Analysis of Common Misconceptions About Soaking and Disinfecting Eel Fry

In many years of fishery production, aquaculture technicians have accumulated rich farming experience. Soaking fish fry in salt water for disinfection is one of the traditional practices of farmers in various regions. However, aquaculture experts in China and some @#@236@#@ farmers have found in practice that the method of soaking and disinfecting fish fry in salt water, which is widely used for other fish species, is not suitable for use in eel farming.

In early 2000, based on experiments, a scholar put forward the view that "using salt water to disinfect eels is unsafe." The experiment showed that after using salt water to disinfect the body of eels, the mucus secreted on the body surface of the eels increased greatly and sloughed off (this is a self-rescue response of eels when encountering external stimulation, similar to sneezing in humans before a cold), and weaker individuals died one after another, with the mortality rate 10-20% higher than that of the control group.

Pan Jianlin of the Jiangsu Provincial Freshwater Research Institute and others conducted experiments in early 2000 that further confirmed this: in ultra-low-concentration (0.2%) salt water, eels showed relatively lively swimming behavior, but quickly returned to normal; compared with the control group, however, more flocculent matter appeared at the bottom of the bucket (the product of sloughed eel mucus).

To further test the safety of salt water for eels, we carried out a special experiment on this in 2002. The experimental results showed that the sensitivity of eels to salt water is closely related to water temperature. At the same concentration, the higher the water temperature, the more obvious the reaction of the eels, and the mortality rate also increased significantly. At low temperatures, after soaking eels in 3-5% salt water, the mortality rate was more than 20% higher than that of the control group. When using 2% salt water to disinfect the body of eels, the survival rate of the eels during rearing was also clearly different from that of the control group (the mortality rate was more than 15% higher). The experiment proved that using salt water for body disinfection and soaking selection of eels does indeed involve unsafe factors.

Eels are "scale-free fish." Because they lack the protection of scales, whether caught with cages or by electrofishing, eel fry inevitably have wounds on their body surfaces. Soaking them in salt water is like pouring salt on a wound, and the stimulation to the eels can be well imagined.

The treatment method adopted by Dazhong Aquaculture Company is carried out in the eel pond, using alternating splashing of a virucidal drug (Shanbao Shadu Xianfeng) and a bactericidal drug (Shanbao Yindian), combined with oral detoxifying and anti-inflammatory drugs (Shanbao Bingduqing and Shanbao Lanpi Chuxue San) for comprehensive treatment. Practice has proved that the effect of this treatment method is obvious.

For those who do have the habit of soaking for disinfection, we suggest that everyone can use the following soaking method: in the container used for purchase and transport, add 5 grams of "Yingjiling" and 2 milliliters of "Shanbao Yindian" per 1 cubic meter of water. If the container used for purchase and transport is relatively small and it is difficult to soak during transport, soaking can be carried out promptly after transport back. The soaking time should be at least more than half an hour. Observation showed that after soaking treatment, the body surface mucus of the eels increased significantly, and the eels' vitality was enhanced. Using this soaking method, on the one hand, it enhances the anti-stress ability of the eels, and at the same time it can kill pathogens on the body surface of the eels, and it does not irritate the eels. After stocking, "Shanbao Shadu Xianfeng" should also be used for disinfection treatment.