Fish are useful ecological indicators because they integrate ecosystem health over large spatial and temporal scales, are sensitive to disturbances like hydrologic alteration, and their biology is often well understood. Developing fish-based indicators is challenging due to the difficulty and expense of effectively sampling fish populations. Setting reference conditions for unimpaired sites is also difficult, especially in areas with widespread human impacts. Two examples of fish-based indicators are the Fish-IBI used in the US and Europe, and Australia's Sustainable Rivers Audit which reports on fish assemblages in the Murray-Darling Basin. Both evaluate community composition, population status, and individual health.

1. The use of fish as ecological
indicators

2. Why use fish as a biological indicator?
1. Important in providing ecosystem “goods and services”
such as fisheries production
2. Integrate ecosystem health over larger spatial and
temporal scales (including via food-webs)
3. Potentially more sensitive to some forms of
disturbance such as:
– Hydrologic alteration
– Longitudinal barriers
– habitat alteration
4. Biology and physiological tolerances often well
understood
– Assists metric development and interpretation

3. Challenges in fish as an indicator
• Harder and more expensive to sample effectively
compared to macroinvertebrates and algae
– Much harder to collect all or „most‟ species present at a site in a
short amount of time
– Individual surveys rarely capture majority of species
• Hard to apply indicators across geographic regions
– High altitute and high latitude regions typically have very low
diversity compared to the tropics
– Greater variation in the tolerance/feeding strategy/life-history of
related species compared to macroinvertebrates/algae
– e.g. Cyprinidae is a very diverse family
• Both of these issues contribute to the challenge of
setting „reference condition‟ or „targets‟.

4. Two examples
• Fish-IBI (index of biotic integrity)
– Widely used index in the USA and Europe
• Sustainable Rivers Audit (Fish Theme)
– Used to report on the health of fish assemblages in the Murray
Darling Basin in Australia
– Derived from IBI type approaches
– Extensive analyses of different survey techniques and effort
• Both incorporate information at 3 levels of organisation:
– Community composition
– Population status
– Individual health

5. Fish-IBI
• Multi-metric index
originally developed
in the mid-western
US (e.g. Karr, 1986).
• Widely used in the
USA and modified
for use in Europe
• Application of the IBI
approach
customised for each
state/region
Source: http://water.epa.gov/scitech/monitoring/rsl/bioassessment/ch08b.cfm

6. Geographic variation in F-IBI metrics
Source: http://water.epa.gov/scitech/monitoring/rsl/bioassessment/ch08b.cfm

7. Both approaches rely on the reference
condition
• Reference condition: the estimated condition that would
have prevailed in the absence of significant human
intervention.
– Problematic for areas where human intervention is widespread
or has been occurring for a long time
– Was not the case where many of these approaches were first
developed – good „reference‟ locations existed
– Difficult for many regions, including Australia and China

8. SRA reporting on the MBD
• Murray-Darling Basin
– 1.06 M km2
– 18 valleys
– 4 zones within each
valley (altitude) for
reporting
– Desert to wet-temperate
to alpine environments
– Low fish diversity ~30-40
species

9. Setting SRA fish ‘reference’ condition
1. Reference conditions derived by combining expert
knowledge, previous research, museum collections and
historical data,
2. Scientists from each State participated in expert committees
to review data on fish distributions throughout the Basin, and
State-based research, leading to predictions of the distribution
of each species in each Valley and Zone under Reference
Condition.
3. Estimates of Reference Condition are based on documented
information that is amenable to revision and re-analysis in
response to future improvements in knowledge.
• A long and difficult process!
From Davies et al. 2008

10. SRA fish indicators
Reporting metrics
Indicator group metrics
Expectedness OE (observed/expected) fish species
richness in each zone and valley
Nativeness Proportion native biomass
Proportion native abundance
Proportion native richness

11. SRA fish indicators
Diagnostic metrics
Indicator Description
Benthic Richness
Pelagic richness
Proportion macro carnivores Eat prey <15mm length
Proportion mega carnivores Eat prey >15mm length
Total abundance Median abundance in a zone
(compared to those for „good‟ sites
Diagnostic metrics
abnormalities Inverse median score of fish with
visible abnormalities
(lesions/parasites/tumors/wounds
etc.)
Intolerant species richness Numbers of native and alien species
intolerant of disturbances (e.g. poor
water quality, sediment, cold-water
pollution, migration barriers)
compared to the numbers predicted.

12. Reporting
• Reporting every 3 years
• Results aggregated to
valley scale
– Detailed valley-scale
reports available
• Other themes includes
invertebrates, waterbird
s, hydrology and
physical form

13. Summary
• IBI type indicators for fish are feasible
• Rely on incorporation of substantial background
information on fish distributions, tolerances etc.
• Sensitive to regional variation in data availability and
the „reference‟ fish assemblage
• Indicator development best guided by a coordinated
sampling program to provide the necessary data to help
develop the indivdual metrics

14. Some background
• Macroinvertebrates most widely used biological
indicator of stream health
– Good performance in evaluating WQ, especially heavy metals,
organic pollution
– Efficient to sample
– “Cosmopolitan” – similar groups in different parts of the world
• However:
– Less sensitive to changes in hydrology and physical form
(geomorphology)
– Do not quantify environmental “goods and services” such as
fisheries production