International eel symposium, 2003 - Quebec August 11, 2003
Oral Presentation

Glass Eel Abundance Trend in the Gironde Basin for the Period 1978-1999 and Speed Migration

Beaulaton, L. Cemagref, unité RAC Cestas 33612 France
Castelnaud, G. * Cemagref, unité RAC Cestas 33612 France

Presenter email address: gerard.castelnaud AT cemagref.fr

Abstract Text: The fishermen of the Gironde basin catch glass eel (Anguilla anguilla) using three fishing techniques : large push net, scoop net and recently small push net. The objective of this study is to obtain the most efficient abundance indicators from fishery data and to contribute to the knowledge of glass eel migration.Total catches, total efforts and CPUE for the three fishing techniques have been calculated with a classical statistic method for the period 1978-1999. Then general linear models have been used to estimate CPUE. The two series (large push net and scoop net) are consistent and indicate that the abundance of glass eel was divided by 3 to 4 beginning of the eighties and remained stable since 1985 with no sign of amelioration. A lag ranging from 30 to 40 days of the maximum of abundance between the rivers (scoop net) and the estuary (large push net) during the fishing season is shown by the analysis of the model effects. Cross-correlograms demonstrated that estuarine fishery (large push net) is correlated with river fishery (small push net). A measure of the mean speed of glass eel migration (from 3 to 4 km/day) has been deducted on a distance of more than 120 km.