Precautions for farming freshwater sharks in northern regions

Freshwater sharks are mainly distributed in Southeast Asia. According to body color, freshwater sharks can be divided into four types: black shark, white shark, gray shark and red shark. The first three body-color types are mostly raised as food fish, with the gray shark growing the fastest; the red shark, also known as the crystal pangasius, is mostly raised as an ornamental fish at the juvenile stage.

Freshwater sharks are tropical fish, with a suitable growth temperature of 20-30°C and an optimum water temperature of 22-28°C. Their tolerance to low temperatures is relatively weak. When the water temperature drops below 18°C, the fish's food intake and activity level decrease markedly; when the water temperature drops to 15°C, they basically stop feeding; and below 12°C, they begin to die. Freshwater sharks are omnivorous with a tendency toward animal food. Juveniles feed on zooplankton, while adults can feed on aquatic plants and artificial feed.

In 2003, the Liaoning Academy of Freshwater Fisheries Sciences introduced broodstock gray sharks and red sharks from Hainan for domestication and rearing. After 2 years of rearing and observation, some issues needing attention in raising freshwater sharks in the north were summarized. They are as follows:

1. Determination of the farming season

Because freshwater sharks are tropical fish, this determines that they can only be farmed in summer in the north, and other seasons are not suitable for the growth of freshwater sharks. If overwintering and stock preservation are needed, hot water resources or a greenhouse with heating measures must be available, but correspondingly, farming costs will increase.

2. Standardization of production operations

Freshwater sharks are timid by nature and easily frightened, and their body surface is smooth and scaleless. This requires that during daily catching and transfer, they be handled gently and operated with care to prevent injury to the fish body. If abrasions are found on the fish's body surface, medication should be applied promptly to reduce inflammation and prevent disease.

3. Requirements for overwintering ponds

If freshwater sharks need to be overwintered for stock preservation, then in view of their large body size and rapid growth, they should be given a relatively large water space, and the water depth should be greater than 1 m to prevent them from swimming wildly due to fright and thus hitting the walls, becoming injured and dying.

4. @#@136@#@ issues

Because of the constraints of temperature conditions, freshwater sharks are destined to be harvested from ponds and marketed in a concentrated manner, an unfavorable reality. If market sales are poor and they cannot be sold within a relatively short time, it is easy to cause economic losses to farmers. This requires farmers, before harvesting from ponds in early to mid-October, to investigate market conditions in advance and contact good sales channels to ensure that all freshwater sharks harvested from the ponds are sold.

5. Issues with medication during the farming process

Freshwater sharks have a smooth, scaleless body surface and are relatively sensitive to chemical drugs. Therefore, during the rearing process, try to avoid using drugs that are highly irritating to the fish body. It is best to use Chinese herbal medicine preparations for prevention and treatment.