FEDZ: Coded-Wire Tags (CWTs)
The coded-wire tag (CWT) is a small piece of magnetized stainless steel wire with a code etched on the surface. A standard-sized CWT is 1.1 mm long x 0.25 mm diameter and is generally used on juvenile salmon larger than 2 g in weight. For smaller salmon averaging as little as 0.2 g, tags half this length can be used (lower picture).
Since the late 1960's, CWTs have been the primary means for marking Pacific salmon (Oncorhynchus spp.) for stock assessment, harvest management, and enhancement evaluation. Because anadromous salmonid stocks range the length of the Pacific coast from California to Alaska in their migrations from natal stream to the ocean and back to spawn, they typically traverse many different fisheries in many different political jurisdictions. Recovery of salmon tagged as juveniles with CWTs has been the principal procedure used by fisheries agencies to assess stock abundance, manage fisheries, and protect stocks which are depressed, threatened, or endangered. Since 1968, 82 Federal, State, Indian, and private agencies in Alaska, Washington, Oregon, Idaho, California, and British Columbia have released over 600 million salmon with CWTs. Currently, over 45 million young salmon are marked with CWTs and released to migrate into the Pacific Ocean every year.
Information on the release, sample, and recovery of all CWT salmonids throughout the Pacific region is available in an on-line coastwide database, the Regional Mark Information System (RMIS). This database is maintained by the Regional Mark Processing Center (RMPC) of the Pacific States Marine Fisheries Commission (PSMFC) to facilitate exchange of CWT data between release agencies, sampling/recovery agencies, and other data users.
The FEDZ program at ABL is responsible for maintaining several different components of this coastwide CWT database:
- Release of CWT salmonids from research programs conducted at Federal facilities in Alaska such as Little Port Walter and Auke Creek.
- Recovery of CWT salmonids from Federal research programs in Alaska such as the Southeast Coastal Monitoring Program and the BASIS surveys , as well as adult returns to the research facilities at LPW and Auke Creek.
- Recovery and catch sample of CWT salmonids from bycatch in two commercial high seas fisheries:
Since 1980, over 5400 CWT salmonids have been recovered on the high seas from releases by 48 agencies.
- Gulf of Alaska groundfish fishery.
- Bering Sea-Aleutian Islands groundfish fishery
For more information on high seas salmonid coded-wire tag recover data:
Auke Bay Laboratories
Alaska Fisheries Science Center, NOAA Fisheries
Ted Stevens Marine Research Institute
17109 Pt Lena Loop Rd
Juneau AK 99801