What are the causes of death during tadpole breeding?

Tadpoles are the larvae of frogs and toads. Newly hatched tadpoles have a spindle-shaped body, no limbs, mouth or internal gills, a long laterally flattened tail, and branched external gills on both sides of the head. They attach to aquatic plants and rely on the residual yolk in their bodies for nutrition. So, what are the causes of death in bred tadpoles?

1. Causes of death in bred tadpoles

1. Germplasm degeneration of parent frogs

Germplasm degeneration of parent frogs not only affects reproduction, but also affects the fertilization rate, hatching rate, and the survival rate of tadpoles and young frogs. Investigations have found that the mass death of young tadpoles is also directly related to the germplasm degeneration of parent frogs.

2. Influence of ecological factors

The decline of dissolved oxygen during hatching is one of the important causes of young tadpole death. Egg hatching consumes oxygen, and newly hatched young tadpoles have a relatively high oxygen demand. In addition, the breakdown of the egg membrane during hatching and the decay of aquatic plants and other attachments that enter the hatching pond with the eggs both consume large amounts of oxygen. According to research, when the dissolved oxygen content in the hatching pond drops below 3 mg/L, young tadpoles will gasp at the surface. Because young tadpoles are delicate, once they gasp at the surface they cannot be rescued, resulting in death. In addition, temperature is also one of the important factors causing young tadpole death. The suitable temperature for young tadpoles is 20-30°C, and the optimal water temperature is 25-3°C. Young tadpoles bred in early summer often die in large numbers because of the large temperature difference between day and night, with nighttime temperatures dropping below 20°C; young tadpoles bred in July and August are in the peak of summer heat, when daytime temperatures often reach above 35°C. Young tadpoles bred in these two periods often die in large numbers. In addition, contaminated water can also cause the death of young tadpoles.

3. Leaving the pond too late

Newly hatched tadpoles should generally wait for a period of time before being caught and removed from the pond, and the exact time should be determined according to the development of internal organs and external environmental conditions. Generally, they should leave the pond 6-7 days after hatching, because by then the tadpoles have shifted from internal nutrition to external nutrition and urgently need to start feeding, and because their increased size raises their oxygen consumption. Missing the favorable time for leaving the pond often causes mass death of young tadpoles due to oxygen deficiency and lack of nutrition.

In response to the above causes of mass death of young tadpoles, corresponding management measures should be taken, such as satisfying the necessary ecological conditions and correctly grasping the time for young tadpoles to leave the pond.