Causes of fish poisoning caused by copper sulfate

Copper sulfate is a commonly used drug for the treatment of fish diseases, but it often causes some harm because some users are not familiar with the medicine.

1 case

Example 1: in March 1987, copper sulfate 0.7g/m3 was used to kill moss in the parent fish pond in Liantang Aquatic Farm, and all the parent fish died three days later. Water quality analysis, ammonia content 0.35g/L.

Example 2: from August 30 to 31, 1999, farmers in Bayi Township, Nanchang County raised a 0.67hm2 fish pond with a depth of 1m. Because of the muggy weather and heavy rain, the fish died for two consecutive days, about 10kg every day, mainly silver carp and grass carp. On the 31st, copper sulfate 4kg (0.6g/m3) and crystal trichlorfon 3 kg (0.45g/m3) were given to check for a small amount of rotifer. A large area of dead fish was found on September 1st and 2nd, totaling about 1000kg. The fish was examined and no other symptoms were found.

Example 3: a 0.5hm2 of Jiangxi Academy of Agricultural Sciences, with a water depth of 0.9m, was a fish pond that had not been silted up for many years. There was a total 145kg of dead fish from August 30 to September 3, 1999, mainly silver carp. Due to the fertilizer water quality, copper sulfate 8kg (1.5 g / m3) was applied at noon on the 3rd to kill algae, and the total amount of dead fish in the pond from 4 to 5 days was 580kg. The dead fish were silver carp, carp, crucian carp and grass carp successively, and the death of freshwater Pomfret was very few. After examination, no other abnormal symptoms were found on the body surface except Gill hyperemia.

Example 4: on September 1, 1999, the two mouth areas of Wanhu Aquatic Farm in Nanchang County were 0.67hm2, and the adult fish pond with a water depth of 3 m was treated with copper sulfate 11.5kg (0.6 g / m3) to treat trichomoniasis, and the dead fish reached 500kg the next day. We noticed at the scene that the dying fish had significantly faster breathing and some fish had spasms. On July 25, 1999, officers and soldiers of professional households in Sanshan Village, Fushan Township, Nanchang County, used copper sulfate 100kg (0.75g / m3) in a contracted water surface 6.67hm2, a closed old river with a water depth of 2m. When copper sulfate was sprinkled, a large number of grass carp, carp, blunt snout bream and crucian carp died, reaching 1500kg, but no silver carp and bighead carp died. There was no more dead fish the next day.

The effective content of copper sulfate used in the above cases is 9296%. With one exception, the others did not exceed the normal dosage.

2 the cause of poisoning

2.1 compound poisoning is mainly caused by high temperature and hypoxia. Case 1 and case 2 are typical examples. Some domestic scholars have done experiments on silver carp. When the water temperature was in the range of 16-30 ℃, the toxicity of copper sulfate increased by 1.7-1.8 times when the temperature increased by 10 ℃. The experiment on bighead carp weighing 12g showed that the safe concentration of copper sulfate decreased from 0.71g/m3 to 0.5g/m3 when the temperature increased from 22.9 ℃ to 26.7 ℃.

[1] the toxic effect of copper sulfate on fish is mainly to destroy the respiratory function of Gill, and it is more toxic under the condition of hypoxia.

[2] there are many factors causing hypoxia in water body. When copper sulfate is used to kill algae, it can cause serious hypoxia in the water and produce toxic substances to poison fish. for example, ammonia has a strong toxic effect on fish. According to Yuan Baoshan (1999), when the concentration of ammonia in the water reaches 0.289mg/L, all carps die.

[3] We also observed at the scene that a large number of fish poisoned by copper sulfate floated on the surface before death. Breathing is accelerated, and groups of 'grab water' are injected with new water, similar to the symptoms of hypoxia. Because of the side effects of high temperature and hypoxia, the toxicity of copper sulfate is greatly increased, so even the conventional dosage often causes acute poisoning of fish.

2.2 case 3 of excessive poisoning is caused by fish poisoning caused by obvious overuse of copper sulfate. It is reported that Pomfret is not sensitive to copper sulfate, and the concentration of spraying in the whole pond can reach 1.5g/m3, while common carp, crucian carp and silver carp are more sensitive to it, and fish species are more sensitive than adult fish.

[4]. This is basically consistent with the phenomenon in example 3. Under laboratory conditions, copper sulfate (calculated by copper ion) on silver carp (without weight) 96LC50=0.062mg/L

[5] (copper sulfate 0.25g/m3). In natural water, although organic matter and suspended matter as well as calcium and magnesium plasma can reduce the toxicity of copper sulfate and increase its safe concentration, the concentration of spraying on the whole pond of common carp, crucian carp and silver carp should not exceed 0.7g/m3 [4].

Of course, there are also those who use high concentration (above 1g/m3) copper sulfate to treat fish diseases and achieve good results, such as 1g/m3 control of cyanobacteria, 1g/m3 combined with the treatment of fulminant infectious diseases, and 1~2g/m3 treatment of rotifer under long-term low temperature, overcast and rain conditions.

[6] and other success stories. However, all these high concentrations of drugs are carried out under strictly controlled environmental conditions, and it is necessary to use drugs for a short time, increase oxygen and change water after drugs, so as to reduce the stress consumption of fish as far as possible.

2.3 case 4 of deep water poisoning, the author believes that the first reason is that the water quality is thin, the sediment is less, and the water body has a weak ability to consume drugs. Second, the water depth is up to 3m, there is a thermocline layer, and the density of the upper and lower layers of the water is different, resulting in high drug concentration in the upper layer and low drug concentration in the lower layer, which will also lead to fish poisoning in the high layer.

2.4 swallowing poisoning can be found from example 5, only dead grass carp, blunt snout bream, common carp, crucian carp and other feeding fish were found in the water, but filter-feeding fish such as silver carp and bighead carp did not die, so we confirmed that they were poisoned by accidental ingestion of undissolved copper sulfate particles. It has also been reported abroad that all carps died three days later after swallowing copper 400mg/kg.

The residue and enrichment of copper is also a factor that can not be ignored in fish poisoning. For example, scallop, cultured in water with copper ion concentration of 0.005mg/L and 0.01mg/L for 45 days, contained copper 17.03mg/kg and 30.81mg/kg, and the enrichment coefficient was 2900-3040 [5]. When fish swallow this kind of food, it can also cause swallowing poisoning. Swallowing poisoning mainly harms eating fish.

3 problems needing attention in the use of copper sulfate

Copper sulfate causes fish poisoning, which is mostly caused by improper use. Therefore, it is particularly important to correctly master the method of using copper sulfate.

3.1 according to water temperature, content of organic matter and suspended matter, dissolved oxygen, ph, hardness, climate, stocking and fish activity, the concentration should be reduced when mixed with other drugs. Specific use of copper sulfate can be 0.7g/m3 as a standard, up and down. Measure the volume of pool water and calculate the dosage accurately. Should choose a sunny morning, when the fish do not float head medication, after administration should be conditional should be inflated to increase oxygen, to prevent algae death consumption of oxygen, water quality.

3.2 when dissolving drugs, do not use metal containers, and the temperature of dissolved water should not exceed 60 ℃ to prevent failure. Never throw undissolved particles into the water to prevent poisoning. The use of copper sulfate in deep water should not be sprinkled once according to the conventional dosage, but should be used twice at intervals of 4 to 5 hours.

3.3 due to the long residual time of copper, it also has adverse effects on the feeding and growth of fish, so it should not be used frequently.