Applying a long lasting and durable mark to the streamlined and slime-coated body of a fish or lamprey is problematic. Generic procedures enable only the marking of groups, for example, by injecting colors under the skin or mutilating fins like the non-regenerative adipose fin of salmons and trout.

Fish Trek only deals with long term behavior of fish that have been tagged with a PIT tag, telemetric emitter, external tag, VIP, or CW tag.

These methods of marking can be distinguished as both external and internal types. Whether a fish is internally tagged cannot be determined from the outside. At best, a small ventral suture indicates that surgery for application of a telemetric emitter or a larger PIT tag was performed. Usually, these tags are found while eviscerating a fish for consumption.

suture implantation site
(Foto: IfÖ)

A colored VIP tag implanted in the transparent tissue near the eye can be found during a close inspection of the fish. The printed code can be read with a magnifying glass. On the other hand, a CW tag placed into the snout tip of a tagged fish can only be found using a metal detector. To read the etched CW code, it must be removed from the tissue.

Even without their unique codes, internal and external markings provide information about the origin of a fish based on color, shape, and size, and we certainly request that you send all such tags to the address in the imprint.