The reason why fish go upstream is that it can increase the relative speed of the current, and it can also increase the gap between the gill filaments, so that it can better absorb oxygen. In addition, if swimming against the water, it can also facilitate fish feeding, but also better control the direction of swimming.
1. Breeding migration: The purpose of most fish migration is to breed. Some fish will migrate from the open sea to the coastal areas, some will swim from streams and rivers to estuaries, and some will swim from the middle of the lake to the lake. This makes it easier for the young to feed and for them to hatch. Generally, breeding migratory fish will stop eating during this period.
2. Baiting migration: If the water where the fish live is short of food, they will also carry out baiting migration, and the destination is often a place with abundant food. This situation is more common in the juvenile period, because the growth process needs a lot of nutrition, so need to migrate to find food, and often in the process of migration, can achieve the goal.
3. Wintering migration: In addition to the first two factors, fish will also migrate during wintering. Because the temperature of the water area will decrease in winter, they have to look for a warmer place. Moreover, the lower the water temperature, the faster they will swim. If the water temperature is normal, they will swim a little slower.
