How Much Water Is Right for Crayfish Farming? Key Points for Controlling Water Level Depth

Once summer comes, crayfish are hard to find, which shows just how popular they are. Crayfish are delicious and highly nutritious, but most people do not know much about how to farm them. If you want crayfish with plump meat, water quality management is very important. Below, the editor will introduce which issues need attention regarding the water used for farming crayfish.

How much water to add when farming crayfish

Do not let the water completely submerge the crayfish. It is best to leave one third of the head exposed outside! This is more suitable for oxygen absorption and exchange, but the water level must not be lower than the crayfish itself. The specific water level height can be decided according to actual conditions.

Crayfish are a freshwater economic shrimp species and are widely welcomed because of their delicious meat. Because they are omnivorous, grow quickly, and adapt strongly, they form an absolute competitive advantage in the local ecological environment. Their feeding range includes aquatic plants, algae, aquatic insects, animal carcasses, and so on. When food is scarce, they also cannibalize each other. In recent years, crayfish have become an important economic aquaculture species in China. In commercial farming, escape must be strictly prevented, especially escape into pristine water bodies rarely visited by people. Their ecological competitive advantage over local species can cause destructive harm.

Water quality management for crayfish farming

1. Fertilization

In crayfish ponds, in addition to applying base fertilizer to enrich water quality before stocking crayfish seedlings, a certain amount of fertilizer should also be applied as a top dressing according to changes in water quality, so as to ensure the supply of zooplankton in the water. The top dressing should mainly be decomposed organic fertilizer, with less chemical fertilizer, and especially no ammonium bicarbonate. When applying top dressing, apply less at a time but frequently; the amount applied each time should not be too much, so as to help control water quality. Generally, apply once a month, with about 100 kg per mu each time. The amount of top dressing should be adjusted according to season, weather, temperature, water color, and so on. Generally, in spring and autumn, because water temperature is low and organic matter decomposes slowly, the fertilization amount can be appropriately increased; in summer and other high-temperature seasons, the fertilization amount should be reduced. On sunny days, more can be applied, while on cloudy and rainy days, less should be applied; do not apply in the muggy weather before thunderstorms. When fertilizing, also observe the water color. Generally, pond water that is grass green or tea brown and not turbid is good water. When its transparency is below 30 cm, do not fertilize; when it is above 30 cm, fertilize in time. If the water color is dark brown or yellow-green blooms accumulate on the water surface, then change the water before fertilizing.

2. Regulating water quality

During crayfish farming, when temperatures are relatively low in early spring, the water level can be lowered and maintained at a depth of 30-60 cm, so that water temperature can rise faster. Later, as temperatures gradually rise, the water level can be gradually raised. In the high-temperature summer season, maintain the water depth at 1.5-2 m. In summer, when temperatures are high, if the water level is too low, it will accelerate gonadal development in crayfish, cause early maturation of the shrimp, and result in smaller individual commercial shrimp. Generally, during crayfish farming, when temperatures are low, add fresh water once every 10-15 days; in summer, add water once every 7-10 days, so as to keep the dissolved oxygen content in the water above 5 mg/L.

Where conditions permit, install aerators so that during high-temperature summer periods, cloudy and rainy days, and sudden weather changes, the excessively low dissolved oxygen content in the water can be replenished in time. For crayfish ponds, choose air-compression aerators and spray-type aerators. Their advantage is that they are not afraid of striking and stirring the water body, avoiding harm to the shrimp. However, impeller aerators and paddlewheel aerators, at the same power, create a larger swirling range in the water area than spray-type aerators and are more likely to injure the shrimp. When using this kind of aerator, the water depth must be kept above 1.5 m.

If on a clear daytime you find large numbers of crayfish climbing out of the water, it proves that oxygen is insufficient and fresh water should be added in time. Usually observe changes in water quality frequently, so that water quality remains in a state of fertile, lively, tender, and refreshing for a long time.

Fertile: refers to an appropriate water color concentration and a relatively large amount of phytoplankton beneficial for shrimp digestion. Generally, transparency is 25-35 cm, and the water color is tea brown or grass green.

Lively: refers to water color and transparency constantly changing with the strength of sunlight. This is mainly because the dominant populations of phytoplankton in the pond appear in alternation, full of vitality. What fishermen often call “clear in the morning and green in the evening”, “red in the morning and green in the evening”, and “half the pond red and half the pond green” all refer to this kind of change. If yellow and green interwoven streaks like cloud-shaped blooms appear in the pond, then there are too many algae in the water that are not easily digested, which is a sign that water quality is deteriorating, and the water should be changed in time. In addition, the liveliness of pond water should not only change at different times each day, but also change periodically every 10-15 days. This means that beneficial algal populations are in a virtuous cycle of being continuously utilized and continuously growing.

Tender: refers to water being fertile but not old. There are mainly 2 signs of old water: one is that the water color turns yellow or yellowish brown, and the other is that the water color turns white. These signs appear because large amounts of blue-green algae that are not easily digested by fish and shrimp multiply in the water body, or because algal cells age and die, leading to deterioration of water quality.

Refreshing: refers to water quality being clear and refreshing, with water color not too dense, and transparency at 25-35 cm.

How many seedlings are suitable for crayfish farming

The specific stocking density depends on many aspects, such as the farming environment conditions, water source conditions, feeding management level, seedling source and specifications, feed source, and so on. In short, adjust measures to local conditions and stock seedlings flexibly according to your own conditions. If they are your own juvenile shrimp, with specifications of 3-4 cm, stock 14000-15000 tails per mu.

Among this, the yield per mu can be estimated based on past many years of output, combined with your own farming conditions and measures; the yield that can generally be achieved is usually 200 kg. The estimated survival rate can generally be calculated at 40-50%. Based on the market specifications needed for farming, generally 30-40 tails/kg, you can calculate roughly how much you need to stock.

How to fertilize water when farming crayfish

1. Crayfish are reclusive animals. Fertilizing the water before releasing seedlings and controlling water transparency in advance can provide a stable growing environment for shrimp seedlings that have just entered the pond.

2. It can effectively control the growth of moss and bottom mats, and can prevent shrimp seedlings from becoming wrapped in moss after entering the pond; dissolved oxygen in the water body is relatively good, which helps shrimp seedlings quickly adapt to the pond environment.

3. Through the reproduction of algae and bacteria, nutrients in the pond can be absorbed in advance, avoiding the adverse effects caused by potential excessive harmful indicators such as ammonia nitrogen, nitrite, and phosphorus compounds.

4. Many farmers are used to putting in snails before releasing seedlings. Fertilizing the water before releasing seedlings happens to provide abundant feed for the snails. If the snails grow well, they in turn become excellent feed for crayfish.

5. Good organic fertilizer, after a fermentation process, can serve as both fertilizer and feed. Fertilizing the water before releasing seedlings indirectly supplements feed for the pond, and shrimp seedlings can feed on it after entering the pond.

6. It can promote the growth of aquatic plants. If aquatic plants grow well, they can better provide hiding places for shrimp seedlings.

In summary, shrimp farming still has requirements for water quality. Water quality can directly affect shrimp yield, which concerns the interests of farmers. Therefore, doing a good job in water quality management is an important part of shrimp farming.