IMIS

The data are retrieved from the Fish Information System (VIS), a database set up to monitor the status of fishes and their habitats in Flanders and are collected in support of the Water Framework Directive, the Habitat Directive, certain red lists, and biodiversity research. The VIS database is described in Brosens et al. 2015. Additional information, such as measurements, absence information and abiotic data are available upon request.
Length and weight measurement data of the individual fishes, absence information, occurrence data since 2015, as well as abiotic data of the sampling points (Ph, temperature, etc.) are not included in the Darwin Core Archive and are available upon request.
Geographic coverage: Flanders is one of the three administrative regions in the country of Belgium, located in the centre of Western Europe. The Flemish region is situated in the north of the country and covers an area of 13,522 km² (44,29% of Belgium). Belgium has a temperate maritime climate that is influenced by the North Sea and the Atlantic Ocean with substantial precipitation in all seasons. The summers are moderate and the winters are mild. The two main geographical regions of Flanders are the coastal plain in the North-West and the Central plain, further inland. With 470 inhabitants/km², Flanders is one of the most densely populated areas of Europe. The three major rivers are the River Yser, the River Scheldt, and the River Meuse. All rivers in Flanders flow into the North Sea, but only the River Yser drains directly into the sea within the jurisdiction of Flanders. The dataset comprises the estuaries of the Zeeschelde, including tidal parts of the rivers Rupel, Durme, Zenne, Dijle and Grote Nete, and the River Yser. The River Scheldt is a 435 km long lowland river originating on the plateau of Saint-Quentin near Gouy, a small town in the French department of Aisne. The river enters Belgium close to Tournai. Then the river turns east, in the direction of Antwerp. After crossing the city of Antwerp, the Scheldt enters the Netherlands where it ends in the North Sea near Vlissingen. The tidal influence extends much further land inward than the freshwater-saltwater boundary. As a result, an extensive freshwater region under tidal influence is present. The tidal activity goes as far as Ghent, 160 km from the river mouth, where the tide is stopped by sluices. In the Zeeschelde (the Belgian part of the estuary), three zones are distinguished following the Venice system (1959): a mesohaline zone (5–18 g salt/kg) between Zandvliet and Antwerp, an oligohaline zone (0.5–5 g salt/kg) between Antwerp and Temse, including the Rupel tributary, and a tidal freshwater zone till Ghent including the Durme tributary. The marshes and mudflats create a valuable landscape for biodiversity. The Zeeschelde estuary is one of the last natural deltas in Western Europe and many areas near its riverbanks are marked as Natura 2000 areas (Figure 7). Especially its freshwater estuary areas are unique. The River Yser is a 78 km long river originating in Kassel, located in French Flanders. It enters Belgium in the province of West Flanders and drains into the sea near the town of Nieuwpoort. Sea and fresh water meet in an estuary, resulting in 130 hectares of tidal mud flats, salt marshes, dunes, beaches, and polders.
Taxonomic coverage: The dataset contains more than 60 fish species found in the estuaries of the rivers Yser and Scheldt, as well as 10 non-target crustacean and 2 gastropod species. The class of Actinopterygii is most represented (55 species). All the crustaceans in this dataset are from the order of the Decapoda.
Sampling methods: Standardized sampling methods were used as described in Belpaire et al. (2000) and Van Thuyne & Breine (2010) and are specified in the dataset as dwc:samplingProtocol. Per water body, the same method was used for each sampling event. The default method is paired fyke netting, which has been intercalibrated by the North East Atlantic Calibration Group, but additional techniques such as anchor netting, seine netting, pound netting, electric fishing, and eel fyke netting were used as well (Breine et al. 2011). All fishes were identified to species level, counted and their length and weight was measured. Fyke nets are relatively unselective fishing gear catching demersal and pelagic species (Hamerlynck and Hostens 1994) and also they are easy to install in a great variety of habitat types. As few studies compare fyke catches with other gear (e.g. Hinz 1989, Thiel and Potter 2001), we compared presence/absence data obtained with fyke nets with presence/absence data of fish impinged at cooling-water filter screens of the nuclear power plant of Doel situated in the study area. The data was collected in the same period between 1995 and 1998. During this period we collected the same species with both survey methods but the species richness per day per fyke net was generally higher than that obtained on the filter screens (Breine et al. 2007). In addition preliminary results from a gear intercalibration exercise in different estuaries in Ireland (Whyte et al. 2007) indicated that for species diversity, the results of fyke net catches are comparable to those obtained with other gear (beach seine, beam trawl, otter trawl).
Study extent: Over 2,000 locations in estuaries, inland rivers, streams, canals, and enclosed waters in Flanders, Belgium have been sampled, from March to November, since 1992. In 2001, these locations were consolidated in a monitoring network (“VISmeetnet”) of 900 sampling points. Four locations in the Yser estuary and 43 locations in the Zeeschelde were sampled since 1995. While the Yser estuary only covers a small geographical area, the Scheldt estuary is with 33,000 hectares one of the largest estuaries in Europe. It is also one of the few remaining European estuaries that includes the entire gradient from fresh to saltwater tidal areas (Van den Bergh et al. 2009). The 43 sampling locations in the Scheldt estuary are mainly located in the Zeeschelde, but also in the Rivers Durme, Rupel, Dijle, Zenne and Nete. The geographic coordinates in the dataset are those of the defined sampling locations (dwc:locationID). However, as these coordinates are not always exact the actual coordinates of the catch, which may be located further up- or downriver, the coordinate uncertainty (dwc:coordinateUncertaintyInMeters) has been set to 250 meter.
Quality control: Strict field protocols where used. The Manual for Application of the European Fish Index (EFI) (Fame consortium 2004) served as a guideline for electrofishing and was used in support of the EU water framework directive.
Purpose: The Fish Information System or VIS is a database created by the Research Institute for Nature and Forest (INBO) which is used to monitor the status of fishes and their habitats in Flanders, Belgium and to calculate the biotic integrity (Karr 1981, Belpaire et al. 2000, Breine et al. 2004, 2007, 2010) of fish assemblages. It contains data regarding occurrences, individual morphometrics, stocks, pollutants, indices, and non-native fish species. Sampling has been going on since 1992, the database model was designed in 1994 (Verbiest et al. 1994), the first database developed in 1996 (Verbiest et al. 1996), and the consolidated database set up in 2001. VIS is used for supporting NATURA 2000, an ecological network of protected areas in Europe and to calculate the EQR (Ecological Quality Ratio) in the framework of the EU Water Directive (Directive 2000/60/EC). Further, the database provides updated information for Flemish Red Lists of fishes and lampreys (Verreycken et al. 2014) and on the distribution status of non-native and invasive fish species. The data are also crucial in fish stock management and for reporting on the status of the European eel stock as required by the Eel Regulation (Council Regulation (EC) N° 1100/2007). This dataset is a standardized extraction of all estuarine species occurrences from VIS.
Issues with the dataset can be reported here.
The publication of this dataset was supported by the INBO as part of the Flemish contribution to LifeWatch.