What are the methods for killing parasites in large-scale aquaculture?
How do you kill parasites in large-scale aquaculture?
In recent years, diseases of aquatic animals in lakes and reservoirs have occurred frequently, among which parasitic diseases and fulminant hemorrhagic disease of fish have the highest incidence rates. Fulminant hemorrhagic disease is mostly a secondary condition of parasitic diseases. Therefore, good prevention and control of parasites is the key to disease prevention in reservoirs and lakes. The parasites are generally anchor worms (Lernaea), Chinese copepods (Sinergasilus), and dactylogyrus worms (Dactylogyrus). Anchor worm, Chinese copepod, and dactylogyrus diseases are generally prevented and treated with ivermectin (1%). The precautions for application are:
1. Calculate the volume of water to be medicated. For lakes with a water depth of less than 2.5 m, the dosage is “water surface area x actual water depth x unit dosage”. When calculating the water volume of relatively deep reservoirs, reference must be made to certain data: the current water level and the reservoir capacity corresponding to the current water level. The method is: [reservoir capacity corresponding to the current water level - reservoir capacity corresponding to (current water level - 2.5 m water level)] x unit dosage. The dosage calculated by the above method must also take into account the pH value and transparency of the water body and be adjusted as necessary.
2. Choose a sunny morning between 8 and 10 a.m. when the fish are not gasping at the surface to apply the medication; application is best when there is no rain within three days.
3. Application should be as uniform as possible; the more uniform, the better the effect. When applying, use more fishing boats and assign more workers to finish applying the medication in a short time.
4. Choose to apply the medication when there is no wind or only a light breeze. When applying in windy conditions, apply less medication or none within 10-15 m from the shore on the downwind side of the water area, and especially reduce the dosage as appropriate in shallow shoals and branching bays on the downwind side.
5. According to the depth and natural form of the water area, allocate the dosage by reasonably dividing it into blocks, so that the medication is applied evenly throughout the water area, avoiding insufficient application in some areas and excessive application in others, which would reduce the treatment effect.
6. After application, use a motorboat to travel back and forth several times along the application route within the water area, which serves to drive the fish schools and mix the medication evenly, thereby improving the medication effect.
In large-scale aquaculture, once parasitic infestation is found, medication should be applied as early as possible rather than late. Delaying the treatment opportunity may further affect fish feeding and growth, and in severe cases may lead to fulminant hemorrhagic disease in fish, causing farmers relatively large economic losses.