Key Technical Points for Overwintering Management in Enclosed-Gully Rana Frog Farming

Rana frogs have the habit of hibernating and overwintering underwater. From late September each year to mid-to-late April of the following year, a period as long as 6 months, overwintering management in artificial enclosed-gully frog farming means, according to the living characteristics and needs of Rana frogs during this period, artificially selecting and creating suitable overwintering sites and water environments to ensure their safe overwintering.

1. Building overwintering ponds

Overwintering ponds, also called hibernation ponds, are places where Rana frogs gather to hibernate. Some natural pools, deep water bays in mountain streams, or reservoirs with good conditions on the frog farm can be used as natural overwintering ponds for Rana frogs, but most frog farms need to build overwintering ponds artificially.

1. Site selection: choose a place where Rana frogs gather and descend the mountain in autumn or nearby, select the side beside a river channel (stream), keep 5-10 m away from the river channel, and choose a flat area with clayey soil as the site for building the overwintering pond.

2. Specifications and quantity of overwintering ponds: when building overwintering ponds, the pond depth is required to be 3-4 m, the water depth 2-2.5 m, the pond bottom flat, and the surrounding slopes 70-80 degrees to prevent collapse after water immersion. If the pond bottom is sandy and loose, it must be padded solid with clay to prevent seepage. The area and number of overwintering ponds to be built depend on the terrain conditions of the frog farm and the number of frogs overwintering in normal years. Where the terrain is flat and open, large overwintering ponds can be built, with a single pond area of 800-1000 sq m; where terrain conditions are poor, small and medium-sized overwintering ponds can be built, with a single pond area of 200-300 sq m. The number of overwintering ponds is determined as appropriate according to the amount of overwintering frogs raised in normal years. Generally, the overwintering density is 80-100 adult breeder frogs per sq m and 200-300 young frogs per sq m. Building 3-4 small and medium-sized overwintering ponds on one frog farm can provide overwintering for 20,000-30,000 breeder frogs and 150,000-300,000 young frogs. When building multiple overwintering ponds, the interval between them should reach 500-1000 m, and each should have separate irrigation and drainage.

2. Preparation before use of overwintering ponds

Overwintering ponds that have been used cyclically for many years have relatively thick sludge at the bottom, which affects water storage capacity and accumulates large amounts of pathogenic bacteria and natural enemy pests of Rana frogs. Therefore, careful repair and treatment must be carried out before the overwintering period arrives.

1. Desilting: release the pond water, remove the sludge at the pond bottom, and restore it to the original bottom layer of the pond.

2. Sun-drying the bottom: after removing the sludge, control the water inflow and let the pond bottom be exposed to the sun for 20-30 days, which can kill some pathogens and pests.

3. Killing insects and sterilizing: 20-30 days before filling with water, spread quicklime on the pond bottom and surrounding pond walls for disinfection. This method can effectively kill pathogenic bacteria of Rana frogs and natural enemy pests such as leeches and parasites.

4. Laying shelter materials: before filling with water, first lay a layer of broadleaf tree leaves about 5 cm thick on the pond bottom, or use grass bundles tied from gramineous weeds, then cover them lightly with crushed stone and mud. These shelter materials help Rana frogs lurk and hibernate underwater.

5. Filling with water: in late October, before Rana frogs enter the overwintering pond to hibernate, fill it with water to a depth of 2.5 m and keep it clean.

3. Overwintering management

In mid-September, when the air temperature drops below 10 degrees C, Rana frogs begin to migrate down the mountain to water sources. They first enter shallow water areas and lurk there. From early November to mid-November, when the air temperature drops below 5 degrees C, Rana frogs enter deep water areas to hibernate until late March to early April of the following year.

1. Management during the scattered hibernation period: mid-September to early November, 45-50 days. The characteristic of this period is that most Rana frogs lurk separately and scattered in shallow water areas, in an unstable hibernation state, and can still move onto land at night. The management focus of this period is: separate the captured Rana frogs into commercial frogs, breeder frogs, and one-year-old young frogs; send breeder frogs and young frogs to storage ponds respectively. The water depth of storage ponds is 40-80 cm, and the storage density is 500-800 frogs per sq m of water surface. Storage ponds can also use incubation ponds and tadpole rearing ponds. If the river water on the frog farm is sufficient, overwintering ponds can also be temporarily used instead, that is, keep the water depth of the overwintering pond at 50-80 cm, put in the overwintering frogs, and before Rana frogs enter hibernation in early November, promptly replenish the overwintering pond water to a depth of 2-2.5 m. Around the storage pond, a fence 50-60 cm high should be formed with plastic sheeting, and the bottom should be compacted firmly to prevent Rana frogs from escaping. Because Rana frogs gather and lurk in shallow water areas, management and protection must prevent human theft and predation harm from various carnivorous animals.

2. Management during the concentrated hibernation period: early November to late March of the following year. The characteristic of this period is that Rana frogs gather in deep water areas, crowd together, do not eat or move, and are in a deep hibernation state. The key management points of this period are:

(1) Promptly send the overwintering frogs in the storage ponds to the overwintering ponds. The frog stocking density in overwintering ponds is 80-100 breeder frogs per sq m and 200-300 young frogs per sq m, maintaining overwintering in flowing water. Winters in Northeast China are cold, and after winter many rivers and streams in many farms become frozen and stop flowing. For such overwintering ponds, the overwintering density of Rana frogs should be appropriately halved.

(2) During the overwintering period, frequently observe the water flow conditions and keep the water level under the ice no lower than 1.5 m.

(3) After snowfall, promptly clear the accumulated snow on the ice surface or sweep out snow paths to enhance the light transmittance of the pond water.

(4) Place mousetraps and rat poison at fixed points around the overwintering ponds to prevent harm from rats and other carnivorous natural enemies.