Although twaite shad (Alosa fallax Lacépède 1803) declined substantially in many European rivers, its numbers increased since 2007 in the Belgian Zeeschelde. Since twaite shad is of conservation concern, further knowledge on its migration and reproductive behaviour is needed and acoustic telemetry would be a relevant tool to assess these behaviours. Shads are very sensitive fish showing adverse reactions to handling and anesthesia, specifically twaite shad. Therefore, this species is rather unsuitable for internal implantation of electronic tags, such as acoustic, radio and data storage tags. Preliminary tests are needed to assess the impact of external tagging on twaite shad survival. Here we describe a fish friendly attachment procedure to externally tag the fish. The procedure is quick and may limit additional drag force on swimming as the tags are firmly attached to the body by a rubber plate. This procedure was developed in Belgium in spring 2015 to tag eight shads in the Zeeschelde. Five of these shads showed a migration pattern that generally corresponded with spawning activities observed visually in the river.
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