Minas Gerais Agency | Climatic variations can have impacts on fish farming in Minas Gerais

Fish farming in Brazil is traditionally practiced in an open environment. In this system, several factors can change the characteristics of the water body and, consequently, the environmental conditions to which the fish are subjected. Temperature variations and rainfall are among the aspects that most affect production.

“Rain can directly influence the level of tanks and reservoirs, altering the concentration of particles and nutrients and significantly affecting water quality parameters. Scarce rains harm the supply of tanks and very intense rains can cause damage by breaking dikes or overflowing the water body”, explains Alisson Gonçalves Meneses, researcher at the Agricultural Research Company of Minas Gerais (Epamig).

Temperature affects water quality parameters, especially dissolved oxygen, which is reduced under high temperatures and can lead to fish deaths. The greatest effect is on the metabolism of fish, as the body temperature of these organisms is regulated by the temperature of the environment.

“Temperatures outside the comfort zone are extremely harmful. Prolonged exposure of fish to low temperatures makes them more susceptible to parasites and diseases and can cause sudden death, especially in species from hot climates. Thermal amplitude is a particular point of concern, since fish are not very tolerant of abrupt variations”, warns the Epamig researcher, who adds:

“Animals generally have a considerable level of tolerance to environmental changes. However, complications can occur due to unexpected changes, such as those resulting from the irregular behavior of the climate in recent years”, adds Alisson.

Concerns and care in autumn

Phenomena such as El niño (which has occurred in recent months) and La niña (which is expected to prevail until spring arrives) create an imbalance in the environmental system and can interfere with fish production. Fish farmers must pay attention to weather conditions to avoid losses and losses in the production cycle and intensify their care with the arrival of autumn. “For this year, we are expecting periods of more intense cold and it is expected that these events will occur at the end of April, and that they will continue in the following months in a more intense and lasting way”, reports Alisson Meneses.

Monitoring and controlling water quality are essential, as is the adoption of measures to ensure the arrival of fish in good sanitary conditions during this period. “It is essential to maintain the renewal and control of the physical-chemical parameters of the water and to ensure that this operation does not further reduce the water temperature in cold periods”, advises the Epamig researcher, who also highlights four other points that fish farmers should be alert:

• pH balance, if the index that determines the degree of acidity of the water is below 6.5 (therefore acidic), it is necessary to lime it, preferably with agricultural limestone, since fish do not tolerate variations in the index;
• Supply of complete and balanced food, taking care to avoid leftovers;
• Monitoring the volume of water in the tank, in order to avoid sudden variations in water quality and temperature;
• Use of aerators to maintain dissolved oxygen levels and assist in water destratification.

Another strategy is the adoption of lower population densities in tanks and breeding sites. And the high consumption of fish during this Holy Week period can be a profitable ally for this measure. “The possibility of intensified slaughter should be considered to reduce the population in the tanks, even if the fish are smaller than desired”, recommends Alisson Meneses.