Fish farming ponds need proper water quality management and drainage equipment in working order to guard against rain

According to the weather forecast issued by the Central Weather Bureau on the 10th, the weather this week is affected by a stationary front and strengthening southwesterly winds, with showers or thunderstorms across Taiwan, especially in the western half where there may be locally heavy rain or above. Recently it is the harvest season for milkfish, white shrimp and hard clams, and Yeh Hsin-li, director of the Mariculture Research Center of the Fisheries Research Institute, suggests that farmers can first store seawater in the ponds, adjust water quality and enhance the ability of aquatic animals to adapt to the environment, and raise the connecting pipes at the pond edge to help drain surface rainwater, avoiding too drastic salinity changes that would affect the farming environment.

In aquaculture, water quality management comes first; depending on the needs of different species, there are freshwater and seawater farming environments, and the depth of the ponds also varies. The possible effects of sudden heavy rainfall include salinity changing too quickly and causing poor reactions in the farmed organisms, and pathogens in the pond causing the farmed organisms to get sick due to changes in water quality and temperature. In shallow ponds such as those for hard clams, heavy rain or overly vigorous drainage can stir up the bottom sediment, letting toxic ammonia nitrogen and hydrogen sulfide products affect water quality and cause hard clams to die.

Yeh Hsin-li suggests that farmers should prepare response measures early for the plum rain season. Whether the farmed organisms are fish, shrimp or shellfish, farmers can first improve water quality and strengthen the animals' resistance, such as by adding photosynthetic bacteria and probiotics, so that the farmed organisms can respond healthily to environmental changes. When a large amount of rainwater enters the pond, there is concern about whether salinity will change too much, so some seawater can first be stored in the pond; when rainwater enters the pond, there is then no fear of salinity dropping too fast. In addition, drainage facilities should be strengthened; for some equipment that uses connecting pipes for drainage, the position of the connecting pipes can first be raised to drain excess freshwater first and avoid affecting the water quality at the bottom. Finally, when the rain reaches a point of stopping, attention should be paid to salinity changes in the pond, and water wheels can be started at the appropriate time to distribute salinity evenly in the water. If the resistance of aquatic animals to the environment was strengthened beforehand, farmers will not suffer too much loss.

In addition to water quality management inside the pond, attention should also be paid outside the pond to the height of the pond embankment, and protective netting can be added when necessary to reduce the chance of fish pond embankments bursting or overflowing. Before heavy rain, the operation of equipment such as generators and water wheels should also be checked. After heavy rain, fish ponds can be sprinkled with an appropriate amount of zeolite powder, lime or calcium carbonate to stabilize water quality. Yeh Hsin-li added that temperatures have varied greatly recently and fish schools are prone to stress from environmental changes, so special attention should be paid.