| Project objectives:
The CITYFISH project combines an investigation of the ecological quality of urban river systems with ecotoxicological risk assessment and risk perception
studies regarding the ecological quality of running waters in cities and their hinterland.
At each site, the ecological quality of the study river will be described on a seasonal basis in terms of biotic indices and chemical water quality, and related
to the population biology of a resident species of coarse (tolerant) fish. Sub-lethal indicators of pollution will then be measured on fish exposed to the prevailing
seasonal water conditions at each site, in floating cages. A range of biochemical indicators (biomarkers) will be used to reveal specific exposure to particular
contaminants or classes of contaminants. These will include: induction of cytochrome P450 and metallothioneins; DNA damage, in terms of strand breaks; estrogenic
activity (measured as vitellogenin induction); brain cholinesterase activity. Measurement of swimming performance will be used as an indicator of physiological
status, revealing seasonal differences and the response to exposure to the complex changes in water chemistry, following flood spates. These measurements
will be related to migration of fish within the river system, using radio-tracking or tag and recapture. The immunological status of fish (e.g. macrophage
activity) will be assessed, as urban waters can be subject to elevated contents of pathogenic bacteria from human waste and, furthermore, fish in poor condition
as a result of pollution and other physico-chemical stresses may have compromised immune competence. Data analysis will use current methodologies for multivariate
statistics to model the ecotoxicological factors limiting fish populations at the study sites, enabling the elaboration of ecological risk assessments
and sensitive water quality criteria for a range of European rivers. A sociological study will be undertaken, to investigate the way that various groups of
people with an interest in rivers (stakeholders) perceive the risks associated with poor ecological quality in urban rivers.
The overall objectives of the project are to determine the ecotoxicological factors limiting restoration of sustainable fish populations in polluted urban
rivers. These factors are being described and modelled for urban river systems in four European countries: the UK, Italy, Germany and the Netherlands. The
rivers are being characterised according to their physicochemical conditions, using passive samplers, and biotic indices, based on resident macro-invertebrates
or plankton. Relatively polluted sites are being compared with cleaner control sites on each river, at different seasons.
The fish population in each river is being compared using mark and recapture techniques, and a dominant species has been selected for further study. In the
UK and Italy the chosen species is chub, (Leuciscus cephalus), in the Netherlands and Germany it is bream (Abramis brama). Fish sampled from the wild population,
plus fish held in cages at each sampling site, are being studied with respect to their swimming performance in relation to the pollution load they have accumulated.
Fish exposed in relatively polluted conditions swim at slower sustainable rates that fish from clean water. This will affect their ability to maintain position
or migrate within the river system.
Their pollution load is being measured as a series of biomarkers. Samples of blood plasma, bile, liver tissue, brain tissue and muscle tissue have been collected
from each fish. These samples are being exchanged between participants to ensure comparability of data and to utilise the development of local expertise in
particular techniques. Measured biomarkers include: DNA damage (Comet assay), cytochrome P450 induction and activity, choline esterase (ChE) activity,
reduced and oxidised gluthione ratios via fluorimetry, western blotting analysis for heat shock protein-70 levels, 8-oxo-deoxyguanosine analysis using
HPLC. Detection of vitellogenin in fish serum is to be compared with data on bile estrogenicity performed by YES (yeast estrogen system). In addition, the gene
sequence for chub metallothionein has been described and registered. This will enable metallothionein mRNA expression be quantified in tissue samples,
A sociological study has been undertaken, to investigate the ways that various groups of people with an interest in rivers (stakeholders) perceive the risks
associated with poor ecological quality and the social advantages of a healthy fish population, in urban rivers. The outcome of the project will be an overview
of the combined technological and socio-economic factors affecting implementation of an urban river ecosystem with a sustainable population of healthy
fish and the development of more sensitive criteria for judging the quality of rivers, based on analysis of their fish populations.