Radio-tracking: a useful tool for the Aulne Atlantic salmon rehabilitation program

Résumé

Atwo-year radio-tracking study of Atlantic salmon was conducted on the Aulne, a small French coastal river. The behaviour of 129 salmon was studied from early July 1999 to mid-December 2000. The objective was to investigate patterns of upstream migration of salmon, in particular through the lower 70 kilometres of the river which is canalised. This enabled us to compare the passability of weirs and how this varied according to the type of fishpass facility. The technique of the cumulative effect of the obstacles indicates that less than 5 percent of the population is likely to get through the canalised part and reach areas that are suitable for spawning. The most serious obstacles were presented by the weirs located the furthest downstream and two others in the middle of the river. The study also enabled both an estimation of the impact of fishing activities and a comparison of the upstream migration capacities of wild and reared salmon. Radio-tracking thus provides managers with a tool for assessing the restoration plan in order to improve its efficiency