Otolith

Otolith temperature marking device of Yakumo Salmon Office, Hokkaido Fisheries Research Institute

The temperature of the housing tank is artificially changed when the eggs are in the tank and the otoliths are marked (barcode).

遊楽部川サケ稚魚:salmon juvenile of Yurappu river

Thus, fish that are labeled in this way can be determined in which river they were released.

In other words, when an adult fish is captured, the otolith can be analyzed to determine whether it was born naturally or artificially inseminated, and if it was captured in a river, whether it returned to its mother river.