CATDOLL : CATDOLL: How many spawning methods do fish have? Sub-cold water fish?

1. How many ways do fish lay eggs?

There are three types of fish reproduction: oviparous, ovoviviparous and viviparous.

1. Oviparity is the reproductive method of most fish. Fish lay eggs outside the body, and the embryonic development takes place outside the body. The embryonic development process completely relies on the nutrients in the eggs.

2. Ovoviviparous fertilized eggs develop in the female reproductive tract, mainly relying on yolk nutrition during development, and have no nutritional relationship with the mother, or the mother's reproductive tract mainly provides water and minerals, and finally the mother produces fry. Such as guppies.

3. The embryos of some viviparous elasmobranch fish are connected to the mother through blood circulation. The nutrients needed for embryonic development are not only provided by the yolk of the embryo itself, but also by the mother. There are some protrusions on the wall of the oviduct where the embryo develops, which are connected to the embryo, forming a structure similar to the placenta. The mother sends nutrients to the embryo through this structure. For example, the gray star shark.

2. Sub-cold water fish?

Silver carp is a typical filter-feeding fish, and its natural bait is the plankton in the water. In the process of fish farming, a lot of food residues and fish feces are produced. When these things decompose in the water, the aquaculture water will become "eutrophic", and when the water is eutrophic, a large amount of plankton will be produced. Then, by controlling the number of plankton in the water through the feeding of silver carp, the water quality can be purified. Of course, this is also what we often say, raising silver carp together with other main fish.

3. Is tilapia a warm water, mild water or cold water fish?

Warm water,

Tilapia, commonly known as African crucian carp, belongs to the order Perciformes, the suborder Perciformes, the family Cichlidae, and the genus Tilapia (also known as the family Cichlidae). This genus is native to Africa and has more than 600 species, of which 15 are currently farmed. Tilapia is a group of small and medium-sized fish. Its appearance and individual size are somewhat similar to crucian carp, and its fins are more like those of mandarin fish. It is a euryhaline fish that can survive in both sea and fresh water; it tolerates low oxygen and generally lives in the lower layer of water, but changes its water layer with changes in water temperature or fish size.

Tilapia has a wide range of diets, most of which are omnivorous and mainly plant-based. They are very poor eaters and have a large food intake. They grow rapidly, especially in the juvenile stage. Tilapia growth is closely related to temperature, with a growth temperature of 16 to 38 degrees Celsius and an optimum temperature of 22 to 35 degrees Celsius.

Tilapia was first introduced to Taiwan Province from Singapore by Wu Zhenhui and Guo Qichang in 1946. In memory of these two people, it was first called "Tilapia". It was introduced to mainland my country from Vietnam in 1957 and is also known as "Vietnamese fish". Because it is native to Africa and looks like local crucian carp, some people call it "African crucian carp".

There are two kinds of tilapia introduced to Yingshan Hot Spring in Hubei: one is called Mozambique tilapia, which was brought to Yingshan Hot Spring from Jingshan County in 1972; the other is called Nile tilapia, which was introduced by Hubei Fisheries Research Institute in 1979. After they settled down, they all lived well.

Dr. Modadugu Vijay Gupta of India won the 2005 World Food Prize for developing and disseminating low-cost technology for freshwater aquaculture (using tilapia).

The main production area of ​​tilapia farming in my country is the southern region. According to statistics, the production of tilapia in Guangdong, Guangxi and Fujian in 2000 exceeded 100,000 tons. Guangdong Province has always been the main production area of ​​tilapia farming in my country. For example, the province's tilapia production in 1999 was 210,000 tons, and the tilapia farming production in 2000 reached 250,000 tons. By 2001, the tilapia farming production reached 270,000 tons, accounting for 40% of the total tilapia production in the country. The production in 2002 was 290,000 tons, 390,000 tons in 2003, and 440,000 tons in 2004, accounting for 49% of the country. Tilapia has become the largest freshwater aquaculture species after grass carp, bighead carp and silver carp. The output of tilapia in Hainan Province was more than 60,000 tons in 2000, more than 70,000 tons in 2001, and 82,000 tons in 2002. In 2003 and 2004, the output of tilapia in Hainan Province remained at about 100,000 tons, accounting for 70% of the province's freshwater fish output. As can be seen from Table 1, tilapia has become the mainstay of aquaculture in these areas. In my country's aquatic product introduction projects, tilapia is the most successful species in terms of both economic benefits and social benefits.

4. How do fish change temperature?

Most fish are cold-blooded animals. They lower their body temperature through their skin, especially through their gills. Fish gills are like windows wide open in winter.

Take the swordfish, for example. It has six eye muscles, one of which is dedicated to generating heat. This muscle is how the swordfish keeps its brain and eyes warm. The other five eye muscles are only used to direct eye movement. In much the same way, the butterfly-finned fish uses another eye muscle to generate heat.

5. What are the signs before fish spawn?

Before fish spawn, the signs vary for different fish.

Mainly, the color of the male fish will become brighter than that of the female fish (nuptial color). When the female fish reaches sexual maturity, her abdomen will be more swollen, and the male fish will constantly chase the female fish.

The reproduction method of oviparous fish is: the male and female broodstock ovulate and fertilize at the same time, and the eggs are fertilized in the water. The vast majority of fish reproduce from oviparous offspring, but due to different species, their maturity, mating, spawning process, egg characteristics, etc. are also different. Even for the same fish, the maturity period varies greatly between different genera and species. Generally, small fish can mature in a few months and can reproduce once in 2-3 weeks or a few weeks; while large fish can mature in several years or more than ten years and reproduce once a year. For female fish to lay floating eggs, male fish will first spit foam to make a nest. Some male fish will gather grass to make a nest, and the fertilized eggs will hatch in the floating nest. Some fish eggs need to hatch in the starting drift of the water flow. For female fish to lay sticky eggs, the fertilized eggs need to adhere to water plants or other objects to hatch. The fertilized eggs of sinking eggs sink into the gaps between gravel to hatch. The spawning process and the time when fertilized eggs hatch fry also vary from species to species. Water temperature, light, water quality, dissolved oxygen content, etc. will also affect the hatching of fertilized eggs. If there are any deficiencies, the incubation period will be prolonged, the hatching rate will be reduced, and even deformed seedlings will be produced. Therefore, when artificially breeding these fish, it is necessary to understand their reproductive characteristics in advance and operate carefully. Female oviparous fish may carry a large number of eggs and lay a large number of eggs, but the number of fry obtained may be small, and some may even be far less than the number of eggs laid. Due to various reasons, the eggs laid by female fish are affected in three aspects: fertilization, hatching and survival of fry.

6. In what season do fish begin to spawn?

Fish usually spawn from March to May, with the largest number of eggs laid in late spring and early summer. There are some differences due to temperature differences. The temperature in the northern region is lower, so the ovulation time is later. The condition for spawning is that the water temperature reaches above 14 degrees Celsius, preferably 18-25 degrees Celsius.

Oviparous reproduction: refers to the reproduction of fish through external fertilization. When the fish reaches sexual maturity, the female fish releases eggs and the male fish releases sperm. When the eggs and sperm meet and combine in the water, the fertilization process is completed. After a period of time, these fertilized eggs will slowly develop and become small fish.

7. Is loach a warm water fish?

yes.

Loach is a warm-water fish with strong adaptability to the environment. It mostly lives in shallow waters such as ponds and lakes with still water or slow water flow. It usually lives at the bottom of the water. When the water is dry, it drills into the mud and can survive out of water. Loach can not only breathe with gills, but also breathe with skin and intestines. Breathing with intestines is a unique physiological phenomenon of loach. The intestinal wall of loach is thin and rich in blood vessels, which can assist breathing and gas exchange. When the water is dry in drought, it will dive into the 10-30 cm mud layer to "hibernate". A small amount of water can moisten the skin to maintain life. Loach is an omnivorous fish, and its food is animal and plant debris and microorganisms.

8. What are the cold water fish?

Common cold-water fish include salmonids, including rainbow trout, brown trout, etc.

It is now a common breeding species in Northeast my country. Pike, Salmoniformes, the white pike in Xinjiang, my country, is a cold-water fish, extremely ferocious, and no worse than the mullet in the Yangtze River Basin. Sturgeons, such as the Russian sturgeon, are typical Siberian cold-water fish. Some species of the Cobitidae, such as the northern loach and the flower loach, are mostly produced in Northeast China. The cod, the burbot, is a fish with many dorsal fins. In addition, there are also some species of the Perch, Cyprinidae, and Sculpinidae that live in cold waters and can be considered cold-water fish.

9. What is the concept of cold-temperature fish?

Cold-temperate fish refer to fish that live in frigid and temperate zones.

10. What are the warm-natured fishes?

Big fish are rarely warm, such as blue shark, smooth sailing, Thai crucian carp, flying phoenix, Thai, Indonesian tiger, stingray and other large fish.

Small fish that are relatively mild include tiger skin, three-lake cichlid, crusader, gold ingot, flag-pulling, mark toast, devil knife, etc.

Warm-temperate tropical fish include: pineapple and swallowfish series, swordfish series, and tetra series.

Whether it is a large fish or a small fish, a fish suitable for alkaline water or a fish suitable for acidic water, or a carnivorous fish or an herbivorous fish, some are used to swimming in the upper layer, some love to play in the middle layer, and some like to move around in the bottom layer.