A Bayesian framework to objectively combine metrics when developing stressor specific multimetric indicator

In the context of the European Water Framework Directive (WFD), monitoring programs and related indicators have been developed to assess anthropogenic impacts on various components of aquatic ecosystems. While great precautions are usually taken when selecting and calculating relevant core metrics, little attention is generally paid to the generation of the multimetric indicator, i.e. the combination of the different core metrics. Indeed, most multimetric indicators are generated by simply averaging or summing metrics, without taking into account their sensitivity and their variability. Moreover, few indicators provide a rigorous estimate of the uncertainty of the assessments, while this estimation is essential for managers. In this context, we developed a Bayesian framework to build multimetric indicators aiming at improving those two weaknesses. This framework is based on two phases. First, pressure-impact statistical models are developed to quantify the impact of pressure on various fish metrics. Then the Bayesian theorem is applied to estimate probabilities of being at a certain anthropogenic pressure level from fish observation and pressure-impact models outputs. The Bayesian theorem allows to combine objectively the different core metrics, taking into account their sensitivity and their variability, and to provide rigorous uncertainty quantification, which is especially valuable in the WFD context. The method is applied as illustrative example on transitional French water bodies to demonstrate its relevance, especially in the Water Framework Directive context though the method is generic enough to be applied in various contexts

Deliverable D4.4-3, Report detailing Multimetric fish-based indices sensitivity to anthropogenic and natural pressures, and to metrics’ variation range

The Water Framework Directive (WFD) aims at achieving good ecological status (GES) for surface water bodies throughout Europe, by 2015. Consequently European countries are currently developing and intercalibrating methods based on biological, hydromorphological and physico-chemical quality elements for the assessment of their transitional waters, including fishes. The present work focuses on the response of fish indicators and indices to anthropogenic pressures and natural factors. For doing that, datasets from the Basque and Portuguese estuaries, in the North East Atlantic, have been used. Hence, biological data from fish (and in some cases, crustaceans), together with different types of pressure (population, industry, ports, dredging, global pressures, pollution, channeling, etc.) and hydromorphological data (flow, estuary volume, depth, intertidal surface, residence time, etc.) have been analyzed. Together with fish assemblages composition and individual metrics (richness, trophic composition, etc.), two fish indices (Basque AFI and Portuguese EFAI) have been investigated. Additionally, the response of five fish indices (AFI, EFAI, ELFI, TFCI, Z-EBI) were tested on a common dataset, within Portuguese estuaries, to check the time lag in the metrics’ response to different human pressures and the variability in the strength of responses to those pressures. This work also focuses on the sensitivity analysis of two European fish-based indices (French ELFI and British TFCI) to changes in their respective metric scores through their observed dynamic range. Sensitivity analyses were run simulating different scenarios of metric score changes, taking into consideration the relationship between metrics. This allowed the metrics with stronger influence in the index score and the resulting water body classification to be highlighted. Importantly, the identification of the most influential metrics could help to guide management efforts in terms of achieving GES by 2015. In general, the fish metrics and indices tested responded to anthropogenic pressures in the Atlantic estuarine sites, yet at the individual metrics level environmental chemical quality was the main driver for observed differences. Also, some metrics did not respond to pressures as expected, which is most likely related to sampling gear efficiency, namely the low capture efficiency of diadromous species with beam trawl. The cause-effect relationship study emphasized that fish-based indices developed to assess the water quality of estuarine systems did not detect all the pressures with the same sensitivity in terms of strength and time-lag, and gave more importance to some pressures, namely chemical pollution. The fish-based indices developed to assess the water quality of estuarine systems do not allow the individualization of pressure effects, which may constitute a problem to put forward the correct specific measures for management and rehabilitation of estuaries. On the other hand, some indices also do not seem relevant, in a short time, to detect changes of the ecological quality which may constitute a handicap for management or an indication for their restructuring. The sensitivity analysis indicates that a number of estuarine resident taxa, a number of estuarine-dependent marine taxa, a number of benthic invertebrate feeding taxa and a number of piscivorous taxa have the greatest influence on the TFCI classification. For the French index ELFI, the most influential metrics are mainly DT (total density) and DB (density of benthic species), followed by RT (total richness). These results suggest a high sensitivity of the quality indication provided by these indices on richness related aspects of the fish assemblages. Management should therefore prioritize efforts to conserve or restore estuarine attributes underpinning abundance and ecological diversity, for example the diversity of fish habitats, food resources and shelter or the hydrological integration between coastal and transitional waters.info:eu-repo/semantics/publishedVersio

Deliverable D4.4-5: Precision and behaviour of fish-based ecological quality metrics in relation to natural and anthropogenic pressure gradients in European estuaries and lagoons

This report summarises the work conducted in Work Package 4.4 – BQE fish in transitional (i.e. estuarine and lagoon) waters (TW) within the project WISER under the sponsorship of the European Commission. It omits most technical details of the analyses given in the four previous Work Package reports, but still provides the necessary information to understand the rationale, approach and underlying assumptions necessary to discuss the results. The focus is therefore to discuss and integrate the results obtained within Work Package 4.4 and with this, make recommendations to improve fish-based ecological assessments in TW, principally estuaries and lagoons. In addition, and to assist with the WFD implementation which is the overarching theme of WISER, the deliverable includes, where appropriate, case studies where we have used multi-metric fish indices currently under development, or already in use for WFD compliance monitoring across Europe. Furthermore, results of the work package have been shared with relevant Geographical Intercalibration Groups (GIGs) supporting the harmonization and equalization process across transitional fish indices in Europe. Development strategies for fish indices in TW vary but generally include: (1) the calibration of metrics to anthropogenic pressures, (2) the development of reference conditions, (3) the calculation of ecological quality ratios, and (4) the designation of thresholds for Ecological Status (ES) class. New fish indices are developed for a defined geographical area, using specific sampling method and under locally relevant pressure fields. The former two factors, area and sampling methods, define the relevant reference condition in the calculation of Ecological Quality Ratios (EQR) and the latter factor, human pressures, define the índex structure and especially the fish metric selection. To assess index relevance across areas, we calculated a suite of transitional fish indices on a standardized WISER dataset and then compared the agreement of the outcomes (using correlation analysis). The application of current indices to areas (or countries) different from the area in which it was originally developed leads to inconclusive or spurious results. The failure to accommodate the diferente indices to a standardized dataset in this work clearly demonstrates the fundamental reliance of current fish indices on the sampling methods and design of monitoring programmes used in the development of the index. Despite this, for some indices, correlations although weaker are statistically significant, also indicating the possible agreement in successful intercalibration between these indices. Harmonization of BQE fish methodologies across Europe (common metrics) is unlikely by adapting or creating new fish indices but inter-comparison assessments are possible and valid using a common pressure index to harmonise diferente indices on a common scale. We found a negative response of fish quality features to pressure gradients which make BQE fish in TW suitable for greater ecological integration than other BQEs. However, successful assessment of Ecological Status (ES) require a matching combination of fish index, reference values and local dataset gathered with compatible sampling methods. Whole indices provide more consistent overall ES assessments but fish metrics considered individually may be more useful as a means to focus restoration measures. Future work is needed to identify those specific pressures affecting fish assemblages providing targets for minimising the effects of stress in mitigation and restoration plans. In order to achieve this, and although the interpretation of outcomes is still difficult, more recent transitional fish indices are leading in the use of comprehensive appraisal and validation exercises to test the responsiveness of BQEs for the assessment of ES. Here we proposed for the first time a simple sensitivity exercise under realistic scenarios of metric change to explore the expected inertia (i.e. the tendency to buffer ES change after quality alterations), dynamic range (i.e. the ratio between the largest and smallest possible ES values) and most relevant metric components (i.e. the those driving the most likely scenarios leading to ES change) from a multi-metric fish índex under relevant human pressure gradients. Overall, the behaviour of multi-metric índices under manipulations of metric scores clearly indicated that metric type, number of metrics used and correlations between metrics are important in determining the index performance, with indices including more and/or uncorrelated metrics or metrics with skewed distribution being less affected by extreme metric manipulations. Results of this analysis may be used to set realistic management targets and also to identify the aspects of the indices that are more likely to affect the outcomes leading to more robust and responsive indices. Further improvements of fish indices may be attained by reducing the variability confounding biological quality metrics. This variability is undesirable noise in assessments and can be technical (i.e. linked to the method of assessment including sampling effort) or natural (physicochemical and biological). The implication for assessments is that different facts might then confound the metric-pressure correlation (the ‘signal’ in the signal-to-noise ratio in the assessments) increasing uncertainty in ES assignment. Models showed that salinity class, depth, season, time of fishing (day vs. night) and year of fishing may influence the values of the fish metrics. The modelling exercise also demonstrated that unexplained variance remains generally much higher within-systems than between-systems suggesting a higher importance of sources of variability acting at the WB level. Modelling and improved standardization in monitoring campaigns should reduce uncertainty in ES assignment. One important factor that was assessed further was the effect of sampling effort. The results suggest that richness-based metrics require larger sampling efforts although a similar effortrelated bias may be an issue for density-based metrics if fish distribution is very patchy (i.e. schooling fish or those aggregated in specific habitats) and insufficient replicates are taken to fully characterise the patchiness in their distribution. It is apparent that to overcome a potential large source of error, the Reference Conditions must be defined according to the level of effort used in the monitoring programme or, conversely, the monitoring must be carried out at the same level of effort used to derive the Reference Condition. The WP finally explored the use of a predictive linear modelling approach to define reference conditions for fish metrics in transitional waters. The fish response data was modelled together with Corine Land Cover (CLC)-derived pressure proxies (% agricultural, urban and natural land coverage). Based on the obtained models, the expected metric score was predicted by setting pressure levels either to the lowest observed pressure in the dataset or to zero in order to define the sample and theoretical reference condition, respectively. Even when significant, the effect of pressures on fish metrics was generally very weak, probably reflecting the use of too-generic pressure indicators (such as land cover data instead of more relevant estuarine proxies such as dredging, port development, waterborne pollutants, etc). The best explanatory models included sampling factors and natural characteristics considered important discriminant features in the definition of water body types. In particular, the present work argues for considering not only estuaries and lagoons as different typologies but also other natural and design characteristic such as the gear type, the sampling season and the salinity class. Furthermore, a relevant reference needs to account for survey design bias, including rare species contribution to assessment datasets, patchiness, choice of pressure proxies or sampling gear. The modelling approach of fish metrics against the physicochemical variables has proved useful to derive Reference Conditions. This is important for the computation of relevant EQRs in Europe where there is a general lack of pristine areas or historical data on fish BQE and it provides an alternative to best professional judgment. Taking all WP analysis and case studies together, the work conducted has highlighted the following key messages and linked research needs necessary to optimize BQE fish for the quality assessment of transitional waters: Key Message 01: Harmonization of BQE fish methodologies across Europe (common metrics) is unlikely by adapting or creating new fish indices but inter-comparison assessments are possible and valid using a common pressure index to harmonise diferente indices on a common scale. Research needs to be focused on more widely-applicable fish indices will require the formulation of completely new indices based on a more flexible use of fish metrics according to system typologies, relevance and, probably, an increased use of functional traits. For current indices, further research on a method of intercalibration is needed. Key Message 02: BQE Fish in TW respond consistently to human pressure gradients across transitional waters providing the means to assess Ecological Status (ES). Further work will be needed to identify those specific pressures affecting fish assemblages providing targets for minimising the effects of stress in mitigation and restoration plans. Key Message 03 Although the interpretation of outcomes is still difficult, more recente transitional fish indices are leading in the use of comprehensive appraisal and validation exercises to test the performance of BQEs in the assessment of Ecological Status (ES). Further appraisal of fish indices behaviour is needed to understand the meaning of the quality outcomes, to set realistic management targets and also to identify the aspects of the índices that are more likely to affect the outcomes leading to more robust and responsive indices Key Message 04 Uncertainty levels associated with metric variability in multi-metric fish indices can be managed to increase the confidence in Ecological Status (ES) class assignment. Further research is needed to include knowledge of habitat partition within systems, to understand metrics behaviour and precision, to test new combination rules allowing metric weighting by robustness and importantly to evaluate more robust sampling tools and methods. Key Message 05 Reference conditions for BQE fish-based quality assessments can be objectively estimated using predictive modelling. Further refinements will require the use of better pressure proxies, robust metrics amenable to modelling and to account for survey design bias (effort & choice of sampling gear) at the relevant scales used in monitoring programmes.info:eu-repo/semantics/publishedVersio

Interactive effects of pesticide exposure and habitat structure on behavior and predation of a marine larval fish

Coastal development has generated multiple stressors in marine and estuarine ecosystems, including habitat degradation and pollutant exposure, but the effects of these stressors on the ecology of fishes remain poorly understood. We studied the separate and combined effects of an acute 4 h sublethal exposure of the pyrethroid pesticide esfenvalerate and structural habitat complexity on behavior and predation risk of larval topsmelt (Atherinops affinis). Larvae were exposed to four nominal esfenvalerate concentrations (control, 0.12, 0.59, 1.18 μg/L), before placement into 12 L mesocosms with a three-spine stickleback (Gasterosteus aculeatus) predator. Five treatments of artificial eelgrass included a (1) uniform and (2) patchy distribution of eelgrass at a low density (500 shoots per m(2)), a (3) uniform and (4) patchy distribution of eelgrass at a high density (1,000 shoots per m(2)), and (5) the absence of eelgrass. The capture success of predators and aggregative behavior of prey were observed in each mesocosm for 10 min of each trial, and mortality of prey was recorded after 60 min. Exposure to esfenvalerate increased the proportion of larvae with swimming abnormalities. Surprisingly, prey mortality did not increase linearly with pesticide exposure but increased with habitat structure (density of eelgrass), which may have been a consequence of compensating predator behavior. The degree of prey aggregation decreased with both habitat structure and pesticide exposure, suggesting that anti-predator behaviors by prey may have been hampered by the interactive effects of both of these factors

Les indicateurs DCE estuariens : état des lieux à l'échelle européenne en avril 2009. Résumé exécutif

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARELa Directive européenne Cadre sur l'Eau (DCE Directive 2000/60/CE) vise à atteindre le « bon état » écologique et chimique des masses d'eau souterraine et de surface, ou le « bon potentiel » pour les Masses d'Eau de surface Fortement Modifiées (MEFM), d'ici à 2015. L'évaluation de l'état des masses d'eau doit être faite via l'utilisation d'indicateurs biologiques, chimiques et hydromorphologiques, dont le développement est à la charge de chaque Etat Membre (EM) et pose aujourd'hui encore de nombreuses questions. Le projet BEEST, « Vers une approche multicritère du Bon Etat/potentiel écologique des grands ESTuaires atlantiques Seine, Loire et Gironde », s'attache à faire un état des lieux (début 2009) des indicateurs estuariens développés en France mais également par les autres EM de la zone géographique Nord Est Atlantique. Les objectifs de cet état des lieux sont de : Identifier pour chaque indicateur les questions clefs sur lesquelles la dynamique française bute pour une application opérationnelle en estuaire de Seine, Loire et Gironde. Voir comment ces questions ont été traitées par les autres EM et si possible identifier des pistes de solution et/ou des contacts clefs sur lesquels les équipes françaises qui le souhaitent pourront s'appuyer. Présenter, à l'échelle européenne, une synthèse claire et succincte des démarches d'élaboration des indicateurs DCE estuariens, de leur état d'avancement, ainsi qu'une liste des principaux contacts et références bibliographiques. Apporter ainsi des éléments au projet Liteau BEEST et plus largement au groupe national DCE eaux littorales pour faire les meilleurs choix en matière d'élaboration d'indicateurs estuariens. Une liste de contacts pour chaque élément de qualité biologique a été dressé pour la France et les autres EM. Les recherches bibliographiques et enquêtes menées auprès des différentes personnes ressource ont permis de mettre en évidence que peu d'indicateurs DCE sont utilisables en zones fluviales tidales et qu'aucun indicateur n'est spécifiquement dédié à ces milieux. Il n'existe à ce jour aucun indicateur DCE estuarien entièrement finalisé même si pour une majorité d'éléments de qualité biologique des « V.1 » existent. Un processus itératif se met en place pour continuer à améliorer les premières versions. Des problématiques communes aux différents indicateurs DCE estuariens ont été identifiées. Il s'agit par exemple des difficultés liées à la représentativité de l'échantillonnage et, plus généralement, à la construction d'indicateurs ayant pour objectif de révéler l'état écologique des milieux naturellement très variables et stressés que sont les estuaires. Des problèmes sont liés à la détermination d'un état de référence en l'absence de consensus sur ce que doit être la référence. D'autres questions liées à la construction d'un indicateur au sens large, comme le choix de la ou des métriques qui le composent, leur assemblage, l'évaluation et la quantification de la fiabilité de l'indicateur (d'ailleurs demandée par la DCE) ont souvent été évoqué. Ainsi cette synthèse argue en faveur de plus d'interdisciplinarité entre les équipes impliquées dans la construction d'indicateurs DCE pour les estuaires, voire même toutes masses d'eau confondues. Enfin, il est à noter que d'autres indicateurs, non mentionnés par la DCE et donc non étudiés dans le cadre de la présente synthèse, pourraient également se révéler pertinents pour évaluer l'état écologique des masses d'eau de transition estuariennes

Les indicateurs DCE estuariens : état des lieux à l'échelle européenne en avril 2009 - Rapport

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARELa Directive européenne Cadre sur l'Eau (DCE Directive 2000/60/CE) vise à atteindre le « bon état » écologique et chimique des masses d'eau souterraine et de surface, ou le « bon potentiel » pour les Masses d'Eau de surface Fortement Modifiées (MEFM), d'ici à 2015. L'évaluation de l'état des masses d'eau doit être faite via l'utilisation d'indicateurs biologiques, chimiques et ydromorphologiques, dont le développement est à la charge de chaque Etat Membre (EM) et pose aujourd'hui encore de nombreuses questions. Le projet BEEST, « Vers une approche multicritère du Bon Etat/potentiel écologique des grands ESTuaires atlantiques Seine, Loire et Gironde », s'attache à faire un état des lieux (début 2009) des indicateurs estuariens développés en France mais également par les autres EM de la zone géographique Nord Est Atlantique. Les objectifs de cet état des lieux sont de : Identifier pour chaque indicateur les questions clefs sur lesquelles la dynamique française bute pour une application opérationnelle en estuaire de Seine, Loire et Gironde. Voir comment ces questions ont été traitées par les autres EM et si possible identifier des pistes de solution et/ou des contacts clefs sur lesquels les équipes françaises qui le souhaitent pourront s'appuyer. Présenter, à l'échelle européenne, une synthèse claire et succincte des démarches d'élaboration des indicateurs DCE estuariens, de leur état d'avancement, ainsi qu'une liste des principaux contacts et références bibliographiques. Apporter ainsi des éléments au projet Liteau BEEST et plus largement au groupe national DCE eaux littorales pour faire les meilleurs choix en matière d'élaboration d'indicateurs estuariens. Une liste de contacts pour chaque élément de qualité biologique a été dressé pour la France et les autres EM. Les recherches bibliographiques et enquêtes menées auprès des différentes personnes ressource ont permis de mettre en évidence que peu d'indicateurs DCE sont utilisables en zones fluviales tidales et qu'aucun indicateur n'est spécifiquement dédié à ces milieux. Il n'existe à ce jour aucun indicateur DCE estuarien entièrement finalisé même si pour une majorité d'éléments de qualité biologique des « V.1 » existent. Un processus itératif se met en place pour continuer à améliorer les premières versions. Des problématiques communes aux différents indicateurs DCE estuariens ont été identifiées. Il s'agit par exemple des difficultés liées à la représentativité de l'échantillonnage et, plus généralement, à la construction d'indicateurs ayant pour objectif de révéler l'état écologique des milieux naturellement très variables et stressés que sont les estuaires. Des problèmes sont liés à la détermination d'un état de référence en l'absence de consensus sur ce que doit être la référence. D'autres questions liées à la construction d'un indicateur au sens large, comme le choix de la ou des métriques qui le composent, leur assemblage, l'évaluation et la quantification de la fiabilité de l'indicateur (d'ailleurs demandée par la DCE) ont souvent été évoqué. Ainsi cette synthèse argue en faveur de plus d'interdisciplinarité entre les équipes impliquées dans la construction d'indicateurs DCE pour les estuaires, voire même toutes masses d'eau confondues. Enfin, il est à noter que d'autres indicateurs, non mentionnés par la DCE et donc non étudiés dans le cadre de la présente synthèse, pourraient également se révéler pertinents pour évaluer l'état écologique des masses d'eau de transition estuariennes

Les indicateurs DCE estuariens : Etat des lieux à l'échelle européenne en avril 2009, mise à jour en décembre 2010 - Rapport

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASARE [Relecteur_IRSTEA]Bagot, C. ; Bruchon, F. ; Dauvin, J.C. ; Desroy, N. ; Fisson, C. ; Lévêque, C. ; Ruellet, T. ; Sottolichio, A.La Directive européenne Cadre sur l'Eau (DCE Directive 2000/60/CE) vise à atteindre le « bon état » écologique et chimique des masses d'eau souterraine et de surface, ou le « bon potentiel » pour les Masses d'Eau de surface Fortement Modifiées (MEFM), d'ici à 2015. L'évaluation de l'état des masses d'eau de surface dites « de transition », telles que les estuaires, se fait via l'utilisation d'indicateurs biologiques (basés sur le phytoplancton, la flore aquatique, les invertébrés benthiques et l'ichtyofaune), chimiques et hydromorphologiques (Directive 2000/60/CE). Le développement de ces indicateurs est à la charge de chaque Etat Membre et pose aujourd'hui encore de nombreuses questions. En France, le projet BEEST - « Vers une approche multicritère du Bon Etat/potentiel écologique des grands Estuaires atlantiques Seine, Loire et Gironde » - est un projet national de recherche appliquée, multipartenarial et interdisciplinaire, qui a pour objectif principal d'appuyer les gestionnaires français dans la mise en place de la DCE sur ces trois estuaires. Il est co-financé par le MEEDDAT (Ministère de l'Energie, de l'Ecologie, du Développement Durable et de l'Aménagement du Territoire), l'ONEMA (Office National de l'Eau et des Milieux Aquatiques) et des partenaires locaux des trois estuaires : le GIP Seine-Aval, le GIP Loire Estuaire et le SMIDDEST. La présente synthèse, qui porte sur les indicateurs DCE estuariens à l'échelle européenne, se place dans le cadre du projet BEEST et a pour objectifs : (i) d'identifier les questions clefs sur lesquelles la dynamique française rencontre encore des problèmes pour la création d'indicateurs DCE en estuaires de Seine, Loire et Gironde, (ii) de rechercher comment ces questions ont été traitées par les autres Etats Membres et si possible d'identifier des pistes de solution et/ou des contacts clefs sur lesquels les équipes françaises qui le souhaitent pourront s'appuyer, (iii) de présenter, à l'échelle européenne, une synthèse claire et succincte des démarches d'élaboration des indicateurs DCE estuariens, de leur état d'avancement, ainsi qu'une liste des principaux contacts et références bibliographiques, et enfin (iv) d'apporter ainsi des éléments au projet BEEST et plus largement au groupe national DCE eaux littorales pour faire les meilleurs choix en matière d'élaboration d'indicateurs estuariens. Afin de répondre au mieux aux questions posées, cette synthèse se focalise sur les pays de l'écorégion Atlantique Nord-Est telle que définie par l'Union Européenne (Anonyme, 2007b), et qui possèdent des masses d'eau de transition estuariennes : Allemagne, Belgique, Pays-Bas, Portugal, Espagne, Irlande, Royaume-Uni et France. L'ensemble des paramètres biologiques cités précédemment, les paramètres physico-chimiques généraux (Directive 2000/60/CE), et les paramètres hydromorphologiques sont étudiés. Pour chacun d'entre eux, les éléments suivants sont présentés : (i) un bref rappel des exigences DCE vis-à-vis de cet indicateur, (ii) son état d'avancement en France ainsi que les principaux problèmes rencontrés pour sa construction et/ou son utilisation en Seine, Loire et Gironde, (iii) un état des lieux des démarches adoptées par les autres Etats Membres, et éventuellement (iv) un approfondissement sur quelques points jugés pertinents. Enfin, quelques points de discussion ainsi que des perspectives de travail ressortant de cette étude sont présentés

Rendu D4.4-1 de Wiser : Bilan des indicateurs poissons pour l'évaluation de la qualité écologique des eaux de transition

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASAREEstuaries (areas where rivers meet with the sea) and other coastal areas have been under the damaging influence of human habitation since historical times. Human alteration to once pristine habitats for wildlife has resulted in symptoms of degradation including alteration of watercourses, water quality problems and loss of aquatic fauna such as fish. It is important that these habitats and wildlife are protected from further damage, and that damaged areas are restored through effective management plans. One way to assess habitat conservation status is to analyse a sample of fish living in an estuary. The presence of any fish species indicates that the basic ecological requirements (food, shelter and reproduction) and a minimum water quality or habitat availability are being met. Likewise, finding species with stricter habitat requirements indicates better conservation status and hence less disturbed conditions for that area. Researchers worldwide have used this basic principle to define habitat integrity in monitoring programs. This work reviews sixteen published fish-based indices of estuarine habitat integrity and summarises common development strategies with the aim of improving fish-based monitoring tools in Europe. Most indices are computed from a number of independent fish diversity measures, presence-absence of key species and composition of functional guilds (i.e. group of fish that rely on the same quality attribute). All index developers invest a large amount of effort on the formulation of the reference values, that is the quality or conservation value given to pristine, undisturbed, condition or reference status. Comparatively less effort is invested in the evaluation of the relevance and precision of the assessment. Only half of the indices reviewed attempt any validation and these are limited to simple comparisons between fish-based quality measures and human disturbance level. As yet, there are no fish-based quality measures applicable to all areas in Europe -also known as common metrics. Widening of the geographical relevance will require better precision in the formulation of reference conditions and greater inclusion of functional guild metrics. Improvements are therefore needed in linking human disturbance (or pressure) intensity to new European-wide fish indices and to improve the confidence and robustness of fish-based environmental quality assessment

Développement d'un indicateur multimétriques de qualité écologique basé sur la composante poissons: une méthode statistique originale de combinaisons des métriques

[Departement_IRSTEA]Eaux [TR1_IRSTEA]QUASAREInternational audienceWater framework directive context: Multimetric index detect anthropogenic pressure effects on biological component