A fish-based index of estuarine ecological quality incorporating information from both scientific fish survey and experts knowledge

Abstract

In the Water Framework Directive (European Union) context, a multimetric fish based index is required to assess the ecological status of French estuarine water bodies. A first indicator called ELFI was developed, however similarly to most indicators, the method to combine the core metrics was rather subjective and this indicator does not provide uncertainty assessment. Recently, a Bayesian method to build indicators was developed and appeared relevant to select metrics sensitive to global anthropogenic pressure, to combine them objectively in an index and to provide a measure of uncertainty around the diagnostic. Moreover, the Bayesian framework is especially well adapted to integrate knowledge and information not included in surveys data. In this context, the present study used this Bayesian method to build a multimetric fish based index of ecological quality accounting for experts knowledge. The first step consisted in elaborating a questionnaire to collect assessments from different experts then in building relevant priors to summarize those assessments for each water body. Then, these priors were combined with surveys data in the index to complement the diagnosis of quality. Finally, a comparison between diagnoses using only fish data and using both information sources underlined experts knowledge contribution. Regarding the results, 68% of the diagnosis matched demonstrating that including experts knowledge thanks to the Bayesian framework confirmed or slightly modified the diagnosis provided by survey data but influenced uncertainty around the diagnostic and appeared especially relevant in terms of risk management.

Incorporating Stakeholder Knowledge Into a Complex Stock Assessment Model, the Case of Eel Recruitment

“…The Bayesian framework allows expert knowledge to be used to build informative priors. Here we follow the approach of [41] to build priors through the analysis of questionnaires sent to stakeholders. The expressed opinions were heterogeneous and thus resulted in very large priors.…”

“…For the two other types of priors, which were based on stakeholders' opinions, we followed the approach of [41]. For each time series of commercial catch and each stakeholder having expressed an opinion, we drew 1000 values of the scaling factor in a uniform distribution ranging from the minimal bound to the maximum bound given by the stakeholder.…”

Early back-calculated size-at-age of Atlantic yellow eels sampled along ecological gradients in the Gironde and St. Lawrence hydrographical systems

“…1b and Table 1). The GIR site is known to be contaminated by anthropic and agricultural activities (Delpech et al 2010;Tableau et al 2013). The DOR site is considered as the least contaminated site in the watershed and the GAR site is located near the city of Bordeaux in a contaminated region (Tapie et al 2011).…”

A technical guide to develop a statistically valid fish-based index in compliance with the water framework directive: an evaluation for Turkish freshwaters

“…Principal component analysis (PCA) and canonical correspondence analyses (CCA) were used frequently to monitor responsiveness (see review, ter Braak and Verdonschot 1995). Multimetric regression models including linear mixed effect models have been favored to select responding metrics in the recent fish-based index studies (Tableau et al 2013;Breine et al 2015;Smolinski and Calkiewicz 2015).…”