CATDOLL : CATDOLL: What’s causing the decline in wild freshwater fish diversity?

1. What is the reason for the reduction in freshwater wild fish diversity?

It is mainly human hunting and urban sewage discharge that have led to the disappearance of a large number of fish.

2. Freshwater fish?

Mullet, silver carp, carp, grass carp, dace, crucian carp, sturgeon, etc. are all freshwater fish.

3. Freshwater fish that eat shrimp?

Tilapia is omnivorous and often eats aquatic plants and shrimps; salmon eats plankton, insect larvae, shrimps and small fish; bream is an omnivorous fish and eats both meat and vegetables; black carp is a carnivorous fish and mainly eats small fish and shrimps; map fish is omnivorous and eats small fish, shrimps, etc.; arowana is omnivorous and eats shrimps, blood worms, feed, etc.; arowana eats animal feed, small fish, shrimps, etc.; crown mullet is omnivorous and eats dry feed, shrimps, etc.; red-tailed crown mullet is a carnivorous fish and likes to eat small fish, shrimps, mealworms, etc.; longspined fish is omnivorous and mainly eats small benthic animals, shrimps, small aquatic insects and some invertebrates.

4. Freshwater herbivorous fish?

Answer: Grass carp

Grass carp, an animal of the genus Grass Carp in the family Cyprinidae of the order Cypriniformes, is included in the "List of Key Protected Economic Aquatic Animal and Plant Resources of China (First Batch)".

It has an elongated body, with a cylindrical front, a flat tail, a round abdomen, and no abdominal ridges. It has a wide, medium-sized head, a slightly flat front, a short and blunt snout, and a snout slightly longer than the eye diameter. Its scales are medium-sized and round, with an arc-shaped lateral line in the front and a straight line in the back, extending to the base of the tail fin. It is a herbivorous fish that lives in rivers and lakes in plain areas. This type of animal is distributed in China, Russia, Bulgaria and other countries.

5. China’s freshwater predatory fish?

1 sea bass

Perch are usually found at the mouths of freshwater rivers. Occasionally they also forage in freshwater areas. In addition, we sometimes see them in reservoirs. However, they are rare and hard to come by. Perch are ferocious carnivorous fish with a big appetite and a strong desire to feed. They can eat 5%-12% of their body weight, especially in spring and summer. Perch grows quickly and can reach more than one meter in length.

2 Mandarin fish

Mandarin fish usually live at the bottom of the water surface. This kind of fish is very common and is distributed in most waters in China. They like to lie in still water or slow-flowing rivers and lakes, especially in shallow lakes with aquatic plants. This kind of fish has high requirements for the surrounding environment and is more sensitive. During the day, they will lie motionless at the bottom of the water and come out to look for food at night, so this kind of fish is suitable for night fishing. Mandarin fish like to make nests and live alone. When the water temperature is 15-30 degrees Celsius, its activity is still very high. When the water temperature is lower than 7 degrees Celsius, it will no longer be active. It is a typical carnivorous fish because they can prey on the fry of other fish as soon as they hatch. They like to stay in places covered by aquatic plants or blocked by rocks. Anglers can pay more attention to these places when fishing.

3. Upturned lips

The black carp is also a common fish, also known as whitefish or big whitefish. It often feeds in the middle and upper layers of flowing water or wide water areas. This fish is fast and good at jumping. It is more common in rivers and reservoirs and usually feeds on small fish. The largest one I have seen is 10 kg. The sexual maturity age of the black carp is 3 years for females and 2 years for males. The most active period is from June to August. They are used to chasing moths on the water surface. The desire to eat is strongest at night and early morning, so you can choose night fishing.

4. Blackfish

Blackfish is also known as mullet and money fish. It is distributed in all waters except the western region of my country. It is also a target fish that lure fishing prefers. Blackfish generally feed on other fish species, and young blackfish prey on some plankton. After the blackfish bites the hook again, it will burst out with amazing power, and the blackfish is the most aggressive. Generally, it will bite the hook when it sees food. The peak season for blackfish foraging is spring and autumn, and April to July is the spawning season. They will spawn in shallows with lush aquatic plants, and then male and female fish will guard their nests together. Of course, it is not recommended for everyone to go fishing for blackfish at this time. After all, we are "fishing for fishing, not for fish". It is still a bit cruel to spawn and fish for blackfish.

6. Northern freshwater economic fish?

Crucian carp, carp, silver carp, grass carp, green carp, horse mouth, whitebait, wheat ear, various trout, salmon, sturgeon, black carp, giant salamander, salmon and more!

7. Are freshwater whales fish?

Freshwater whales are fish, also known as freshwater dolphins

Freshwater dolphins are also known as river dolphins, freshwater dolphins, and freshwater whales. They are poisonous and are not a single species, but a general term for some cetaceans that have adapted to freshwater habitats such as rivers, lakes, etc., so they are also called freshwater dolphins and freshwater whales. The various freshwater dolphins are distantly related and come from different evolutionary branches, so freshwater dolphins are a general concept and have no taxonomic significance.

8. Fujian freshwater fish?

Fujian has a rich variety of freshwater fish. In addition to the four major fish species, there are many different species in various mountain streams, such as horse mouth, river grouper, loach, army fish, etc. For example, there are more than a dozen species of small fish in the stream at an altitude of 1,000 meters in Shiniu Mountain, Quanzhou City. There are also foreign species in common reservoirs, and the most common one now is tilapia.

9. Hainan freshwater fish?

1. Horsemouth fish;

2. Silver carp;

3. Tang fish;

4. Basin-lipped Chinese carp, etc.

10. Complete list of freshwater fishes?

Fish

Fish are the oldest vertebrates. They live in almost all aquatic environments on Earth, from freshwater lakes and rivers to saltwater seas and oceans.

There are about 24,000 species of fish in the world. Two-thirds of them live in seawater, and the rest live in freshwater. There are 2,500 species in China, of which more than 100 can be used for medicinal purposes. Common medicinal animals include seahorses, sea dragons, eels, carp, crucian carp, sturgeons (swim bladder is fish swim bladder glue), large yellow croaker (otolith is fish brain stone), sharks, etc. In addition, they are often used as raw materials in the pharmaceutical industry. For example, the liver of cod, shark or ray is the main raw material for extracting cod liver oil (vitamin A and vitamin D). Hydrolyzed protein, cytochrome C, lecithin, cephalin, etc. can be extracted from various fish meats. The liver and ovaries of pufferfish contain a large amount of tetrodotoxin, which can be extracted to treat neuropathy, spasms, tumors and other diseases. The bile of large fish can be used to extract "bile pigment calcium salt", which is the raw material for artificial production of bezoar.

Fish live their entire lives in seawater or freshwater. Most of them have a body shape and fins suitable for swimming. They breathe with gills and hunt with their upper and lower jaws. They have a beating heart with one atrium and one ventricle. The blood circulation is a single cycle. The appearance of the spine and head has enabled the fish class to evolve into the most adaptable vertebrate to life in water. This is because water has different depths and the pressure in different places is different. The sea level is 1 atmosphere, while the deep sea area can reach 1000 atmospheres. The salt content of freshwater and seawater ranges from 0.001 to 7% from freshwater to saltwater. In addition, the temperature difference and oxygen content of water vary greatly depending on the geographical environment. Due to the diversity of these waters, water layers, water quality, biological factors and non-biological factors in the water, the body structure of fish has undergone different changes to adapt to different changes in the outside world. It is higher than the Cyclostomata.

Fish is the largest class in the existing vertebrate subphylum. From the perspective of animal evolution, this class is the beginning of jawed fish, so it is the most primitive and ancient class of jawed fish. This is the largest classification group in the vertebrate subphylum. As early as the Devonian period, many marginal branches were derived, and they have developed and evolved into various complex fish. Existing fish are divided into cartilaginous fish and bony fish.

1. Chondrichthyes

This system is the lowest group of existing fish, with about 200 species in the world and more than 140 species in my country, most of which live in the sea.

Its main features are:

① There are no hard bones throughout life, and the internal skeleton is composed of cartilage.

② Most of the body surface is covered with scales.

③ The gill septa are well developed and there is no gill cover.

④ Crooked caudal fin. This system is divided into two subclasses, namely, the Elasmobranch subclass and the Holocephalus subclass.

2. Osteichthyes

Bony fishes are the most numerous group of fish in the world, with more than 20,000 species. Most of them live in marine waters, and some live in fresh water.

Its main features are:

① The bones harden to different degrees.

② The body surface is covered with hard scales, round scales or comb scales, and a few species are degenerate and scaleless. The mucous glands of the skin are well developed.

③ The gill slits are partially or completely degenerated, the gills do not open directly to the body, but are protected by bony gill covers. The water flowing out of the gill slits is discharged through the posterior edge of the gill cover, and most of them have a swim bladder.

④ The fish tail is usually straight, but it can also be original or crooked.

⑤ Most are fertilized in vitro and are oviparous, and a few have abnormalities in their development.

The first fish were round-mouthed, jawless fish that appeared on Earth 450 million years ago during the Cambrian period. Fish are easily distinguished by their appearance and form the largest group of vertebrates: there are more than 22,000 species of fish out of a total of 50,000.

Not all animals that live in water are fish. Whales, for example, are mammals. However, all fish are well adapted to life in water. They use their fins to move. Fish have two pairs of fins - pectoral and pelvic fins, one on each side of the body; a caudal fin, located at the tail; and, depending on the species, one or two dorsal fins on the back and one anal fin on the buttocks. They have a gas-filled sac called a swim bladder, which enables fish to sink, float, and maintain their position in the water. Only rays and sharks do not have this organ. Fish also have gills for breathing, which are covered by operculum in most species. The gills are located on either side of the head, behind the mouth, and are used to filter the water taken in through the mouth, extract oxygen from the water, and then expel the water through openings called gill slits. Different species of fish vary greatly in size. Their bodies are made up of three parts: the head, the trunk, and the tail. The skin is covered with scales, which vary in size and number. There is a distinct line on each side called the lateral line, which is a sensory organ used to determine direction. The muscles of some bony fish are separated by tiny bones.

The first fish to appear on Earth had a round, jawless mouth. Today, only 70 species of these fish exist, forming the jawless fish. Among these fish, the lamprey is the most famous. It has no scales, and its elongated body is round and looks like an eel. The lamprey attaches itself to other fish with a mouth with a suction cup and feeds on the host's blood. Other fish are divided into two major categories: bony fish and cartilaginous fish.

Bony fish have a skeleton. This group includes primitive bony fish, which have only a portion of their skeleton made of bone. Examples include lobefins (including the coelacanths), lungfish, and sturgeons (such as sturgeons), which differ from more advanced bony fish in that their skeletons are made entirely of bone. Moray eels, soles, and crappie are examples of bony fish that vary in appearance, but all have a very symmetrical tail fin covered with tiny scales (with a few exceptions, including eels and some carp). Bony fish are divided into several groups. Anguilla are fish whose larvae look very different from the adults. Herring are fish that live in groups. Carp include almost all freshwater fish. Perch and tunas are fish whose tail fins are supported by hard spokes. They are called "thorn-finned" fish, and they make up the largest group of bony fish.

Cartilaginous fish have a skeleton made entirely of cartilage, reinforced with calcium. This group of fish includes sharks and rays.

Eels are born as small, flattened fish called "young eels". When they mature, they have a long, smooth body, usually scaleless, with a continuous fin along their back. Eels live in rivers and lakes in Europe and America, and migrate to the Sargasso Sea northeast of the West Indies in the North Atlantic, where they breed. The young die after they are born. Young eels take on their adult form on their way back across the Atlantic, and on their way back, they also begin to breed in the Sargasso Sea.

Herring live in the North Sea, the English Channel and the Baltic Sea. Adults have a light-colored belly and a dark blue or nearly black back. Like sardines and sprats, they live in groups, sometimes in groups of several thousand. This is an effective method of self-defense for each individual fish, since a predator can only choose one target among many. When attacked, the school of fish disappears almost immediately.

There are several thousand species of fish belonging to the carp family, which are found almost all over the world. These freshwater fish have large scales and their teeth are not fixed in the jaws but in the throat. Their mouths can be moved forward to suck up food. Many species of the genus Cyprinus live mainly in calm rivers, small ponds and lakes in Asia and Europe. The shapes and colors of the species vary greatly. Some species have only a few large scales (mirror carp) or almost no scales (grass carp). These fish are easy to breed, and breeders have created many varieties. Carp mainly feed on plants and invertebrates. The spawning season depends on the water temperature, which should not be too cold (at least 20°C). Female fish produce hundreds or thousands of eggs, but most of the small fry become food for other fish and even adult carp as soon as they are born.

The spiny-finned fish appeared about 60 million years ago. The typical representative of this group of fish is the perch, which has fins supported by hard, sharp spokes and a large tail fin with spines. Perches live in lakes and rivers in Europe and North America. They eat invertebrates and small fish, including their own young. Other species of these fish live in the ocean, such as tuna and swordfish, which are powerful swimmers and can swim up to 100 kilometers per hour. Tuna can weigh up to 500 kilograms and are carnivorous. They have the unique ability among fish to maintain a body temperature higher than the water temperature. Their species include the albacore tuna in the Pacific and the bluefin tuna in the Mediterranean and Atlantic.

Sharks and rays are the main representatives of modern cartilaginous fish, which may have appeared 410 million years ago. As their name indicates, they have a skeleton made of cartilage. Cartilage is a flexible material that hardens when filled with calcium and is as solid as bone. Cartilaginous fish grow in large numbers in temperate and hot oceans. They breathe in the water with gills. The gills communicate directly with the outside world through several gill slits at the back of the head. There are about 550 species of cartilaginous fish, of which 370 are sharks, and the rest are basically flat-bodied skates and electric rays.

As experimental research objects or materials in the fields of biomedicine, environmental protection science, etc., fish animals have achieved many scientific research results all over the world. For example, the research of Gordon in 1950, Klontz and Smith in 1968, etc., in the twelve years before 1968 alone, major biological science journals in various countries published 2,500 reports on this topic. In the past 20 years, there are more related documents. Among the known vertebrate species, there are 30,000 fish species (estimated to be 40,000 species), 8,600 birds, and only 4,500 mammals (i.e., mice, rats, rabbits, dogs, etc. commonly used today). It can be seen that using fish animals as experimental materials is indeed an inexhaustible resource, which has prompted people to widely develop, study and try to apply such rich potential resources.

The use of fish for biomedical research, especially drug toxicology and pharmacology testing, has many unique advantages: fish are very sensitive to certain drugs and poisons, and can cause strong reactions as long as they contain very small amounts of ingredients; in addition to using death as an indicator for pharmacology and toxicology testing on fish, the impact on their habits may be more sensitive; it is appropriate to directly put smaller fish into different concentrations; this may be more suitable for studying certain Chinese herbal medicines with low content or weak pharmacological effects that require long-term oral administration; fish are more sensitive to certain central nervous system stimulants or inhibitors; the results of the fish test method are clear and easy to grasp; in terms of breeding and management, fish are a relatively economical experimental animal.

So far, there are pure fish experimental animals with more than 20 generations of inbreeding (Gordon, 1950); the development of sterile fish experimental animals is also being explored (Luckey, 1936). Fish experimental animals have been widely used in experimental research fields such as embryology, genetics, endocrinology, toxicology, behavioral science, comparative pathology, and environmental protection science (Mitruka et al., 1976). Fish animals have certain unique advantages and characteristics that cannot be replaced, and their biological traits can be completely compared with the corresponding traits of humans. In China, there are many studies on fish disciplines and their breeding, but the development, research and application of fish as experimental animals is very lacking (Zhu Xi et al., 1960, 1962).

The application of fish experimental animals has achieved fruitful results. Fish animals (especially small freshwater fish) have been used in cancer research in the field of oncology, and a lot of observation and experimental work has been done. It is known that all tissues of freshwater fish animals will develop neoplastic lesions, and their clinical course and morphological manifestations are similar to tumors of other vertebrates (including humans). Therefore, fish experimental animals have become indispensable materials in experimental oncology, especially comparative tumor oncology and exploration of suspected carcinogens in the environment (especially in water sources). In fact, the research on fish oncology has gone through the stages of systematic classification and experimental analysis, and has reached a new stage of prevention and treatment research (Squire et al., 1978), with broad prospects.

The use of goldfish (Carassius Auratus Linnaeus) in biomedical research has been reported. Diethylnitrosamine was added to the water in the goldfish tank (less than 120 ppm) for 4 months, and then kept for 6 months. It was found that among the 13 experimental animals, 1 fish had liver cancer in its liver, and 4 other fish had precancerous cell lesions in their livers (Bannsch, 1976). The livers of the control group animals were all negative. This suggests that it is possible to use goldfish as experimental animals to establish a model of induced tumors.

Fish have unique uses in toxicology. Fish are often used for acute toxicity tests. When conducting such tests, various experimental conditions must be strictly followed before and during the test: representative test fish in the region must be selected, and this fish species is more sensitive to harmful substances. Bait organisms must also meet the experimental requirements. During the test, the concentration of harmful substances in the water should be kept as stable as possible, and toxic reactions should be found at the specified concentration. When conducting toxicity tests, it is required that the average body length of freshwater fish, marine freshwater fish or marine fish should be less than 50 mm when tested. It is best to domesticate the newly collected fish for less than one week until they gradually adapt to the experimental conditions. The amount of feed should be small during the domestication process, and feeding should be stopped 2 days before the experiment. Within 4 days before the experiment, the mortality rate and morbidity rate of domesticated fish must be above 10%. The water temperature should be kept within a certain range. Warm water fish require 20-28℃, and cold water fish should maintain 12-18℃. The general range of variation should not exceed 4℃. If more than 10 test fish are placed in each experimental concentration group, a flow-through test device should be used to continuously replace the water in the test tank, and the water should be changed 6 to 10 times a day. If a static water test method is used, the experimental concentration should be kept below 1 gram per liter of freshwater water; the seawater should be kept below 0.3 grams. All water should be replaced at least once every 24 hours. 5 to 10 levels of test concentrations of 100, 75, 56, 42, 32, 24, 18, 13.5, and 10 ml/L should be selected with equal logarithmic intervals. An exploratory test should be conducted in advance, and the preliminary concentration must include a concentration with a mortality rate of about 50% within 24 to 96 hours. The dissolved oxygen content in the experimental water should not be less than 4 mg/L for warm water fish; and not less than 5 mg/L for cold water fish. Whether the test fish is dead or not, a glass rod can be used to tap the tail handle of the fish. If the fish does not move, it is determined to be dead. A control experiment is required at the same time. When the death rate of fish in the control group exceeds 10% or there are unhealthy fish, the experimental results obtained cannot be used.

Qishan fighting fish (Macropolecs Opercularis) or Thai fighting fish (Betta Splendens) are sensitive animals for determining whether drugs inhibit instinctive behavior. Fighting fish grow in Southeast Asia and are available in Guangdong Province, my country. The breeding temperature is 27-29℃. If tap water is used for breeding, it needs to be placed in the open air for more than 24 hours. It should be avoided to put in undiluted drugs, as rabbit fish will be poisoned by drinking high concentrations of drugs. Female and male fish do not fight when living in groups. When breeding, if a mature male fish that has been isolated for one day meets another male fish, fighting will occur. If two male fish are kept in square glass tanks, the two tanks are separated by cardboard. When the cardboard is removed, the gill covers of the two fish can be seen to open, and the dorsal and caudal fins are stretched out, and they rush to each other. If chlorpromazine hydrochloride is put into the tank at a content of 2 mg/L, the fighting behavior of the fighting fish can be stopped. If a certain drug can inhibit instinctive behavior, it can prevent the two fighting fish from fighting. Some people divide the fighting fish into five stages according to the degree to which drugs can inhibit their fighting ability: Stage 0 means no inhibition of fighting; Stage 1 means tameness, with suppressed fighting movements and normal feeding; Stage 2 means imbalance or sideways movement; Stage 3 means anesthesia, sideways movement, and slight or absent reaction to touch; Stage 4 means death.

Catfish (Ictalurus nebulous) has no electric organs, but has sensitive electrical sensations. Four electrical sensory centers have been discovered, namely the posterior lateral linear lobe of the medulla oblongata, the posterior lateral lobe of the cerebellum, the semicircular process of the midbrain, and the anterior prominence nucleus. It is suitable for studying the response of the electrical sensory center to static and dipole electric fields.

Catfish are 15 to 20 cm long. They are anesthetized by cooling (1 to 4°C), and then a small hole is made on the top of the head to expose the brain to be recorded. After the operation, 0.5 mg/kg of tubocurarine is injected intramuscularly. The catfish is sunk into the experimental tank, with only the surgical site exposed above the water surface. Water containing saturated air is introduced into the mouth through a latex tube, and artificial respiration is performed. Glass microelectrodes (35 to 60 MΩ) or tungsten microelectrodes (3 to 12 MΩ) are used for extracellular recording. The recording sites are the posterior cerebellar lobe and the anterior prominence nucleus.