1. morphological characteristics of fish during spawning season
Reproduction-related morphological changes called "secondary sexual characteristics" are observed in salmon that return from the sea to the river for spawning. Males and females, which were difficult to distinguish in the open ocean, are also easier to distinguish due to secondary sexual characteristics.
2. Measurement of Body Length and Weight
Students measure the length and weight of males and females while anticipating them.
3. Observation of organs and removal of the brain Caution: this video contains dissection images.
First, the abdomen of the male during the spawning season is opened, and the gonads (testes), liver, pyloric caeca, stomach, etc. are observed. Next, the brain is removed to explain each part, and the pituitary gland, which is the center of hormone secretion, is taken out.
4. Otolith sampling Caution: this video contains dissection images.
The otolith in the head is taken out. The salmon at the Hatchery of the Fisheries Resources Research Institute are labeled with temperature on the otoliths so that their origin can be identified even in the open ocean.
5. Scale sampling Caution: this video contains dissection images.
Scales are collected from males during the spawning season. You can see the age and growth history from the scale pattern. However, it is difficult to remove the scales of fish during the spawning season, and it seems that they are having a hard time.
6. Observation of ovulated eggs Caution: this video contains dissection images.
The abdomen of the female during the spawning season is opened, and the eggs that have been ovulated and just before spawning are observed. Explains egg growth and maturation, egg membrane hardening and digesting enzymes.
