Supporting Information

Reservoirs and Water Management Influences on Fish Mercury Concentrations in the

Western United States and Canada

James J. Willacker1*, Collin A. Eagles-Smith1, Michelle A. Lutz2, Michael T. Tate2, Jesse M.

Lepak3, and Joshua T. Ackerman4

1U.S. Geological Survey, Forest and Rangeland Ecosystem Science Center, 3200 SW Jefferson

Way, Corvallis, OR 97331, USA

2U.S. Geological Survey, Wisconsin Water Science Center, 8505 Research Way, Middleton, WI

53562, USA

3Colorado Parks and Wildlife, 317 West Prospect Rd., Fort Collins, CO 80526, USA

4U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800

Business Park Drive, Suite D, Dixon, CA, 95620, USA

*Corresponding author: e-mail: jwillacker@usgs.gov; phone: (541) 750-0957

15 pages, 2 figures, 4 tables

Southern Semiarid Highlands

Temperate Sierras

North American Deserts

Northern Forests

Great Plains

Mediterranean California

Northwestern Forested Mountains

Taiga

Tundra

Marine West Coast Forests

0 1,500 3,000750

Kilometers

¯

AK

YT NWT

BC AB SK

SD

NDMT

WY

UT

AZ

NV CO

NM

ID

CA

OR

WA

Figure S1: Map of study area depicting states, provinces, and territories included and Level I

ecoregions.

Jan.0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.

Fish

TH

g C

once

ntra

tion

(µg/

g w

w)

Month of Minimum Water Storage

a)

R2 = 0.67

Between-year Change in Water Storage (%)-40 -20 0 20 40 60 80 100 120 140 160

Parti

al R

esid

ual o

f Fis

h f T

otal

M

ercu

ry C

once

ntra

tion

-0.6-0.4-0.20.00.20.40.60.81.01.21.4

b)

R2 = 0.19

Within-year Change in Water Storage (%)0 2000 4000 6000 8000 10000

Parti

al R

esid

ual o

f Fis

h T

otal

Mer

cury

Con

cent

ratio

n

-0.4

-0.2

0.0

0.2

0.4

0.6c)

Figure S2: Relationships between total mercury (THg) concentrations (µg/g ww ± standard error) in size-standardized fish and reservoir water management parameters across ecoregions of western North America. a) Least squares mean fish THg concentrations from reservoirs with minimum water storage occurring in different months. Least squares mean account for the effects of ecoregion, within- and between-year changes in water storage, site, and species. b) Partial residual plot depicting the relationship between fish THg concentrations and between-year changes in maximum water storage. Partial residuals account for the effects of ecoregion, timing of minimum storage, within-year changes in water storage, site, and species. c) Partial residual plot depicting the relationship between fish THg concentrations and within-year changes in maximum water storage. Partial residuals account for the effects of ecoregion, timing of minimum storage, between-year changes in water storage, site, and species

Table S1: Groups, sample size (N), number of waterbodies, and length for 131 species from

reservoirs and lakes in the western United States and Canada. Species with bolded lengths were

size corrected with models based on the larger dataset presented in Eagles-Smith et al. (2016).

Species Group Common NameScientific Name N #

Waterbodies

Median ForkLength (cm)(min – max)

Anadromous salmonids

Arctic CharSalvelinus alpinus 16 3 62.0

(46.5 – 75.0)Atlantic Salmon

Salmo salar 3 1 30.8(24.1 – 31.0)

Chinook SalmonOncorhynchus tshawytscha 59 7 65.8

(30.0 - 101.6)Coho Salmon

O. kisutch 4 4 30.0

Sockeye SalmonO. nerka 30 1 -

steelheadO. mykiss 12 1 79.1

(60.5 - 90.2)

Unspecified salmonid 3 2 77.5(29.1 - 81.2)

Arctic Grayling Arctic GraylingThymallus arcticus 167 38 35.7

(6.8 – 47.5)

Silversides Inland SilversidesMenidia beryllina 3 2 -

Black Bass

Largemouth BassMicropterus salmoides 5086 405 33.2

(4.0 – 64.0)Smallmouth Bass

M. dolomieu 1407 137 30.0(4.4 - 71.4)

Spotted BassM. punctulatus 123 10 27.5

(12.1 - 45.9)Unspecified black bass

Micropterus spp. 51 2 31.9(25.1 – 36.0)

Burbot BurbotLota lota 737 90 60.1

(12.4 - 88.9)

Carp

Common CarpCyprinus carpio 1137 250 45.7

(2.9 - 75.8)Goldfish

Carassius auratus 27 14 36.2(24.5 - 40.4)

Grass CarpCtenopharyngodon idella 1 90 41.5

Catfishes

Black BullheadAmeiurus melas 354 120 26.0

(11.1 – 66.0)Blue Catfish

Ictalurus furcatus 4 1 28.3(27.0 - 33.9)

Brown BullheadA. nebulosus 183 37 22.7

(7.1 – 40.0)Channel Catfish

I. punctatus 946 147 43.0(15.1 - 78.5)

Group cont.next page

Flathead CatfishPylodictis olivaris 4 2 48.0

(32.4 – 54.0)Continued on next page

Table S1 Continued

Species Group Common NameScientific Name N #

Waterbodies

Median ForkLength (cm)(min – max)

Catfishescont.

White CatfishA. catus 52 11 28.0

(23.9 - 31.5)Yellow Bullhead

A. natalis 30 6 21.9(17.3 - 29.6)

Unspecified bullheadAmeiurus spp. 237 18 23.8

(14.5 - 55.8)

Unspecified catfish 10 4 56.9(35.6 – 67.0)

Char

Arctic CharSalvelinus alpinus 22 3 26.7

(18.0 – 58.0)Brook TroutS. fontinalis 986 119 20.9

(3.9 - 59.3)Bull Trout

S. confluentus 118 11 31.9(19.3 - 78.8)

Dolly VardenS. malma 105 14 18.1

(1.5 - 60.6)Lake Trout

S. namaycush 4269 276 53.0(8.6 – 113.4)

SplakeS. namaycush X S. fontinalis 61 10 29.6

(12.6 - 38.3)

Chub

Bigeye ChubHybopsis amblops 1 1 12.8

Bonytail ChubGila elegans 2 1 -

Flathead ChubPlatygobio gracilis 2 1 -

Lake ChubCouesius plumbeus 29 3 11.4

(8.1 – 14.0)Tui ChubG. bicolor 247 22 8.9

(3.2 - 35.8)Utah ChubG. atraria 28 6 14.6

(13.3 - 28.7)Yaqui ChubG. purpurea 3 1 -

Cichlids TilapiaTilapia spp. 10 1 21.7

(16.2 – 33.0)

Cisco

Cisco (Lake Herring)Coregonus artedi 143 18 33.5

(9.0 – 60.5)Least Cisco

C. sardinella 30 2 22.3(13.5 – 37.0)

Unspecified ciscoCoregonus spp. 67 4 24.9

(15.5 – 36.0)

Clupeiformes

American Gizzard ShadDorosoma cepedianum 18 7 16.9

(3.4 - 36.5)American Shad

Alosa sapidissima 12 2 20.7(16.8 - 21.2)

Threadfin ShadD. petenense 14 5 16.1

(14.8 - 17.6)Unspecified clupiforme 22 1 -

Continued on next pageTable S1 Continued

Species Group Common NameScientific Name N #

Waterbodies

Median ForkLength (cm)(min – max)

Crappie

Black CrappiePomoxis nigromaculatus 508 137 20.7

(2.7 - 39.2)White CrappieP. annularis 105 27 22.1

(13.9 - 30.6)Unspecified crappie

Pomoxis spp. 99 18 26.3(12.2 - 34.5)

Freshwater Drum

Freshwater DrumAplodinotus grunniens 53 5 43.5

(15.0 - 72.3)

Gar Longnose GarLepisosteus osseus 1 1 74.9

Goldeye GoldeyeHiodon alosoides 504 10 33.0

(13.7 - 42.2)

Inconnu InconnuStenodus nelma 69 5 65.4

(44.0 – 93.2)

Killifish

Desert PupfishCyprinodon macularius 2 1 -

Pecos GambusiaGambusia nobilis 5 2 -

Pecos PupfishC. pecosensis 10 2 -

Plains KillifishFundulus zebrinus 6 2 -

Sailfin MollyPoecilia latipinna 32 1 -

Western MosquitofishG. affinis 102 22 3.4

(2.4 - 5.2)

Minnows

Brassy MinnowHybognathus hankinsoni 21 4 4.0

(3.0 - 9.8)California Roach

Hesperoleucus symmetricus 13 2 -

ChiselmouthAcrocheilus alutaceus 8 5 21.9

(15.5 – 30.0)Common Dace

Leuciscus leuciscus 9 1 6.1(5.1 - 7.1)

Emerald ShinerNotropis atherinoides 3 2 7.5

(7.1 – 8.0)Fathead Minnow

Pimephales promelas 57 15 7.4(3.8 - 8.2)

Finescale DacePhoxinus neogaeus 11 2 7.9

(6.0 - 10.8)Golden Shiner

Notemigonus crysoleucas 14 5 8.8(8.0 - 9.6)

HardheadMylopharodon conocephalus 5 3 -

HitchLavinia exilicauda 3 2 23.5

Group cont.next page

Longnose DaceRhinichthys cataractae 5 1 -

Continued on next page

Table S1 Continued

Species Group Common NameScientific Name N #

Waterbodies

Median ForkLength (cm)(min – max)

Minnowscont.

Northern Redbelly DaceChrosomus eos 23 3 7.7

(6.9 – 9.0)Peamouth

Mylocheilus caurinus 41 16 20.9(13.7 - 26.4)

Pearl DaceMargariscus margarita 50 6 8.1

(6.5 - 10.9)Red Shiner

Cyprinella lutrensis 27 8

Redside ShinerRichardsonius balteatus 17 4 7.5

(5.1 - 13.5)Rudd

Scardinius erythropthalmus 2 2 33.4(30.9 - 35.9)

Sacramento BlackfishOrthodon microlepidotus 70 5 34.5

(18.9 – 46.0)Sand Shiner

Notropis stramineus 3 2 4.4(3.9 - 9.1)

Speckled DaceRhinichthys osculus 10 1 20.1

(3.9 - 22.2)Spottail Shiner

Notropis hudsonius 96 6 7.0(6.5 - 8.3)

Unspecified minnow 7 3 6.6(6.5 - 7.1)

Morone bass

Striped BassMorone saxatilis 417 17 40.0

(11.9 - 93.4)White BassM. chrysops 342 33 30.9

(10.3 - 60.9)Whiterock Bass

M. chrysops X M. saxatilis 169 20 36.5(10.7 - 71.7)

Pike

MuskellungeEsox masquinongy 19 4 73.6

(67.3 - 97.1)Northern Pike

E. Lucius 13905 860 59.4(8.7 - 130.0)

Tiger MuskellungeE. masquinongy X E. lucius 8 4 67.5

(38.7 - 92.4)

Pikeminnow

Colorado PikeminnowPtychocheilus lucius 1 1 -

Northern PikeminnowP. oregonensis 141 39 22.0

(9.0 - 53.0)Sacramento Pikeminnow

P. grandis 31 3 38.5(18.5 - 46.7)

Sculpin

Mottled SculpinCottus bairdii 1 1 8.6

Prickly SculpinC. asper 10 3 9.2

(7.7 - 15.4)Reticulate Sculpin

C. perplexus 1 1 -

Group cont.next page

Riffle SculpinC. gulosus 17 2 -

Continued on next page

Table S1 continued

Species Group Common NameScientific Name N #

Waterbodies

Median ForkLength (cm)(min – max)

Sculpincont.

Slimy SculpinC. cognatus 203 12 5.8

(4.1 – 12.2)Torrent Sculpin

C. rhotheus 25 2 6.4(4.4 - 12.6)

Unspecified sculpinCottus spp. 9 2 -

Stickleback

Brook SticklebackCulaea inconstans 3 2 -

Ninespine SticklebackPungitius pungitius 1 1 4.8

Threespine SticklebackGasterosteus aculeatus 24 4 4.5

(3.8 - 6.5)

Sturgeon

Lake SturgeonAcipenser fulvescens 44 2 111.5

(42.7 - 155.8)Shovelnose Sturgeon

Scaphirhynchus platorynchus 17 2 -

White SturgeonA. transmontanus 14 3 130.1

(97.0 - 168.2)

Unspecified sturgeon 7 2 56.0(51.0 – 104.0)

Suckers

Bigmouth BuffaloIctiobus cyprinellus 36 5 57.5

(35.0 – 73.0)Blue Sucker

Cycleptus elongatus 3 2 -

Bridgelip SuckerCatostomus columbianus 9 4 33.2

(29.2 - 42.3)Carpsucker

Carpiodes carpio 14 7 42.3(31.4 - 50.8)

Cui-UiChasmistes cujus 1 1 -

Flannelmouth SuckerCatostomus latipinnis 2 1 19.7

Largescale SuckerCatostomus macrocheilus 240 40 43.0

(21.8 - 56.3)Longnose Sucker

Catostomus catostomus 484 42 37.1(6.7 – 61.0)

Lost River SuckerDeltistes luxatus 3 1 -

Mountain SuckerCatostomus platyrhynchus 7 1 -

QuillbackCarpiodes cyprinus 4 1 -

Razorback SuckerXyrauchen texanus 55 3 -

Sacramento SuckerCatostomus occidentalis 62 24 40.4

(24.3 - 46.8)Group cont.next page

Shorthead RedhorseMoxostoma macrolepidotum 11 3 28.5

(25.5 – 40.0)Continued on next page

Table S1 continued

Species Group Common NameScientific Name N #

Waterbodies

Median ForkLength (cm)(min – max)

Suckerscont.

Silver RedhorseM. anisurum 14 1 21.1

(10.2 - 23.4)Smallmouth Buffalo

I. bubalus 7 2 56.2(39.6 - 63.9)

Tahoe SuckerCatostomus tahoensis 6 2 24.5

(21.8 - 30.4)Utah Sucker

Catostomus ardens 18 6 42.5(36.5 - 46.2)

White SuckerCatostomus commersonii 905 136 37.5

(5.3 - 55.4)Unspecified redhorse

Moxostoma spp. 8 4 31.8(16.0 - 39.4)

Unspecified sucker 78 21 48.0(23.8 - 61.8)

Sunfishes

BluegillLepomis macrochirus 693 162 16.3

(2.6 – 27.0)Bluespotted Sunfish

Enneacanthus gloriosus 4 1 16.8(14.8 - 19.5)

Green SunfishL. cyanellus 94 33 16.9

(4.8 – 39.0)PumpkinseedL. gibbosus 63 11 14.0

(6.6 - 20.6)Redear SunfishL. microlophus 53 16 20.7

(13.1 - 28.8)Rock Bass

Ambloplites rupestris 11 5 19.0(15.2 - 24.8)

Sacramento PerchArchoplites interruptus 11 4 16.3

(10.8 - 25.7)Tule Perch

Hysterocarpus traskii 14 3 12.4

WarmouthL. gulosus 1 1 -

Unspecified sunfish 4 2 15.8(12.1 - 16.8)

Trout

Apache TroutOncorhynchus apache 25 3 32.6

(25.1 – 37.0)Brown TroutSalmo trutta 442 109 36.7

(10.5 - 76.6)Chinook SalmonO. tshawytscha 128 2 14.1

(5.8 – 19.0)Cutthroat Trout

O. clarkia 773 101 27.8(12.1 - 64.2)

Golden TroutO. aguabonita 45 1 15.1

(11.0 - 17.2)KokaneeO. nerka 333 57 27.9

(11.5 - 50.5)Lahontan Cutthroat Trout

O. clarkii henshawi 24 7 29.3(21.3 - 48.5)

Group cont.next page

Rainbow Trout 2364 401 30.7

O. mykiss (8.0 - 88.9)Continued on next page

Table S1 continued

Species Group Common NameScientific Name N #

Waterbodies

Median ForkLength (cm)(min – max)

Troutcont.

Redband troutO. mykiss sspp. 66 12 21.5

(18.2 - 25.1)Tiger trout

S. trutta X Salvelinus fontinalis 30 9 34.2(10.7 - 56.2)

Unspecified trout 42 7 37.4(17.2 - 73.4)

Walleye & Sauger

SaugerSander canadensis 327 23 39.0

(18.4 – 55.0)Saugeye

S. canadensis X S. vitreus 24 5 45.0(29.7 - 67.8)

WalleyeS. vitreus 16140 695 43.2

(4.5 - 85.7)

Whitefish

Bonneville WhitefishProsopium spilonotus 20 1 36.9

(25.0 - 45.6)Broad WhitefishCoregonus nasus 40 6 43.2

(36.0 – 53.0)Humpback Whitefish

C. pidschian 80 4 43.4(30.1 – 59.8)

Lake WhitefishC. clupeaformis 2893 169 42.9

(5.0 – 90.9)Mountain Whitefish

P. williamsoni 315 31 24.0(8.4 - 44.2)

Round WhitefishP. cylindraceum 282 22 33.9

(17.3 – 55.0)

Unspecified whitefish 166 24 41.9(15.3 - 85.5)

Yellow Perch

Yellow PerchPerca flavescens 1958 283 20.5

(4.1 - 44.4)

Unspecified perch 679 53 22.0(3.4 - 33.2)

Table S2: Comparison of least squares mean fish total mercury concentrations (µg/g wet weight ± standard error) from lakes and reservoirs using alternative models. Degrees of freedom (D.F.), F-statistic (F), and P-value (P) are given for each comparison.

Ecoregion # Lakes

# Res Lake Mean Reservoir

Mean D.F. F P

Selected ModelAll ecoregions 1350 850 0.09 ± 0.006 0.13 ± 0.011 1, 2146 22.59 < 0.001

Great Plains 149 240 0.12 ± 0.010 0.13 ± 0.009 1, 2947 0.24 0.624Marine West Coast Forest 72 17 0.13 ± 0.013 0.11 ± 0.022 1, 2010 0.28 0.595Mediterranean California 59 139 0.05 ± 0.007 0.14 ± 0.012 1, 2140 56.51 < 0.001North American Deserts 84 194 0.09 ± 0.009 0.13 ± 0.010 1, 5198 16.50 < 0.001Northern Forests 567 6 0.08 ± 0.005 0.12 ± 0.019 1, 19437 8.83 0.003Northwestern Forested Mountains 280 251 0.11 ± 0.008 0.12 ± 0.009 1, 2239 1.40 0.236Taiga 139 3 0.10 ± 0.009 0.18 ± 0.067 1, 1723 2.17 0.141

Selected Model Excluding Rare TaxaAll ecoregions 1,323 836 0.10 ± 0.010 0.15 ± 0.016 1, 2113 23.07 < 0.001

Great Plains 147 239 0.14 ± 0.014 0.15 ± 0.014 1, 2798 1.78 0.182Marine West Coast Forest 68 16 0.14 ± 0.017 0.13 ± 0.026 1, 1981 0.31 0.578Mediterranean California 55 138 0.06 ± 0.009 0.16 ± 0.017 1, 2055 52.82 < 0.001North American Deserts 80 187 0.10 ± 0.012 0.14 ± 0.014 1, 5271 15.88 < 0.001Northern Forests 563 6 0.09 ± 0.008 0.14 ± 0.023 1, 19305 8.57 0.003Northwestern Forested Mountains 273 247 0.12 ± 0.012 0.13 ± 0.013 1, 2205 1.29 0.256Taiga 137 3 0.12 ± 0.012 0.20 ± 0.078 1, 1699 2.21 0.138

With Soil Mercury(F1,9354 = 0.65, P = 0.42)

All ecoregions 470 750 0.09 ± 0.008 0.11 ± 0.010 1, 1131 10.42 0.001Great Plains 121 174 0.12 ± 0.011 0.12 ± 0.010 1, 1902 0.03 0.858Marine West Coast Forest 30 14 0.10 ± 0.017 0.09 ± 0.020 1, 988 0.56 0.454Mediterranean California 48 130 0.05 ± 0.008 0.13 ± 0.013 1, 1065 38.18 < 0.001North American Deserts 80 489 0.08 ± 0.010 0.13 ± 0.011 1, 3015 9.95 0.002Northern Forests - - - - - - -Northwestern Forested Mountains 191 243 0.11 ± 0.010 0.11 ± 0.010 1, 1169 0.23 0.633Taiga - - - - - - -

With Surface Area(F1,1490 = 0.00, P = 0.95)

All ecoregions 527 783 0.10 ± 0.008 0.12 ± 0.010 1, 1921 10.01 0.002Great Plains 124 195 0.13 ± 0.013 0.12 ± 0.010 1, 2209 0.18 0.675Marine West Coast Forest 59 17 0.12 ± 0.015 0.11 ± 0.023 1, 1138 0.18 0.669Mediterranean California 52 136 0.06 ± 0.009 0.13 ± 0.012 1, 1252 28.91 < 0.001North American Deserts 79 191 0.08 ± 0.010 0.13 ± 0.011 1, 2099 17.06 < 0.001Northern Forests - - - - - - -Northwestern Forested Mountains 213 244 0.11 ± 0.011 0.11 ± 0.010 1, 1504 0.06 0.814Taiga - - - - - - -

Table S3: Comparison of species composition (mean % ± standard error) and mean tropic position (± standard error) of fish sampled from lakes and reservoirs throughout the western United States and Canada.

Ecoregion-Foraging GuildLakes Reservoirs

Percent of Sample

Trophic Position

Percent of Sample

Trophic Position

Great PlainsBenthivore 4.4 ± 1.2 2.8 ± < 0.1 7.1 ± 1.1 2.8 ± < 0.1Planktivore 0.3 ± 0.2 3.4 ± < 0.1 1.7 ± 0.6 3.4 ± < 0.1Generalist invertivore 2.3 ± 1 3.3 ± < 0.1 2.1 ± 0.6 3.6 ± < 0.1Generalist 24.9 ± 2.4 3.4 ± < 0.1 20.9 ± 1.8 3.4 ± < 0.1Piscivore 68.1 ± 2.7 4.2 ± < 0.1 68.1 ± 2.1 4.2 ± < 0.1

Marine West Coast ForestBenthivore 3.4 ± 1.9 3 ± < 0.1 0.6 ± 0.4 3 ± < 0.1Planktivore 2.3 ± 1.3 3.3 ± < 0.1 1 ± 1 3.2 ± < 0.1Generalist invertivore 8.5 ± 3 3.4 ± < 0.1 19.8 ± 8.2 3.7 ± < 0.1Generalist 37.4 ± 4.9 3.4 ± < 0.1 23 ± 8.2 3.4 ± < 0.1Piscivore 48.4 ± 5.1 4.3 ± < 0.1 55.5 ± 10.7 4.2 ± < 0.1

Mediterranean CaliforniaBenthivore 20.6 ± 5.3 3 ± < 0.1 9.2 ± 1.5 3 ± < 0.1Planktivore 0 ± 0 3 ± 0.1 0 ± 0 3.6 ± < 0.1Generalist invertivore 11.1 ± 4.8 3.2 ± < 0.1 1.3 ± 0.8 3.2 ± < 0.1Generalist 8.6 ± 4.4 3.5 ± < 0.1 5.9 ± 1.7 3.5 ± < 0.1Piscivore 59.8 ± 6.9 4.4 ± < 0.1 83.6 ± 2.4 4.4 ± < 0.1

North American DesertsBenthivore 8.8 ± 3.1 3 ± < 0.1 9.6 ± 1.5 3 ± < 0.1Planktivore 2.7 ± 1.6 3.3 ± < 0.1 1.8 ± 0.6 3.3 ± < 0.1Generalist invertivore 8.6 ± 3.4 3 ± < 0.1 4.1 ± 1 3.2 ± < 0.1Generalist 41.1 ± 5.6 3.5 ± < 0.1 36.7 ± 2.9 3.5 ± < 0.1Piscivore 38.9 ± 5.7 4 ± < 0.1 47.7 ± 2.9 4.1 ± < 0.1

Northern ForestsBenthivore 1.8 ± 0.4 2.6 ± < 0.1 0.1 ± 0.1 3.2 ± 0.1Planktivore 2.4 ± 0.4 3.4 ± < 0.1 0.2 ± 0.2 3.4 ± < 0.1Generalist invertivore 4.9 ± 0.8 3.4 ± < 0.1 2.7 ± 2.7 3.7 ± < 0.1Generalist 2.8 ± 0.5 3.4 ± < 0.1 5 ± 4.1 3.3 ± < 0.1Piscivore 88.1 ± 1.2 4.2 ± < 0.1 92 ± 5.1 4.2 ± < 0.1

Northwestern Forested MountainsBenthivore 1.7 ± 0.6 3 ± < 0.1 4.7 ± 1 3 ± < 0.1Planktivore 7.6 ± 1.2 3.4 ± < 0.1 6.6 ± 1.3 3.3 ± < 0.1Generalist invertivore 27.6 ± 2.4 3.5 ± < 0.1 5.9 ± 1.3 3.5 ± < 0.1Generalist 42.9 ± 2.6 3.4 ± < 0.1 47.9 ± 2.8 3.5 ± < 0.1Piscivore 20.2 ± 2.1 4 ± < 0.1 34.8 ± 2.7 4.1 ± < 0.1

TaigaBenthivore 1.9 ± 0.7 2.8 ± < 0.1 - -Planktivore 28.4 ± 2.7 3.4 ± < 0.1 61.3 ± 18.2 3.4 ± < 0.1Generalist invertivore 0.9 ± 0.6 3.4 ± < 0.1 - -Generalist 0.3 ± 0.3 3.4 ± < 0.1 - -Piscivore 68.6 ± 2.7 4.1 ± < 0.1 38.7 ± 18.2 3.9 ± < 0.1

Table S4: Distribution of reservoirs, sample size, and sampling years among reservoir ages.Reservoi

r Age # Res N Sampling Years

Reservoir Age # Res N Sampling

Years

0 3 254 1991 - 1993 41 40 574 1972 - 20111 4 224 1984 - 1994 42 36 550 1973 - 20092 10 211 1970 - 2007 43 38 466 1970 - 20083 9 275 1970 - 1997 44 26 543 1971 - 20104 10 336 1971 - 1997 45 38 802 1971 - 20115 9 118 1972 - 2007 46 27 547 1984 - 20126 9 174 1970 - 1999 47 30 166 1970 - 20117 10 87 1969 - 2001 48 23 249 1982 - 20128 13 126 1970 - 2011 49 22 193 1980 - 20119 7 93 1971 - 2002 50 20 209 1973 - 201110 10 133 1972 - 2010 51 31 504 1986 - 201111 9 230 1969 - 2011 52 32 386 1982 - 201112 13 332 1970 - 2009 53 28 325 1984 - 201113 13 143 1971 - 2010 54 31 257 1970 - 201214 18 145 1971 - 2007 55 28 242 1982 - 201115 7 25 1970 - 1997 56 15 111 1985 - 201016 11 176 1970 - 2009 57 17 223 1971 - 201417 9 24 1970 - 2006 58 16 127 1970 - 201118 17 116 1970 - 2011 59 16 114 1970 - 201119 14 86 1973 - 2008 60 14 119 1981 - 201120 11 45 1984 - 2008 61 15 109 1972 - 201021 19 209 1972 - 2004 62 15 221 1974 - 201122 18 266 1970 - 2001 63 16 302 1970 - 200723 11 266 1980 - 2011 64 16 54 1972 - 200724 19 130 1970 - 2005 65 17 127 1970 - 201125 27 142 1977 - 2011 66 13 64 1971 - 201226 15 88 1980 - 2006 67 16 83 1982 - 200827 19 162 1970 - 2011 68 20 183 1989 - 200928 29 338 1970 - 2010 69 26 341 1979 - 201129 19 275 1971 - 2007 70 21 426 1985 - 201130 20 150 1970 - 2007 71 16 118 1985 - 201131 35 288 1970 - 2011 72 27 240 1984 - 201032 23 423 1970 - 2011 73 9 95 1994 - 201233 23 224 1970 - 2010 74 15 161 1992 - 201234 23 227 1972 - 2007 75 12 86 1995 - 201235 25 258 1972 - 2011 76 18 154 1986 - 201136 22 490 1977 - 2011 77 13 67 1991 - 201237 29 354 1979 - 2010 78 12 106 1989 - 201238 36 541 1977 - 2008 79 13 106 1986 - 200939 26 261 1970 - 2011 80 18 156 1985 - 201040 47 558 1971 - 2011 81 13 116 1986 - 2011

Continued on next page

Table S3 Continued

Reservoir Age # Res N Sampling

YearsReservoi

r Age # Res N Sampling Years

82 8 85 1992 - 2011 131 2 42 2001 - 201183 11 86 1991 - 2011 132 2 7 200884 11 115 1994 - 2011 133 2 16 2005 - 200885 7 58 1991 - 2008 136 1 19 200886 12 107 1992 - 2011 137 2 14 200787 8 28 1991 - 2010 139 1 20 201188 6 31 1992 - 2007 141 1 6 200789 11 82 2000 - 2011 148 1 19 200390 9 138 2001 - 2011 151 1 11 200791 8 18 1998 - 2008 157 1 4 200792 13 152 1999 - 201293 9 65 1997 - 200794 6 58 2005 - 201295 9 52 2002 - 201096 14 96 2003 - 201197 9 108 1989 - 201298 5 29 2005 - 200899 10 91 1992 - 2011100 9 92 2006 - 2011101 4 29 2006 - 2008102 3 9 1990 - 2007103 3 31 2007 - 2011104 4 39 2006 - 2009105 1 3 2007106 8 161 2005 - 2011107 1 3 2008108 1 8 2001109 1 10 2006110 1 3 1991111 1 20 2011113 3 9 2005 - 2008114 1 6 2008115 4 32 2007 - 2008116 2 15 2007117 1 8 2007118 3 4 1994 - 2010119 2 24 2007123 1 3 2008124 1 4 2006129 1 25 2011

Literature Cited

Eagles-Smith CA, Ackerman JT, Willacker JJ, Tate MT, Lutz MA, Fleck JA, et al. Spatial and temporal patterns of mercury concentrations in freshwater fishes across the western US and Canada. Science of the Total Environment 2016; XX: XX-XX.