will be important
for developing management approaches commensu-
rate with the wide geographical distribution and high
socioeconomic value of salmonid populations (Isaak
et al. 2015; Snyder et al. 2015).
Temperature exerts a fundamental physiological
influence on fish metabolism, which regulates
growth, survival and reproduction of individuals
(Dodds & Whiles 2010) and ultimately the dynamics
Correspondence: A. K. Carlson, Department of Fisheries and Wildlife, Center for Systems Integration and Sustainability, Michigan State University, East Lansing,
MI, 48824 USA. E-mail: carls422@msu.edu
190 doi: 10.1111/eff.12267
Ecology of Freshwater Fish 2017: 26: 190204 Ó2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd
ECOLOGY OF
FRESHWATER FISH
of populations and communities. For example, water
temperature is an important factor determining fish
distribution and assemblage composition (Magnuson
et al. 1979). Temperatures above species-specific
thermal maxima cause mortality; temperatures below
maxima alter fish growth, reproduction, abundance
and population size structure (Magnuson et al. 1997).
In addition, thermal warming can indirectly decrease
fish growth and survival by degrading water quality
(e.g., reduced dissolved oxygen; Ficklin et al. 2013).
Climate change is predicted to increase stream tem-
peratures and thereby alter thermal habitat suitability
(Lyons et al. 2010) and fish community composition
(Isaak et al. 2012). Moreover, dams, culverts, and
other anthropogenic barriers increase water tempera-
tures and decrease population and habitat connectiv-
ity (Lessard 2000; Hayes et al. 2006). Regardless of
mechanism, stream salmonids are sensitive to thermal
warming because they are adapted to cold and cool
water environments (Raleigh 1982a,b; Raleigh et al.
1986; Wehrly et al. 2007). Climate-driven increases
in water temperature may reduce salmonid growth,
reproduction, and survival in streams currently near
thermal optima. Thus, it is imperative that fisheries
professionals develop management strategies to pro-
mote thermal resilience and thereby conserve salmo-
nid populations in a warming climate.
The State of Michigan, USA, has ecologically and
socioeconomically valuable populations of brook charr
(Salvelinus fontinalis), brown trout (Salmo trutta), and
rainbow trout (Oncorhynchus mykiss) distributed
throughout 31,000 km of streams (Godby et al. 2007;
Tyler & Rutherford 2007). Projected air temperature
warming resulting from climate change is predicted to
increase stream temperatures in the Midwestern Uni-
ted States by 0.84.0 °C (Pilgrim et al. 1998; Lyons
et al. 2010). If temperatures exceed thermal optima for
these species, growth, reproduction, and/or survival
will decline, particularly during the warmest month of
the year (i.e., July; Zorn et al. 2011). Thus, Michigan
is an ideal study area for investigating how thermal
warming will impact coldwater streams and salmonid
population dynamics. This information will enable
fisheries professionals to develop resilience-based
management programmes: collaborative efforts among
scientists, managers, policymakers and public stake-
holders to maintain stream ecosystem structure and
function amidst global change.
The goal of this study was to evaluate the effects of
projected air temperature warming on salmonid ther-
mal habitat suitability in coldwater streams in Michi-
gan to facilitate the development of a resilience-based
management programme. Our first objective was to
measure the accuracy of stream-specific airwater tem-
perature regression models by backcasting stream tem-
peratures in 2006 and 2012, years with pre-existing air
and stream temperature metrics. Our second objective
was to forecast stream temperatures in 2036 and 2056
and project thermal habitat suitability for brook charr,
brown trout and rainbow trout growth and survival.
We predicted that water temperatures would increase
overall from 2006 to 2056 but unevenly among
streams and time periods (e.g., 20122036, 2036
2056) due to system-specific patterns of thermal warm-
ing and temporal variability in projected carbon diox-
ide (CO
2
) emissions (Arblaster et al. 2014). We
expected that thermal habitat impairment would occur
more frequently in streams with extensive surface run-
off than in groundwater-dominated, thermally buffered
systems (Sear et al. 1999; Krider et al. 2013).
Methods
Study area
Our study encompassed 30 coldwater streams
throughout the State of Michigan, USA (Fig. 1).
Streams were chosen in three Michigan Department
of Natural Resources (MDNR) management regions
[i.e., Upper Peninsula (UP), northern Lower Penin-
sula (NLP) and southern Lower Peninsula (SLP);
Table 1] to conduct the study at a statewide scale rel-
evant for salmonid management that also spanned a
latitudinal thermal gradient in which temperatures
increased from north (47.03°N) to south (42.64°N).
In addition, streams were selected to encompass a
hydrological gradient from surface runoff to ground-
water dominance by evaluating their relative base
flow, the component of streamflow attributable to
groundwater. We used a United States Geological
Survey report (Neff et al. 2005) to obtain each
streams base flow index (BFI), the mean rate of base
flow divided by the corresponding mean rate of total
streamflow. Baseflow index ranges from zero to one
with increasing groundwater input (Wahl & Wahl
1988); streams in our study ranged from 0.44 to 0.73
(Table 1). All BFI calculations were made using a
digital filter hydrograph separation technique (Arnold
& Allen 1999; Kelleher et al. 2012) whereby daily
streamflow records were partitioned into groundwater
and surface runoff components. Moreover, all streams
were important from a management standpoint as
they supported recreational fisheries for brook charr,
brown trout, rainbow trout or a combination of these
coldwater species. Only streams that had necessary
historical data for development of stream-specific
temperature regression models (i.e., field-measured
air and water temperatures) were selected. We devel-
oped a list of streams meeting these criteria (i.e., lati-
tudinal gradient, hydrological gradient, recreational
importance and historical data) using information
from the MDNR Better Fishing Waterswebpage
191
Resilience-based salmonid management
(MDNR 2015) and through personal communication
with MDNR Fisheries Division personnel (Tracy
Kolb, Todd Wills) and employees of the Michigan
Council of Trout Unlimited (Trout Unlimited 2015).
A minimum of five streams per region were selected
for each species to ensure regional replication. One
exception was the SLP, where brook charr and rain-
bow trout are not widely distributed and only four
streams contained one or both of these species. In
total, 16, 18 and 11 streams contained brook charr,
brown trout and rainbow trout, respectively. Eleven
streams supported more than one species, and four
supported all species (Table 1).
Stream-specific regression models
Historical air and water temperatures for each stream
were used to create stream-specific regression mod-
els. Daily air temperatures collected in summer
months (i.e., June, July and August) from 1990 to
2010 were compiled using the United States Histori-
cal Climate Network online interface (http://
cdiac.ornl.gov/). Air temperatures were measured at
the gauging station closest to each streams headwa-
ters, where MDNR water temperature gauges
recorded daily temperatures in summer months from
19902010. The most upstream gauge on each stream
was selected because temperatures are typically cool-
est and most optimal for salmonids in headwater
reaches. As such, we focused on these areas because
if their thermal habitat is degraded, downstream habi-
tat and salmonid populations will also be impaired.
Hydrological unit codes (HUCs) for each streams
sub-basin (HUC8) and subwatershed (HUC 12) were
identified using the National Hydrography Dataset
Plus Version 1 (NHDPlusV1) and the Watershed
Boundary Dataset (USEPA 2005). The North Ameri-
can Anthropogenic Barrier Dataset was used to locate
and omit gauges directly below dams, which elevate
temperatures compared to upstream reaches (Lessard
2000). For streams without MDNR gauges, a substi-
tute gauge on the nearest stream within the same sub-
watershed was used. Stream-specific regression
models were developed by pairing mean summer air
and water temperatures from recent years (i.e., 2002
2010) in Microsoft Excel (Table 2). Air temperature
coefficients represented indices of stream thermal
sensitivity (i.e., relative susceptibility to temperature
change; Kelleher et al. 2012) and were coupled with
air temperature projections (see below) to predict
future water temperatures. In addition, historical
warming in each stream was evaluated by comparing
air temperatures in 1976 and 2006 and multiplying
this temperature change by each streams air tempera-
ture coefficient to determine the magnitude of stream
warming.
Fig. 1. Map of brook charr, brown trout
and rainbow trout streams used for air
stream temperature modelling in Michigan,
USA. Streams and corresponding
identification numbers are listed in
Table 1. Triangles denote locations of
MDNR stream temperature gauges.
192
Carlson et al.
Air temperature projections
Three coupled climate models (CCMs) were used to
backcast mean June, July and August air tempera-
tures in 2006 and 2012 and forecast mean tempera-
tures in the same months in 2036 and 2056 for each
sub-basin: the Third Generation Coupled Global Cli-
mate Model (CGCM3, Canadian Centre for Climate
Modelling and Analysis), the CM2 Global Coupled
Climate Model (CM2, Geophysical Fluid Dynamics
Laboratory at the National Oceanic and Atmospheric
Administration) and the Hadley Centre Coupled
Model version 3 (HadCM3, Met Office, United King-
doms National Weather Service). All CCMs were
based on the World Climate Research Programme
(WCRP) Coupled Model Intercomparison Project
phase 3 (CMIP3) multimodel data set. Spatial down-
scaling was performed using the Bias-correction spa-
tial disaggregation (BCSD) approach to adjust the
resolution of the climate model (~200 9200 km) to
a scale germane for Michigan streams (12 912 km;
Maurer et al. 2007). The United States Forest
Services (USFS) Eastern Forest Environmental
Threat Assessment Center (EFETAC) in North
Carolina supplied mean June, July and August air
temperatures for Michigan sub-basins containing
coldwater salmonid streams. Projections were made
based on the CGCM3, CM2, and HadCM3 models
using area-weighted means for all years assuming the
Special Report of Emission Scenarios A2 and B1 cli-
mate forcing scenarios. The A2 scenario describes a
future world with rapid economic growth and effi-
cient energy technologies and predicts atmospheric
CO
2
concentrations to be 820 ppm in 2100. In con-
trast, the B1 scenario projects a convergent world
with a service and information economy and reduced
material consumption and predicts atmospheric CO
2
concentrations 550 ppm in 2100. Combining scenar-
ios was informative as they represent upper and
lower emission thresholds for stream temperature
prediction.
Stream temperature and thermal habitat suitability
projections
Stream temperatures were backcasted in 2006 and
2012 and forecasted in 2036 and 2056 by inputting
CCM air temperature predictions into stream-specific
Table 1. Descriptive information about 30 salmonid streams used for temperature modelling in Michigan, USA. Region refers to Michigan location [i.e., Upper
Peninsula (UP), northern Lower Peninsula (NLP) and southern Lower Peninsula (SLP)]. Sub-basin denotes the National Hydrography Dataset sub-basin (i.e.,
8-digit hydrological unit code). Map number refers to stream identifiers in Fig. 1. Species refers to salmonids present in each stream [i.e., brook charr (BKC),
brown trout (BNT) and rainbow trout (RBT)]. BFI denotes baseflow index, the mean rate of base flow divided by the corresponding mean rate of total
streamflow (Neff et al. 2005).
Stream Region Subbasin Map number Species BFI
Bark River UP Cedar-Ford 18 BNT 0.60
Bear Creek SLP Kalamazoo 14 BNT 0.58
Black River NLP Black 1 BKT 0.63
Boardman River NLP Boardman-Charlevoix 2 BKT, BNT 0.58
Bryan Creek UP Escanaba 19 BKT 0.62
Canada Creek NLP Black 3 BKT 0.63
Carp River UP Carp-Pine 20 BKT, BNT, RBT 0.64
Cedar Creek SLP Lower Grand 10 BKT, BNT 0.50
Cedar River SLP Cedar-Ford 11 BNT 0.60
Chocolay River UP Betsy-Chocolay 25 RBT 0.62
Davenport Creek UP Brevoort-Millecoquins 26 RBT 0.65
Duke Creek SLP Lower Grand 15 BKT, BNT 0.50
East Branch Fox River UP Manistique 27 BKT, BNT 0.73
Elm River UP Keweenaw Peninsula 21 RBT 0.45
Escanaba River UP Escanaba 22 BKT, BNT 0.44
Iron River UP Brule 28 BKT 0.59
Little Indian River UP Manistique 29 BKT 0.73
Little Muskegon River NLP Muskegon 4 RBT 0.62
Manistee River NLP Manistee 5 BKT, BNT, RBT 0.65
Martin Creek SLP Pere Marquette-White 16 BKT 0.61
Pere Marquette River NLP Pere Marquette-White 6 BNT 0.61
Pigeon River NLP Cheboygan 7 BNT, RBT 0.65
Pine River SLP Pine 12 BNT 0.65
Pine River NLP Manistee 8 BKT, BNT, RBT 0.49
Prairie Creek SLP Lower Grand 13 BNT 0.50
Rogue River SLP Lower Grand 17 BNT, RBT 0.50
Salmon Trout River UP Keweenaw Peninsula 23 BKT 0.45
Tahquamenon River UP Tahquamenon 24 BNT 0.55
West Branch Sturgeon River NLP Cheboygan 9 BKT, BNT, RBT 0.65
Yellow Dog River UP Dead-Kelsey 30 RBT 0.52
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Resilience-based salmonid management
Table 2. Stream-specific temperature regression models, with summary statistics, historical warming and projected future warming for each system. F(i.e., F
1,7
) and Pvalues refer to the air temperature (A) parameter
used to predict stream temperature (S). DAand DSdenote changes in air and stream temperatures over corresponding time periods. For 20062012, 20122036 and 20362056, predicted changes in Aand Sare
provided for the A2 and B1 climate forcing scenarios (B1 in parentheses).
Stream name Regression SE FPR
2
ΔA1976
2006
ΔS1976
2006 ΔA20062012 ΔS20062012 ΔA20122036 ΔS20122036 ΔA20362056 ΔS20362056
Bark River S=0.32A +12.98 0.05 49.41 <0.01 0.86 +1.72 +0.55 +1.09 (+1.23) +0.35 (+0.39) +2.74 (+3.16) +0.88 (+1.01) 0.69 (0.65) 0.22 (0.21)
Bear Creek S=0.23A +11.61 0.03 46.74 <0.01 0.85 +0.94 +0.22 +0.58 (+0.82) +0.13 (+0.19) +2.40 (+3.10) +0.55 (+0.71) +0.72 (0.29) +0.17 (0.07)
Black River S=0.29A +8.74 0.04 57.04 <0.01 0.88 +3.17 +0.92 +0.60 (+0.59) +0.17 (+0.17) +2.58 (+3.79) +0.75 (+1.10) 0.77 (1.15) 0.22 (0.33)
Boardman River S=0.14A +11.99 0.02 72.85 <0.01 0.90 +3.17 +0.44 0.56 (0.77) 0.08 (0.11) +2.49 (+3.77) +0.35 (+0.53) 0.87 (1.04) 0.12 (0.15)
Bryan Creek S=0.42A +7.69 0.08 28.86 <0.01 0.78 +2.33 +0.98 +1.01 (+1.48) +0.43 (+0.62) +2.83 (+3.11) +1.19 (+1.31) 0.62 (0.83) 0.26 (0.35)
Canada Creek S=0.60A +6.91 0.08 61.72 <0.01 0.88 +3.17 +1.90 0.79 (0.59) 0.47 (0.36) +2.58 (+3.79) +1.55 (+2.27) 0.77 (1.15) 0.46 (0.69)
Carp River S=0.28A +12.06 0.04 41.63 <0.01 0.84 +2.00 +0.56 +0.65 (+1.14) +0.18 (+0.32) +2.78 (+3.62) +0.78 (+1.01) 0.49 (1.29) 0.14 (0.36)
Cedar Creek S=0.56A +6.32 0.09 39.10 <0.01 0.83 +0.72 +0.40 +0.58 (+0.65) +0.33 (+0.37) +2.48 (+3.14) +1.39 (+1.76) +0.48 (0.49) +0.27 (0.28)
Cedar River (SLP) S=0.25A +11.42 0.03 97.82 <0.01 0.92 +2.61 +0.65 0.68 (0.23) 0.17 (0.06) +2.74 (+3.16) +0.69 (+0.79) 0.69 (0.65) 0.17 (0.16)
Chocolay River S=0.23A +10.29 0.03 77.99 <0.01 0.91 +2.72 +0.63 0.64 (+0.43) 0.15 (+0.10) +2.71 (+3.36) +0.62 (+0.77) 0.42 (1.31) 0.10 (0.30)
Davenport Creek S=0.13A +8.97 0.01 99.55 <0.01 0.92 +2.00 +0.26 +0.55 (+0.79) +0.07 (+0.10) +2.63 (+3.53) +0.34 (+0.46) 0.54 (1.26) 0.07 (0.16)
Duke Creek S=0.48A +4.45 0.08 37.27 <0.01 0.82 +0.72 +0.35 +0.65 (+0.74) +0.31 (+0.36) +2.48 (+3.14) +1.19 (+1.51) +0.48 (0.49) +0.23 (0.24)
East Branch Fox River S=0.33A +7.73 0.04 86.45 <0.01 0.91 +2.00 +0.66 +0.56 (+0.87) +0.19 (+0.29) +2.61 (+3.44) +0.86 (+1.14) 0.50 (1.27) 0.17 (0.42)
Elm River S=0.82A +2.11 0.06 193.20 <0.01 0.96 +2.72 +2.23 +0.99 (+1.79) +0.82 (+1.47) +3.19 (+2.65) +2.62 (+2.17) 0.75 (0.39) 0.62 (0.32)
Escanaba River S=0.88A +3.03 0.14 39.26 <0.01 0.83 +2.72 +2.40 +1.01 (+1.48) +0.89 (+1.30) +2.83 (+3.11) +2.49 (+2.73) 0.62 (0.83) 0.54 (0.73)
Iron River S=0.30A +12.76 0.04 52.58 <0.01 0.87 +1.89 +0.57 0.77 (0.03) 0.23 (0.01) +3.13 (+2.82) +0.94 (+0.85) 0.74 (0.35) 0.22 (0.11)
Little Indian River S=0.06A +14.86 0.01 83.65 <0.01 0.91 +2.72 +0.16 0.61 (+0.21) 0.04 (+0.01) +2.61 (+3.44) +0.16 (+0.21) 0.50 (1.27) 0.03 (0.08)
Little
Muskegon River
S=0.34A +12.09 0.04 69.13 <0.01 0.89 +2.56 +0.87 0.79 (0.80) 0.27 (0.27) +2.48 (+3.41) +0.84 (+1.16) 0.12 (0.72) 0.04 (0.24
Manistee River S=0.13A +10.67 0.02 57.70 <0.01 0.88 +3.17 +0.41 +0.76 (+0.49) +0.10 (+0.06) +2.47 (+3.56) +0.32 (+0.46) 0.54 (0.81) 0.07 (0.11)
Martin Creek S=0.38A +9.61 0.05 62.93 <0.01 0.89 +2.11 +0.80 0.82 (0.83) 0.31 (0.31) +2.48 (+3.32) +0.94 (+1.26) +0.05 (0.55) +0.02 (0.21)
Pere
Marquette River
S=0.18A +12.50 0.02 51.89 <0.01 0.86 +2.11 +0.38 0.82 (0.83) 0.15 (0.15) +2.48 (+3.32) +0.45 (+0.60) +0.05 (0.55) +0.01 (0.10)
Pigeon River S=0.11A +11.93 0.01 60.49 <0.01 0.88 +3.17 +0.35 +0.67 (+0.50) +0.07 (+0.06) +2.52 (+3.78) +0.28 (+0.42) 0.83 (1.11) 0.09 (0.12)
Pine River (NLP) S=0.22A +10.89 0.03 73.41 <0.01 0.90 +2.11 +0.46 +0.76 (+0.49) +0.17 (+0.11) +2.47 (+3.56) +0.54 (+0.78) 0.54 (0.81) 0.12 (0.18)
Pine River (SLP) S=0.40A +9.23 0.04 119.15 <0.01 0.94 +2.56 +1.02 +0.68 (+0.72) +0.27 (+0.29) +2.49 (+3.25) +1.00 (+1.30) +0.23 (0.69) +0.09 (0.27)
Prairie Creek S=0.74A +0.95 0.07 106.03 <0.01 0.93 +1.94 +1.44 +0.58 (+0.65) +0.43 (+0.48) +2.48 (+3.14) +1.83 (+2.32) +0.48 (0.49) +0.35 (0.37)
Rogue River S=0.23A +13.17 0.04 27.46 <0.01 0.77 +0.72 +0.17 +0.65 (+0.74) +0.15 (+0.17) +2.48 (+3.14) +0.57 (+0.72) +0.48 (0.49) +0.11 (0.11)
Salmon Trout River S=0.29A +8.23 0.05 33.60 <0.01 0.80 +2.33 +0.68 +0.99 (+1.79) +0.29 (+0.52) +3.19 (+2.65) +0.92 (+0.77) 0.75 (0.39) 0.22 (0.11)
Tahquamenon River S=0.50A +12.29 0.05 115.88 <0.01 0.93 +2.00 +1.00 +0.75 (+1.32) +0.38 (+0.66) +2.72 (+3.51) +1.36 (+1.75) 0.41 (1.36) 0.21 (0.68)
West Branch
Sturgeon River
S=0.06A +11.93 0.01 67.49 <0.01 0.89 +3.17 +0.19 +0.67 (+0.50) +0.04 (+0.03) +2.52 (+3.78) +0.15 (+0.23) 0.83 (1.11) 0.05 (0.07)
Yellow Dog River S=0.38A +9.90 0.06 45.58 <0.01 0.85 +2.33 +0.89 0.63 (+0.39) 0.24 (+0.15) +2.98 (+2.96) +1.13 (+1.13) 0.63 (0.81) 0.24 (0.31)
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Carlson et al.
regression models. Mean July stream temperatures
were projected because this month is typically the
warmest and most thermally stressful for salmonids
in Michigan (Zorn et al. 2011). To incorporate the
range of air temperatures projected by each CCM and
the intrinsic uncertainty and unique characteristics
(i.e., atmospheric pressure, sea ice rheology, forest
canopy density and soil layering) of each model, pre-
dictions were averaged across the three CCMs. Spe-
cies-specific thermal habitat suitability status was
assigned for each stream based on conditions for
growth and survival associated with projected July
temperatures. Status 1, 2, 3, and 4 corresponded with
optimal growth, suboptimal (i.e., reduced) growth, no
growth and extirpation, respectively (Table 3). Uni-
ted States Fish and Wildlife Service (USFWS) Bio-
logical Reports (e.g., Raleigh 1982a,b; Raleigh et al.
1986) contained thermal habitat status temperature
ranges for juveniles and adults of each species. Other
sources (i.e., Fry et al. 1946; Baldwin 1957; Wurts-
baugh & Davis 1977; Elliott & Hurley 2000; Hay
et al. 2006) contained temperature ranges for juve-
niles and/or adults and were used to confirm tempera-
tures reported in the USFWS reports. When threshold
temperatures (e.g., thermal minima, maxima) differed
between juveniles and adults, we reported juvenile
temperatures under the premise that resilient salmo-
nid fisheries can only be conserved if young fish
survive to adulthood.
Analyses
The accuracy of stream-specific regression models
was evaluated by comparing each streams projected
temperature and thermal habitat suitability status in
2006 to its actual (i.e., field measured) temperature
and associated habitat status obtained from the
MDNR database. The association between BFI and
air temperature regression coefficients, which are
indices of stream thermal sensitivity, was assessed
using simple linear regression (Kelleher et al. 2012).
Results
Model accuracy
Stream-specific models accurately projected tempera-
ture and thermal habitat suitability status in brook
charr, brown trout, and rainbow trout streams. Under
the A2 scenario, the mean deviation between pre-
dicted and actual temperatures was 0.46 °C
(SD =0.56; Table 4). Under the B1 scenario, the
mean deviation between predicted and actual temper-
atures was 0.58 °C (SD =0.59; Table 4). Under
the A2 and B1 scenarios, stream-specific models pre-
dicted thermal habitat status with 93.0 per cent over-
all accuracy in streams with brook charr (94.0 per
cent accuracy, N=15), brown trout (89.0 per cent
accuracy, N=16) and rainbow trout (100.0 per cent
accuracy, N=11; Table 4).
Thermal habitat suitability: brook charr
Stream-specific regression models projected that cli-
mate-induced air temperature elevation will have sub-
stantial effects on stream temperature and thermal
habitat suitability, with impacts varying by BFI (i.e.,
streams with lower BFI were more thermally sensitive;
Fig. 2) as well as species, region, time period and cli-
mate forcing scenario. From 1976 to 2006, the mean
temperature of brook charr streams increased by
0.74 °C as mean air temperature increased by 2.34 °C
(Table 2). In the UP under the A2 and B1 scenarios,
thermal habitat suitability was predicted to be optimal
in the East Branch Fox and Little Indian rivers and
suboptimal in the Iron River from 20062056 (Fig. 3a,
b). From 2006 to 2012, thermal habitat was projected
to be optimal in Bryan Creek and the Salmon Trout
River and suboptimal in the Carp and Escanaba rivers
under both scenarios. From 2012 to 2036, thermal
habitat was projected to become suboptimal in Bryan
Creek with predicted warming by 1.19 °C (A2 scenar-
io) and 1.31 °C (B1 scenario; Table 2). Similarly, ther-
mal habitat was forecasted to become unsuitable for
growth in the Escanaba River with projected warming
by 2.49 °C (A2 scenario) and 2.73 °C (B1 scenario;
Table 2). Habitat suitability was predicted to remain
the same from 2036 to 2056 under both scenarios in all
brook charr streams evaluated.
In the NLP from 2006 to 2056, thermal habitat
was projected to be optimal in most streams (Black,
Boardman, Manistee, Pine, West Branch Sturgeon
Table 3. Thermal habitat suitability status (habitat status) designations and
corresponding temperature ranges (temperature) and growth conditions
(growth) for juvenile and adult brook charr (BKC; Fry et al. 1946; Baldwin
1957; Raleigh 1982a), brown trout (BNT; Raleigh et al. 1986; Elliott &
Hurley 2000; Hay et al. 2006) and rainbow trout (RBT; Wurtsbaugh &
Davis 1977; Raleigh 1982b).
Species Habitat status Temperature Growth
BKC 1 11.0 °C<16.5 Optimal
2 16.5 °C<20.5 Suboptimal
3 20.5 °C<25.3 None
4°C25.3 Extirpation
BNT 1 12.0 °C<17.0 Optimal
2 17.0 °C<20.0 Suboptimal
3 20.0 °C<26.2 None
4°C26.2 Extirpation
RBT 1 12.0 °C<16.4 Optimal
2 16.4 °C<22.5 Suboptimal
3 22.5 °C<25.0 None
4°C25.0 Extirpation
195
Resilience-based salmonid management
rivers) under the A2 and B1 scenarios (Fig. 3c,d).
From 2012 to 2036, thermal habitat was forecasted to
become unsuitable for growth in Canada Creek under
the B1 scenario with predicted warming by 2.27 °C
(Fig. 3d; Table 2). In the SLP under the A2 and B1
scenarios, thermal habitat was predicted to be subop-
timal from 2006 to 2056 in Martin Creek and Cedar
Creek (Fig. 3e,f). From 2012 to 2036 under the B1
scenario, thermal habitat was forecasted to become
suboptimal in Duke Creek with predicted warming
by 1.51 °C (Fig. 3f; Table 2).
Thermal habitat suitability: brown trout
From 1976 to 2006, the mean temperature of brown
trout streams increased by 0.65 °C as mean air tem-
perature increased by 2.09 °C (Table 2). In the UP
under the A2 and B1 scenarios, thermal habitat suit-
ability was predicted to be optimal in the East Branch
Fox River from 2006 to 2056 (Fig. 4a,b). From 2006
to 2012, thermal habitat suitability was projected to
be optimal in the Bark River, suboptimal in the
Escanaba River and unsuitable in the Tahquamenon
Table 4. Actual versus projected stream temperatures and thermal habitat suitability (THS) status for brook charr (BKC), brown trout (BNT) and rainbow trout
(RBT) as predicted by stream-specific airwater temperature regression models. Temperatures are predicted in 2006 under the A2 (820 ppm atmospheric CO
2
by 2100) and B1 (550 ppm atmospheric CO
2
by 2100) scenarios. Dsymbols denote differences between projected and actual stream temperatures obtained
from the Northeast Climate Science Center. The first and second THS numbers represent statuses associated with actual and projected temperatures,
respectively.
Stream name Actual A2 ΔTHS B1 ΔTHS
Bark River 19.91 18.95 0.96 BNT: 2,2 18.88 1.03 BNT: 2,2
Bear Creek 15.75 16.54 0.79 BNT: 1,1 16.54 0.79 BNT: 1,1
Black River 15.05 14.46 0.59 BKC: 1,1 14.36 0.69 BKC: 1,1
Boardman River 15.02 14.88 0.14 BKC: 1,1 14.85 0.17 BKC: 1,1
BNT: 1,1 BNT: 1,1
Bryan Creek 16.66 15.27 1.39 BKC: 2,1 15.06 1.60 BKC: 2,1
Canada Creek 19.95 19.41 0.54 BKC: 2,2 19.09 0.86 BKC: 2,2
Carp River 17.61 17.05 0.56 BKC: 2,2 17.00 0.72 BKC: 2,2
BNT: 2,2 BNT: 2,2
RBT: 2,2 RBT: 2,2
Cedar Creek 18.30 18.27 0.04 BKC: 2,2 18.32 0.02 BKC: 2,2
BNT: 2,2 BNT: 2,2
Cedar River (SLP) 17.15 16.59 0.56 BNT: 2,1 16.46 0.69 BNT: 2,1
Chocolay River 15.23 14.77 0.46 RBT: 1,1 14.52 0.71 RBT: 1,1
Davenport Creek 11.50 11.39 0.11 RBT: 1,1 11.34 0.16 RBT: 1,1
Duke Creek 15.32 14.69 0.63 BKC: 1,1 14.73 0.59 BKC: 1,1
BNT: 1,1 BNT: 1,1
East Branch Fox River 14.23 13.76 0.47 BKC: 1,1 13.62 0.61 BKC: 1,1
BNT: 1,1 BNT: 1,1
Elm River 17.48 16.96 0.52 RBT: 2,2 16.40 1.10 RBT: 2,2
Escanaba River 19.95 18.88 1.07 BKC: 2,2 18.45 1.50 BKC: 2,2
BNT: 2,2 BNT: 2,2
Iron River 18.61 18.53 0.08 BKC: 2,2 18.34 0.27 BKC: 2,2
Little Indian River 16.16 16.09 0.07 BKC: 1,1 16.03 0.13 BKC: 1,1
Little Muskegon River 19.89 19.24 0.65 RBT: 2,2 19.22 0.67 RBT: 2,2
Manistee River 13.55 13.29 0.26 BKC: 1,1 13.29 0.26 BKC: 1,1
BNT: 1,1 BNT: 1,1
RBT: 1,1 RBT: 1,1
Martin Creek 18.33 17.86 0.47 BKC: 2,2 17.87 0.46 BKC: 2,2
Pere Marquette River 16.62 16.41 0.21 BNT: 2,2 16.41 0.21 BNT: 2,2
Pigeon River 14.45 14.12 0.33 BNT: 1,1 14.10 0.35 BNT: 1,1
RBT: 1,1 RBT: 1,1
Pine River (NLP) 15.97 15.26 0.71 BKC: 1,1 15.27 0.70 BKC: 1,1
BNT: 1,1 BNT: 1,1
RBT: 1,1 RBT: 1,1
Pine River (SLP) 18.42 17.55 0.87 BNT: 2,2 17.56 0.86 BNT: 2,2
Prairie Creek 18.35 16.57 1.78 BNT: 2,1 16.64 1.71 BNT: 2,1
Rogue River 18.36 17.95 0.41 BNT: 2,2 17.97 0.39 BNT: 2,2
RBT: 2,2 RBT: 2,2
Salmon Trout River 14.62 13.51 1.11 BKC: 1,1 13.31 1.31 BKC: 1,1
Tahquamenon River 20.02 21.16 1.14 BNT: 3,3 20.86 0.84 BNT: 3,3
West Branch Sturgeon River 13.30 13.12 0.18 BKC: 1,1 13.11 0.19 BKC: 1,1
BNT: 1,1 BNT: 1,1
RBT: 1,1 RBT: 1,1
Yellow Dog River 18.00 17.33 0.67 RBT: 2,2 16.96 1.04 RBT: 2,2
196
Carlson et al.
River under both scenarios (Fig. 4a,b). During the
same time period, thermal habitat was forecasted to
become suboptimal in the Carp River under the B1
scenario with predicted warming by 0.32 °C
(Table 2). From 2012 to 2036, thermal habitat was
projected to become unsuitable for growth in the
Escanaba River with predicted warming by 2.49 °C
(A2 scenario) and 2.73 °C (B1 scenario; Table 2).
From 2036 to 2056, habitat suitability was predicted
to remain the same under both scenarios in all brown
trout streams evaluated.
In the NLP from 2006 to 2056, thermal habitat was
forecasted to be optimal under the A2 and B1 scenar-
ios in all brown trout streams evaluated, including the
Boardman, Manistee, Pere Marquette, Pigeon, Pine
and West Branch Sturgeon rivers (Fig. 4c,d). In the
SLP under the A2 and B1 scenarios, thermal habitat
suitability was predicted to be optimal in Duke Creek
and suboptimal in the Rogue River from 2006 to 2056
(Fig. 4e,f). From 2006 to 2012, thermal habitat was
projected to be optimal in the Cedar River and subop-
timal in Cedar Creek and the Pine River under both
scenarios. During the same time period, thermal habi-
tat was predicted to become suboptimal in Prairie
Creek under the B1 scenario with projected warming
by 0.48 °C (Table 2). From 2012 to 2036, thermal
habitat was forecasted to become suboptimal in the
Cedar River and Bear Creek and unsuitable for growth
in Cedar Creek under both scenarios. From 2036
2056 under the A2 scenario, thermal habitat was pro-
jected to become optimal in the Cedar River and
unsuitable for growth in Cedar Creek with predicted
cooling and warming by 0.17 °C and 0.27 °C respec-
tively (Fig. 4e; Table 2). Thermal habitat suitability
was forecasted to remain the same from 2036 to 2056
under the B1 scenario in all brown trout streams eval-
uated (Fig. 4f).
Thermal habitat suitability: rainbow trout
From 1976 to 2006, the mean temperature of brown
trout streams increased by 0.64 °C as mean air tem-
perature increased by 2.42 °C (Table 2). In the UP
under the A2 and B1 scenarios, thermal habitat suit-
ability was predicted to be optimal in the Chocolay
River and Davenport Creek and suboptimal in the
Carp, Elm and Yellow Dog Rivers from 20062056
(Fig. 5a,b). Similarly, thermal habitat was projected
to be optimal (Manistee, Pigeon, Pine and West
Branch Sturgeon rivers) and suboptimal (Little
Muskegon River) in the NLP from 2006 to 2056
under the A2 and B1 scenarios (Fig. 5c,d). Thermal
habitat in the Rogue River, the only rainbow trout
stream in the SLP, was predicted to be suboptimal
under both emissions scenarios from 20062056
(Fig. 5e,f).
Discussion
Our study is the first broad-scale investigation of cli-
mate-driven stream temperature warming in Michigan
with implications for salmonid management. Water
temperatures were projected to increase by 0.19
5.94 °C in 30 coldwater salmonid streams over the
next 40 years due to predicted air temperature warm-
ing. This finding supports a previous study in the
State of Minnesota, USA (Pilgrim et al. 1998), in
which temperatures in 39 streams increased by 0.30
6.90 °C under a doubling of atmospheric CO
2
con-
centrations comparable to the A2 climate forcing sce-
nario. In addition, our study supports a previous
investigation in the State of Wisconsin, USA (Lyons
et al. 2010), in which thermal habitat degradation
was projected for brook charr and brown trout in 282
streams forecasted to warm by 0.804.00 °C over the
next 45 years. In our research, the magnitude of
warming and thermal habitat impairment varied
among streams and time periods, with the greatest
warming and habitat degradation occurring from
1976 to 2006 (2.72 °C) and projected from 2012 to
2036 (2.492.62 °C) in the Elm and Escanaba rivers,
systems with the lowest BFI (<0.45). In contrast, the
magnitude of warming from 1976 to 2006 (0.16
0.66 °C) and projected warming from 2012 to 2036
(0.160.86 °C) was considerably lower in the East
Branch Fox and Little Indian rivers, systems with the
highest BFI (0.73). This finding supported our
hypothesis that temperature and thermal habitat alter-
ations would vary spatially and temporally due to
system-specific patterns of warming. It also rein-
forces previous research indicating fish assemblages
in Michigan streams with stable discharge from
groundwater inputs are more resilient to thermal
warming than those in streams with less stable dis-
Fig. 2. Relative influence of baseflow index on thermal sensitiv-
ity (i.e., air temperature regression coefficients) of streams in the
State of Michigan, USA. The regression equation is: Thermal sen-
sitivity =1.78 9Baseflow index +1.38 (P<0.01, R
2
=0.44).
197
Resilience-based salmonid management
charge (Zorn et al. 2012). Thermal habitat degrada-
tion was projected to occur least frequently in rain-
bow trout streams as this species has a wider
temperature range (12.022.5 °C) for growth and sur-
vival compared to brook charr (11.020.5 °C) and
brown trout (12.020.0 °C) (Wurtsbaugh & Davis
1977).
Warmer air temperatures are projected to increase
stream temperatures both directly (i.e., advection) and
indirectly through effects on precipitation, evapora-
Fig. 3. Projected temperatures in individual Michigan brook charr streams in 2006, 2012, 2036 and 2056 under A2 (820 ppm atmospheric
CO
2
by 2100) and B1 (550 ppm by 2100) scenarios. Plots are organised by region and emissions scenario: (a) Upper Peninsula, A2 scenar-
io; (b) Upper Peninsula, B1 scenario; (c) northern Lower Peninsula, A2 scenario; (d) northern Lower Peninsula, B1 scenario; (e) southern
Lower Peninsula, A2 scenario; (f) southern Lower Peninsula, B1 scenario. Dotted lines represent transitions between thermal habitat suit-
ability statuses. Stream abbreviations are as follows: BRC =Bryan Creek, BLR =Black River, BOR =Boardman River, CAC =Canada
Creek, CAR =Carp River, CEC =Cedar Creek, DUC =Duke Creek, EFR =East Branch Fox River, ESR =Escanaba River, IRR =Iron
River, LIR =Little Indian River, MAR =Manistee River, MAC =Martin Creek, PIR =Pine River (northern Lower Peninsula),
STR =Salmon Trout River, WSR =West Branch Sturgeon River.
198
Carlson et al.
tion and transpiration. Predicted effects of climate
change include more variable (and overall lower) pre-
cipitation (Parry et al. 2007; Stoner et al. 2013),
increased evaporation (Compagnucci et al. 2001) and
decreased discharge. These impacts would increase
stream temperature by reducing the volume of water
exposed to solar radiation. However, in Michigan
streams near the Great Lakes, precipitation will likely
Fig. 4. Projected temperatures in individual Michigan brown trout streams in 2006, 2012, 2036 and 2056 under A2 (820 ppm atmospheric
CO
2
by 2100) and B1 (550 ppm by 2100) scenarios. Plots are organised by region and emissions scenario: (a) Upper Peninsula, A2 scenar-
io; (b) Upper Peninsula, B1 scenario; (c) northern Lower Peninsula, A2 scenario; (d) northern Lower Peninsula, B1 scenario; (e) southern
Lower Peninsula, A2 scenario; (f) southern Lower Peninsula, B1 scenario. Dotted lines represent transitions between thermal habitat suit-
ability statuses. Stream abbreviations are as follows: BEC =Bear Creek, BOR =Boardman River, BRC =Bryan Creek, CAR =Carp
River, CEC =Cedar Creek, CER =Cedar River, DUC =Duke Creek, EFR =East Branch Fox River, ESR =Escanaba River,
MAR =Manistee River, PMR =Pere Marquette River, PGR =Pigeon River, PNR =Pine River (southern Lower Peninsula), PIR =Pine
River (northern Lower Peninsula), PRC =Prairie Creek, ROR =Rogue River, TAR =Tahquamenon River, WSR =West Branch Stur-
geon River.
199
Resilience-based salmonid management
intensify in fall and winter due to predicted increases
in snowfall (Norton & Bolsenga 1993; Primack
2000), increasing surface runoff and water volume
and decreasing temperature compared to systems
without this source of precipitation (Kurylyk et al.
2013). Increased canopy and soil surface evaporation
is projected to decrease groundwater recharge and
increase water temperature (Ge et al. 2013), although
streams high BFI are expected to warm at a slower
rate than those with low BFI due to groundwater-dri-
ven thermal buffering (Menberg et al. 2014). Tran-
spiration of water from plants has been reported to
contribute to stream warming by reducing streamflow
and groundwater recharge (Federer & Lash 1978;
Bond et al. 2002). Effects of climate warming on
transpiration and stream temperature will depend lar-
Fig. 5. Projected temperatures in individual Michigan rainbow trout streams in 2006, 2012, 2036 and 2056 under A2 (820 ppm atmo-
spheric CO
2
by 2100) and B1 (550 ppm by 2100) scenarios. Plots are organised by region and emissions scenario: (a) Upper Peninsula,
A2 scenario; (b) Upper Peninsula, B1 scenario; (c) northern Lower Peninsula, A2 scenario; (d) northern Lower Peninsula, B1 scenario; (e)
southern Lower Peninsula, A2 scenario; (f) southern Lower Peninsula, B1 scenario. Dotted lines represent transitions between thermal habi-
tat suitability statuses. Stream abbreviations are as follows: CAR =Carp River, CHR =Chocolay River, DAC =Davenport Creek,
ELR =Elm River, LMR =Little Muskegon River, MAR =Manistee River, PGR =Pigeon River, PIR =Pine River, ROR =Rogue
River, WSR =West Branch Sturgeon River, YDR =Yellow Dog River.
200
Carlson et al.
gely on changes in the species composition and leaf
characteristics (e.g., stomatal conductance, water-use
efficiency) of riparian plants and trees (Compagnucci
et al. 2001; Kirschbaum 2004). We encourage
researchers to incorporate the thermal effects of tran-
spiration, riparian shading and watershed land cover
(Wehrly et al. 1997; Wiley et al. 2010) into future
stream temperature modelling to improve predictive
accuracy.
Projected increases in Michigan stream tempera-
tures will result in thermal habitat conditions less
conducive for salmonid growth and survival during
the warmest period of the year (Raleigh 1982a,b;
Raleigh et al. 1986), particularly in thermally sensi-
tive streams with low BFI values. This will likely be
manifested by declines in availability and changes in
spatial arrangement of optimal thermal habitat, with
potential effects on salmonid distribution and sur-
vival. For instance, if stream warming restricts cold-
water habitats to specific areas (e.g., headwater
reaches), salmonid populations will become isolated,
which could increase interspecific competition and
decrease survival (Tsuboi et al. 2013; Dugdale et al.
2015). Previous research in Michigans Muskegon
River suggested warmer water temperatures resulting
from climate change will restrict the distribution and
decrease the survival of brook charr, brown trout,
and rainbow trout (Steen et al. 2010). Researchers in
the State of Wisconsin, USA, predicted that by 2060
the total length of streams suitable for brown trout
would decline by 8, 33, and 88 per cent under limited
(summer air temperatures increase 1.0 °C and water
0.8 °C), moderate (air 3.0 °C and water 2.4 °C), and
major (air 5.0 °C and water 4.0 °C) climatic warming
(Lyons et al. 2010). Results were more extreme for
brook charr, with distributional declines of 44 and 94
per cent under limited and moderate warming, and
complete extirpation under major warming. Although
our models did not project extirpation of any species
in the Michigan streams evaluated, summer growth
limitation may be coupled with decreased reproduc-
tion as lower oxygen levels resulting from stream
temperature warming and/or groundwater withdrawal
may reduce egg survival or prevent spawning
(Raleigh 1982a,b; Raleigh et al. 1986). Although
annual salmonid growth may remain stable or
increase due to longer growing season length and
increased prey availability, projected reductions in
growth and survival during the warmest period of the
year have important management implications.
Management implications
We encourage scientists, biologists, policymakers and
public stakeholders to collaboratively develop resili-
ence-based management programmes to conserve sal-
monid populations amidst global change. Our
research represents a step in this direction as it pro-
jects consequences of stream thermal warming for
salmonid growth and survival in Michigan. Our
results indicate it is important for fisheries profession-
als to manage streams for thermal resilience by form-
ing publicprivate partnerships to protect watershed
land cover types that facilitate high groundwater
recharge (e.g., grasslands; Waco & Taylor 2010; Sii-
tari et al. 2011), preserve riparian vegetation and
associated shading (Blann et al. 2002), and maintain
longitudinal connectivity to promote salmonid move-
ment to cold headwater reaches (Drake & Taylor
1996; Hayes et al. 1998). We recommend these
strategies play prominent roles in resilience-based
management programmes for coldwater streams and
their important salmonid fisheries. As documented in
our study, streams with low thermal sensitivity (i.e.,
high BFI) will likely maintain thermal conditions
(e.g., cool summer temperatures, seasonal flow stabil-
ity; Wiley et al. 1997; Baker et al. 2003) that are
more conducive for salmonid growth and survival
than systems with high thermal sensitivity in the next
40 years. Thus, we encourage managers to allocate
resources (i.e., time, money and personnel) to priori-
tise protection of streams with low thermal sensitivity
and inform public stakeholders about realistic expec-
tations for stream fish communities amidst global
change (e.g., salmonid decline, centrarchid expan-
sion; Pease & Paukert 2014). Moreover, because
streams with high BFI were less susceptible to tem-
perature change, we suggest that managers use spatial
BFI maps as tools for understanding stream thermal
sensitivity across large geographical areas. Moreover,
we encourage managers to increase the spatial and
temporal coverage of air and stream temperature
monitoring networks and thereby expand their utility
for salmonid management.
Fisheries professionals and public stakeholders can
also collaboratively implement additional strategies
for resilience-based salmonid management. They can
promote thermally resilient salmonid populations by
removing dams and installing fish ladders at roadside
crossings and culverts to restore stream habitat con-
nectivity, particularly in cold headwater reaches,
which function as thermal refugia during warm sum-
mer months. Fisheries professionals can also foster
salmonid population resilience by implementing regu-
lations (e.g., protected slot limits, reduced creel lim-
its) that reduce harvest and increase survival during
thermally stressful periods. In addition, we recom-
mend fisheries professionals protect a diversity of sal-
monid size classes, genetic stocks and prey species
that tolerate a wide range of temperatures predicted
from climate change models (Hansen et al. 2015).
We encourage fisheries managers and policymakers
201
Resilience-based salmonid management
to provide incentives (e.g., financial assistance,
open space tax deduction, fast-track permitting;
Knight 2009) for land developers and property
owners to protect coldwater habitat and thermal
buffering mechanisms on their lands. Moreover,
because it is infeasible to protect salmonid popula-
tions and thermal habitat in all streams, it will be
necessary for fisheries professionals to implement a
triage approach with specific criteria for stream pro-
tection (e.g., species composition, habitat quality
and recreational importance). In summary, resili-
ence-based salmonid management programmes will
require effective collaboration among scientists,
biologists, policymakers and public stakeholders.
Our research promotes resilience-based management
by providing a methodology to project stream tem-
perature and thermal habitat suitability. Fisheries
professionals can use this approach to protect cold-
water habitats and drivers of stream cooling and
ultimately conserve resilient salmonid populations
amidst global change.
Acknowledgements
We thank Jennifer Moore Myers (USFS EFETAC) for assis-
tance with air temperature projection models and data acqui-
sition. We thank Kyle Herreman and Wesley Daniel
(Michigan State University), Tracy Kolb and Todd Wills
(Michigan Department of Natural Resources) and Henry
Quinlan (United States Fish and Wildlife Service) for provid-
ing initial environmental and trout population data critical for
development of this study. We acknowledge the Programme
for Climate Model Diagnosis and Intercomparison (PCMDI)
and the WCRPs Working Group on Coupled Modelling for
assisting in procurement of the WCRP CMIP3 multimodel
data set.
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... Nearly 650 000 kg of brook charr, representing approximately 70% of all stocked fish, are released into Québec lakes each year [44]. Brook charr is highly sensitive to thermal stress [42,45,46] and thus to climate change. An increase in summer air temperature of 1°C is sufficient to delay spawning by one week and reduce redd production by 22 to 65% [45]. ...
... Populations show little variation in their capacity to respond to temperature changes [47,48], though there is some evidence that populations from cooler climates have lower thermal tolerance [49]. Based on predicted climate scenarios, it is expected that suitable brook charr habitat will decrease over time across much of its native range [46,[50][51][52][53], including in Québec and eastern Canada, where suitable habitat would shift to the northeast [54], resulting in reduced growth and survival of individuals and ultimately persistence of populations [46,48,55]. Due to the thermal sensitivity and economic importance of the species, a thorough understanding of the mechanisms through which brook charr acclimate and cope with thermal stress is needed to refine predictions of climate change impacts on this species. ...
... Populations show little variation in their capacity to respond to temperature changes [47,48], though there is some evidence that populations from cooler climates have lower thermal tolerance [49]. Based on predicted climate scenarios, it is expected that suitable brook charr habitat will decrease over time across much of its native range [46,[50][51][52][53], including in Québec and eastern Canada, where suitable habitat would shift to the northeast [54], resulting in reduced growth and survival of individuals and ultimately persistence of populations [46,48,55]. Due to the thermal sensitivity and economic importance of the species, a thorough understanding of the mechanisms through which brook charr acclimate and cope with thermal stress is needed to refine predictions of climate change impacts on this species. ...
Article
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Epigenetic inheritance can result in plastic responses to changing environments being faithfully transmitted to offspring. However, it remains unclear how epigenetic mechanisms such as DNA methylation can contribute to multigenerational acclimation and adaptation to environmental stressors. Brook charr ( Salvelinus fontinalis ), an economically important salmonid, is highly sensitive to thermal stress and is of conservation concern in the context of climate change. We studied the effects of temperature during parental sexual maturation and offspring rearing on whole-genome DNA methylation in brook charr juveniles (fry). Parents were split between warm and cold temperatures during sexual maturation, mated in controlled breeding designs, then offspring from each family were split between warm (8°C) and cold (5°C) rearing environments. Using whole-genome bisulfite sequencing, we found 188 differentially methylated regions (DMRs) due to parental maturation temperature after controlling for family structure. By contrast, offspring rearing temperature had a negligible effect on offspring methylation. Stable intergenerational inheritance of DNA methylation and minimal plasticity in progeny could result in the transmission of acclimatory epigenetic states to offspring, priming them for a warming environment. Our findings have implications pertaining to the role of intergenerational epigenetic inheritance in response to ongoing climate change.
... The known thermal tolerances between salmonid species does differ depending on the type of study conducted. A study by Carlson et al. 2017 found the following preferred growth temperature ranges: brown trout (12.0-20.0°C), brook trout (11.0-20.5°C), ...
... The stress from increasing temperature can affect physiological and behavioral responses. Directly, changes in metabolism can hinder growth rate and overall survival rates (Bell, JM 2006;Carlson et al. 2017;Wehrly et al. 2007). Reproduction can also be impacted by temperature differences because spawning ques for salmonids are based on a specific temperature range, prolonged elevated temperatures can affect spawn timing which possibly leads to the eggs hatching during an undesirable period with increased competition or limited resources (Bell, JM 2006;Cook et al. 2018;Merriam et al. 2017). ...
... ). Furthermore, a study byPoole and Berman 2001 listed phreatic ground water as high importance in the stabilization of stream temperatures in stream orders 1 & 2 and moderate importance in stream orders 3 & 4. Subsequent studies have also reported that riparian zones may have minimal effect on headwater streams due to groundwater inputs that stabilize the temperature(Cross et al. 2013;Rutherford et al. 2004).The monthly maximum temperature did surpass thermal limits (20.0-22.5 °C) for the salmonid species in 14 out 16 sites during the summer collections and cold-water abundances were lessened in response to temperature increases(Baldwin, NS 1957;Carlson et al. 2017;Coutant, CC 1977;Elliot & Hurley 2000;Wurtsbaugh & Davis 1977). These temperature exceedances occurred over half of the days during the collection month in 6 out of 8 sites with the longest duration of temperature pulses ranging between 6.75-14.25 hours depending on the sub-basin. ...
... Compte tenu de l'intensification des pressions, notamment d'ordre climatique, qui pèsent d'ores et déjà et vont de plus en plus peser sur les hydrosystèmes dans le futur (réchauffement, événements hydrologiques extrêmes, invasions biologiques), il existe un large consensus scientifique pour attirer l'attention des décideurs sur la nécessité de préserver ou de développer au maximum les propriétés de résilience des systèmes (Folke et al., 2002 ;Folke, 2003 ;Benson et Garmestani, 2011 ;McCluney et al., 2014 ;Hansen et al., 2015 ;Waldman et al., 2016 ;Carlson et al., 2017 ;Boltz et al., 2019 ;Falkenmark et al., 2019). ...
... -identification, spatialisation et modélisation des afférences de nappes phréatiques d'une région pour repérer les espaces de résilience thermique naturelle, les protéger et les interconnecter (il s'agit ici d'une « offre » naturelle de températures plus fraiches favorables au maintien des salmonidés (Etat du Michigan, USA, Carlson et al., 2017), -mise en pratique de la théorie des métapopulations de Hanski (1999), qui énonce que l'existence dans un même bassin de sous populations au fonctionnement asynchrone, moyennant une bonne interconnexion des différents habitats, garantit une plus grande stabilité et pérennité temporelle à l'ensemble de la population, de même qu'à diverses autres métriques écologiques. Ce principe de bon sens populaire (« ne pas mettre tous ses oeufs dans le même panier ») est rapproché du principe financier de la bonne gestion des portefeuilles d'actions . ...
Technical Report
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(FR) Les réservoirs biologiques constituent des espaces vitaux pour la biodiversité aquatique : ce sont des espaces de vie pour la flore et la faune, habitats, zones de reproduction, nourriceries ou refuges. Ils sont choisis et définis géographiquement de façon à « irriguer » biologiquement un ensemble plus vaste du réseau hydrographique. Ils sont sources de dispersion des propagules ou des juvéniles de différentes espèces pour ce réseau. Enfin, ils sont considérés comme un des leviers de la politique de préservation ou de restauration des milieux aquatiques, notamment pour garantir le bon état écologique des masses d’eau. Le concept a été entériné par décret du 14/12/2007. Il a été matérialisé depuis 2007. Le SDAGE Rhône Méditerranée 2016-2021 a préconisé un travail d'expertise du réseau existant. C’est l’objet de la présente étude. La dispersion des organismes est une fonction essentielle en écologie, en particulier pour les milieux aquatiques continentaux avec leurs contraintes spécifiques liées au réseau hydrographique, à son fonctionnement (hydrologie, fonctionnement hiérarchique emboité, écoulement unidirectionnel), et à son environnement (bassins versants et leurs pressions multiples, morphologie). Le rapport traite des poissons, espèces clé pour la définition initiale des réservoirs biologiques, mais porte également un regard nouveau sur les macroinvertébrés, compartiment important de la faune aquatique, utilisé notamment pour l'évaluation des milieux (indices biologiques participant à la définition de l’état écologique). (ENG) Biological reservoirs are key areas for aquatic biodiversity: they are living spaces for flora and fauna, habitats, breeding grounds, nurseries or refuges. They are selected and defined geographically to biologically supply a larger part of the hydrographic network. They are sources of dispersal for propagules or juveniles of different species regarding this network. Finally, they are considered as one of the leverage points for the preservation or restoration policies of aquatic environments, in particular to guarantee the good ecological status of water bodies. The concept was ratified by French decree of 14/12/2007. It has been materialised since 2007. The SDAGE Rhône Méditerranée 2016-2021 recommended an expert evaluation of the existing network. This is the object of the present study. Dispersal is an essential function in ecology, particularly for continental aquatic environments and their specific constraints related to the hydrographic network, its functioning (hydrology, hierarchical nested functioning, unidirectional flow), and its environment (watersheds and their multiple pressures, morphology). The report deals with fish, the target species for the initial definition of biological reservoirs, but also takes a second look at macroinvertebrates, an important compartment of aquatic fauna, used in particular for the assessment of environments (biological indices involved in the definition of ecological status).
... Freshwater environments are expected to experience alterations in the flow and thermal regimes of streams and rivers owing to climate change [1,2]. Given that freshwater ecosystems are dependent on the flow and thermal regimes [3][4][5], changes in these are expected to affect the growth, migration, spawning, survival, and distribution of freshwater fish [6][7][8]. Specifically, environmental variables such as water depth, velocity, and temperature are important to freshwater fish habitats [9,10]. Therefore, the effects of climate change on the habitat of freshwater fish should be evaluated for future risk assessment. ...
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Full-text available
Climate change, which has the potential to alter water flow and temperature in aquatic environments, can influence the freshwater fish habitat. This study used an ecological habitat suitability model (EHSM), which integrates hydraulic (water depth and velocity) and physiologic (water temperature) suitability, to investigate the impact of climate change on two native freshwater fish species (Zacco platypus and Nipponocypris koreanus) in South Korea. The model predicted that in 2080 (2076–2085), the decrease in average ecological habitat suitability (EHS) will be higher for N. koreanus (19.2%) than for Z. platypus (9.87%) under the representative concentration pathway (RCP) 8.5 scenario. Under the same condition, EHS for Z. platypus and N. koreanus at 36.5% and 44.4% of 115 sites, respectively, were expected to degrade significantly (p < 0.05). However, the habitat degradation for Z. platypus and N. koreanus was much lower (7.8% and 10.4%, respectively) under the RCP 4.5 scenario, suggesting a preventive measure for carbon dioxide emission. Partial correlation analysis indicated that the number of hot days (i.e., days on which the temperature exceeds the heat stress threshold) is the variable most significantly (p < 0.05) related to EHS changes for both species. This study suggests that the EHSM incorporating the effect of water temperature on the growth and heat stress of fish can be a promising model for the assessment of climate change impacts on habitat suitability for freshwater fish.
... Work originating beyond the UK further supports the likelihood of spatially-variable water temperature responses to air temperature change. For example, high groundwater contributions to streamflow (high baseflow) in some systems may serve to dampen stream water temperature change (Carlson et al., 2017, Briggs et al., 2018. Global-scale studies (including UK fresh waters) show similar among-habitat variability for standing waters: O'Reilly et al. (2015) found that trends in lake surface water temperatures can exceed or fall below coincident air temperature trends. ...
Technical Report
Full-text available
The CCRA is a comprehensive assessment of the risks to the UK from climate change, as required by Act of Parliament every 5 years (Climate Change Act)
... Due to the ectothermal nature of most freshwater invaders and the physical properties of freshwater systems, bioenergetics models have been used to predict the likely distributions of invasive species through river and lake systems (Shelton et al. 2018). However, the implications of climate change mean that future distributions of native and invasive species are also going to change (Rahel and Olden 2008;Kao et al. 2015;Carlson et al. 2017), and freshwater species management must be able to respond to the changing needs of native species as their ranges within watersheds move. This latter question of intraand inter-basin migration of freshwater species habitat due to climate change is still nascent in freshwater ecology and conservation. ...
... El calentamiento del agua se verá acentuado por la reducción de caudal en muchos ríos, como ha sido mostrado por varios autores (Moatar y Gailhard 2006, Pekarova et al. 2008. Los ríos con caudal base bajo son más sensibles al calentamiento (Carlson et al. 2015). Aunque no se espera que aumenten las sequías en un futuro próximo en el área Mediterránea (IPCC 2013), el incremento de la temperatura del aire podría producir un aumento de la evapotranspiración y una reducción del agua disponible en ríos y arroyos. ...
Thesis
Full-text available
Climate change is one of the most important global processes that the Biosphere is experiencing, and fish are not stranger to it. Coldwater fish and, particularly the Brown trout (Salmo trutta), are very sensitive to the predicted changes in temperature of rivers and streams. Fish are poikilotherms and their body temperature and physiological rates are dependent on the environmental temperature, as this is a key factor of their ecological niche. This dissertation addresses the viability of the brown trout populations at the rear edge of its native distribution in the climate change scenario. To do this, realized thermal niche are determined, stream temperatures and flow are modelled, they have been related to each other and with basin lithology, and both thermal and physical habitat changes of the different life stages of brown trout are modelled. One set of 14 mountain rivers and streams belonging different main basins are studied in Central Spain. Stream temperature modelling is made by improving the time resolution of O. Mohseni, H.G. Stefan and T.R. Eriksson model. It is modified with functions introducing the temperature drift and streamflow. Therefore, streamflow is modelled using machine learning techniques. Both models work at daily resolution. Thereafter, climate predictions built for RCP4.5 and RCP8.5 scenarios of the 5th Assessment Report of the IPCC (Intergovernmental Panel on Climate Change) are applied to the stream and flow temperature models made in this thesis to generate projections of the conditions that will occur in the thermal and physical (hydraulic) habitat of the different trout life stages. The threshold daily mean stream temperature defining the brown trout realized thermal niche is described in streams at Central Iberia, and streamflow reductions up to 49% and stream temperature increases up to 4°C are predicted. It is also shown how the synchronization of flow reductions and temperature increases will act synergistically affecting fish, and how geology can be a main factor in the response of trout populations to climate change by influencing the thermal regime of streams. As a consequence of the physical changes in the environment, a bottleneck of the physical and thermal habitat will occur in summer, which will put trout populations in a hard demographic stress. There will also be another major reduction in habitat suitability for sessile stages (eggs and larvae) at the beginning and the end of the breeding season, and embryo and larval development times will be shortened but will not compensate the also shortened breeding season. As a general conclusion, the factors combination will put the viability of many trout stocks on the ropes, although the form and extent of these limitations will be very specific to the conditions of each river. Methodologically, this thesis makes contributions in the field of modelling and spatial-temporal resolution of the climatic, thermal and flow models, which results in the quality of the predictions of the effects of climate change on the fish habitat. Approaches as showed are useful in planning prevention and mitigation of the negative effects of climate change by differentiating rivers and zones based on the level of predicted risk and the viability of populations. Future research should go in depth to the climate change effects on the demographic and biological parameters to refine the predictive and management models, which are the necessary tool for anticipation of problems. In addition, monitoring the effects of climate change must serve to correct and refine shortcomings of the predictions. This thesis was published in the following papers: * Santiago, J.M.; García de Jalón, D.; Alonso, C.; Solana, J.; Ribalaygua, J.; Pórtoles, J. y Monjo, R.. Brown trout thermal niche and climate change: expected changes in the distribution of a cold-water fish in Central Spain. Ecohydrology, 9(3): 514-528. DOI: 10.1002/eco.1653, (2016). ISSN: 1936-0592 * Santiago, J.M. Thermal ecology of brown trout and the climate change challenge In: Richardson, B. (Ed.), Tilapia and Trout: Harvesting, Prevalence and Benefits, pp. 79-119. Nova Science Publishers, New York. (2017). ISBN: 978-1-53610-557-5 * Santiago, J. M.; Muñoz-Mas, R.; Solana, J.; García de Jalón, D.; Alonso, C.; Martínez-Capel, F.; Pórtoles, J.; Monjo, R. & Ribalaygua, J.. Waning habitats due to climate change: the effects of changes in streamflow and temperature at the rear edge of the distribution of a cold-water fish, Hydrology and Earth System Sciences, 21(8): 4073-4101 DOI: 10.5194/hess-21-4073-2017, (2017). ISSN 1027-5606 eISSN 1812-2116 * Santiago, J. M.; Alonso, C.; García de Jalón, D.; Solana-Gutiérrez, J. & Muñoz-Mas, R. Effects of climate change on the life stages of stream-dwelling brown trout (Salmo trutta Linnaeus, 1758) at the rear edge of their native distribution range. Ecohydrology (early view) DOI: 10.1002/eco.2241, (2020). ISSN: 1936-0592
Article
Certain habitat features of stream ecosystems can reduce their sensitivity to climate change and help protect the integrity of cold-water aquatic resources. Identifying such features is imperative for conserving the climate refugia of cold-water species. Using a combination of stream temperature and fish assemblage data, we quantified thermal sensitivities of 192 headwater streams in Northwest Pennsylvania to identify which landscape features best explained stream susceptibility to temperature change. We then projected changes in native brook trout (Salvelinus fontinalis) distributions, non-native brown trout (Salmo trutta) distributions and declines in cold-water thermal integrity under future climate warming and land use change scenarios. Brook trout were predicted to become increasingly relegated to smaller streams under future stream warming. However, we found that streams with intact forest cover at the watershed level had low thermal sensitivities, which slowed rates of projected warming. As a result, streams with forested watersheds were predicted to have smaller declines in thermal integrity and lower extirpation probabilities of brook trout. Additionally, non-native brown trout were not predicted to expand distributions under projected warming, suggesting minimal synergistic effects between non-native species and climate change. Forest cover buffers headwater streams from the effects of global change, similar to how groundwater inputs reduce the rate of stream warming. Forest restoration at riparian and watershed levels should help mitigate thermal-induced degradation of cold-water aquatic resources.
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Studies predicting how the distribution of aquatic organisms will shift with climate change often use projected increases in air temperature or water temperature. However, the assumed correlations between water temperature change and air temperature change can be problematic, especially for mountainous, high elevation streams. Using stream fish assemblage data from 1,442 surveys across a mountain - plains gradient (Wyoming, USA; 1990-2018), we compared the responsiveness of thermal guilds, native status groups, and assemblage structure to projected climate warming from generalized air temperature models and stream-specific water temperature models. Air temperature models consistently predicted greater range shift differences between warm-water and cold-water species, with air temperatures predicting greater increases in occurrence and greater range expansions for warm-water species. The "over-prediction" of warm-water species expansions resulted in air temperature models predicting higher rates of novel species combinations, greater increases in local species richness, and higher magnitudes of biotic homogenization compared with water temperature models. Despite differences in model predictions for warm-water species, both air and water temperature models predicted that three cold-water species would exhibit similar decreases in occurrence (decline of 1.0% and 1.8% of sites per 1 °C warming, respectively) and similar range contractions (16.6 and 21.5 m elevation loss per 1 °C warming, respectively). The "over-prediction" for warm-water species is partially attributable to water temperatures warming at slower rates than air temperatures because local, stream-scale factors (e.g., riparian cover, groundwater inputs) buffer high elevation streams from rising air temperatures. Our study provides the first comparison of how inferences about climate-induced biotic change at the species- and assemblage-levels differ when modeling with generalized air temperatures versus stream-specific water temperatures. We recommend future studies use stream-specific water temperature models, especially for mountainous, high elevation streams, to avoid the "over-prediction" of biotic changes observed from air temperature variables.
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In response to accelerated temperature shifts due to climate change, the survival of many species will require forms of thermal acclimation to their changing environment. We were interested in how climate change will impact a commercially and recreationally important species of fish, Atlantic salmon (Salmo salar). As climate change alters the thermal environment of their natal streams, we asked how their muscle function will be altered by extended exposure to both warm and cold temperatures. We performed a thermal acclimation study of S. salar muscle mechanics of both fast‐twitch, or white, and slow‐twitch, or red, myotomal muscle bundles to investigate how temperature acclimated Atlantic salmon would respond across a range of different temperatures. Isometric contraction properties, maximum shortening velocity, and oscillatory power output were measured and compared amongst three groups of salmon—warm acclimated (20°C), cold‐acclimated (2°C), and those at their rearing temperature (12°C). The Atlantic salmon showed limited thermal acclimation in their contraction kinetics, and some of the shifts in contractile properties that were observed would not be predicted to mitigate the impact of a warming environment. For instance, the maximum shortening velocity at a common test temperature was higher in the warm acclimated group and lower in the cold‐acclimated group. In addition, critical swimming speed did not vary with temperature of acclimation when tested at a common temperature (12°C). Our results suggest that Atlantic salmon populations will continue to struggle in response to a warming environment. Research Highlights • Atlantic salmon will experience significant warming in their natural environments. Although thermal acclimation can help mitigate the impact of climate change, the salmon show very little acclimation response in their myotomal or swimming muscle.
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Freshwaters are being transformed by multiple environmental drivers, creating uncertainty about future conditions. One way of coping with uncertainty is to manage for resilience to unanticipated events while facilitating learning through adaptive management. We outline the application of these strategies to freshwater recreational fisheries management using a case study in Wisconsin, USA, where black bass (Micropterus spp.) populations are increasing, while Walleye (Sander vitreus) populations are decreasing. Managing for heterogeneity in functional groups (e.g., age classes and prey species of sport fishes), fishery objectives, and regulations can increase resilience, although heterogeneity must be balanced with replication to facilitate learning. Monitoring designed to evaluate management objectives and inform about critical uncertainties, when combined with heterogeneity, creates opportunities for adaptive management, another critical resilience strategy. Although barriers exist to implementing resilience strategies, management designed to accommodate uncertainty and illuminate its consequences is needed to maintain critical fisheries in a rapidly changing world.
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The distribution and future fate of ectothermic organisms in a warming world will be dictated by thermalscapes across landscapes. That is particularly true for stream fishes and cold-water species like trout, salmon, and char that are already constrained to high elevations and latitudes. The extreme climates in those environments also preclude invasions by most non-native species, so identifying especially cold habitats capable of absorbing future climate change while still supporting native populations would highlight important refugia. By coupling crowd-sourced biological datasets with high-resolution stream temperature scenarios, we delineate network refugia across >250 000 stream km in the Northern Rocky Mountains for two native salmonids-bull trout (BT) and cutthroat trout (CT). Under both moderate and extreme climate change scenarios, refugia with high probabilities of trout population occupancy (>0.9) were predicted to exist (33-68 BT refugia; 917-1425 CT refugia). Most refugia are on public lands (>90%) where few currently have protected status in National Parks or Wilderness Areas (<15%). Forecasts of refuge locations could enable protection of key watersheds and provide a foundation for climate smart planning of conservation networks. Using cold water as a 'climate shield' is generalizable to other species and geographic areas because it has a strong physiological basis, relies on nationally available geospatial data, and mines existing biological datasets. Importantly, the approach creates a framework to integrate data contributed by many individuals and resource agencies, and a process that strengthens the collaborative and social networks needed to preserve many cold-water fish populations through the 21st century. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.
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In response to concerns over increased use and potential diversion of Michigan’s freshwater resources, and the resulting state legislative mandate, an advisory council created an integrated assessment model to determine potential for water withdrawals to cause an adverse resource impact to fish assemblages in Michigan’s streams. As part of this effort, we developed a model to predict how fish assemblages characteristic of different stream types would change in response to decreased stream base flows. We describe model development and use in this case study. The model uses habitat suitability information (i.e., catchment size, base-flow yield, and July mean water temperature) for over 40 fish species to predict assemblage structure in an individual river segment under a range of base-flow reductions. By synthesizing model runs for individual fish species at representative segments for each of Michigan’s eleven ecological stream types, we developed curves describing how typical fish assemblages in each type respond to flow reduction. Each stream type-specific, fish response curve was used to identify streamflow reduction levels resulting in adverse resource impacts to characteristic fish populations, the regulatory standard. Used together with a statewide map of stream types, our model provided a spatially comprehensive framework for evaluating impacts of flow withdrawals on biotic communities across a diverse regional landscape.
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Forecasting climate change effects on aquatic fauna and their habitat requires an understanding of how water temperature responds to changing air temperature (i.e., thermal sensitivity). Previous efforts to forecast climate effects on brook trout (Salvelinus fontinalis) habitat have generally assumed uniform air-water temperature relationships over large areas that cannot account for groundwater inputs and other processes that operate at finer spatial scales. We developed regression models that accounted for groundwater influences on thermal sensitivity from measured air-water temperature relationships within forested watersheds in eastern North America (Shenandoah National Park, Virginia, USA, 78 sites in nine watersheds). We used these reach-scale models to forecast climate change effects on stream temperature and brook trout thermal habitat, and compared our results to previous forecasts based upon large-scale models. Observed stream temperatures were generally less sensitive to air temperature than previously assumed, and we attribute this to the moderating effect of shallow groundwater inputs. Predicted groundwater temperatures from air-water regression models corresponded well to observed groundwater temperatures elsewhere in the study area. Predictions of brook trout future habitat loss derived from our fine-grained models were far less pessimistic than those from prior models developed at coarser spatial resolutions. However, our models also revealed spatial variation in thermal sensitivity within and among catchments resulting in a patchy distribution of thermally suitable habitat. Habitat fragmentation due to thermal barriers therefore may have an increasingly important role for trout population viability in headwater streams. Our results demonstrate that simple adjustments to air-water temperature regression models can provide a powerful and costeffective approach for predicting future stream temperatures while accounting for effects of groundwater.