VI Alpha Tags

Figure 1: VI Alpha in ambient light.

Figure 2: VI Alpha in UV Light

The VI Alpha tag is a small fluorescent tag with an alphanumeric code designed to identify individual specimens. VI Alpha tags are implanted internally but remain externally visible for easy recovery.

The tags are implanted with syringe-like injectors, and are available in several colors (black letters on a red, orange, or yellow fluorescent background or the reverse), and in two sizes: standard - 1.0 x 2.5 mm and large 1.5 x 3.5 mm. Because the tags are made from a biocompatible medical grade elastomer, they do not irritate the tissue at the implant site and seem to have little negative effect on the host animal when properly used.

Although many fish have transparent tissue (adipose eyelids, fin membranes, clear boney tissue, etc.), tag retention varies by species. For example, the adipose eyelids of salmonids have generally proven to be suitable locations for these VI Alpha tags, but implants into larger masses of similar appearing tissue in mullet (Mugulidae) have been rapidly shed, (further discussion of adipose eyelid tissue). Size of the tagged specimens is also important. Shedding rates from adipose eyelids of salmonids less than 150 mm total length have been excessive while retention in larger fish often exceeds 90%

Tagging sites in other body locations may also be used successfully. Various sites on the head appear to be particularly useful ( e.g., mandible in walleye Stizostedion vitreum (Larscheid 1995), and elsewhere on heads as reported by Buckley 1994 [Abstract]). Dorsal, anal, and adipose fins also provide potential targets (Crook and White 1995 [Abstract], Blankenship and Tipping 1993 [Abstract], Wenburg and George 1995 [Abstract]). Buckmeier and Irwin (2000) [Abstract] found that 100% of VI Alpha tags implanted in the dorsal fin of channel catfish Ictalurus punctatus were shed. However, researchers with the Iowa Department of Natural Resources have developed a very successful method of implanting VI Alpha tags into the tongue of flathead catfish (Pylodictis olivaris). Please see our Spring 2000 newsletter (PDF 45K) for further details.

Advantages of soft VI Alpha tags:

Provide individual identification
High retention rates in suitable tissue/species
Low capital costs
Tags detected visually and readable in live specimens without removal
Minimal impact on survival, growth and behavior
Visibility is enhanced using the VI Light.

Limitations of soft VI Alpha tags:

Unsuitable for very small fish
Not all species have suitable tissue.
Tag readability may become occluded by pigmentation.

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VI Alpha Tags

Advantages of soft VI Alpha tags:

Limitations of soft VI Alpha tags:

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