VIS - Reference freshwater monitoring in Flanders, Belgium (post 2013)

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. 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. Information on the data collected before 2013 can be found in Brosens et al, 2015. From 2013 data was collected, only by using a subset of the Fish Reference Network, the Flemish Reference Freshwater Monitoring. This subset holds about 300 measuring points. The methodology before and after 2013 is equal, except that in the post 2013 survey period multiple fishing events were performed on the same location (Depletion fishing).

Sampling

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 electric fishing, but additional techniques such as gill nets, fykes, and seine netting (variable sizes) were used as well. Electric fishing was carried out using a 5 kW generator with an adjustable output voltage of 300–500 V and a pulse frequency of 480 Hz. The number of electric fishing devices and hand-held anodes used depends on the river width (Belpaire et al. 2000). In riverine environments, electric fishing was carried out on both riverbanks in upstream direction. All fishes were identified to species level, counted, and their length and weight was measured (measurement data available upon request). Since 2013, electric fishing was carried out until depletion.

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.

Method steps

1. Water type: Running freshwaters (width: 1.5 m, depth: < 1.30 m) Method: electrofishing with 1 anode by wading Effort: 100 m
2. Water type: Running freshwaters (width: 6 m, depth: < 1.30 m) Method: electrofishing with 2 anodes by wading Effort: 100 m
3. Water type: Running freshwaters (width: > 6 m, depth: < 1.30 m) Method: electrofishing with 2 anodes by wading Effort: 250 m with 1 anode on each riverbank, 2 m from bank
4. Water type: Running freshwaters, streaming rivers (width: > 6m, depth: > 1.30 m) Method: electrofishing with 2 anodes by boat Effort: 250 m with 2 anodes on each riverbank, 2 m from bank
5. Water type: Canals, slowly running rivers (width: > 6 m, depth: > 1.30 m) Method: electrofishing with 2 anodes by boat AND 2 fykes Effort: 250 m with 2 anodes on each riverbank, 2 m from bank AND 1 fyke for 48 hours parallel with and on both riverbanks
6. Water type: Canalized rivers with too high conductivity for electrofishing (depth: < 1.30 m) Method: seine netting Effort: 100 m, two times complete seine netting

The dataset contains 64 fish species reported from Flemish watercourses, as well as a number of non-target species (mainly crustaceans). This dataset also includes a number of typical brackish water fish species which sometimes can be found in inland water sites in proximity to the sea and/or behind the sluice gates. The class of Actinopterygii is best represented (63 species), along with one Petromyzontida (Lampetra planeri) and 7 crustaceans from the order Decapoda.

1. Animalia
   rank: kingdom
2. Actinopterygii
   rank: class
3. Petromyzontida
   rank: class

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 enclosed waters, including cut off river arms, gravel pits, ponds, natural lakes, and artificial lakes; and riverine habitats, including head streams, tributaries, and canals part of the drainage basins of the rivers Yser, Scheldt and Meuse. These three drainage basins are divided into eleven Flemish river catchments, which are divided into 102 subbasins. Overall, there are 48 unique enclosed waters sampled at 792 locations and 419 streams and rivers sampled at 1,452 locations.