CWT Program Overview

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cwt_collage.jpg The invention of micro-sized coded wire tags (up to 1.5 mm length) that could be easily implanted into the tough nasal cartilage of juvenile salmonids (see figure) greatly changed marking studies because of the numerous advantages over fin clipping.  

The first tags were developed in the 1960's and carried a dozen different colors and up to five longitudinal stripes enabling many different release groups of fish to be identified.  

Binary coded tags were later introduced in 1971 by Northwest Marine Technology, Inc. quickly replacing the color coded tags because of the greatly improved readability and the exceptional number of available codes.  In the late 1990s the new decimal coded tags were introduced further increasing the availability of unused codes while improving accuracy and readability.  This will be more than adequate for many years at today's tagging rates.  

The coded wire tag (CWT) is widely used by fisheries agencies on the West Coast as a major information collection tool for stocks of salmon and steelhead (Oncorhynchus spp.)  Resource management projects include hatchery contribution studies, differential treatment studies, fishery contribution studies, and a variety of other related studies which are important for fisheries management and research.  

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