Comparison of tagging and tracking studies to estimate mobility and home-range in Barbus barbus

The mobility patterns of the cyprinid Barbus barbus were investigated in the River Ourthe (main tributary of the R. Meuse in Belgium; mean gradient : 1,63 p/1000; mean annual discharge: 24 m3/s) by tagging and radio-tracking fish (> 20 cm) in the same 25 km stretch of the river over the period 1972-1991. Water quality and fish habitats were well preserved in the area and no obstacle impeded the fish to move freely. Tagging study. From June 1973 to November 1974, barbel were caught with electricity and tagged individually with labelled oval bars (PRESADOM). Out of 3000 individually tagged fish, 736 individuals were recaptured at least once by electric fishing or angling over two years. Ninety percent of the fish move less than 2 km and only 0,8 % of the fish strayed further than 8 km (up to 42,9 km upstream). The home range of 129 fish recaptured at least twice (two to four times) extended over an average 1173 m (SD = 1339 m). The tagging study thus provided large samples of information on the overall mobility pattern of the barbel through precision on daily or seasonal variations in fish movement was lacking, especially with respect to the emigration-immigration component for population assessment. Radio-tracking technics were used to bridge this gap during a second research programme from 1989 to 1991. Tracking was done manually from the banks and we recorded around 40.000 locations of 21 fish equipped with surgically implanted transmitters (40 MHz, ATS). Barbel definitely showed home range behavior (75-2600 m) except under high floods and during the spawning season (late April-early June) when daily movements extended up to 12,6 km. Migration were almost followed by a precise (+/- 1 m2) homing to the residence occupied before. During winter, summer and early autumn, the home range was restricted to the size of the daily activity area. These results substantiated the mark-recapture research programme with respect to the emigration component, since the movements of barbel were minimum at the time of the year when fish were sampled by electric fishing.