We surveyed the River Durme and River Rupel, Flanders, between 5 April and 17 April 2007 respectively. Both rivers are transitional waters belonging to the Schelde estuary. The Durme River is a tributary of the Schelde River in Flanders. It is a relatively small tidal river meandering through the valley. This valley consists of generally low-lying terrain, which is currently nearly entirely protected by dykes against the tides. The Rupel connects the Rivers Nete, Dijle, Zenne, Demer and Gete with the River Schelde. Since 22 March 2007 the water purification station Brussels North is functional. This will improve the water quality of the River Zenne and will therefore reduce the pollution load of the river and has its impact on the Zeeschelde as well.

Fish assemblage data were obtained using fyke nets placed for a period of 24 hours. The nets were placed at low tide, emptied the next day at low tide and removed. We surveyed three sites in each river using two fyke nets per site. Table 1 and map in annexe provide the co-ordinates of the sites.
Table 2 gives the methodology used.

We only recorded abiotic parameters at one site. They are pH, oxygen concentration and water temperature (Table 3). Table 3 also provides descriptive information of the sampled sites. Additional information on abiotic parameters were obtained by the Flemish Environment agency.

Fish data include species, individual total length and weight. Table 4 gives an overview of the collected species according to the methodology used. Table 5 presents the catch per unit effort per species. Table 6 gives EBI (Estuarine Biotic Index) values for the sites in the river Rupel for different campaigns.

River Rupel:
In total we caught 14 species: roach, bitterling, three-spined stickleback, perch, wels catfish, carp, crucian carp, eel, ruffe, rudd, ide, pumpkinseed, common goby and stone moroko. This indicates that the water quality in the River Rupel is improving. This is the result of the improved water quality in the Rivers Scheldt and Nete as well as the start of the purification of the River Zenne.

River Durme:
Here too we collected 14 species: bleak, chub, perch, bitterling, roach, Stone moroko, bream, carp, white bream, eel, ruffe, common goby, three-spined stickleback and ide. The catches indicate that the water quality slightly improved;

In general we are optimistic for both the River Rupel and Durme. The water quality for the River Rupel will improve and we hope this will be reflected in a diverse and sustainable fish population. For the River Durme we believe that it has an ecological potential and where possible its natural state should be respected and maintained.

This report is a contribution to the European Interreg IIIb North Sea project Harbasins, aiming at harmonising European river basin management.