United States	Environmental Research
Environmental Protection	Laboratory
Agency	Corvallis OR 97333
Research and Development	EPA-600/D-84-053 Mar. 1984
ENVIRONMENTAL
RESEARCH BRIEF
Evaluation of an Index of Biotic Integrity:
Temporal Variability and Regional Application in the Midwest
James R. Karr,1 Philip R. Yant,2 Kurt D. Fausch,3 and Isaac J. Schlosser4
Background
Assessment of biotic integrity in water resource systems
has been hampered by lack of indices suitable for evaluating
biological conditions. {Biotic integrity is defined as presence
of a balanced, integrated, adaptive community of organisms
having a species composition, diversity, and functional
organization comparable to that of a natural habitat for the
region.) Classical water quality assessments are usually
based on chemical, bacterial, or thermal criteria. This
approach neglects factors such as structural (habitat)
characteristics, and patterns of temporal variation in
environmental characteristics, both of which affect biolog-
ical conditions and are subject to human alteration.
An Index of Biotic Integrity (IBI), based on analysis of fish
communities in streams, was introduced by Karr (1981).
The chief advantages of using fish communities to assess
biological integrity are: fish integrate effects of watershed
degradation; fish are typically present in all but the most
ephemeral or polluted aquatic habitats; fish are compara-
tively easy to identify; fish communities include a range of
species representing a variety of trophic levels; and state-
ments about the condition of the fish community are better
understood by the general public (Karr 1981). Furthermore,
the fish community is a valued resource and, although the
quality should be monitored and maintained for its own
sake, the fish community is often overlooked by water
quality managers. Although fish are routinely sampled by
state and federal agencies, toolsfor analysis and interpreta-
tion of such data have been inadequate (Weber 1981) until
now.
The IBI is designed to assess biotic integrity directly by
evaluating twelve attributes offish communities in streams.
These attributes, called community metrics, fall into several
categories, as listed in Table 1. They include: species
richness and composition, trophic composition, and fish
abundance and condition.
Ideally, criteria for scoring each metric should be adjusted
to reflect changes in fish communities with stream size and
region. However, some of the metrics change only slightly
among stream fish communities while others vary substan-
tially. Five species richness metrics are known to vary
substantially with stream size and region. As listed in Table
1, the metrics are: total number of fish species, number of
intolerant species, and numbers of darter (Etheostoma-
tinae), sunfish (Centrarchidae including green sunfish but
excluding Micropterus), and sucker {Catostomidae) species.
Intolerant species were determined from regional ichthy-
' University of Illinois. Champaign, IL 61820.
*University of Michigan. Ann Arbor, Ml 48109.
3Colorado State University, Ft Collins, CO 80523.
4University of North Dakota, Grand Forks, ND 58202.

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Tabh 1. Metrics Used in Assessment of Fish Communities (Modified from Karr 1981 and farnch et al. 1984)
Scoring Criteria
Category
Metric
5 (best)
1 (worst)
Species Richness and
Composition
Trophic Composition
Fish Abundance and
Condition
Total number offish species
Number and identity of darter species
Number and identity of sunfish species
Number and identity of sucker species
Number and identity of intolerant species
Proportion of individuals as green sunfish
Proportion of individuals as Omnivores"
Proportion of individuals as insectivorous
cyprinids
Proportion of individuals as top carnivores
Number of individuals in Sample
Proportion of individuals as hybrids
Proportion of individuals with disease, tumors.
fin damage and other anomalies
Varies with stream size and region
Varies with stream sue and region
Varies with stream size and region
Varies with stream size and region
Varies with stream size and region
<5%	5-20%	>20%
<20%	20 45%	>45%
>45% 20 45%	<20%
>5% 1 5%	<1%
Varies with stream size
0 0-1%	>1%
0-1%
>1%
*Omnivores are species with diets composed of >25% plant material and the rest animal material (Schlosser 1382b).
ologv references such as those from Smith (1979) for
Illinois.
In Table 1 the proportion of individuals as green sunfish
{Lapomis cyanellus), the trophic composition metrics, and
proportions of individuals that are hybrids or diseased seem
to vary little and have been assigned fixed criteria for
scoring. Number of individuals per sample was expressed
as catch-per-unit-effort and relative criteria for scoring
were determined for each watershed.
Each metric is evaluated against the standard conditions of
an unimpacted site of similar size and regional location.
Scores are determined for each metric under one of three
headings: Deviates Strongly From (score of 1), Deviates
Somewhat From (score of 3), or Approximates Expectations
(score of 5). An overall site score, the lil score, is the sum of
the twelve individual metric scores with a range from 12 to
60.
Karr (1981) assigned total scores to five classes according
to the following scale: Excellent 57-60; Good 48-52; Fair
39-44; Poor 28-35; Very Poor <23. When repeated
sampling failed to produce any fish, sites were assigned to a
sixth category: no fish. Fish communities receiving scores
falling between these ranges must be assessed by informed
biologists after careful consideration of individual criteria.
The IBI distills data in progressive steps (Figure 1) allowing
more complete use of information obtained in the original
labor-intensive and cost-intensive collection stage, and
also permits easier identification of community aspects that
may havp resulted in an overall unsatisfactory IBI value.
Thus, tha metric(s) causing a low IBI value can be pin-
pointed. Depending on study objectives, this information
can lead to further investigations and/or to actions for
mitigation.
Activities during the project reported here were restricted
to applications of IBI in Midwestern U S This restriction is
Fish
Community
I
Collection
I
S ummariiation
by
Species & Numbers
Summarization
by
Metrics
I
Rating of Metrics
I
IBI
Figure 1. The stepwise calculation of IBI.
reflected in some of the taxa used for certain metrics
(darters, suckers, sunfish). Application of the index toother
geographical regions requires some alteration of metrics.
Recommendations for those modifications are being de-
veloped.
The Currant Project
This research brief concentrates on discussion of the
assessment and application of the IBI. first, evaluations
were made of seasonal and year-to-year variations in the
IBI at locations which were sampled over an extended
period. The goals of this analysis were to determine, using
the IBI, the extent to which the season of sample collection
affects site evaluations. Also examined was the year-to-
year variability in IBI values at a number of sites with and
without intervening perturbations.
Second, evaluations were made of the reliability of the IBI
for assessing biotic integrity in regions of North-Central
United States outside the immediate Illinois-Indiana
2

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streams for which the index was originally developed. This
phase of the study developed more precise ways to set
criteria for scoring metrics, and also examined the agree-
ment of IBI inferences about sites and regions with opinions
from other researchers.
Temporal Variability
Evaluation of temporal variability in stream communities
requires an extensive series of data from many sampling
sites. During the past decade, data were collected by J. R,
Karr and associates with support from the U.S. Environ-
mental Protection Agency. These data reveal both the rigor
of sampling protocols and the conditions of the stream
environments. Data from three streams were analyzed:
Black Creek, Allen County, Indiana (sampled from 1973-
82); Big Ditch, Champaign County, Illinois (1978-80); and
Jordan Creek, Vermilion County, Illinois (1978-80).
Big Ditch and Jordan Creek. Analyses of data from these
two streams addressed the following questions: Does IBI
rank sites similarly during each sampling period (assuming
no major changes in channel, wate quality, etc.}? Do these
rankings reflect prior assessments of site qualities, based
on known effluent/habitat conditions? How much variabil-
ity occurs within a site among sampling dates, and is this
variability related to site quality? Does site assessment vary
predictably with season? Within Big Ditch, can we discover
differences among metrics in response to effluent vs.
habitat degradation?
Big Ditch is a channelized tributary Sangamon River Near
its headwaters, it receives municipal effluentfrom Rantoul,
IL (Sehlosser and Karr 1981, Sehlosser 1982a). Big Ditch
was sampled at ten locations along its length, during early
and late summer, in 1978, 1979. and 1980. Jordan Creek
has been channelized upstream but not downstream
(Sehlosser and Karr 1981, Sehlosser 1982a, b). Part of the
channelized section passes through a wood tot and, conse-
quently, has better habitat quality. Jordan Creek does not
receive any significant point effluent. This stream was
sampled at 5 to 14 locations, three or four times each year
from early summer to autumn in 1978, 1979, and 1980.
Although IBI values are not invariant among seasons and
years, site ranks are concordant (Friedman Test) over time
. within each stream (Figures 2 and 3). Furthermore, these
rankings accord with prior assessments of site quality
based on water quality and physical habitat measurements
(documented in Sehlosser and Karr 1981, Sehlosser
1982a, b). For example, in Big Ditch (Figure 2), quality
declines below the effluent discharge (site 2) and increases
progressively downstream until reaching the section (sites
7 and 8) with lower habitat quality, where the IBI indicates
lower fish quality. IBI values increase below these sites,
where habitat quality improves.
In Jordan Creek (Figure 3), IBI values are low in the severely
channelized section (sites 1B, 1C, 1E) but do not increase
where the stream passes through a wood tot (sites 2A, 2B,
and 2D). The increase in IBI values is more dramatic,
however, where the stream passes through a well-
established pasture {sites 3D and 3E) and then on through a
more heavily forested area (sites 4A-4E).
60
§
5
X
!
I
5 4°
30
20
Big Ditch
1
Good
Mean
Standard
\Deviatio" Fair
^Range_\
Poor
J	i	I	I	it	I	A.
1 23456789 10
Station
Figun 2. IBI values for 10 sample stations in Big Ditch, IL
SO
§ 50
40
30
Jordan Creek
Excellent
11
H u\*-Mean n
^ tp-r Standard J Good
" i Deviation
- — Range
Pair
Poor
1C 2A 2D 3D 4A 4C 4£
IB 1E 28 3A 3E 4B 4D
Station
Figun 3. IBI values for 14 sample stations in Jordan Creek, IL.
In both of these streams, the IB! gave similar rankings of
sites among time periods and these rankings agreed with
water quality and habitat quality conditions, both within
each stream and between the two streams.
Variability in IBI values at each site was related to the
quality of the site and also to the quality of the entire
stream. Higher quality sites within each stream were less
variable among dates than were lower quality sites (Figure
4) Paradoxically, sites in higher quality Jordan Creek had
more variable IBI values than did sites of similar average
quality in Big Ditch.
This latter pattern of between-stream differences in vari-
ability as a function of quality is due to the mobility offish. In
streams with a broader range of suitable environments,
movement among high and low quality areas is possibly
due to proximity of higher quality areas that serve as
refuges. The perceived quality of a poorer site can increase
at times, thereby increasing variability in assessments.
3

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Jordan
* Creek
5.0
9
c
.0
¦8
| 30
1
m
± c Big
Ditch
1.0
Pooled Slopes
forANCOVA
30
SO
40
60
IBI Value
Figure 4. Relationship between means and standard devi-
ations of IBI values in Jordan Creek and Big Ditch. IL.
Jordan Creek has a more extensive high quality area than
does Big Ditch (Figures 2,3). Therefore, poor sites in Jordan
Creek have a greater potential for temporary increases in
quality
Data from Big Ditch and Jordan Creek provide less definitive
answers to questions concerning the best season to sample
and the implications of individual metrics. However, some
inferences can be drawn. Within each stream, late summer
collections usually produced higher IBI values than did
samples from earlier in summer. This tendency varied
among years, was more noticeable at poorer sites and is
apparently related to the overall cause of site variability, i.e.,
movement of fish to the best available refuge sites and
short-term effects of seasonal recruitment. These factors
may inflate estimates of species richness and abundance at
poor sites by including individuals that presumably cannot
persist at that site. Predictably, this effect is variable among
years, probably reflecting variability in recruitment.
Although Big Ditch has been completely channelized, two
sites (7 and 8) had lower habitat quality, and two sites (2 and
3) were degraded by municipal sewage. Values of individual
metrics at those four sites were examined to determine if
each type of degradation was associated with changes in
certain metrics. Conclusions from these comparisons must
be evaluated with consideration of the small sample size
and with recognition that each group of sites was affected
to some degree by both types of degradation.
When compared to the two sites with exceptionally poor
habitat quality, the two sites affected by municipal effluent
had lower overall abundances, fewer insectivorous cypri-
nids, but more green sunfish and more species of darters.
Conversely, sites with poor habitat had higher abundances
with more insectivorous cyprinids but fewer darter species
and few green sunfish. These conditions were noted in
conjunction with toxic or hypoxic environments around the
effluent, resulting in fewer individuals and greater preva-
lence of the very tolerant green sunfish. Where habitat is
poorer, overall fish abundance is high but the more silty
benthic habitat precludes some species of microhabitat-
specialized darters.
In summary, examination of two streams in East-Central
Illinois revealed that the IBI provided consistent evaluations
of site quality in agreement with prior assessments. The
evaluation of poor sites was more variable than that of good
sites; there was greater likelihood of over-assessment of
poor sites than of under assessment of good sites. Over-
assessment of poor sites was more likely in the late
summer of certain years. Finally, behavior of individual
metrics did tend to coincide with the nature of degradation.
Black Creek. Fish community data were collected in the
Black Creek, Indiana watershed as part of a USEPA-
supported study of the impact of agricultural land use on
water quality (Morrison 1981). Many collections were
made at several sites between 1973 and 1982. During this
period, habitat and water quality varied in such complex
ways, that interpretations of IBI values are not as straight-
forward as they were in Big Ditch and Jordan Creek.
However, data from Black Creek were used to address
several specific questions: Could impact of known habitat
perturbations be assessed with the IBI? Was post-
perturbation recovery observable with the IBI? Did the IBI
show other patterns of seasonal or year-to-year variation?
Taken over the whole project period, IBI values increased
from upstream to downstream, probably reflecting both
greater project-related impact upstream and the effect of
better riparian habitat downstream. The latter effect was
made clearer by reference to a tributary that passes through
a wood lot {Wertz Woods) where higher IBI values reflected
better habitat quality (sinuous channel, pools and riffles,
trees shading channel) than that found in sites on the
unforested main channel.
Two notable periods of project impact occurred. First, early
channel modifications resulted in sharp decreases in quality
at most sites. After this impact, downstream sites showed
rapid recovery and upstream sites, slower recovery. The
second impact involved the Wertz Woods site (Figure 5).
Although this site was not intentionally modified, project
Excellent
\60
Wertz Woods
Good
Fair
Poor
¦20
' 74
82
75 76 77 78
80
Pigum 5. Project impact and recovery of Wertz Woods site.
Black Creek watershed, as shown by IBI.
4

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activities upstream (a poorly executed effort at bank stabil-
ization) during 1976 resulted in transport of sediment Into
this site and deterioration of habitat quality. In turn, IBI
values declined markedly, becoming similar to those of
poorer sites in the watershed. A slow recovery towards
pre-disturbance conditions began but has not yet returned
this site to its former, relatively high quality state.
Both seasonal and year-to-year variations in IBI were
observable in Black Creek as well as in another nearby
stream unaffected by project activities. The amplitude of
these variations was greater in poorer upstream sites. As in
the Illinois streams, early summer IBI values were less
variable among years than late summer values.
In summary, the IBI was useful in documenting effects of
project activities, showing both initial reductions in quality
and subsequent rate and extent of recovery. Both seasonal
and year-to-year variation in IBI values were discernable,
with early summer values often being lower, but less
variable among years, than were late summer values.
Regional Application
In addition to evaluating behavior of the IBI over time at
selected sites, this study evaluated the Index over a wider
geographic area. That effort produced extensive data sets
from seven additional rivers (Figure 6): three in Illinois and
one each in Michigan, Kentucky, Nebraska, and the
Dakotas. For each river one sample was obtained for each of
33 to 139 sample sites. In addition, some sites were
replicated in the Nebraska watershed. For five of the seven
rivers, both species lists and relative abundance data were
available; for the other two (Rock River, IL and James River,
ND and SD) only species lists were available (Fausch et al.
1984).
These data were used in two analyses. First, all data were
used to develop expectations of species richness in each
watershed as a function of stream size (stream order and
watershed area) Second, for those rivers from which were
Figure 6. Locations of Red (1), Raisin (2), Embarras (4), rivers,
Chicago area (5). Rock River (6), Sait Creek (81 and
Jamas River (91
obtained both species lists and relative abundances, each
site was assessed using the IBI. Results from the IBI were
then compared with other information about conditions
among sites and rivers
Expected values of certain metrics used in calculation of IBI
vary with stream size and/or geographic region. Thus, the
study sought to establish protocols to determine those
expectations as well as to determine if rivers throughout
the midwest exhibited similar stream size vs. species
richness relationships. If generality could be demonstrated
at some useful level, considerable time could be saved in
application of IBI to other rivers.
Expectations for total species were generated using the
concept (Fausch et al. 1984) of the Maximum Species
Richness Line (MSRL). Plots of species richness versus
stream order (or watershed area) at each collection site
produce a right triangle of points bounded on the upper side
by a hypothetical line representing the expected maximum
number of species to be found at each stream size (Figure
7). Aline with slope fit by eye that forms the upper bound for
95 percent of the sites is a better measure of true species
¦A	o
Maximum Species
Richness Line
>^8
8
oo
<0
•s
£
I
40
& 30
20
10
rB
* L + S
¦ T * H
3	4
Stream Order

A° °o
* %oo
0^-»o <9	o%-
° JHL «° -°-'8
s ° „ °
' 1 till/
t l I 8 i t 111
to	100	7000
Watershed Area (km1}
5000
Figure 7.
Total number of fish species vs. stream order (A),
andlogn watershed area (B)for 72 "least disturbed"
sites from the Embarras River. See text for explan-
ation of Maximum Species Richness lines. Dashed
lines in (A) trisect the right triangle into regions used
in scoring IBI metrics (see text). Linear regressions
for data oflarimote and Smith (1963, triangles and
solid line) and Thompson and Hunt (1930, squares
and dashed line) are shown in B. Maximum Species
Richness line (not shown) in B is nearly identical to
Larimore and Smith (1963) regression.
5

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richness over stream orders than that provided by a linear
regression. Points may lie far below this line due to
sampling inadequacies or to site-degradation.
Although MSRLs for the seven rivers differed, they
generally form two groups of similar lines (Figure 8). The
uppermost group is a set of woodland streams in the
eastern region of the midwest. These rivers generally have
more species at any stream order than do Great Plains
streams, the lower group. Within each group, maximum
species richness tends to be similar, particularly at inter-
mediate stream orders (e g., 2-4)
Ideally, application of IBI to a river would be preceded by
determination of its M8RL However, if this information
were not available, tentative IBI values were derived from
expectations of rivers in the same geographical area (Figure
8).
published and unpublished evaluations of researchers
(Familiar with those areas.
The IBI was clearly applicable to each of these five rivers
(Figure 9). Furthermore, overall assessments accorded with
prior evaluations. The two least disturbed watersheds—
Red River, KY and Embarras River, IL—had most sites
ranked "Good" or above (92% and 83%, respectively). The
two most disturbed watersheds—the Chicago area, IL and
Salt Creek, NE—had most of their sites "Fair" or poorer
(90% and 96%. respectively). Raisin River. Ml, a watershed
with a range of disturbance, had IBI values throughout the
available range—"Excellent" to "No Fish."
IBI values did not correlate with stream order in streams
that were considered of uniform quality—Salt Creek, which
has generally "Fair" or "Poor" sites, and the least disturbed
parts of the Embarras River, which had mostly "Good"
This analysis of mid western streams indicates that maxi-
mum species richness of higher order sites tends to decline
in an east to west direction. Nearby streams tend to have
similar maximum species richness; more distant streams
toward the east tend to have more species at a similar order
and distant streams toward the west, fewer species.
Therefore, if information from a nearby river is unavailable,
interpolation of information from two rivers on either side
could be used as an acceptable first approximation.
Once the MSRL has been drawn, operational limits for
scoring observed species richness can be determined. The
right triangle defined by the MSRL is divided into three
zones by radiating lines and scored accordingly.
Using this approach to determining expectations for species
number and number of species in the darter, sunfish, and
sucker groups, IBI values were calculated for five rivers. The
goals of this analysis were to examine applicability of the IBI
to rivers in Kentucky, Michigan, Illinois and Nebraska; to
determine if IBI is dependent on stream order; and to
compare IBI values with conditions within and between
rivers based on knowledge of each river as well as on
Lines of
Maximum Species Richness
1
•55
I
,, KY (Red)
- / ,L
// (Embarras)
IL
(Chicago)
ILfRock)
NB (Salt)
NO, SO
(James)
1 2 3 4 5 6
Stream Order
Figure 8. Maximum species richness lines for six midwestarn
rivers.
601-
20
Bed
N - 37
SOr-
40
w
C
Q
¦£.
<9
<0
c
5
S
Embarras
N= 12
i	i i	'*
40
Raisin
N- 139
40
Salt
N- 125
Chicago
N* 87
Mean
NF VP
P F G
IBI Category
Figure 9.
Frequency distributions of IBI values in five water-
sheds with both species lists and relative abundance
data available.
6

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sites. Exceptions were in the other three, in which first
order sites often had somewhat higher scores than did most
sites farther downstream. This pattern, apparently due to
decreased disturbance in smaller streams, represented real
differences and thus did not indicate a weakness of the
Index.
Summarf
The Index of Biotic Integrity (IBI) is a useful tool for
evaluating fish community data. The IBI ranks sites
according to relative quality. When environmental impacts
have occurred which should reduce fish community quality,
the IBI documents both the impact and subsequent
recovery. The IBI does show systematic seasonal and year-
to-year variations which may reflect actual short-term
changes in quality.
The IBI can be used in areas of the Mississippi Valley
outside of Illinois and Indiana. When expectations of
species richness are not available from the user's experi-
ence, these expectations can be generated with data from
the watershed of interest, or from other watersheds nearby.
When used with fish community data from Kentucky,
Michigan, Indiana, Illinois, and Nebraska, the IBI has given
site assessments which agree with independent assess-
ments of biologists familiar with the regions.
Literature Cited
Fausch, K. D.. J. R. Karr, and P. R. Yant. 1984. Regional
application of an index of biotic integrity based on stream
fish communities. Trans. A mar. Fish Soc. 113:in press.
Karr, J. R. 1981. Assessment of biotic integrity using fish
communities. Fisheries 6:21-27.
Larimore, R. W. and P. W Smith. 1963. The fishes of
Champaign County, Illinois, as affected by 60 years of
stream changes. Illinois Natural History Survey Bulletin.
28:299-382
Morrison, J. 1981. Environmental impact of land use on
water quality. Final report on the Black Creek project
Phase II. USEPA, Chicago, IL. EPA-905/9-81 -003.
Schlosser, I J. 1982a Trophic structure, reproductive
success, and growth rate of fishes in a natural and
modified headwater stream. Can J. Fish and Aquat. Sci.
39:968-978.
Schlosser, I. J. 1982b. Fish community structure and
function along two habitat gradients in a headwater
stream. Ecological Monographs 52:395-414,
Schlosser, I. J. and J. R. Karr. 1981. Water quality in
agricultural watersheds: impact of riparian vegetation
during base flow. Water Resour. Bull. 17:233-240.
Smith, P. W. 1979. The fishes of Illinois. University of
Illinois Press, Urbana, Illinois.
Thompson, D. H. and F. D. Hunt. 1930. The fishes of
Champaign County: a study of the distribution and
abundance of fishes in small streams. Illinois Natural
History Survey Bulletin 19.
Weber, C. 1.1981. Evaluation of the effects of effluents on
aquatic life in receiving waters: an overview. Ecological
Assessments of Effluent Impacts on Communities of
Indigenous Aquatic Organisms. ASTM STP 730. J. M.
Bates and C. I. Weber (Eds.) American Society for Testing
and Materials, pp. 3-13.

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