A zone-specific fish-based biotic index as a management tool for the Zeeschelde estuary (Belgium)

Abstract

Keywords:Biotic integrity Fish-based index Meso-and oligohaline estuary Freshwater European Water Framework Directive Zeeschelde a b s t r a c t Fish-based indices monitor changes in surface waters and are a valuable aid in communication by summarising complex information about the environment (Harrison and Whitfield, 2004). A zone-specific fish-based multimetric estuarine index of biotic integrity (Z-EBI) was developed based on a 13 year time series of fish surveys from the Zeeschelde estuary (Belgium). Sites were pre-classified using indicators of anthropogenic impact. Metrics showing a monotone response with pressure classes were selected for further analysis. Thresholds for the good ecological potential (GEP) were defined from references. A modified trisection was applied for the other thresholds. The Z-EBI is defined by the average of the metric scores calculated over a one year period and translated into an ecological quality ratio (EQR). The indices integrate structural and functional qualities of the estuarine fish communities. The Z-EBI performances were successfully validated for habitat degradation in the various habitat zones.

MONEOS – Geïntegreerd datarapport INBO: Toestand Zeeschelde 2016: Monitoringsoverzicht en 1ste lijnsrapportage Geomorfologie, diversiteit Habitats en diversiteit Soorten

“…De EQR waarde en beoordeling per jaar per zone in de Zeeschelde berekend met de zone specifieke index (Breine et al, 2010a …”

Strength and time lag of relationships between human pressures and fish-based metrics used to assess ecological quality of estuarine systems

“…A bibliographic review allowed us to select 8 fish-based indices used to assess ecological quality in estuaries composed by several metrics (Table 1; Chun et al, 1996;Deegan et al, 1997;Meng et al, 2002;Borja et al, 2004;Harrison and Whitfield, 2004;Coates et al, 2007;Uriarte and Borja, 2009;Breine et al, 2010;Delpech et al, 2010;Cabral et al, 2012). All the metrics constituting these indicators, i.e.…”

“…Indeed, methodologies to select metrics were often based on the response of biological/ ecological measures to a combination of pressures or few specific pressures (e.g. Deegan et al, 1997;Breine et al, 2010;Delpech et al, 2010), not necessary taking into account for the diversity of pressures but mainly constrained by available data, used then as a proxy for general human pressures. In some cases, because metric selection did not consider the strength and the time lag of the pressure-metric relationships (sometimes because of the initial objectives of indices), the indices sensitivity to some pressures were quite low.…”

“…Index and pressures abbreviations are detailed respectively in the Table 1 and in the Table 2. Whitfield, 2004;Breine et al, 2007;Coates et al, 2007;Breine et al, 2010;Delpech et al, 2010;Cabral et al, 2012) or averaging (i.e. Breine et al, 2010;Delpech et al, 2010) individual metrics scores, without taking into account their sensitivity and their variability.…”

“…In order to detect the impact of anthropogenic pressures on estuarine fish assemblages, a measure or a proxy of the stressor is often used to point out significant relationships (Deegan et al, 1997;Meng et al, 2002;Borja et al, 2006;Breine et al, 2007; Coates et al, 2007;Martinho et al, 2008;Franco et al, 2009;Uriarte and Borja, 2009;Breine et al, 2010;Delpech et al, 2010;Cabral et al, 2012), but it does not necessarily take into account all the diversity of anthropogenic disturbances. Furthermore, Courrat et al (2009) noticed that even if processes of biological response to pressures are known, they were never demonstrated in studies proposing fish-based indices for the assessment of estuarine systems.…”