In aquaculture, parasites are like lurking "invisible killers", quietly eroding the health of fish and shrimp, causing slow growth and weakened immunity. In severe cases, they can even lead to large-scale deaths, causing heavy losses to farmers.
Today, we will thoroughly explain the types and sources of common parasites in aquaculture at one go, as well as practical deworming techniques. It's full of valuable information. It's recommended to save it!
I. "Blacklist" of Parasites in Aquaculture: These 5 Types of Killers Are the Most Lethal!
There are many types of parasites, but the following five are the most harmful:
Protozoa: including Eimeria, Amoeba enterotica, Tetrahymena piriformis, etc., mainly parasitize the intestinal tract, liver and other organs of fish, causing corresponding inflammation and functional disorders.
Worms: such as nematodes, flukes and tapeworms, they parasitize the body cavities, muscles and internal organs of fish, consuming the host's nutrients and causing symptoms such as emaciation and anemia.
Crustaceans such as the anchor head 鳋 and the Chinese 鳋 mainly parasitize on the skin, fins and gills of fish, causing inflammation and trauma, and affecting the breathing and movement of fish.
Others: Such as ciliates, bell worms, etc., which parasitize on the skin, gills or mouth of fish, also pose a threat to the health of fish.
Ii. Where do Parasites Come From? These four sources must be understood
The outbreak of parasites is not accidental but the result of the superimposition of three factors: pathogen, environment and fish body.
1. Accumulation at the pond: Years of aquaculture activities have turned the bottom mud of the pond into a "base camp" for parasite eggs, larvae and intermediate hosts. When the environment is suitable, they start to multiply rapidly and infect fish with weak constitutions.
2. Introduction of larvae: When purchasing fish larvae, it was not found that they carried parasites. This was mainly because the water temperature was relatively low when the larvae were released, and the parasites were in a latent state. Once the temperature rose, they began to fall ill in large numbers.
3. Cross-infection: When water is introduced into ponds, the external water source may carry eggs or parasites. If a parasite outbreak occurs in one pond of the same intake channel, the surrounding ponds will follow one after another.
4. Environmental factors: They play the role of catalysts in parasitic outbreaks. Deterioration of water quality, accumulation of organic matter, and insufficient dissolved oxygen can all reduce the resistance of fish and create favorable conditions for the reproduction of parasites.
Iii. Four-step Scientific Deworming Method
1. Purify water first, then kill pests: When the water is turbid or there is too much algae, suspended matter will adsorb pesticides, reducing the insecticidal effect. It is recommended to purify the water quality first (such as by using flocculants or changing the water) before applying the medicine. For ponds with excessive algae, the dosage of medicine can be appropriately increased.
2. Adjust pH to enhance efficacy: Most insecticides are acidic. If the pH of the water is too high (alkaline), it will neutralize the efficacy. The best time for application is around 9 a.m. (when the pH is relatively low). If the pH is greater than 8.5, it is recommended to adjust it with organic acid first and then kill the insects.
3. Enhance permeability and uniform diffusion: When the water density is high (such as excessive organic matter), fat-soluble drugs tend to float in the middle and upper layers and have difficulty penetrating to the bottom. Before applying the pesticide, organic acid can be sprinkled and the aerator can be turned on for half a day to improve the uniformity of drug diffusion.
4. Even application for comprehensive pest control: Fish instinctively avoid areas with high concentrations of pesticides. If the application is uneven, some parasites may escape. It is recommended to adopt the "well" shaped or cross-sprinkling method to ensure the even distribution of the medicine throughout the pool.