Alaska Department of Fish and Game
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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.
Since 1968, 80 agencies in 6 states and British Columbia have used 52,818 codes and 1,166 miles of wire to tag 1.70 billion salmon and steelhead.
Since 1973, 22 agencies representing 53 different hatchery sites have used 9,130 unique codes and 74 miles of wire to tag 127 million salmon and steelhead released at 336 locations in Alaska.
Alaskan Sampling Information
Since 1976, 135 million salmon were sampled in commercial, cost recovery, and sport fisheries and spawning grounds at 222 locations throughout Alaska. To date, 376,117 individual sampling events have been recorded on forms and entered into the database. 1 million heads weighing approximately 1,098 tons were removed from adipose clipped salmon and sent to the lab in Juneau for tag removal and decoding.
Database and Report Generation Statistics
Forty-One years of Alaskan catch statistics, sampling information and CWT tag recoveries, and 49 years of coast-wide release data are maintained in a dedicated database. Catch/sample statistics for 609 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 run by lab staff upon request. Contact us if you need assistance with customized data retrieval.
Field Sampling with hand held computers
In 2006, the Division of Commercial Fisheries of the Alaska Department of Fish and Game instituted an Electronic Sampling application named CWT Mobile for the purposes of reducing paper form data capture of Commercial Samples.
When sampling commercial deliveries of salmon our personnel now enter all information into a hand held computer.
The data are transmitted over the internet to servers at the MTA Lab, validated and moved into the centralized database nightly.
This approach speeds up sampling, reduces errors, and provides managers with very accurate and current data.
For more information here is a Power Point presentation of the Electronic Sampling application and process:
Electronic Sample Acquisition in Alaska (PPT 1,963KB)