Coded Wire Tag Fact Sheet

What is a Coded Wire Tag? Coded Wire Tags (CWT) are small pieces (0.25 x 0.5 or 1.0 mm) of stainless steel wire that are injected into the snouts of juvenile salmon and steelhead. Each tag is etched with a binary code that identifies its release group. Until recently all tagged fish also had their adipose fin removed. The adipose clip is the external flag identifying which adult fish bear a CWT to samplers, processors and fishers. Heads of all adipose clipped fish recovered in Alaskan waters are sent to a lab in Juneau where the tags are found using very sensitive metal detectors, dissected out of the head and decoded. Release, catch/sample and recovery data are merged and estimates of contribution of tag groups to sampled fisheries are updated each day. This stock identification tool is used by researchers and managers to evaluate success of hatchery practices, estimate survival, find out where release groups are caught and to determine stock contribution of sampled fisheries. Alaska's CWT release and recovery program is an integral part of a large coordinated coastwide program Coastwide Releases Since 1968, 75 agencies in 5 states and British Columbia have used 39 thousand codes and 671 miles of wire to tag 1.1 billion salmon and steelhead.

Alaskan Releases

Since 1973, 21 agencies representing 61 different hatchery sites have used 7 thousand unique codes and 61 miles of wire to tag 99 million salmon and steelhead released at 322 locations in Alaska.

Alaskan Sampling Information

Since 1976, 122 million salmon were sampled in commercial, cost recovery, and sport fisheries and spawning grounds at 215 locations throughout Alaska. To date 262,000 individual sampling events have been recorded on forms and entered on the computer.  1 million heads weighing 775 tons were removed from adipose clipped salmon and sent to the lab in Juneau for tag removal and decoding.

Database and Report Generation Statistics

Twenty-six years of Alaskan catch statistics, sampling information and CWT tag recoveries, and 34 years of coast-wide release data are maintained in a dedicated database. Catch/sample statistics for 574 strata and fishery contribution estimates are updated daily. Access to CWT information is provided over the World Wide Web through a report generator which allows users to filter data on a wide variety of variables. Results of queries can be provided to requestors as web screens, email attachments, or FTP files.  They are suitable for further manipulating using tools like Excel and Access.  Also, customized reports can be set up by our data processing staff, run on schedule and the results made available. Contact us if you need assistance with customized data retrieval.

Related Web Sites

Northwest Marine Technology is the provider of most tags and specialized equipment used for tagging Pacific salmonids.   The Regional Mark Processing Center maintains the authoritative U.S. copy of the complete coastwide Coded Wire Tag database. They also coordinate salmon fin marking.   The North Pacific Anadromous Fish Commission is primarily concerned with high seas salmon issues. It includes Japan, Russia, the U.S., and Canada. An extensive library of reports are available.    Columbia River Inter-Tribal Fish Commission maintains technical papers of Washington and Oregon salmon based on CWT analysis.   The Pacific Salmon Commission relies extensively on CWT studies to oversee treaty compliance.