Detailed Guide to Eel Cage Culture Technology: How to Raise Eels in Cages

In recent years, although eel market prices have fluctuated, choosing eel species such as the European eel, which has abundant fry resources and low prices, for seawater cage culture still offers promising prospects and very considerable economic returns.

Water quality environment It is advisable to choose an area near an estuary with an open water surface, good water quality, low wind speed, and a water depth that can remain above 4 m at low tide for placing cages. The water temperature should range from 8°C to 30°C, and the sea current speed should be below 1 m/s, with waters having a flow speed of 0.5 m/s being the best. Cage specifications For eel seawater culture, seamless mesh cages of 3 m×3 m×3 m or 6 m×3 m×3 m are suitable. The mesh sizes are: 0.5 cm for raising black fry eels and young eels, and 0.8 cm for growing adult eels. Place a 1 m×0.5 m×1 m multi-layer mesh rack inside the cage as an eel resting platform, and leave a 15 cm anti-escape mesh brim at the open top of the cage to prevent eels from escaping. Fry stocking For stocking eels, young eels are best, with a stocking density of 150 tails per sq m. If no young eels are available and black fry eels are stocked instead, the density is 500 tails per sq m. Before stocking, eel fry should first undergo medicated bath disinfection to prevent disease. Feeding management 1. Water quality management Water quality management in eel culture is especially important. The seawater specific gravity is required to be 1.01-1.02, dissolved oxygen above 5 mg/L, and pH 7-8.5. In recent years, some aquaculture farms have used the microbial preparation EM Original Dew produced through China-Japan cooperation to regulate water quality, soak and mix feed, and prevent fish diseases, gaining successful experience and achieving very good economic returns. 2. Feed feeding Eel feeding should follow the “four fixeds.” That is, fixed time: except in early spring and winter, when feed is given once at 8 p.m. every day, at other times feed is given once each at 5 a.m. and 8 p.m. every day. Fixed location: feed on fixed feeding platforms. Fixed quality: feed a complete formula feed supplemented with multiple vitamins specially used for eels. Fixed quantity: the total daily ration is calculated as a percentage of the total body weight of the eels: 15% during the adult eel stage, 3% during the young eel stage, about 5% during the black fry eel stage, and 0.5%-1% during high-temperature and overwintering periods. 3. Timely cage separation After about one month of rearing, eel density increases greatly and individual differences become even more pronounced, so screening and separate cage rearing must be carried out promptly, separating them according to physical strength and individual size. During screening and cage separation, operations should be careful and meticulous to avoid scratching the fish body, prevent infection, and carry out medicated bath disinfection. 4. Replacing cages To keep cages clean and sanitary, cages should be replaced in a timely manner. In summer and autumn, replace once every 10 days; in early spring and winter, replace once every 50 days. The replaced cages should be cleaned immediately for next use. 5. Daily management Implement group management for cages. Test water quality every day, and keep detailed records of weather, water temperature, pH, feeding, and disease prevention and treatment. Observe eel feeding and growth conditions, and handle problems promptly when found. Disease prevention and treatment To raise fish, first raise water; good water quality is the key to preventing eel diseases. If the water quality in the cage is polluted and not eliminated, gill rot, tail rot, “running frenzy disease” during high-temperature periods, and various parasitic diseases may break out. Keeping the water body always under the effective control of beneficial microorganisms is a necessary condition for successful eel culture, and one must never be careless. When symptoms such as bacterial gill rot disease appear, soak the diseased fish in a 100-fold high-concentration EM Original Dew dilution, or directly apply a 10-fold to 50-fold ultra-high-concentration EM Original Dew dilution to the affected area; generally, recovery occurs in 4 to 5 days. When bacterial enteritis occurs, a high-concentration EM Original Dew dilution can be mixed with feed and fed immediately, with very good results.