FISH ASSEMBLAGE INDICATORS OF BIOLOGICAL INTEGRITY IN

NORTHWESTERN RIVERS, MOUNTAIN STREAMS, AND

DESERT STREAMS

Christopher A. MebaneIdaho Department of Environmental

Quality

• Fish assemblages probably less used in bioassessment in western U.S. than Midwest or East

• Issues using fish assemblages as ecological indicators in the western U.S. include:– Naturally low species richness– Species richness may increase in response to

disturbance– Extensive stocking of salmonids blurs

assemblages– Human disturbance patterns overlay natural

longitudinal river continuum patterns

• Mountain streams

• Desert streams

• Rivers

River IBI development: – compiled data

Tested potential indicators and constructed metrics

Reference DisturbedR T0

20

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100

Reference Disturbed

<=0 (10,20] (30,40] (50,60] (70,80] (90,100]0

0.2

0.4

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R T0

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Perc

ent

<=0 (10, (30, (50, (70, (90,0

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36-E47.24E38.5

039.0014.02 xx

xy+−−

+=y= 0.0143x

Percent Percent

Percent

Prop

ortio

n

Prop

ortio

n

<=0 (10,20] (30,40] (50,60] (70,80] (90,100]

Percent sensitive native individuals

Scor

e

Percent coldwater individuals

Percent

0

0 10 20 30 40 50 60 70% Coldwater individuals

0

10

0 20 40 60 80 100% Sensitive native individuals

10

% Tolerant individuals

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0 1 2 3

# Coldwater native species

00 1 2 3 4 5# Non-indigenous species

10

Salmonid age classes

0

10

0 2 4 6 8 10% DELT Anomalies

Sculpin Age Classes

0

0 2 4 6 8 10% Carp

Metrics for the River IBI

Score

Score

Score

Score

0

10

0 1 2 3 4 5 00 1 2 3 4

# Cold/ min. E-fish

10

0 1 2 3 4 5

0

10

0 5 10 15

% Sculpin (alternate)

00 20 40 60 80 100

Longitudinal changes in fish assemblages and IBI scoresSalmonids - Trout and salmon

Salmonids-Mountain whitefishCottidsCatostomids

Cyprinids

##

#

#

##

#

s

0

0

5 kmIBI - NA

10 km87

100 kmIBI - 95

525 km82 300 km

IBI - 85

600 kmIBI - 51

190 kmIBI - 93

200 km

Sampling considerations – what’s a representative sample of the assemblage?

A comparison of EMAP and NAWQA results, Snake River at Nyssa, OR

EMAP – E-fishing from paddle raft, target reach length 100X channel widthNAWQA – E-fishing from power boat plus backpack shocking wadable riffles, target reach length 1 km

EMAP and USGS results, Snake River at Nyssa, OR

Miles sampled0

2

4

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8

10

EMAP Mean NAWQA mean

Fish captured0

200

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1200

Species0

4

8

12

16

20

IBI0

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n = 4

Stream IBI - Mountain and desert streamsEcoregion

Mountain Ecoregions

NR, MR, BM, WUM

Semi-arid Basin EcoregionsSRB & WB

NBR CB

Elevation

Desert Index• Percent Coldwater Individuals• Percent cyprinids as longnose dace• Percent Omnivores & Herbivores• Percent DELT anomalies• Jaccard genus similarity • Relative abundance of coldwater

fishes (CPUE, # coldwaterindividuals/minute electrofishing)

•Plus secondary metricPresence of native amphibians

In steep gradient streams (≥ 4% slope), does assemblage consist solely of salmonids?

Mountain Index (6 metrics)• Number Coldwater Native species• Number of Sculpin Age Classes• Percent sensitive native individuals• Percent Coldwater Individuals• Number of Salmonid Age Classes• Relative abundance of coldwater fishes (CPUE, #

coldwater individuals/minute electrofishing)Plus secondary metrics

Presence of tailed frogs, orPresence of other native amphibians

Mountain Index (5 metrics)• Number Coldwater Native species• Percent sensitive native individuals• Percent Coldwater Individuals• Number of Salmonid Age Classes• Relative abundance of coldwater fishes (CPUE, #

coldwater individuals/minute electrofishing) • Plus secondary metrics

Presence of tailed frogs, orPresence of other native amphibians

Yes No

Yes

<1600m <1750m <1200mNo

Forest Index

Stream IBI, trout density, and sculpin presence compared with zinc aquatic life criteria exceedence factors

0

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0.001 0.01 0.1 1 10 100

Per

cent

scu

lpin

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2 0

4 0

6 0

8 0

1 0 0

0 .0 0 1 0 .0 1 0 .1 1 1 0 1 0 0

Str

eam

IBI

Zn/Zn ALC

0

1 0

2 0

3 0

4 0

0 .0 0 1 0 .0 1 0 .1 1 1 0 1 0 0

Trou

t per

100

m2

Zn/Zn ALC

• IBI provided a graded response to criteria exceedences, trout had little response, whereas the sculpin were abruptly extirpated

Site

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am F

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300TC-4 TC-1 Thompson Creek Flow

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fs)

TC-4 TC-1 SQ-3 SQ-2 LI S0

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80828486889092949698

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300SQ-3 SQ-2 Squaw Creek Flow

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IDEQSitesStream IBI -

Temporal Variability

Figure provided courtesy of Steve Canton, Chadwick Ecological Services, Littleton, CO

Conclusions

• Fish assemblages can be useful indicators of biological condition in depauperate NW streams and rivers

• IBI approach provides a functional model• Several apparently confounding problems

may be resolved through careful stratification, and metric construction and testing

• The IBI and the mountain-stream IBI appear useful over broad areas.

• Speculate that these or similar indexes could be more broadly applicable than tested so far.– Wherever a trout-sculpin-sucker-minnow

natural assemblage occurs.

What is the study question? Is it:

• Broadscale indication of how similar or different streams and rivers are from a regional, best attainable, reference condition?– IBIs appropriate

• Setting measurable biological benchmarks or to evaluate maintenance or restoration of biological integrity? IBIs appropriate

• Impact assessment – BACI monitoring for biological effects from waste outfalls, remedial or BMP effectiveness (e.g. monitoring for effects following timber harvest, ecological risk assessment, EIS, NRDA, NPDES monitoring, …)– More specific test questions and measurements

endpoints probably needed, but IBIs probably complementary

Familiarity with study area and data inspection necessary!

• We need to take care in dumbing-down bioassessment (I.e. over-standardizing and over-simplifying).

• Over-reliance on IBI scores could have missed the Mystery of the Missing Sculpin– There is a role for judgment

Ascertain Biological Condition Done