Disease and enemy damage of fish and its control methods

Cyanobacteria diseases: cyanobacteria, including Microcystis aeruginosa and Microcystis aeruginosa, generally occur in summer and early autumn, it likes to grow in high temperature and alkaline water, when the pH is 8-9.5, the water temperature is 28 ℃-32 ℃, the reproduction is the fastest. For example, when there are more than 500000 groups in a liter of water, the dissolved oxygen in the water is often insufficient for its needs, and a large number of people will die. After the death of the algae, the protein is easy to decompose, producing toxic substances such as hydroxylamine and hydrogen sulfide, which accumulate in the water, which can poison not only fish, but also cattle and sheep.

Prevention and control methods: (1) frequent injection of new water, water makes the content of organic matter in the water too high, pay attention to the adjustment of PH value of water (regularly sprinkle lime) can control the reproduction of microcystis. (2) sprinkle with 0.7ppm copper sulfate in the whole pool, start the aerator or add new water the next day. (3) when the algae floats and accumulates in the early morning, sprinkle non-damp plant ash for 2-3 days. It can disappear, and the next day it will spread quicklime all over the pond (15-20 kg per mu), and the effect will be better.

Second, dinoflagellate diseases: dinoflagellates that do harm to fish in ponds are dinoflagellates and dinoflagellates, which like to grow in slightly alkaline water with more organic matter, hardness and slightly alkaline, especially in the warm season. Dinoflagellate is very sensitive to changes in the environment. If the water temperature and pH value suddenly change, a large number of dinoflagellates will die. Some of these two types of dinoflagellates are not easy to digest, and the death of fish is caused by the poisoning of fish caused by a large amount of dinoflagellate produced after death.

Prevention and control methods: (1) according to the sudden change of environmental conditions such as water temperature and pH value of these two kinds of dinoflagellates, they will die in large numbers quickly. When they breed in large numbers, they can change water immediately. Make the water temperature and quality of the pool water suddenly change and restrain their reproduction. (2) sprinkling 0.77ppm copper sulfate in the whole pool can effectively kill dinoflagellate.

Third, Chrysophyta diseases: there are mainly hemolysin and fish toxins secreted by Chrysophyta when they multiply in large numbers in the pond, causing fish death. The characteristics of water quality less than that of Phaeophyta are as follows: salinity 4% Mel 5%, oxide content more than 2000 mg / L, water hardness above 40 ℃, pH 7.2-9.6. Therefore, in the fish ponds built in saline-alkali land, the phenomenon of dead fish often occurs as a result of algal toxin poisoning; fish poisoning usually begins in the early morning, but the symptoms and floating head phenomenon are different. At first, the fish are concentrated in the four corners of the pond, but they disperse immediately, and with the aggravation of poisoning, almost all the fish are concentrated on the bank of the pond, their heads are motionless toward the shore, and sometimes they rush to the shore, and when people walk through the drive, they can be dispersed temporarily, and the horses die and concentrate after they leave. The fish that stayed on the shore began to lose their balance, lay on their side, had difficulty breathing, and finally died in a coma.

Prevention and control methods: (1) the whole pool of copper sulfate of 0.7ppm can inhibit the function of toxin secreted by this kind of algae or weaken the activity of fish toxin. (2) the whole pond of 5-10ppm ammonium sulfate was sprinkled or put 1-1.5kg urea and 2-3kg calcium phosphate per mu to propagate plankton and inhibit the growth of trichaeophyta. (3) in the early stage of the disease, poisonous water can be discharged, fresh water can be injected or fish can be caught and transferred to fish ponds with non-toxic water quality.

4. Diseases of green mud moss: green mud moss includes some species of the three genera of Spiraceae, double star algae and Chlamydomonas. With the rise of water temperature in spring, the shallow part of the fish pond begins to germinate, growing into strands of green filaments, standing in the water, breaking off from the bottom of the pool when aging, forming clumps of disorderly filaments, rising to the surface, and young fish swimming into green mud moss. Often entangled by disorderly filaments can not swim out, resulting in death. At the same time, there are a lot of moss in the pond, which also consumes the nutrients in the pond water, so that the pond water becomes thinner, and the plankton needed for fish fry can not reproduce in large quantities, affecting the growth of fish fry.

Prevention and control methods: (1) cleaning the pond with quicklime can kill moss. (2) A pond without fish can be sprinkled with 50 kilograms of plant ash per mu on the moss, so that it can die without sunlight. (3) the moss appears in the pond where the fish has been released, which can be sprinkled with 0.7ppm copper sulfate in the whole pond to kill the moss effectively.

Fifth, water net algae disease: water net algae is a kind of green algae, which grows in shallow ditches and ponds, especially in fertile water rich in organic matter. When the water net algae in the fish pond is long, it is like a lot of snares in the water. after the fish fry mistakenly enter the "snare", they can't swim out and die.