Environmental determinism of year-to-year recruitment variability of European eel Anguilla anguilla in a small coastal catchment, the Fremur River, north-west France

The influence of environmental factors (mainly the river flow) on the year-to-year variability of European eel Anguilla anguilla fluvial recruitment in a small coastal catchment, the Fremur River (north-west France) was examined. A comprehensive survey of catches from fixed traps at two weirs located at 4.5 km (Pont es Omnes Dam) and 6.0 km (Bois Joli Dam) above the river mouth was carried out between 1997 and 2004. Young pigmented elvers (mean +/- s.d. total length, 133.7 +/- 29.6 mm) were recruited in eel-passes from February to October, but the main runs followed a modal curve from April to September with a peak centred in May to June. Catches varied greatly between years, from 381 to 26 765 elvers. For each trap, a positive linear relationship between monthly mean river flow that preceded the maximal intensity of captures and annual total catches was observed. These relationships explained 73.1% (P