The use of fish as ecological indicators

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

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‟.

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

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

Source: http://water.epa.gov/scitech/monitoring/rsl/bioassessment/ch08b.cfm

Geographic variation in F-IBI metrics

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

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

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

SRA fish indicators

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

Reporting metrics

SRA fish indicators

Diagnostic metrics

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

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.

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

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

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