First record of the round goby, <i>Neogobius melanostomus</i> (Actinopterygii: Perciformes: Gobiidae) in Belgium

Almost six years after the first finding of the round goby Neogobius melanostomus (Gobiidae) in the Netherlands, several specimens of this invasive Ponto-Caspian benthic fish were also recorded in the Belgian part of the River Scheldt and in the Albert Canal. This is the first record of the round goby in Belgium

Modelling the migration opportunities of diadromous fish along a gradient of salinity and dissolved oxygen in the Zeeschelde estuary (Belgium)

The relationship between poor water quality and migration opportunities for fish remains poorly documented, although this knowledge is essential for a correct implementation of the EU water legislation. In this chapter, we model environmental constraints that control the movements of anadromous and catadromous fish populations that migrate through the tidal watershed of river Schelde, a heavily impacted estuary in Western Europe. Local populations of sturgeon, sea lamprey, sea trout, Atlantic salmon, houting and allis shad were essentially extirpated around 1900. For remaining populations (flounder, three-spined stickleback, twaite shad, thinlip mullet, European eel and European smelt), a data driven logistic model was parameterized. The presence or absence of fish species in samples taken between 1995 and 2004 was modelled as a function of temperature, dissolved oxygen concentration, river flow and season. Probabilities to catch individuals from all diadromous species but three-spined stickleback, increased as a function of the interaction between temperature and dissolved oxygen. The hypoxic zone situated in the freshwater tidal part of the estuary was an effective barrier for upstream migrating anadromous spawners since it blocked the entrance to historical spawning sites upstream. Similarly, habitat availability for catadromous fish was greatly reduced and restricted to lower brackish water parts of the estuary. The model was applied to infer preliminary dissolved oxygen criteria for diadromous fish, to make qualitative predictions about future changes in fish distribution given anticipated changes in water quality and to suggest necessary measures with respect to watershed management

A reference list of fish species for a heavily modified transitional water as defined by the Water Framework Directive: the Zeeschelde estuary (Belgium)

A crucial step in the development of a fish-based index for the ecological assessment of water bodies as provided by the European Water Framework Directive is the development of a fish reference. This reference consists of a fish assemblage present in pristine water bodies of the same category. Based on historically reported fish survey data of the Zeeschelde estuary and its tributaries under tidal influence (Belgium), presence/absence reference lists were compiled for different salinity zones. These historical lists were then adjusted using information from recent catches. Inclusion of fish species in the reference lists depended on their natural geographical distribution and ecological demands. Fish species are attributed to guilds (functional groups) and therefore these reference lists contain guild specific information for the different zones within the estuary and its tidal tributaries. The reference corresponds with an ecological status that is referred to as Good or Maximal Ecological Potential (GEP/MEP)

Fish assemblage in European Western Highlands and Western Plains: a type-specific approach to assess ecological quality of running waters

After typological pre-classification of 398 calibration sites, fish-based metric models were used to predict the impact of human activities on river quality in European Western Highlands and Western Plains ecoregions. Calibration sites were grouped into six assemblage types and according to their geomorphology; test sites were assigned to their corresponding assemblage type. Five anthropogenic variables were used to describe the impact level of each site and stepwise discriminant analysis was performed to: (i) avoid redundancy between metrics; (ii) examine how selected metrics discriminated impact classes and (iii) predict ecological status for each site of the given fish type. Globally, this approach predicted the impact class correctly for 64% of sites. The difference between observed and predicted impact was more than one class for only 2.5% of the sites. When validating this approach with an independent data set, differences between observed and predicted impact values never exceeded 2 impact classes, but these differences varied in size among countries

Ecological goals and associated habitat needs for fish in estuaries: a case study of the Zeeschelde (Belgium)

We describe habitat needs for fish populations in estuaries needed to ensure the realisation of ecological goals. We take the view that Good Ecological Status (GES), as defined by the European Union Water Framework Directive (2000/60/EEC), is obtained when those ecological goals are fulfilled. The Zeeschelde estuary is presented as a case study for the description of ecological goals, but the described approach can be applied to all North Sea estuaries. In order to make the method widely applicable we first classify fishes into guilds, relevant for the formulation of ecological goals. Next we describe guild-specific ecological goals for fish. Based on the literature, habitat requirements for specific fishes are defined and used to define habitat needs allowing a proper functioning of the estuarine ecosystem. We describe habitat needs at a guild level and indicate how these can be achieved

Tidal marshes as habitat for juvenile fish in the Zeeschelde estuary (Belgium)

Little is known about the use by fishes of tidal marshes located in the mesohaline, oligohaline and freshwater tidal zone of an estuary. Two different fishing protocols were applied in order to assess: 1) spatial and temporal effects and 2) the influence of creek characteristics on the fish assemblages. In 2007 fish were sampled monthly from creeks in four tidal marshes, located in different salinity zones in the Zeeschelde. In 2008 nine creeks within one tidal marsh but each with different characteristics were sampled in spring, summer and autumn.Fish were caught in the creeks with winged fyke nets (1.5 cm mesh size in the cod end). For each creek we measured mouth width, level of bottom (versus mean low water level of the main river) and slope of the bank. Creek volume was calculated using cross section data, creek length and number of adjacent creek branches. In addition we recorded the presence of debris and permanent pools in both creeks and tributaries. In total we recorded 24 different fish species between 2007 and 2008 and catches were dominated by juveniles. The most abundant species was flounder. Multivariate analyses examined the variations of the fish assemblage in relation to position in the estuary and also to creek characteristics within one marsh. The influence of the salinity gradient is reflected in the different fish assemblages present in the four marshes. The highest number of fish tidal frame and containing permanent pools. The study emphasizes the importance of creeks in tidal marshes as habitats for juvenile fish

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

Fish-based indices monitor changes in surface waters and are invaluable to summarise complex information on the environment (Harrison & Whitfield, 2004). A Zone-specific fishbased 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 preclassified using indicators of anthropogenic impact. Metrics showing a monotone response with pressure classes were selected for further analysis. Thresholds for Good Ecological Potential (GEP) were defined from zone-specific 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 within each zone and translated into an Ecological Quality Ratio (EQR) to comply with the European Water Framework Directive (WFD). The indices measure fish community characteristics such as species richness and composition, species abundance and nursery function, as well as trophic functions when appropriate. As such they 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. Results indicate that the indices distinguish among various levels of degradation (94% matches)