Migrations, home range and seasonal habitat use of adult Barbel in the Border Meuse (Poster)

Fourteen adult (F.L. 47,5 -57,0 cm) barbel (Barbus barbus) were radio tagged (40 MHz) in the Border Meuse (Borgharen- Maaseik): 5 in May 2001, 3 in October 2001 and 6 in April 2002. From May 2001 till September 2002 fishes were localised weekly throughout the year and daily in April and May in order to localise spawning grounds and investigate seasonal migrations and habitat use. In winter with flows ranging from 250 to 2.500 m3/s four barbel present at the time were found in the main river bed at all times. Large structures such as boulders and trees were used as shelter. No migrations to different parts of the river occurred. In spring five out seven fishes near Maasmechelen migrated to a spawning ground near one of the islands. Both upstream (0,2 km) and downstream migrations (up to 2,6 km) were observed. The spawning ground was characterised by the presence of fine gravel. Three barbel present in the Geul, a tributary of the Meuse, showed distinctive different migrations towards potential spawning places. Migrations in summer and autumn are directed by changes in flow and habitat suitability. The home ranges of the barbel, ranging from 0,5 to 27,3 km, differ significantly in size between different parts of the river. Microhabitat suitability is determined by water depth, water current, flow and bottom structure. In spring daily migrations of up to 1,1 km are observed. In summer and winter daily migrations are usually limited. Reproduction of barbel in this part of the river Meuse is hypothecated by the availability of fine gravel, high water velocities and hydro peaking in spring. Home ranges of fishes occupying highly structured parts in the river, with continuous availability of suitable habitat for spawning as well as resting and foraging in both summer and winter, are significantly smaller.