Shantou City, Guangdong Province, Chenghai District, Yanhong Town, Honggou Village Forest Boss breeding bullfrog tadpole, an area of about 2.8 acres, a total of 8 rectangular ponds, each pond length of about 40 meters, about 6 meters wide, water depth of 30-50 cm (Figure 1), April 8, 2019 put "toothpick seedlings" about 1000 / square meter, about 250,000 tails per pond, feeding tadpole powder, feed crude protein content of 40%, feeding 2 meals a day, the pond in the early water conditions are better, change the water twice a day, the source water quality is poor in May, the frequency of water change is reduced.
Figure 1 Pathogenesis pond
On 5 May, the pond was filled with "red worms" (bare-bellied), red in color, and insecticidals were used to kill insects using a certain plant's insecticide "Spider Rapid Extinction" (labeled avermectin).
On 6 May, more than 200 tadpoles in the pond were belly-up, floating on the surface of the water and then sinking, and so on, but no deaths occurred.
On 8 May, another plant's insecticide, Ciliate Qing (without specifying the specific ingredients), was used to kill insects.
From May 9 to 11, the tadpole died about 2000-3000 tails per day, on the morning of the 11th, contact Liyang technicians to see the pond, to the pond to see the water color turbid with green, the water surface organic matter, oil film, with a hash dissolved oxygen meter measured pond dissolved oxygen is generally less than 3mg / L, with a simple test box to measure the water quality index: pH 7.6, ammonia nitrogen 1.0mg / L, nitrite 0.05mg / L (Figure 2). Tadpoles have poor overall viability, with floating heads, slow swimming, and swelling of the abdomen of dead tadpoles (Figure 3), and intraintestinal bleeding is seen in dissection (Figure 4). A total of 2 packs of "Rapid Relief (Enhanced)" and 3 Packs of "Activation II." were used for all ponds on the day, and 1 pack of "Bottom Aeration (Enhanced)" was used in the evening.
Fig. 2 Water quality indicators at onset
Fig. 3 The abdomen of the dead tadpole is expanded
Figure 4 Dissecting intestinal bleeding
On May 12, the tadpole death decreased significantly, the number of deaths was about 400, and on the same day, it was reduced and internally taken "enteroside kang + defeat kang + oligosaccharide -500", 1:1:1 mixed with 60 pounds of material, fed in 4 times.
On May 13, about 100 tadpoles died, and the tadpoles ate and their vitality became better, and they took health care "Lidojing + Ligan + Nutrition Express", 1:3:5 mixing 600 pounds of material.
On 14 May, customers reported that pond tadpoles had returned to normal.
On May 16, the return visit, the water color is good, and the water quality index was measured with a simple test box: pH value of 6.5 or less, ammonia nitrogen 0.9 mg/L, nitrite was not detected (Figure 5).
Figure 5 WCQos for 16 May
Analysis
1. The normal water quality index of tadpole culture pond in Chenghai area is low pH (below 6.8), high ammonia nitrogen (about 1.0mg/L), and nitrite cannot be detected, but when the pond is onset, most of them can detect nitrite and the pH value reaches more than 7.6. High pH, ammonia nitrogen converted into non-ionic ammonia, easy to ammonia poisoning, in addition, when the pond dissolved oxygen is very low, nitrite is easy to convert to nitrogen, tadpoles are prone to nitrogen bubble disease, reducing the survival rate.
2, after multiple insecticidals, the branches die, sink to the bottom, the tadpole feeding fierce, after eating a large number of dead branches and horns caused by enteritis caused death, while excessive feeding is also easy to damage the intestine secondary bacterial infection, coupled with the local "white rain" in May, insecticide damage to the pond environment, resulting in lack of oxygen is an important cause of aggravated death. (Source: Liyang Aquatic Products, Wu Jiayan, Chen Zhenhong)