Freshwater Fish Introduction: Common Species, Farming Costs, Density and Fish Egg Incubation Management Techniques

Fish are the oldest vertebrates. They inhabit almost all aquatic environments on Earth—from freshwater lakes and rivers to salty seas and oceans.So what are freshwater fish? Which ones are commonly eaten? How much does farming cost? What is a reasonable density? What are the fish egg incubation management techniques?

What are freshwater fish?

1. In a broad sense, fish that can live in freshwater with a salinity of 3 parts per thousand can be called freshwater fish. In a narrow sense, it refers to fish that must spend part of their life history, such as only the "juvenile stage" or the "adult stage", or their entire life, in freshwater. There are about 26,000 known species of fish in the world, of which about 8,600 are freshwater fish. China currently has nearly 3,000 species of fish, including more than 1,000 species of freshwater fish.

2. There are about 26,000 known species of fish in the world, making them the largest group of vertebrates, accounting for about 48.1% of all vertebrate species. The vast majority of them live in the ocean, and there are about 8,600 species of freshwater fish. China currently has nearly 3,000 species of fish, including more than 1,000 species of freshwater fish.

What are the commonly eaten freshwater fish?

1. Mandarin fish

Also known as guiyu or jihuayu, it has long been regarded as a "fine fish". Its flesh is plump, thick and tender, delicious, and has relatively few bones. Spring is the season when mandarin fish is at its fattest and most delicious, so it is also called a "spring seasonal delicacy". As a delicacy at banquets, mandarin fish is deeply loved by people, and the main cooking methods are steaming, braising and deep-frying. The most famous dish, "squirrel mandarin fish", is known to everyone.

2. Common carp

Also known as red-tailed fish, longmen fish and so on. Its body is spindle-shaped, the mouth is at the front of the head, and there are two pairs of barbels beside the mouth. The body color is greenish-yellow, and the lower lobe of the caudal fin is red. The dorsal fin and anal fin both have hard spines, and the rear edge of the last spine is serrated. There are many kinds of common carp. In particular, Yellow River carp is one of China's four famous fish, and its taste is even more tender and delicious. It is usually cooked by braising in soy sauce, steaming, or braising in soy sauce.

3. Grass carp

Because it feeds on grass, it is also known as caoyu, caohuan, caobang, caoging or houyu. Grass carp comes in green and white colors, and the white one tastes better. Grass carp has tender flesh, few bones and rich nutrition. It contains abundant unsaturated fatty acids and rich selenium, and regular consumption has anti-aging and beauty benefits.

4. Crucian carp

Also known as xitou, jiguaizi (Hubei), jiguazi (Northeast China), hejiyu (Shanghai), and yuejizai (Guangdong). Crucian carp is rich in animal protein and unsaturated fatty acids. Regular consumption can not only strengthen the body but also help lower blood pressure and blood lipids, helping people live longer. Eating crucian carp can stimulate the appetite and strengthen the spleen, regulate nutrition and promote fluid production. It not only supplements the nutritional protein needed for milk production, but a healthy spleen can also promote milk secretion. Therefore, eating crucian carp does indeed increase milk secretion in mothers with little milk or poor milk flow.

5. Silver carp

Also known as bailian, tiaolian, lianziyu and so on. The scales are silver-gray, the mouth is relatively large, the eyes are positioned lower on the sides, there are fleshy ridges on the ventral surface both before and after the pelvic fins, and the tips of the pectoral fins reach the base of the pelvic fins. Silver carp has tender flesh and can be cooked into dishes such as fried fish, smoked fish and braised fish.

6. Bighead carp

Also known as fathead fish, spotted silver carp and so on. Its flesh is noticeably concentrated in the head, and its body color is dark green with indistinct patterns. Bighead carp is a high-protein, low-fat, low-cholesterol fish species and has a protective effect on the cardiovascular system. Bighead carp has a relatively large head and rich, delicious meat, suitable for making casserole fish head, hot pot or chopped chili fish head.

7. Catfish

Also known as huzilian, tangshi fish or shengzai fish. It has no scales over its whole body, its body surface is covered with mucus, its head is flat and its mouth is wide, and it has four barbels on the upper and lower jaws. The best season to eat catfish is between mid-spring and mid-summer. Catfish contains relatively large amounts of protein and fat and has a good dietary therapeutic effect on weakness, deficiency and malnutrition. Catfish is mostly cooked by braising, stewing and boiling.

8. Snakehead

Also known as caiyu, shengyu, wubang, wuliyu and so on. The snakehead has a cylindrical body, a slightly flattened tail, a pointed, long and flat head, and scales on top that resemble a snake's head. In Guangdong and Guangxi, snakehead has long been regarded as a tonic. In the north it is mostly prepared Sichuan-style in water, while in the south it is mostly simmered into soup.

How much does freshwater fish farming cost?

For common freshwater fish, such as the four major Chinese carps, at ordinary stocking density, including feeding machines and oxygen generators, it costs 50,000-60,000 yuan. If it is famous, special and high-quality fish, the same setup costs 90,000-100,000 yuan.

What is a reasonable density for freshwater fish farming?

A reasonable stocking density should be determined according to the farming method, technical level, water exchange conditions and feed supply. The stocking density used in each place should be adapted to local conditions according to the pond conditions. For farmers using the 80:20 pond fish farming technique for the first time, the weight of the main cultured fish at harvest per mu of water surface should not exceed the following limits:

1. In ponds where aeration is restricted and water cannot be flushed in, the fish weight is set at 167 kg;

2. In ponds where aeration is not restricted but water flushing is restricted, the fish weight is set at 267 kg;

3. In ponds where neither aeration nor water flushing is restricted, the fish weight is set at 400 kg;

4. Together with the 20% weight of companion-cultured fish, the total fish production weights of pond types a, b and c are 209 kg, 333 kg and 400 kg respectively.

5. If the desired average size at pond harvest is 500 g, then the total stocking numbers of fish in pond types a, b and c are 418, 666 and 800 respectively. Among them, the main cultured fish account for 80%, and companion-cultured fish account for 20%.

For warm-water fish farming, the general water temperature is 15_30℃, such as common carp, grass carp, silver carp, bighead carp, crucian carp and blunt snout bream; for cold-water freshwater fish farming, the suitable temperature is generally 10_20℃, such as rainbow trout and fine-scaled fish; for hot-water fish farming, the suitable temperature is generally 18_30℃, such as tilapia and freshwater pomfret.

Appendix: Fish egg incubation management techniques

1. Cleaning and disinfection of incubation containers. Before putting fish eggs into the incubation container, wash the incubator clean, disinfect it thoroughly, and check it carefully to strictly prevent water leakage and loss of fry. After the fish eggs are put in, frequently wash the sieve silk net, especially before the fry hatch, to prevent egg membranes from sticking to the sieve silk.

2. Regularly water temperature, water quality and embryonic development. Focus on preventing water mold and predators.

3. During the incubation period, provide different water flow rates according to different embryonic development stages. From cleavage to before the fry hatch, the flow rate should be controlled so that the eggs and larvae do not sink and accumulate, generally 7.5 L to 12 L/min; after the fry hatch and before horizontal swimming, the flow rate can be appropriately increased, and after horizontal swimming it should be appropriately reduced to about 5 L/min to avoid excessive water flow, which would make the fry swim against the current and consume energy.

4. Stop water flow to dissolve membranes. When about 5% of the fish eggs have hatched, close the water inlet valve so that the water in the incubator stops flowing and the fish eggs sink. Generally after about 15 min, 95% of the fry have hatched, and at this time immediately open the valve to wash the fry upward.