No.23 Salmon

It is a freshwater fish belonging to the family Salmonidae of the order Salmonidae, and is found in both rivers and the sea. They are born in rivers, migrate to the sea in search of suitable water temperature and food, and return to the river where they were born during spawning season. It is believed that they return to the river where they were born based on scent and magnetism. Salmon in the ocean are silver in color, while salmon in the river appear red in nuptial color, so the difference can be recognized by their appearance.
This sample was conducted at the request of NHK Enterprises, Inc. as part of NHK E-television's “Gyogyotto Sakana★Star” project.
The program HP of “Giggle at Sakana Star”: https://www.nhk.jp/p/ts/P58QMGP4K1/

CT scans showed that the basic skeletal structure was the same, but the river salmon had pointed tips on the upper and lower jaws.

In addition, the teeth of the ocean salmon are embedded in the flesh of the jaw, whereas the teeth of the river salmon are protruding due to the thinning of the jaw flesh. This is thought to be because they fast for two months before breeding. They use these teeth to protect their eggs from enemies.