Detecting Coded Wire Tags with Handheld Wands: Effectiveness of Two Wanding Techniques

Abstract In the Pacific Northwest, magnetic detectors manufactured by Northwest Marine Technology are critical tools for recovering coded wire tags (CWTs) from Pacific salmon Oncorhynchus sp. without an external identifying mark. The handheld wand detector is commonly used at hatcheries and during stream surveys for sampling adult chinook salmon O. tshawytscha and adult coho salmon O. kisutch. The standard wanding technique recommended by the manufacturer was compared with a recently developed mouth wanding technique for their efficacy in detecting CWTs. For chinook salmon, the mouth wanding technique detected 98% of the tags present, which was significantly greater than the standard wanding technique (89% detection rate). Detection rates were more consistent among hatcheries using the mouth wanding technique than the standard wanding technique. In coho salmon, both techniques detected about 96% of the CWTs present. Neither technique matched the 100% detection rate of the tunnel, but the consecutive use o...