Thanks, Theo.
This biologist is holding a small walleye that just had a freeze brand. Down in the lower right hand side of the image is the actual marking device. The wooden box is holding the insulated bottle of liquid nitrogen. What is down in the bottom right of the picture is the metal fitting that connects to that bottle, thus connected to the cold temperature of the liquid nitrogen, and that fitting then sticks out through the wooden box. You simply hold the fish up against that cold fitting for 2-3 seconds, and you have your mark. It works best for simple marks like horizontal or vertical line, an x, an o, etc. More complex symbols tend to bleed together. Walleyes marked like this had pretty good mark retention, still being visible on most 18 inch walleyes 3 years later.
Obviously, if I would just post pictures myself, Theo wouldn't have to do stuff for me!!
