Why use fish as a biological indicator?1. Important in providing ecosystem “goods and services” such as fisheries production2. 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 alteration4. 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
Geographic variation in F-IBI metrics Source: http://water.epa.gov/scitech/monitoring/rsl/bioassessment/ch08b.cfm
Both approaches rely on the referencecondition• 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 indicatorsReporting metricsIndicator group metricsExpectedness OE (observed/expected) fish species richness in each zone and valleyNativeness Proportion native biomass Proportion native abundance Proportion native richness
SRA fish indicatorsDiagnostic metricsIndicator DescriptionBenthic RichnessPelagic richnessProportion macro carnivores Eat prey <15mm lengthProportion mega carnivores Eat prey >15mm lengthTotal abundance Median abundance in a zone (compared to those for „good‟ sitesDiagnostic metricsabnormalities 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