generalizedIn other words, it means being able to live insalinityOf three thousandths of fresh waterfishIt can be called freshwater fish.narrow senseIn other words, it refers to fish that have only "juvenile stage" or "adult stage" in some stages of their life history, or must spend their whole life in freshwater.There are about 26000 kinds of known fish in the world, and about 8600 kinds of freshwater fish.There are nearly 3000 species of fish in China, including more than 1000 species of freshwater fish.
There are more than 26000 known fish species in the worldvertebrateThe largest category in vertebrates, accounting for 48.1% of the total vertebrates.Most of them live in the sea, and there are about 8600 kinds of freshwater fish.There are nearly 3000 species of fish in China, including more than 1000 species of freshwater fish.
Fish living in waters with salinity below 0.05%.It is generally divided into two categories: primary and secondary.There are more than 30 orders and more than 8400 species of freshwater fish in the world, including 11 orders and more than 4050 species of native freshwater fish.There are 13 orders and more than 850 kinds of freshwater fish in China.Cypriniformes (more than 2420 species)Siluriformes(more than 2210 species), Lipocyprinidae (more than 1330 species).There are more Cypriniformes (about 600 species) and Siluriformes (more than 80 species) in China.[1]
classification
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Classification based on the concentration of salt in water
Arhat
The most commonly used classificationPrimary freshwater fish
Fish that can only live in fresh water all their lives.It accounts for 33.1% of the total global fish species, about 8600 species.
Living in fresh water for most of his life, occasionally moving or inhabitingBrackish water Fish in the sea.It accounts for 8.1% of the total global fish species, about 2100 species.
Fish inhabiting in sea water or brackish water, whose life history will also live in fresh water, or live in brackish water.includeAnadromous fish、Marine fishesAnd accidental entryriverLivingMarine fish。It accounts for 0.6% of the total global fish species, about 160 species.
In his career history, he lived in fresh water, ocean and other waters with different salinity for a certain period of time.includeAnadromous fish、Marine fishes。
Terrestrial migratory fish isolated from the sea by geography.
The most common, abundant and prosperous fish in modern times.
Of the 1050 freshwater fishes in China, except for a few 13 species, the rest are all bony fishes.
structure
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mudskipper
Fish fin
The fins are the necessary tools for fish to swim. There are five kinds of fins: pectoral fin, pelvic fin, dorsal fin, anal fin and caudal fin.
Thoracic and ventral fins - help change direction and stop swimming to maintain balance.Some will be very special:
mudskipperThe pectoral fin can support the body and even walk like a foot.
Dorsal finHip fin - maintain balance and reduce resistance.
Tail fin - generates forward power
Body color
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Most freshwater fishes have special colors and stripes, or the body color is consistent with the surrounding environment, so they can hide themselves or confuse the enemy and prey to protect themselves or sneak attack prey.shallow waterIn the middle, the body color of the fish is usually blue and green on the back, and the belly isLight whiteThese colors are called extinction colors. When you look at the bottom of the water, you think it is the sky. When you look down, you feel it is sea water. In deep water, your body color is very gloomy, often calledCrimson, black, etc.
Protective color
Fish like to swim in groups on the water
The stripes on the fish body often have longitudinal stripes. When swimming, it looks faster than it actually is.
The body color of adults is different from that of children.
For example:formosan landlocked salmon(When I was young, there were obvious stripes that were protective colors. When I was an adult, my back turned bluish black, my abdomen was light white, and there were about nine oval blue spots.).
organ
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To survive, freshwater fish must hunt and defend against enemies.Not all fish have such organs.
touch
Attract small fish. When attracting enough small fish, suddenly inhale into the mouth.
spine
Protect yourself from being eaten by natural enemies.
Bone plate
The skin between the plates of this kind of fish bones is covered with granular small protrusions, which are extremely rough. There are obvious small spines on the back of the head in the larva.
long beak
Feeding on fish, you can catch benthic fish with a long beak
sucker
Most evolved from pectoral fins.
The fish can absorb the rocks, seaweed and the bottom of the boat calmly.
Generating organ
It can release current and has the following functions:
Corona the fish and eat it.
Protect yourself and generate electricity in case of danger.
The poison gland can usually be found at the base of the poison thorn.
It can effectively defend itself. Once stabbed, the glandular tube will break and the venom will enter the wound.
food
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Freshwater fish are mostly herbivorous and omnivorous, but there is also a small amount of carnivorous.
Upper reaches of rivers
Mostly insectsAdherent algaeFor food.
Lower reaches of rivers
They often feed on plankton and organic debris.
Growth habit
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Basically, as long as there is fresh water, there are freshwater fish to live in. From warm and pleasant hot springs to the North and South Poles frozen into the heart and lungs, you can find traces of freshwater fish.
Upper reaches of rivers
At an altitude of more than 1500 meters, the current is rapid.
There are ponds and crevices made of large stones.
The body can move freely up, down, left and right by swinging from side to side. The fins and fish buoys help swimming.
Longitudinal flat fish
Swordfish
It is easy to move horizontally and has excellent mobility, which is convenient for hunting food and avoiding predators.For example:Hemimyzon formosanum 。
Linear fish
Although the swimming speed is slow, it can swing and sneak like a snake.
There is an inverse ratio between the way of egg protection and the number of eggs laid.The better the way to protect eggs, the fewer eggs are laid, and vice versa.
Roe
Fish eggs are divided into floating eggs and sinking eggs.
Freshwater fish usually live inInland watersHowever, in recent decades, economic development, population growth, environmental pollution, over reclamation, over construction, damming, arbitrary introduction of non-native species, over harvesting and other problems have caused irreparable damage to the natural habitat and water quality of freshwater fish, and caused a sharp decline in the species and quantity of aquatic animals, of which about 1800 species of freshwater fish are endangered,Some species have even become extinct.If a species becomes extinct, it will also destroy the food chain, seriously affectingecological equilibrium。
Inbreeding will affect human offspring, and this law also applies to fish. If fish are inbred, it will cause fish miniaturization.This is common in fish farms.
Therefore, people should actively care about protecting the remaining threatenedFreshwater fish species。
Situation in China
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executive summary
There are about 800 species of freshwater fishes in China.Among them,CyprinidaeThere are more than 400 genera and species, accounting for about half of all freshwater fish;Siluridae andMisguriaceaeThere are more than 200 species in both families, accounting for about a quarter of all freshwater fish;Other families such as AsteridaeOphiocephalidae SynbranchiaceaeThere are more than 200 species, accounting for about a quarter of all freshwater fish.
With the geographical location moving southward, there are more and more temperate fishes in rivers, and less and less cold water fishes.Liaohe River SystemThere are about 70 species of fish, and there are also northern species in the upstream;There are about 140 kinds of Yellow River water systems,Yangtze River systemThere are about 300 species of cold water fish, and there are very few cold water fish in bothgrass、silver carp、variegated carp、Bream、Megalobrama amblycephala、The Secretary General、Squaliobarbus curriculus、MulletBesides important economic fishes, there are also endemic species such as shad.
The upper reaches of the Yellow River and the Yangtze River systems and some rivers in the northwest plateau have very special fish species due to the terrain, such as 13 species of Schizothorax of Cyprinidae and 8 species of Epinephelus.Endemic speciesGymnocypris eckloni 、Diptychus dy-bowskii 、Spinibarbus sinensisandWhite turtleEtc.
Pearl River systemThere are more than 260 species of fish in total. In addition to the species widely distributed throughout the country, there are also some special types of fish, such asBoschium、Silver carpAnd other endemic species in South China, such asDace、Qishanyu、Sixu disc、Straight mouth dace、Tangyu、South China carpEtc.
After 20 years of re breeding, there are more than 6000 Formosan salmon, which were once endangered. The "national treasure fish" has been preserved.However, scholars found that there are 51 species of freshwater fish in Taiwan, which are even more critical than Formosan salmon. The top five includeLarge scale bream, Bab's silver goby, Iijima's silver goby, yellow fin stone goby and tail scale smiling shrimp tiger.
"The habitat of the bream has been seriously damaged, which is the most critical." Zeng Qingxian said that the bream has long been extinct in Taiwan, leaving a small section of Jinsha River in Jinmen, which is less than the Formosan salmon.Recently, the fixed riverbed project of Jinmen County Government has worsened the situation. Next month, it will be rescued with ecological construction methods.
In addition, for the first time, the silver goby was included as an endemic species in Taiwan, but it was also considered "extremely critical". Its living range was limited to Wuxi in Taichung, but it was located around the Bird's Mouth Pond project, which was full of crisis.The silver gobnow of Iijima's family distributed in Touqian Creek and Houlong Creek are also faced with the invasion of exotic species.Also threatened by the alien species are the yellow fin crabs;The smiling tail scale shrimps and tigers, who live in the southeast streams and Lanyu, are also facing a survival crisis. They are in urgent need of conservation.
Yesterday, the Forestry Bureau released the first Taiwan Freshwater Fish Red Book in China, which was completed by Shao Guangzhao, a researcher of the Chinese Academy of Sciences, Zeng Qingxian, a professor of Tsinghua University, and Chen Yixiong, a professor of Ocean University, who spent five years collecting information and conducting field surveys, listing 52 threatened freshwater fish.
What is worrying is that fish species in lakes and wild ponds are declining rapidly."Ninety percent of the Sun Moon Lake has been captured by alien species", Zeng Qingxian said that in addition to the threat of alien species and the rapid disappearance of Pi Pond, the crisis is mainly due to the lack of Chinese people's understanding of fish. Most of the alien species are released by religious groups and fishermen.He sighed that all the green fish were missing in the Pitang, and many star species that were once the indicators of the rehabilitation of engineering units were also included in the threat list, including the striped barbel on Caotun Interchange Road, No. 6 National Highway.
However, this survey also found that some ethnic groups have recovered their vitality, including the tall shovel jaw fish, perch eel and Taiwan betta.In addition, for the first timeHigh screen horse mouth, silver gobnow, rock climbing loach in Shenshijian, and Pingdong Leopard are listed as endemic to Taiwan.
Of the 52 threatened species in the Taiwan Freshwater Fish Red Book, there are still 42 species not included in the conservation list. The Forest Service Bureau said that, although the Red Book does not have the legal force of obstinacy, the next review and revision of the wildlife conservation list will give priority to the discussion, and more urgently needs the cooperation of the local government to prevent Taiwan freshwater fish from disappearing.
Rainbow trout, Salmonidae, is a fish treasure.It is named because there are rainbow like pigment bands on the side of the body.It is native to the rivers, lakes andPacific coastAfter artificial domestication and breedingFreshwater aquacultureOne of the fishes, known as freshwater“Fish King”It is called.
Distribution type
In different periods, the statistical results in different books are quite different.According to the latest publishedVertebrate Anthology of ChinaAnd being printedZoology of ChinaAccording to rough statistics, there are 1050 species of freshwater fishes distributed in China (including coastal estuaries), belonging to 294 genera, 52 families, 18 orders.Among them, 967 species are pure freshwater fish, 15 species are sea river migratory fish, and 68 species are estuarine fish.Of the 1050 species of fish, they can be roughly divided into the following four categories:
Round mouth freshwater fish
1. Roundmouth: This kind of fish is the most primitive fish like vertebrate.The fish mouth has no real upper and lower jaws, and the mouthparts form suction cups, living a parasitic or semi parasitic life.There is no real spine, only the spinal cord.From the evolutionary period, the round mouth class first appeared inMiddle Ordovician, onSilurianandLower DevonianIt was the most developed, and gradually disappeared in the Lower Devonian, with only a few species left today.Among fresh water in China, onlyLampetraThe three species of the species are from Heilongjiang toLiaohe RiverIn all rivers.
2．ChondrichthyesChondrichthyes were found in the Upper Devonian Period and developed most in the Carboniferous Period. With further evolution, they became modern sharks and rays.The whole skeleton of this kind of fish is cartilage, the scales are small shield scales, and there are spiral flaps in the intestine.This is a group of low-grade real fishes. Almost all living cartilaginous fishes live in the sea, and only a few species live in fresh water, among which the red ray lives in large numbersYu HaiyangBesides, a small group settled in Nanning, Guangxi, ChinaLongzhouOfXijiang River SystemZuojiangFrom its evolutionary history,Red rayIt is a marine fish.According to the paleogeological research, Guangxi was originally an ocean. Due to the orogenic movement of the crust, it was all in the late Pliocene of the Neogene. When the sea water withdrew from Guangxi, it was "sealed" and settled in the inland water body.
Cartilaginous Scleroderma Freshwater Fish
3. Cartilaginous Scleroderma: This kind of fish belongs to hard bone fish, but the skeletal system is cartilaginous.The scales on the body surface are rhomboid primitive scales of bone, the caudal fin is crooked, and there are spiral flaps in the intestine.The primitive cartilaginous ichthyes appeared in the Devonian period and lived on the earth for a long time, until the Mesozoic when most species were extinct.ViviparousSturgeonsAppears inCretaceousThere are only a few species living now, which are only distributed in the Arctic Ocean at high latitudes, and live in fresh water in ChinaPolyodontidae And 2 genera and 8 species of Acipenser.4. Bony fish: This is a common and real fish now. It is the most popular fish in modern times. Among the 1000 and 50 freshwater fish species in China, almost all of them are bony fish except a few (13 species).Freshwater fish in ChinaCypriniformesMost of them are Cyprinidae, which accounts for about half of the total.amongClupeiformes1 family, 3 genera and 5 species,Salmoniformes6 families, 17 genera and 32 species,Anguilliformes1 family, 1 genus and 2 species, 6 families, 170 genera and 740 species of Cypriniformes, 10 species, 27 genera and 110 species of Siluriformes, 2 families, 3 genera and 4 species of Pycniformes,Jaw needlefishes1 family, 1 genus and 4 species,Codiformes1 family, 1 genus and 1 species, 1 family, 2 genera and 2 species of Spiniformes, 1 family, 3 genera and 7 species of Mugiliformes, 1 family, 1 genus and 1 species of Synbranchia,PerciformesThere are 12 families, 51 genera, 110 species, 1 family, 4 genera, 8 species of Sebastiformes, 3 families, 3 genera, 5 species of Pleuromorpha, 1 family, 2 genera, 6 species of Triggeriformes, totaling 1037 species of 15 orders, 49 families.
Bony fish Freshwater fish
Bony fish Freshwater fish
Euosteichthyes occur injurassic periodIn the Cretaceous period, the ancient teleosts evolved into modern teleosts, and their morphology and structure changed greatly.The maxilla and mandible of the skull are generally shortened. The advanced type of maxilla is specialized as a bone stick without teeth. The teeth are concentrated on the premaxilla. The caudal fin has become a fully symmetrical tail or an orthomorphic tail. The internal skeleton is highly ossified. The odd and even fins show various shapes. The abdominal fins often move from the abdomen to the head, and the scales become thin and round.The internal and external structures of teleosts have perfect aquatic adaptive structures. Since Cretaceous, they have developed along many radiation adaptive routes, making them becomeEarth surfaceLiving in all waters.
Ornamental value
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Goldfish, the earliest ornamental fish raised in the world
Grass goldfish
Goldfish is the earliest developed ornamental fish in the world, and is also one of the most famous ornamental fish in the world.Goldfish originated in China, and its ornamental value was first discovered and its breeding can be traced back toSong dynastyIn the early years, peopleNatural waterFound wild inRed crucian carp, move it inFish pondAfter nearly 800 years of rearing in ponds, pots (vats) and other stages, it has gradually become a modern goldfish family with a wide variety of varieties.
The strains of goldfish can be roughly divided into five categories: grass species, culture species, dragon species, egg species and dragon back species.
1．Grass goldfish: Also calledCarassius auratus。It is the ancestor of goldfish. It looks like a crucian carp, has a flat spindle body, normal dorsal fin, and a single caudal fin.
There are two types of grass species, one is short tailed crucian carp, the other is long tailed swallow tailed.
2．fantail goldfish : Generally, the body is short, each fin is long, and the dorsal fin has four forked caudal fins;The eyeball is straight without protruding.There are rare varietiescrest of a crane, PearlTiger headEtc.
The languages can be divided into six categories: the smooth top of the head is the type of aragona;Sarcoma on the top of the head is of high head type;The head sarcoma is developed and covers both cheeks, and the eye is trapped in the flesh, which is a tiger head type;The double pompons formed by the developed nasal membrane are pompons;The turnover growth of operculum is a turnover type;There are translucent bubbles outside the eyeball, which are blister eyes.
3．Dragon goldfishThe appearance is similar to the language, but the eyeball protrudes out of the orbit.Since ancient times, dragon species have been regarded as authentic goldfish.There are more than 50 varieties of dragon goldfish, including rare onesWind Tail Dragon Eyes、Black Dragon Eyes、Magpie Dragon Eyes、Agate eye、Grape eye、Bulb eyeEtc.There are seven types of dragon seeds: smooth topFor the DragonEye type;Sarcoma on the top of the head is of tiger head and dragon eye type;The developed nasal membrane forms double pompons, which is dragon ball type;The gill cover turned over and grew into the type of dragon eye turning over the gill;The eyeball is slightly convex, and the head is triangular;The eyeball grows upward as a dragon with flag pulling and facing the sky;The bulbous corneal protrusion.
4．Egg goldfish: The shape is quite different from that of crucian carp.The body is short and fat, the eyeball is not protruding, and the back is straight without dorsal fin.There are rare varietiesRed egg、Pompon egg、Chicken egg、Vesicular eye、Lion's headEtc.
There are seven types of eggs: egg fish type with short tail;The tail length is egg chicken type;The head sarcoma is only limited to goose head type at the top;The head sarcoma is developed and covers both cheeks, and the eyes trapped in the flesh are lion head type;The developed nasal membrane forms double pompons, which is egg ball type;The operculum turned over and grew into a gill turning type;Translucent blebs outside the eyeball are blister eyes.5．Longbei goldfishThe shape is similar to that of eggs, but the eyeball protrudes out of the orbit.There are rare varietiesChaotian Dragon、Longbei、Longbei bulb eye、Hutou Longbei Bulb Eye、Toad headEtc.
There are seven types of dragon back species: short tail is dragon back type;Sarcoma on the top of the head is of tiger head and dragon back type;The developed nasal membrane forms double pompons, which is a dragon back ball type;The triangular head is a toad head;The eye grows upward to the sky dragon type;The operculum turned over and grew into the type of Longbei turning over the gills;The corneal protrusion is of the light bulb eye type.
The most in the world
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Largest freshwater fish
Scientists from 17 countries will study the world's largest freshwater fish in order to find better protection methods for freshwater ecological species.Scientific activities to find the world's largest freshwater fishMekongAs a starting point, researchers will continue to search farther and wider, fromAmazonTo the rivers around the Mongolian grassland.Their goal is to evaluateGiant catfish, StingrayGar、carp, salmon, sturgeon and other freshwater fish species that can grow to at least 2 meters long and 100 kilograms in weight.
According to scientists, the survival of many aquatic giants has been seriously threatened due to overfishing and the destruction of living environment.However, because these fish generally live in dark deep water in remote areas, people know little about them.
Researchers also hope to determine the world's largest freshwater fish species through this survey.according toGuinness World RecordsAt present, the record holder of the world's largest freshwater fish isMekong giant catfish, the challenger who may compete with one of them is fromCambodiaStingray in a big river and fish from ChinaYangtze RiverChinese sturgeon.
This scientific activity is supported by the World Wildlife Fund (WWF) andNational Geographic SocietyIt is jointly supported by more than 100 scientists from 17 countries.Robin Abel, a freshwater conservation biologist at WWF, said that the research should help identify animal species that need priority protection and improve people's awareness of these poorly known species.She said: "These giant fish species are equivalent to elephants and rhinoceroses in fresh water. If we can see them everywhere on land, the world will not last long once they disappear. This research will give us a new perspective to understand the living habits and survival threats of these species."
The biologist Ada Hogan is the main scientist of this research, and he is also a worldWildlife protectionEda said, "This is the first time to investigate and study all the giant freshwater fish in the world. Like the past research on coral reefs and deep sea, this research will also become a wonderful way to goUnderwater WorldA window of. "
Hao Gan is currently collecting data in the Mekong River basin in Cambodia. This area is home to many freshwater giant fish. The Mekong giant catfish here can weigh more than 300 kilograms. In addition, there are other noteworthy Mekong giant fish species, including giant carp, Pangasius catfish andGiant Stingray。Next month, Hogan and other researchers will travel along CambodiaMekongSearching for clues about the past and current distribution of these giant fish, scientists will ask local fishermen to determine where these fish may appear.
The Mekong giant catfish is considered to be the most endangered fish in Southeast Asia. Last year, the World Conservation Union listed it as an endangered species.
Hao Gan believes that the extinction risk of this kind of fish mainly comes from overfishing, dam construction and the controversial Mekong Rivernavigation engineering He said: "The Mekong River navigation project carries out dredging and blasting operations at the place where giant catfish spawn, which is undoubtedly very dangerous for the survival of giant catfish."
Hao Gan pointed out that species such as giant carp are extremely sensitive to the negative impact of fishing once they grow to 300 kg, because it takes them a long time to grow to sexual maturity.He said: "This kind of big fish has huge reproductive potential. A good spawning year may cause great changes in the number, but killing too many adult fish may also cause a sharp decline in the number."
Scientists believe that the giant stingray is also in danger of extinction in rivers like the Mekong River.It is reported that this kind of fish can reach 500 kg and 5 meters long. If it is true, it will exceed the current world record holder, the Mekong giant catfish.
Hogan said: "According to the original report of the fisherman, we believe that the stingray may still appear in the deep pools in northern Cambodia, but until now, no one has clearly indicated that this species has been found
Class. "
Freshwater fish
The largest catfish, weighing 293 kg, was caught in the Mekong River in Thailand.
"Kuno the Killer", a catfish, was previously recognized as the largest freshwater fish before it was found in the Mekong River in Thailand. It was famous for swallowing a dog.
breed
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There are many forms of freshwater fish farming. Pond fish farming and paddy field fish farming are common in rural areas.
freshwater fish
The assortment of fish species in pond culture is very important. Generally, the amount of high-quality fish species (such as grass carp, bream, black carp, carp, etc.) accounts for more than 60% of the total amount of fish species. It is also necessary to mix some fish species (such as tilapia) that do not compete for food.The feed for pond fish farming is very extensive, mainly including plant feed and animal feed.Cereals such as soybeans, wheat and rice, by-products such as bean cake, bran, distiller's grains and flour residue, aquatic and terrestrial plants such as wuping, bitter grass and barnyard grass, coarse fodder such as rice straw, corn cob, sesame stem, peanut shell, earthworms, snails, fly maggots, planktonAquatic insectFish meal and leftovers from slaughtering are good feed for fish farming.The formula feed popularized in production (made of rice straw powder, silkworm pupa powder, barley powder, rapeseed cake and a small amount of minerals) has a good effect on raising green, grass, carp, bream and other fish.One kilogram of fish can be raised with 0.8kg formula feed.Before stocking fingerling, the pond shall be cleaned and disinfected first by dissolving with lime or bleaching powder and then sprinkling.Fish fingerling shall also be disinfected. Common disinfectants include 3-5% salt water, 10PPM bleaching powder water, 8PPM copper sulfate water, etc.Soak the fish seeds for 5-15 minutes, and then put them in.The key to pond fish culture is to achieve: deep water and live water, good breed and strong, sufficient bait fertilizer, reasonable close breeding, multiple mixed breeding, rotation catch and rotation release, disease prevention and control, and careful management.
The key to fish farming in rice fields is to prevent escape. Before stocking, the ridge should be raised to 0.5m, beaten firmly, and fish ditches and fish slips dug to shelter fish in shallow irrigation, sun drying, pesticide and fertilizer application.Generally, carp are the main fish in paddy fields, and silver carp and bighead carp are not suitable.The stocking quantity should not be too large, and should be timely released early. The fish seeds can be put in the same year after the seedlings turn green.Fish species of the next year are generally released about half a month after transplanting.Generally, biological control or high efficiency and low toxicity pesticides are used for rice field application.The use of chemical fertilizers must be small in quantity and many times.[2]
disease control
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In recent years, due to the blind pursuit of freshwater fish production by farmers, the increase of breeding density and the large-scale promotion and application of pellet feedBacterial septicemiaQuite a lot.
Symptoms and diagnosis At the early stage of the disease, the mouth, abdomen, gill cover, orbit and both sides of the fish were slightly congested.Then the disease became worse, and there was congestion around the orbit,ExophthalmosThe abdomen is swollen, red and swollen, the liver and spleen are enlarged during dissection, the intestinal tract is congested, and there is no food, the gill filament is gray, and in serious cases, the gill filament is purple, and the end is rotten.From March to April, the diseased fish mostly showed hyperemia and inflammation in the head, mouth, gill cover, orbit and other parts, as well as on both sides of the fish body surface.After May, most of the diseased fish showed congestion and inflammation of the lower edge of the gill cover, fin base and viscera.
The causes of the disease are (1) high stocking density;(2) Poor water quality of pond;(3) Inbreeding results in decline of fish species;(4) Too much commercial feed and too little natural feed lead to too much fat in fish body, decreased resistance and increased mortality;(5) The farmers lack the awareness of disease prevention, and littering diseased and dead fish leads to the increase of pathogens in natural waters;(6) In the process of netting in winter, the failure of disinfection led to the pathogen invading the injured part of the fish body.
Preventive measures: Disinfect the area around the food court regularly, and deal with the disease in time if found.The diseased and dead fish shall be fished out in time and buried deeply, and lime, bleaching powderchlorine dioxideSprinkle and disinfect the whole pool.Timely start the aerator and add new water.Add proper amount ofvitamin CAnd improve the disease resistance of fish.Control the feeding amount and maintain good water quality.
Treatment measures (1) oral administrationGentamicin sulfate5 pieces per 100 kg of fish weight has significant effect on the treatment of crucian carp and bream hemorrhage.(2) This disease can also be induced by parasitic infection such as anchor head flea. Kill the fish on the first dayEctoparasite；Use water disinfectant for disinfection the next day, and disinfect again every other day;At the same time, mix 2~2.5 grams of feed per kilogramEnrofloxacin, continuous feeding for 5-7 days (stop feeding for 1 day before administration);On the sixth day or so, the whole tank is sprinkled with quicklime slurry once to regulate the water quality.
White skin disease
White skin disease, also known as "white tail disease", is bacterialfishOne of the diseases.The disease is mainly caused by poor water quality, which makes bacteria multiply, or improper operation in the breeding process, which causes fish injury and bacteria invasion.
Pathogen: whitePseudomonas, 0.8X0.4 microns in size.
Epidemic situation: It is one of the main diseases of silver carp and silver carp at the fingerling stage, and the epidemic season is from June to August every year. Especially before and after the summer flower pond, when the fish body is injured due to careless operation or there are a large number of protozoa parasitic on the surface, such as wheelworm, the pathogenic bacteria take the opportunity to enter, leading to an outbreak of epidemic.It mainly harms silver carp and bighead carp. Grass carp and black carp can also be injured sometimes. It takes only 2-3 days from the onset to death, and the mortality rate is as high as 50%.
Symptom: At the initial stage of the disease, white spots appear under the dorsal fin or at the caudal handle of the diseased fish, and the caudal handle turns white and spreads rapidly.With the development of the disease, the body surface behind the dorsal fin base turns white, commonly known as "white flower waist".When the disease is serious, the tail fin of the diseased fish rots or is incomplete. The head is downward and the tail is upward, perpendicular to the water surface. Sometimes it swims in a struggling way, sometimes it hangs in the water, and soon dies.
Course of disease: the course of disease is short, the onset is fierce, the epidemic area is wide, and the death rate is only 2-3 days from the onset to the death. The death rate of fish species can reach more than 50%.The epidemic period is from May to August every year.
Prevention and control methods: 1. Preventive measures: 1. The pond should be thoroughly cleaned, and medicine baskets or baits should be hung in the season of onset for prevention;2、 The summer flower seedlings should be separated from the pond in time. During the process of fishing, transportation and stocking, the fish body should be avoided as much as possible;When parasites are found on the body surface, they should be promptly killed;Keep the water quality of the fish pond clean, and do not use unfermented manure.
Prevention: (1) Thoroughly clean and disinfect the pool, regularly spray 25ml/mu · m of net mold orDithiocyanomethane25ml/mu · m;
