INLAND MIGRATION STUDY OF SEA-TROUT (SALMO-TRUTTA) INTO THE RIVERS RHINE AND MEUSE (THE NETHERLANDS), BASED ON INDUCTIVE COUPLING RADIO TELEMETRY

A new telemetric method, the NEDAP TRAIL System(R), has been developed to study sea trout migration in the delta area of the rivers Rhine an d Meuse. This method is based on inductive coupling between an antenna loop on the bottom of a river or canal and ferrite rod antenna incorp orated in a tag of the transponder type. Field tests showed that the d etection system functions well with a maximum antenna length of at lea st 550 m, a water depth of 15 m and a passing speed of the tag with 5- 6 m s(-1) at maximum. A first group of 18 sea trout (of the total numb er of 600 that will be tagged) was tagged in December 1996. By March 1 997 two of them had already been detected at different detection stati ons.