Coded wire tags size 1 millimeter. Size comparison to a penny.
Coded wire tags are placed in the snout of some fingerling salmon. The coded wire tag has numbers laser etched on the tag.
When adult fish return , fish are checked for tag with metal detector. Information about the fish are taken (sex, length, species)and a section of the head removed for dissection of the tag at a later date.
When the tags are read, the information is placed in a data base that is available to numerous agencies.
You are free to use this image with the following photo credit : Ron Wong/USFWS