Precut Sequential Coded Wire Tags (CWT)

Refunds — there are no refunds on orders of Coded Wire Tags.

The CWT is a length of magnetized stainless steel wire 0.25 mm in diameter. The tag is marked with rows of numbers denoting specific batch or individual codes. Tags are cut from rolls of wire by an injector that hypodermically implants them into suitable tissue. The standard length of a tag is 1.1 mm. For very small animals half-length (0.5 mm) are used. For larger specimens or improved magnetic detection, one and a half (1.6 mm) or double length (2.2 mm) may be utilized.

Salmonid fishes are usually tagged in the snout, but "cheek" muscle and certain other tissue offers superior sites for many other species.

NMT has yet to encounter a fish, of sufficient size, that cannot be tagged. Arctic char Salvelinus alpinus as small as 22 mm total length have been successfully snout-tagged with half-length CWT (Champigneulle, et al. 1987 [Abstract]). Since body muscle also provides a suitable and much larger target than the snout of a char, it appears that smaller fish and other organisms can be successfully tagged. Although designed originally for small fish, Coded Wire Tags have been applied successfully in a number of crustacean studies.

CWT Tag Formats

The decimal coding (etching) allows for either batch or individual identification. Batch codes, identifying a group of animals sharing one or more characteristic, are most commonly used for fisheries management purposes.

Standard CWT have batch coding; the same code is repeated over a specific length of wire. Sequential CWT are designed to identify individuals or small groups; the code advances over a specific length of wire. The use of these sequential tags is somewhat more complex in requiring the saving or "archiving" of a CWT before and after the implanted tag or tags.

NMT produces five formats of CWT. Download the reading instructions for a complete description of each format.

- Standard.
- One and a half-length.
- Half-length.
- Sequential. > Only option for Precut Coded Wire Tags
- Agency-only.