1. INDEX OF BIOTIC
INTEGRITY
Presentation by
Livi Wilson and Jitendra Kumar
COF Mangalore
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2. IBI
 A scientific tool used to identify and classify
water pollution problems.
 An IBI associates anthropogenic influences
on a water body with biological activity in the
water body, and is formulated using data
developed from biosurveys
 The IBI concept was formulated by Dr. James
Karr in 1981
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3. HISTORY
 Water quality act ( 1972) stimulated many
efforts to monitor the quality of water
resource systems
 It resulted in development of thresholds &
criteria levels for specific contaminants ,often
based on acute toxicity tests
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4. Drawbacks
 They have not taken into account naturally
occurring geographic variations of
contaminants (eg:asbestos,iron,zinc)
 Considered the synergistic effects of
numerous contaminants
 Not considered sub lethal effects of most
contaminants(eg:reproduction,growth)
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5. Cont…
 Chemical monitoring misses many of the
man-induced perturbations (eg:flow
alterations,habitat degradation,heated
effluents)
 In short ,criteria that emphasize physical &
chemical attributes of water are unsuccessful
for measuring biotic integrity
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6. Pollution
 Clean Water Act of 1977 defines pollution as
 “the manmade or man-induced alteration of
the chemical,physical,biological &
radiological integrity of water
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7. Biological integrity
“the capability of supporting & maintaining a
balanced,integrated,adaptive community of
organisms having a species
composition,diversity ,& functional
organization comparable to that of the
natural habitat of the region”(Frey 1977)
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8. Why monitor fish???
 Life history information is extensive for most
fish species
 Fish communities generally include a range of
species that represent a variety of trophic
levels
 Their position at the top of the aquatic food
web in relation to diatoms & invertebrates
also help to provide an integrative view of
the watershed environment
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9. Cont..
 Fishes are relatively easy to identify.
Technicians require relatively little training.
 Both acute toxicity (missing taxa) & stress
effects (depressed growth & reproductive
success) can be evaluated
 Fishes are typically present ,even in the
smallest streams & in all but the most
polluted waters
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10. Biotic integrity classes
class
Attributes
Excellent
Comparable to the best situations without influence of man, with most
intolerant forms, full array of age& sex classes; balanced trophic structure
Good
Species richness somewhat below expectation, loss of most intolerant
forms, trophic structure shows some signs of stress
Fair
Signs of additional deterioration include fewer intolerant forms, more
skewed trophic structure
Poor
Dominated by omnivores, pollution –tolerant forms,& habitat
generalists, growth rate & condition factors commonly depressed
;hybrids & diseased fish often present
Very poor
Few fish present, mostly introduced or very tolerant forms; hybrids
common ,disease, fin damage ,other anomalies regular
No fish
Repetitive sampling fails to turn up any fish
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11. Parameters used in assessment of fish
communities
Species composition &
richness
 Number of species
Ecological factors
 Number of individuals in
 Presence of intolerant
species
 Species richness &
composition of
Darters,Suckers,Sunfish
 Proportion of Hybrid
individuals




sample
Proportion of Omnivores
Proportion of Insectivores
Proportion of top
carnivores
Proportion with disease
,tumor, fin damage, other
anomalies
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12. IBI system
 Several species composition metrics are
evaluated
 Each fish species has characteristic tolerance
for water quality ,habitat,& other conditions
 Within each family,sets of species may be
ranked for their tolerances
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13. Cont…
 Presence of intolerant species is an important
criterion
 Eg of intolerant species found in mid-western
warm waters include rock bass. Banded
darter,longear sunfish….
 Another metrics is the presence & abundance
of green sunfish ,often the dominant or only
sunfish present at degraded sites(>20% of
individuals indicate degraded condition)
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14. Presence of hybrids
Hybridization probably occurs as a result of
habitat degradation
 Frequency of hybrids seems to increase in
modified streams
 Finally in very degraded conditions, hybrids
of carp & goldfish become quite common
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15. Ecological factors
 When a site declines in quality ,the
proportion of individuals that are omnivores
increases
 The most degraded streams are commonly
support large population of the
omnivores(gold fish)
 Their dominance is due to degradation of
food base, especially invertebrates.
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16. Cont…
<20% of individuals as omnivores as good
>45% omnivores to be badly degraded
 Presence of top carnivore is another
important indicator
Viable & healthy population of top carnivore
species indicate a relatively
healthy,trophically diverse community
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17. References
 Assessment of biotic integrity using fish
communities. Karr, J. R. 1981
 U.S.Environmental protection agency
(EPA)”BIOLOGICAL INTEGRITY”
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