Inhaltszusammenfassung

We quantified the loss of detection efficiency of passive integrated transponders as a function of group size in groups of marked fish and dummies for two different single half-duplex (HDX) antenna systems in the lab and in the field. Video cameras were used to determine group size, and detection efficiencies were calculated from the num- ber of tags successfully detected. We used Cyprinidae species tagged with 12-mm tags in the lab and dummies containing 12- and 23-mm tags (separately and co...We quantified the loss of detection efficiency of passive integrated transponders as a function of group size in groups of marked fish and dummies for two different single half-duplex (HDX) antenna systems in the lab and in the field. Video cameras were used to determine group size, and detection efficiencies were calculated from the num- ber of tags successfully detected. We used Cyprinidae species tagged with 12-mm tags in the lab and dummies containing 12- and 23-mm tags (separately and combined) in the field. Detection efficiencies decreased sharply with increasing group size, independently of experimental conditions. With three tags passing as a group, estimated detection efficiencies were as much as 85%. For groups of 15 tags, the detection efficiency was as low as 16%. Using different sized tags together revealed that the presence of larger tags can reduce the detection efficiency for smaller tags to values close to zero (3%). We conclude that the detection efficiency of HDX antennas are reduced when two or more tags appear simultaneously. This potential reduction of detection efficiency has to be considered carefully in experimental design.» weiterlesen» einklappen

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