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1.Blue Moss
【Etiology】 The general term for the filamentous green algae sponge, double star algae and transfer plate algae of the green mud moss.
In the spring, as the water temperature gradually rises, the mud moss germinates in the shallow water of the pond, grows into a wisp of green silk attached to the bottom of the pond or suspended in the water like a net, and becomes yellow-green when aging, floating on the surface of the water, forming a mess of silk.
Fry and summer flower fingerlings often swim into the mud and moss and are entangled and cannot swim out and die. At the same time, due to the large number of mud moss, the nutrients in the water are consumed, which makes the water quality thinner and affects the growth of fish. It mainly harms fry and fingerlings. It occurs from May to September.
【Prevention and control method】
1) Clearing the pond with quicklime can kill the mud moss.
2) In the fish pond with green mud moss, sprinkle copper sulfate to make the pool water 0.7 g/m³. It is mainly sprinkled in areas where the moss is concentrated.
3) The quicklime is ground into a powder and sprinkled on the area of evergreen mud moss, and the heat is released when the quicklime chemically reacts with water to produce a strong alkali, and at high temperatures, the green mud moss will soon turn white and die.
4) Kill the mud moss with masson pine leaf juice. Each acre of water depth of 1 meter with fresh masson pine 20 kg, soaked, ground and added water to make a slurry of 25 kg, the whole pool spilled. Once a day, for 2 to 3 days.
2. Lake indigo - microcystis
【Cause】 Microcystis in the pond, mainly aeruginosa microcystis and splash microcystis multiply in large quantities, forming a layer of emerald green bloom on the water surface, which is called "lake indigo" in Jiangsu and Zhejiang, guangdong and Guangxi are called "consumption", and Fujian is called "patina water".
Microcystis multiply in large quantities, and after its death, protein decomposition produces toxic substances such as ammonia and hydrogen sulfide, which can not only poison the water producer, but also poison the cattle and sheep that drink this water.
Microcystis prefers to grow in waters with higher temperatures (10 to 40 °C, optimum temperature of 28.8 to 30.5 °C), higher alkaline (pH 8.0 to 9.5), and eutrophication.
【Symptoms】 During the day when cyanobacteria photosynthesis, the water pH can rise to about 10, at this time can increase the activity of the fish body thiamine enzyme, under the action of thiamine enzyme, vitamin B1 is rapidly fermented and decomposed, so that the fish lack vitamin B1, resulting in central nervous system and peripheral nervous system failure, increased excitability, sharp activity, spasm, the body out of balance.
【Diagnostic method】 Diagnosis can be made based on symptoms such as rapid activity, spasms, and loss of balance in the body.
1) Ponds are desilted and disinfected.
2) Master the amount of feeding, often fill with water, do not make the organic matter content in the water too high, adjust the pH of the water, and control the reproduction of microcystis.
3) When microcystis has been multiplied in large quantities, the whole tank can be sprinkled with a dose of 0.7 g / m³ of copper sulfate or copper sulfate and ferrous sulfate mixture (5:2) 0.7 g / m³, after sprinkling should start the aerator, or in the next morning as appropriate to add water, in order to prevent the fish "floating head".
4) When the algae body floats and accumulates in the early morning, sprinkle quicklime powder for 2 to 3 times in a row to basically kill the algae.
3. Golden algae
【Cause】 Caused by the large growth and reproduction of golden algae (also known as terrestrial algae).
Due to the large number of golden algae in the water, a large number of fish toxins, cytotoxins, hemolytic toxins, neurotoxins, etc. are produced, causing the poisoning and death of fish and animals breathing with gills.
The ecological conditions suitable for reproduction are: salinity 0.9~10.88, hardness 1.776~10.80 mmol/L, total ammonia (ammonium nitrogen) 0~0.25 g/m³, phosphate 0~0.16 g/m³, pH 7.4~9.3, water temperature of 1.5~29.0 °C.
The salinity that can be grown is 0.6 to 70, and the higher salinity in low salinity is faster;
It can still grow and produce harm at water temperature -2 °C, and growth above 30 °C is unstable, but it is still stable at high temperature growth at high salinity (30); pH of 6.5 can survive for a long time.
【Prevalence】 Semi-brackish waters such as ponds and reservoirs that are prevalent in saline-alkali land, such as Tianjin, Shandong, Hebei, Guangdong, Jiangsu, Zhejiang, Shanghai, Liaoning, Inner Mongolia, Shaanxi, Ningxia and other places, endanger silver carp, bighead carp, bream, bream, grass, shuttle, carp, crucian carp, eel, loach and other fish and aquatic organisms breathing with gills, from summer flowers to broodstock can be harmed.
Occurs all year round, mainly in spring, autumn and winter, because the water temperature is low at this time, other algae are affected by low temperature, slow reproduction, small number, three-cent golden algae can tolerate low temperature and become a dominant species, causing harm;
In the summer, it generally occurs less, due to the high water temperature in summer, cyanobacteria and green algae multiply in large quantities, thereby inhibiting the development of golden algae, but when the water quality conditions are suitable for the reproduction of golden algae, especially when the total ammonia content is low, cyanobacteria and green algae can not become the dominant species, then the harm of golden algae can occur.
【Symptoms】 At the beginning of poisoning, the fish is restless, the breathing rate is accelerated (silver carp with a total length of 3 cm, breathing 138 to 150 times per minute), swimming rapidly, and the direction is uncertain;
Soon it tends to be calm, the response gradually slows down, the fish begin to concentrate on the leeward shallow water corner of the fish pond, a small number of fish are stationary, the arrangement is irregular, disturbed, that is, swimming to the deep water, soon returning, the fish body secretes a lot of mucus, the base of the pectoral fin is hyperemiatic, gradually the base of each fin is engorged, the color of the back of the fish body becomes lighter, the response is more sluggish and calm, and the respiratory rate is gradually reduced;
With the prolongation of the poisoning time, the fish body after the pectoral fin is paralyzed and stiff, the dorsal fin and the abdominal fin cannot swing, only the pectoral fin can still swing, but can not move forward, there is no response to the touch, the gill cover, around the orbit, the jaw, the body surface is congested, forming erythema of different sizes, some are connected into pieces, the sick fish are covered with the four corners of the pool and shallow water, generally head to the shore, neatly arranged, stationary under the water surface, but not "floating head", disturbed and unresponsive, then breathing is extremely difficult and weak, 22 times per minute or less, Before dying, they struggle to breathe intermittently and die soon after losing their balance, but some fish remain in their natural state after death.
Throughout the poisoning process, the fish does not "float its head", does not absorb the air on the surface of the water, but dies under calm paralysis and difficulty breathing. After some fish die, there is no congestion on the surface of the body except for the fin-based congestion;
After some fish die, the gill lid is open, the eyes are prominent, and ascites accumulates.
The erythrocytes of the dying fish swell, the cytoplasm is concentrated and surrounded by the nucleus, and finally the cell membrane ruptures, leaving behind the bare nucleus and cell debris.
The pool water of the pathogenic pool is tan, the transparency is greater than 50 cm, the dissolved oxygen is rich (8 to 12 g / m3), the nutrient salt is poor, the total ammonia content is less than 0.25 g / m3, the total hardness and alkalinity are high, and other water quality conditions are suitable for the reproduction of golden algae.
1) When the total ammonia content in the water exceeds 0.25 g/m³, golden algae cannot become the dominant species, so the regular (small number of times) ammonium salt fertilizer, urea, ammonia, nitrogen and phosphorus compound fertilizer, and organic fertilizer are applied to the pond, so that the total ammonia is stabilized at 0.25 ~ 1.00 g / m³, which can achieve the preventive effect.
2) In the early onset of the disease in the saline-alkali land when the pH is about 8 and the water temperature is 20 ° C, the whole pond is sprinkled with ammonium salt drugs (ammonium sulfate, ammonium chloride, ammonium bicarbonate) containing about 20% ammonia, the dose is 20 g / m3, or the dose of urea is 12 g / m 3, so that the ionic ammonium in the water reaches 0.06 ~ 0.10 g / m 3, which can make the golden algae expand and disintegrate until all die.
Ammonium salt drugs kill faster than urea, so the effect is better. However, mullet and barracuda fry ponds cannot be used in this method.
3) Early onset of fish pond, the whole pool is sprinkled with 0.3% clay mud water to absorb toxins, and the poisoned fish can return to normal within 12 to 24 hours, not polluting the water body, but the golden algae is not killed.
4. Red tide
【Causes】 In the ocean, especially in the inner bay and shallow sea areas, it often occurs due to abnormal reproduction of some plankton and high density accumulation, causing water quality to deteriorate, odor, and discoloration of seawater.
In fact, different red tide organisms cause different discoloration of seawater, such as brownish red, pink, brown, yellow, green, lead gray, black brown and so on.
In recent years, due to the rapid development of industry and agriculture, especially the increasing number of industries in coastal areas, a large amount of industrial wastewater and urban domestic sewage have been discharged into the sea, resulting in serious pollution and eutrophication of the water quality of estuaries, inland bays and coastal waters, resulting in frequent occurrence of red tide, an increase in areas where red tides occur, and an expansion of the scope of harm.
Red tide occurs mainly in summer, and red tide organisms are more concentrated in the upper layers of water. There are three main types of hazards to fisheries.
1) Red tide organisms directly secrete toxins in water, or produce toxins after death, such as knee groove algae, psilocybin algae, etc.
2) Red tide organisms are adsorbed on the gills of marine animals and cause them to suffocate and die, such as luminous algae.
3) In the late stage of red tide, due to the decomposition of a large number of red tide organisms after death, a large amount of oxygen is consumed, causing seafood animals to suffocate and die.
1) Strengthen environmental protection work, control water quality, and strictly prevent pollution and eutrophication.
2) When red tide occurs, copper sulfate can be sprinkled in the aquaculture sea area to kill seaweed, or clay can be splashed to adsorb harmful substances.
3) Lay ventilation pipes on the seabed around the breeding area, apply a large number of bubbles upwards, form an upward and downward vertical circulation barrier, and isolate the red tide from the breeding area to achieve the purpose of defense.
4) Do a good job in forecasting and forecasting, and do not drain and irrigate water when red tide occurs. It is best to use a sand filter to filter the water or the water of the sedimentation tank.
5. Copepods
【Causes】 Copepods are the main components of zooplankton and are good food for fish.
In addition to copepods, some species harm fish eggs and hatchlings, affecting the hatching rate of fish eggs and the survival rate of fry.
There are two common types: sword water fleas and dart water fleas. After 5 days of hatching, the copepods no longer have a harmful effect on them.
1) Sprinkle 90% of the crystalline insects to make the pool water 0.5 g/m³.
2) Incubation water, filtered with copper sand mesh, nylon yarn mesh, sand and gravel filter wall, do not allow copepods to enter the incubator with the flow of water.
3) Wait for the fry to hatch for 5 days before putting them into the "Fat Pond".
6. Ferocious fish
【Cause】 There are often carnivorous and fierce fish in the pond, and these fierce fish feed on fry and juvenile fish.
1) Eel: Feeds on other fish for a living, can swallow fish larger than itself, 1.4 cm long eel fry can prey on the fry of other fish.
2) Mandarin fish: mainly preys on small fish and shrimp.
3) Snakehead: 500 grams of snakehead can swallow 100 to 150 grams of grass carp, crucian carp, carp, and can eat shrimp, tadpoles, insects and other animals.
4) Catfish: The head has 2 pairs of tentacles, and it often inhabits the bottom of aquatic grass during the day, and preys on small fish, shrimp and aquatic insects at night.
5) Yellowtail: Benthic fish, feeding on aquatic insects, shrimp and fry.
1) Completely clear the pond with drugs before stocking the fish pond.
2) Before stocking fingerlings, remove wild fish in time.
7. Crawlers
【Causes】 Turtle (harmful to juvenile fish, often feeding on juvenile fish, shrimp, snails), water snake (fish, amphibians as food).
2) The fish hook is tied with miscellaneous fish, distributed around the pond, and the water snake eats the bait and is hooked by the hook, so that some water snakes can be eliminated.
8. Insects
【Causes】 Water centipedes, pine algae worms, red nianghua, water axe worms, field turtles, water nymphs, osmanthus cicadas, etc. can prey on fish fry.
1) Quicklime clear pond.
2) Sprinkle with the whole pond of crystal enemy insects, so that the water content is 0.45 ~ 0.50 g / m³, when the water temperature is 20 ~ 26 ° C, 24 ~ 36 hours can kill the water centipede.