Experiences and results with telemetry track-ing of smolts and parrs in Belgium

Abstract

1. History of the Meuse salmon project in Walloon Region

A 'Meuse Salmon' project aiming at restoring an Atlantic salmon run in the River Meuse basin was put forward in 1983 (after the discovery of several 'sea trout' in the Meuse near Liège) and started officially in 1987 as a contribution of Wallonia to the European Year of Environment. In the course of this programme, most dams (3-8 m in height) obstructing the canalised River Meuse in Belgium and The Netherlands have been fitted with modern fish-ways in order to restore the free circulation of diadromous fish species. A second facet of the Salmon Meuse programme consisted in restocking salmonid streams in the Belgian Ardennes with hatchery reared salmon parr and smolt (maximum 200.000 fish per year) from foreign origins (Scotland, Ireland and France). Returning adult salmon have been scientifically recorded in the Meuse in The Netherlands (estuary and lower course) since 1994 but only since the year 2002 in Belgium: 13 (61-79 cm FL) fish in 2002 and 2 (71-76 cm FL) fish in 2003 caught mostly (13 fish) in a new big fish-pass at the Visé-Lixhe dam and (2 fish) in the River Berwinne, a small tributary of the Meuse known as the last spawning place for S. salar in Belgium in the 1920's. In 2004 returning adult salmon were not recorded in Belgian waters. Female and male returning salmon in 2002 were successfully artificially reproduced in order to build a captive freshwater brood stock to be used for production of parrs and smolts of the new Meuse strain. In 2006 a new salmon farming center will be inaugurated in Erezée (River Aisne) and will produce 200.000 juvenile Atlantic Salmon per year.

2. Monitoring of the downstream migration of smolts

As the return of adult A. salmon in spawning tributaries will be permitted by the building of efficient fish passes, the success of the Meuse salmon project will mainly be influenced by the potentiality of smolts to migrate downstream. Hydroelectric power plants are frequent in the River Meuse and in its tributaries and new installations are scheduled in the next years. In wallonia, the dynamic of the downstream migration of A. salmon smolts was essentially studied in a small downstream fish trap located in the river Samson, a small tributary of the R. Meuse. Precious informations on the timing of migration and on the characteristics of the migrants were annually collected since the late eighties. In 2000, a downstream migration trap was experimented in the Visé-Lixhe dam in the main course of the river Meuse. Results bring additional information on the potential cumulate mortality between the River Samson and the Lixhe dam using mark-recapture techniques. Currently our objective is to study the entire dynamic of the downstream migrations of the smolts from the tributaries, to the Belgian border using biotelemetry techniques. A first successful experiment was carried out on 2004 on a single sea trout smolt individual that was continuously radio-tracked from Liège to Lixhe from a small boat. This spring, a similar experiment on a greater scale (up to 20 tracked individuals) will be carried out in the river Meuse and its tributaries.

The communication briefly presents the different results of the monitoring of the downstream migration of smolts in Wallonia and give informations on the techniques and methodologies employed as well as new challenges for the future. An additional part of the communication reports on results of a parallel research axis as concerns the behavioural ecology of A. salmon parrs using radio telemetry.