Photo #1: Full length Coded Wire Tag sitting on a penny. Actual length is approximately 1 mm.
PHOTO #2: A thermal marked chum otolith. Here the rings are formed by temperature changes in the incubation water. Each of these light and dark rings was created over a 12 hour period, with the exception of the last ring in each band. Since it’s expensive to heat water with a boiler, only the last 12 hours of the 2 day period between bands receives heated water. This results in a “smear”, where the last ring in a band becomes very wide. Three of them are visible here: one just below the arrowhead pointing to the heat cycle, and another just above the arrowhead pointing to the chill cycle. Can you find the third one?
PHOTO #3: A dry marked coho otolith. The first band of the mark has 2 rings, and the second band has 5 rings. Each dark ring was the result of moist eggs being exposed to the air for 24 hours. The light rings (the spaces between the dark rings) were caused by incubation water submerging the eggs for 24 hours. The light colored space between the 2 bands was created by submerging the eggs for a period of 4 days. When the final dark ring is made, the incubation water is turned back on and remains on thereafter. This mark is read as 2,5H. The “H” represents the hatch, and indicates that the entire mark was produced before hatching occurred, which is a requirement when dry marking.