THE piracema is a phenomenon that occurs with several species of fish around the world, being an important reproductive strategy. The word piracema comes from Tupi and means “fish climb”. The process gets its name because, every year, some species of fish swim upstream in search of suitable places for reproduction and feeding.
the piracema guarantees that the fish complete your life cycle and continue your species. When the phenomenon is interrupted in some way, reproduction is impaired, as the interruption interferes with the development of the gonads, the maturation of the gametes and in the spawn.
the piracema occurs in rainy periods and, as Brazil is a country of great proportions, it does not occur in the same period throughout its territory. During the piracema period, fishing must comply with regulations in each region. Examples of piracema fish are:
- piapara,
- salmon,
- piramutaba,
- Golden.
Read too: What are the differences between bony fish and cartilaginous fish?
What is piracema?
The piracema is the period when certain species of fish face
great journeys upriver in order to ensure a suitable place for their spawning and feeding. During the piracema, fish swim against the current in shoals, overcoming natural obstacles, such as waterfalls, and also those created by man, such as hydroelectric dams. Some species swim more than two thousand kilometers to reach the springs, which is an exhausting journey, but essential for reproduction.
Fish migration is extremely important for reproductive success, as it stimulates the development of ovaries and testes, gamete maturation and spawning. During the journey upstream, a series of hormonal changes are triggered, preparing the animal for reproduction. Environmental factors such as rain and temperature are related to hormone production.
At the time of fertilization, that occurs externally in migratory fish, the female releases eggs into the water for the males to fertilize. After fertilization, the current takes the eggs, which can reach calmer waters, which guarantee the development of the fingerlings. It is noteworthy that eggs can suffer from predators and unfavorable environmental conditions, causing many of them not to reach adulthood.
When does piracema occur?
The piracema occurs in the rainy periods, times when there is a greater abundance of food, which is fundamental for migrating fish. In addition, as debris accumulates in rivers, visibility in the water is reduced, which helps fish protect themselves from predators.
as the period of rains varies in each region, there is no way to accurately determine a period of occurrence of piracema throughout the national territory, however, in a large part of the country the period starts in November and extends to the end of February of the following year.
The influence of dams on piracema
A big obstacle for piracema is the presence of dams, which are responsible for interrupting the courses of the rivers. The fish, when trying to go upstream, encounter this obstacle and often get seriously injured, in addition to being very exhausted. It is at this point that many predators are fed up with food. Furthermore, the dam prevents the fish from finding the proper place to reproduce and feed.
To minimize the effect of these constructions, fish transposition systems were created. These systems often consist of a kind of ladder that facilitates the rise and fall of fish. This ladder was very useful in the countries of the northern hemisphere, however, in our country, the fish ladder still generates a lot of controversy.
A study conducted in 2008 showed that the fish ladder could favor extinction of these animals, as entire schools would be attracted to relatively poor places. The researchers concluded that the fish went up the river, but not down. This is because the post-dam environment is not suitable for spawning or for the development of fingerlings. Other works, however, show the opposite, that stairs are important and would be beneficial.
A work carried out in a dam on the upper Paraná River showed that many fish were observed repeating the movements up and down the river annually using the fish ladder, showing that these ladders guaranteed one good connection between the environments above the dam and below it.
Read too: 10 largest hydroelectric plants in the world
Fishing restriction during piracema
During the piracema phenomenon, fishing is prohibited (closed period), since the large shoals are in their reproduction period. The capture of large amounts of these fish at this time can lead to a decrease in the population of a certain species, thus harming the environment and everyone who takes their sustenance.
The spawning period varies in the different states of our country, therefore, the closing period of the piracema also varies. In Goiás, for example, the closing period of the piracema usually extends from November 1st to November 28th. February, while in Paraná, the period starts on October 1st and extends until the 1st of February.
Is important meet the resolutions published in each region and observe if changes occurred from one year to another. In Paraná, for example, the closed season ended on February 28th, but the observation of an anticipation of the fish maturation process caused the date to be changed.
Remember that the disrespect for the law can lead, for example, to the imposition of a fine and seizure of the fished material, therefore, before packing your gear and enjoying a fishery, find out about the species that can be caught, their minimum and maximum sizes and the amount that can be caught.
It is also important to make it clear that the subsistence fishing, carried out by riverside dwellers and traditional populations for consumption only domestic, with no commercial purpose, has different standards and should also be consulted in the normative.
By Vanessa Sardinha dos Santos
Biology teacher