Key Points of Eel Farming Technology and Daily Management Methods
The secret to farming eels is "have principles, no fixed rules!" and it relies on accumulated experience! This is the wisdom passed on to us by eel farmers, and in farming technology it relies even more on accumulated experience. Below is the farming technology we have summarized by combining the views of books, eel research experts, and eel farmers.
I. Farming Density
Farming density varies according to the size of the eels. Usually during the glass eel stage, because they need special care, they are all kept in the same pond for easy tending, so the stocking density is relatively high; as the eels grow larger and larger, the farming density must become lower and lower. For example: to produce 100000 tons per hectare, 83000 glass eels or 60000 eel fry need to be stocked; by the time each one reaches 10 grams, the stocking rate is 3-6 kg/sq m. Generally speaking, for one ping, 3.3 sq m, stocking one kilogram is most suitable.
II. Water Quality Management
Eels grow in water, and the quality of the water is the key to eel farming; maintaining good water quality can protect the health of the eels in the pond. In water quality management, pay attention to:
1. Hydrogen ion concentration: the pH value represents the acid-base nature of the water. The pH range in which fish can live is between 5-10, and slightly alkaline water quality is better than acidic.
2. Dissolved oxygen: oxygen is an important element for living things to sustain life. Terrestrial organisms obtain oxygen from the air, while aquatic organisms rely on dissolved oxygen in the water. Eel farmers all have aeration equipment, with all kinds of electric paddle wheels, using the paddle wheels to stir the pond water to replenish oxygen.
3. Waste discharge: half an hour after the eels feed, the bottom is cleaned and about 10 cm of water is drained, then water is added back to the original level.
4. Stabilizing water quality: 0.5-2.0 ppm of potassium permanganate, or 10-30 ppm of formalin, can be added.
5. Aquatic plants: an appropriate amount of aquatic plants can absorb nutrients in the water, reduce water pollution, and help stabilize water quality.
6. Polyculture with other fish: some eel farmers will polyculture other fish species, which on one hand serve as indicators of water quality and on the other hand can help purify the water, but care must be taken about competition for food from other fish species. Commonly polycultured fish species include Zacco platypus, snakehead, silver carp, and grass carp, etc.
III. Common Eel Diseases and Treatment Methods
1. How do you know an eel is sick?
When feeding the eels every day, eel farmers carefully observe the eels' feeding behavior and their appearance. Once signs of illness are found, appropriate treatment is given.
2. What should be done when an eel gets sick?
When eels get sick, you do not catch them one by one to feed them medicine! Usually the treatment drugs are mixed into the feed, or sprinkled throughout the pond. Will these treatment drugs accumulate in the eels' bodies and harm the people who eat them? Usually these drugs have a certain effective period, and after the effective period has passed, they have already been digested and metabolized in the eels' bodies and will not harm the human body.
3. Common eel diseases include bacterial diseases and parasitic diseases. The following lists several common diseases and treatment methods.
(1) Bacterial diseases include vibriosis, red fin disease, red spot disease, etc. Symptoms include reduced appetite, enlarged spleen, bleeding in the gills and muscles, reddened fins, skin inflammation, generalized pinpoint bleeding, etc. Treatment methods include changing the water, improving water quality, reducing the salt concentration in the water, removing dead and diseased fish, raising the water temperature to 26°C~27°C, antibiotic treatment, etc.
(2) Parasitic diseases include white spot disease, wheel worm disease, Dactylogyrus disease, Gyrodactylus disease, Chilodonella disease, swim bladder nematode disease, etc. Symptoms include reduced appetite, itching, white spots, ulceration, etc. Treatment methods include raising the water temperature, soaking in 0.9~1.5% salt water at 25°C