NMT visible and coded marking

Northwest Marine Technology, Inc. (NMT) is one of the leading U.S. manufacturers of fish and aquatic animal tagging systems, widely used in fisheries science, aquaculture, and ecological monitoring. NMT provides tagging solutions suitable for small research projects as well as large-scale marking programs.

Coded Wire Tags (CWT) — Internal coded tagging

Principle:
Coded Wire Tags are very small magnetic stainless-steel wire tags (≈1.1 mm long), laser-etched with a numeric code. They are implanted into fish tissue (commonly in the head) using a specialized injector.

Key features:

• Individual or batch identification using numeric codes

• Invisible once implanted, ideal when external identification is not desired

• Detection using handheld or tunnel magnetic detectors

Typical CWT kit / system includes:

• Spools of coded wire tags

• Mark IV injector (automatic cutting and insertion)

• Needles, head molds, and positioning accessories

• Tag detectors and quality control tools

• Technical documentation and manuals

The Mark IV system is the industry standard for high-volume tagging (thousands to millions of fish).

Visible Implant Elastomer (VIE) — Visible color marking

Principle:
VIE tagging uses a biocompatible colored elastomer injected under the skin or into translucent tissue. Once cured, the mark remains visible for long periods.

Key features:

• Available colors: red, yellow, green, orange, blue, pink, and non-fluorescent options

• Fluorescent visibility: some colors fluoresce under blue or UV light using a VI Light

• Applications: ideal for batch marking and distinguishing multiple groups by color and injection location

Typical VIE kit includes:

• Colored elastomer vials and curing agent

• Injection syringes and needles

• VI Light (fluorescent detection lamp)

• Coding guides and user manuals

Commonly used for small fish, juveniles, and studies requiring direct visual identification without electronic equipment.

Visible Implant Alpha (VI Alpha) — Visible alphanumeric tags

Principle:
VI Alpha tags provide visible individual identification using small alphanumeric characters embedded in a fluorescent implant.

Key features:

• Unique alphanumeric codes, available in sequential sets

• Two standard sizes (small ≈1.2 × 2.7 mm; large ≈2 × 5 mm)

• Easy implantation using a dedicated VI Alpha injector

Typical VI Alpha kit includes:

• Sets of alphanumeric tags

• Injector and specialized needles

• VI Light for improved visibility and reading

• Storage case and documentation

 Particularly suitable for individual-based studies, such as growth, movement, or behavior monitoring.