THE piracema can be defined as a migratory movement in which some fish they move to the headwaters of the rivers, that is, upstream. The term piracema has an indigenous origin and means “the ascent of the fish” (pyre: fish and hundred: climb).
→ What is the function of piracema?
The fish's ascent is carried out because they seek to find the ideal place for reproduction. Usually the piracema fish are looking for a place with warm water, rich in oxygen and cloudy, since the clear water facilitates predation.
→ When does piracema occur?
Piracema occurs when fish notice changes in the environment that indicate that the season is favorable for reproduction. This season is when it rains more frequently, the water becomes more oxygenated and the days are warmer.
In the ideal environment, fish begin their migration upstream. This climb is extremely stressful for these animals, as the headwaters of the river may be located several kilometers from the starting point. Fish can reach the headwaters or settle in marginal ponds formed by increased rainfall.
Upon reaching the proper location, the fish are ready for mating. In the species that make the piracema, fertilization is external, that is, the female and male gametes are released into the water, where fertilization takes place. The eggs formed there can go down the river, being carried by the current or develop in the marginal lakes. It is noteworthy that, due to predation and other environmental factors, few individuals reach adulthood.
→ Why is piracema a period in which fishing must be controlled?
At the time of piracema, the closed season for rivers and inland waters. During this period, it is not possible to carry out any fishing other than subsistence fishing, which guarantees food for several people who live near river areas. During the piracema, a minimum size of fish that can be caught and the maximum amount per fisherman is established.
It is extremely important to control the fishing, since, when going up rivers, the fish become exhausted, which facilitates the action of fishermen, who can easily catch a large amount of fish. As piracema is a period of reproduction, the capture of adults reduces the number of individuals in the population.
→ The problem of dams
The construction of dams has a great impact on the piracema, as they form a great barrier for fish. The solution found in some places was the construction of steps that make it easier for the fish to climb, preventing them from tirelessly trying to cross the dam. However, the problem is that fish that go up hardly ever return and, furthermore, the environment is not suitable for the reproduction and development of new individuals, which hinders the maintenance of the species.
By Ma. Vanessa dos Santos
Source: Brazil School - https://brasilescola.uol.com.br/o-que-e/biologia/o-que-e-piracema.htm
