Bottle-necks for restoration of the eel population, Anguilla anguilla (L.) of the river Yser basin (Flanders)

This paper describes some preliminary results on the status of eel populations in the river Yser and its tributaries. Data on glass eel migration at the river mouth during recent years are presented and compared with earlier observations. Populations of yellow eel were studied at several localities during 3 successive periods. Attention was given to all factors limiting development of normal eel stocks, especially migration obstruction to all stages. Suggestions for improving the aquatic habitat in order to ensure normal migration and restore the Yser eel population are proposed.