We know that it is not easy to cultivate the industry, and seek the prosperity of the aquatic industry. Not misleading, not exaggerating, not hyping, not headlined the party. With the context of breeders, let you enjoy a fine product in a short period of time!
1. Classification status
Salmo gairdneri Richardson (color figure 2-1) belongs to the class TeIeostei, Clupeiformes, Salmonoidei, Salmonidae, Salmoninae, salmoninae, and Salmoninae.
Since the establishment of the taxonomic system, there are many views on its taxonomic status, different researchers have given rainbow trout different names, in addition to the current scientific name, rainbow trout has also had many names such as Salmo gairdnerii Richardson and Salmo irideus Gibbons (Table 2-1). It was not until 1988 that the taxonomic status of rainbow trout was changed from salmon genus Salmo to Salmon genus Oncorhynchus (Walbaum, 1988), and the species name was finally determined as mykiss (Call and Crandell, l992; Zhang Juemin, 1995).
Table 2-1 Latin names and nomenclatures used by rainbow trout
<col>
Latin name
Name the person
Usage status
Oncorhynchus mykiss
Salmo mykiss
Parasalmo mykiss
Salmo purpuratus
Salmo gairdneri
Fario gairdneri
Salmo gairdnerii
Salmo gairdnerii gairdnerii
Salmo gairdneri irideus
Salmo gairdnerii irideus
Rainbow Psalm
Salmo irideus
Salmo rivularis
Salmo stellatus
Salmo truncatus
Psalm masoni
Salmo kamloops
Oncorhynchus kamloops
Salmo rivularis kamloops
Salmo gairdneri shasta
Oncorhynchus mykiss nelsoni
Salmo nelsoni
Salmo kamloops whitehousei
(Walbaum,1972)
Walbaum,1972
Pallas,1814
Richardson，1836
(Richardson，1836)
Gibbons，1855
Ayres，1855
(Girard, 1856)
Suckley，1859
Suckley，1860
(Jordan，1892)
Jordan，1892
Jordan，1894
Evermann，1908
Dymond，1931
Now
The original Latin name
Former name
Note: The namer is braceed to indicate a change in the named genus name.
2. Biological characteristics
(1) Morphological characteristics
1. External form: the body is elongated, spindle-shaped, nearly cylindrical, slightly flattened. There is a fat fin. Rounded, blunt snout protrusions. There are many finely conical, pointed teeth on the jaw. The jaw extends to the posterior edge of the lower part of the eye, and the head is smaller. The mouth is large, slightly oblique, and the end is positioned. The eyes are slightly smaller, located above the body axis, and the gills are connected to the cheeks. The scales are small and rounded. The ventral fins are scaled both front and back. The dorsal fin is short, without hard spines, and the ventral fin is anterior to the beginning. The pectoral fin is smaller, far away from the ventral fin, the ventral fin is smaller, far away from the fin, the dorsal fin is 4,9 to 12, and the pectoral fin is 1,11 to 12. Ventral fins 1, 8 to 10. fins 4,8 to 12. Lateral scales 100× 17 to 27/21 to 29×150. The head length ratio is 3.0 to 4.5. The body height ratio is 3.5 to 4.2.
The back and top of the head are pale blue, blue-green, yellow-green or brown. The sides are silvery white, white, light yellowish green or gray, and the abdomen is silvery white, white or off-yellow. The body side has a wide , bright purple-red rainbow band along the middle of the lateral line , extending to the base of the caudal fin , with small black spots half or all of the body side.
2. Internal form: vertebrae 60~66. The number of gill rakers in the first gill arch is 17 to 21, and the pylorus is 54 to 91. Gills 9 to 13.
3. Egg, baby fish, juvenile fish form: ovoid shape, diameter 4 ~ 7 mm. Egg yolk pale yellow, orange yellow, orange red or red.
Hatch 26 days after fertilization (water temperature 12 °C) or 75 days (5 °C). The total length of the juvenile fish is 15 to 18 mm, and the yolk sac is 5 to 9 mm long and 3 to 6 mm wide. The mouth opens and gill rakers form. Cartilaginous fins of the dorsal fin, scales, and caudal fins begin to appear.
23 days after incubation (water temperature 12 °C) or 50 days (6 °C), the yolk sac absorbs 2/3 and begins to float. The total length of the upper floating fish is 18 to 28 mm, and the finned turtle has disappeared except for the ventral surface of the ventral fin and the caudal fin. The number of fins is basically fixed. Subsequently, 5 to 13 black salmon spots appear on the side of the body. Disappears at 15 cm in length and is replaced by a purple-red rainbow band.
(2) Life habits
The ecological habits of rainbow trout have the typical characteristics of salmonids, and there is no obvious lower limit temperature for reproduction, development and growth, and the upper limit temperature is much lower than the biological characteristics of other fish, which is obviously different from other fish.
On the west coast of North America, wild rainbow trout have two ecological groups, freshwater and descending, and freshwater types include river groups and lake groups. The rainbow trout of the river prefers to inhabit the cold waters of the upper reaches of the river with a sandy bottom, and the lake swamp group lives in low-temperature lake areas with clear water quality. Descending rainbow trout, juvenile fish descend to the sea, sexual maturity after the river breeding.
Rainbow trout are fierce and predatory, initially feeding on aquatic zooplankton, followed by aquatic insects, falling insects and small fish. Captive-reared rainbow trout feed is fed from one opening. Its stomach is very large, there are many pyloric pyloric pylorus, has a strong ability to digest protein, the intestine is very short, is the main organ of food digestion and nutrient absorption.
Rainbow trout, which inhabit rivers, usually live in upper and middle reaches of water with clear water quality and gravel bottoms. Its upper limit of water temperature and lower limit of activity are 24 °C and 5 °C, respectively. The limno-type rainbow trout mostly live in deep, cold waters or coastal zone waters. Descending rainbow trout are usually divided into two groups: winter into the sea and summer into the sea.
The suitable temperature of rainbow trout is 10 °C, and the suitable living water temperature after 50 grams is 13 ~ 18 °C. In the right temperature range, the feeding is vigorous, the growth is rapid, and the body maintains a good metabolic state. Below 8 ° C or above 20 ° C, appetite decreases, growth slows down. Above 24 ° C, feeding stops, the body collapses and even dies. In natural waters, temperatures above 24 °C can be tolerated due to abundant water and dissolved oxygen, while on farms, when the temperature rises to about 22 °C, it is dangerous.
Abundant water for rainbow trout, more important than other freshwater fish, due to the stimulation of water flow, causing the normal movement of rainbow trout, because the movement accelerates the metabolism of matter in the body, thereby enhancing appetite, health; water flow also plays a role in taking away the excrement of rainbow trout, and the most important role of water flow is to continuously supply rainbow trout with fresh, oxygen-rich water to meet its demand for oxygen. Therefore, the culture of rainbow trout has always been different from other freshwater fish, and the method of water culture has been adopted. The suitable flow rate for rainbow trout life is 2 cm/s to 30 cm/s. When dissolved oxygen in water is less than 3 mg/L, mass deaths occur. This value is the lethal point of summer rainbow trout. Below 4.3 mg/L, the fish are densely clustered in the inlet for a long time, and the top of the fish's head is yellow, and the gill cover is open, which is the phenomenon of rainbow trout "floating head", and death occurs at the same time. Below 5 mg/L, the respiratory rate increases and discomfort is felt. For rainbow trout to grow well, dissolved oxygen in water is preferably above 6 mg/L. Rapid growth above 9 mg/L. The embryonic development of rainbow trout eggs and the absorption rate of yolk sacs, in addition to temperature factors, are also related to the amount of dissolved oxygen in water. Slows down at low oxygen and accelerates at high oxygen.
Although the spawning time of rainbow trout is not fixed, most rainbow trout choose to spawn in the spring, which is related to the increase in water temperature. When the female spawns, she mostly digs the spawning pit in the gravel and deposits eggs in the pit, laying 500 to 2500 large eggs (50 to 150 mg / grain) each time, and the male is fertilized by the deposited eggs at the same time. The development and incubation time of a fertilized egg depends on the temperature of the water body. In water bodies at 4.5 °C, it takes 80 days for eggs to hatch, 30 days for l0 °C, and 19 days for 15 °C (Leitritz and Lewis.1980). From the second day after fertilization to the embryonic stage when fully developed (at water temperature of 10 ° C), during which the fertilized egg is very sensitive to interferences such as various treatments or external vibrations. Once the fertilized egg has a color (about 16 days at l0 ° C), this means that its sensitive period has ended. From this period until the incubation, the fertilized eggs can be transported and other treatments. During the incubation period, the juveniles are always attached to the yolk, and the juveniles are called yolk sacs, which shuttle through the gaps in the gravel and continuously absorb all the energy and nutrients needed for growth from the yolk sacs and continue to grow and develop. When the nutrients of the yolk sac are about to be depleted and the belly of the fish is surrounded by skin, the fry can be called "buckle fish". The length of time it takes to develop from hatching to upper floating fish depends on the water temperature, it takes about 20 days at l0 ° C, and 10 days or less at 15 ° C, when the small fish have the ability to eat, they emerge from the gravel, surface to feed, at this time it can be called the upper floating fish. The entire period from spawning to floating out of the gravel happens to be in the spring, and fry emerge when natural foods are abundant. In the entire geographical scope of rainbow trout growth, due to its different water temperatures and food abundance, local residents should arrange suitable spawning and rearing time according to local conditions.
In addition to temperature and oxygen, its suitable water quality indicators are listed in Tables 2-2. Although rainbow trout can live in water with a pH of 5.5 to 9.2, the optimal pH range is 6.5 to 6.8. The ability to adapt to salinity increases as the individual grows. Juvenile fish 5 to 8 ‰, first year fish 20 ~ 25 ‰. , adult fish 35 ‰. Usually more than 55 to 100 grams of fish species can be adapted to seawater life through the transition of brackish water.
Table 2-2 Water quality index of rainbow trout aquaculture
(Quoted from Liu Xiong, 1990)
index
unit
Optimal value
chroma
transparency
dissolved oxygen
Free carbon dioxide
hydrogen sulfide
pH
alkalinity
Total hardness
Biochemical Oxygen Demand*
Ammonia nitrogen
chloride
nitrite
nitrate
phosphate
sulfate
Total iron
Suspended solids
degree
mg/L
mg, concentration / L
<30
Clear and transparent
6-10
6.5～7.5
1.5
8～12
<10
<0.0075
<5.0
<0.5
<1.0
<0.2
<15
*5-day biochemical oxygen demand
Rainbow trout also prefers clean and transparent water. Suspended solids in the water fall on the gills, causing difficulty breathing. Feeding stops in murky water and feels uncomfortable. Turbid water during heavy rain or flood periods, if it lasts for two or three days, is not a big obstacle to adult fish and fingerlings, but it is very harmful to the rearing of juvenile and juvenile fish, which can cause more deaths. Especially juvenile fish under 1 gram, it is necessary to ensure that they are raised in clean water.
(3) Growth and age
1. Growth
The growth of rainbow trout varies greatly due to water temperature, environmental conditions, and the amount of bait given. Unlike mammals, fish growth is lifelong, with a lifespan of 8 to 11 years. The largest individuals vary depending on the place of origin and the region of growth. Under rearing conditions, the largest individual can reach a total length of up to 90 cm and a weight of 7.2 kg. In natural waters, 10-year-old rainbow trout can weigh up to 25.4 kg (Robins and Ray, 1986), but rarely exceed 9 kg.
2. Mature age
Usually males are two years old and females are three years old. Mature individuals vary in amplitude between 15 and 40 cm. Under the conditions of culture environment, males live for 5 to 6 years and females for 6 to 8 years, and it is known that the same individual has bred five times.
3. Environmental factors affecting growth
(1) Water temperature can affect the amount of bait, metabolic intensity and growth rate of rainbow trout. The optimal temperature is 12 to 18 °C. Within this range, the higher the temperature, the faster it grows; the more you exceed this range, the slower it grows. Unlike other fish, rainbow trout has the characteristics of cold-water fish growth physiology, the upper limit of normal growth is very low, 20 °C, there is no obvious lower limit growth temperature, and it can still feed and grow in 0.5 °C under ice water.
The growth of rainbow trout under rearing conditions varies greatly due to water temperature, bait and water quality Table 2-3 lists the general growth of rainbow trout at different water temperatures.
Table 2-3 Growth of rainbow trout under rearing conditions
The average annual water temperature is °C
1 year of weight
2 years of weight
3 years of weight
12-14
100-200
400-1000
1000-2000
8-9
40-50
200-400
800-1000
(2) Dissolved oxygen Rainbow trout prefer to inhabit high dissolved oxygen waters, and the level of dissolved oxygen in the water body in the breeding environment will directly affect the respiration, bait and growth of the fish. The minimum value of dissolved oxygen required to sustain life activities is called the safety threshold of dissolved oxygen. In general, the safety threshold for dissolved oxygen in rainbow trout is 3.15 mg/L. When dissolved oxygen is less than 5 mg/L, the respiratory rate is accelerated, and when it is below 4 mg/L, swimming is slow, and when the fish cluster in the fish pond inlet is floating, the dissolved oxygen in the water has dropped to about 3 mg/L or less, at which time the life of the fish has been threatened. The safety threshold of dissolved oxygen varies depending on the water temperature, the higher the water temperature, the lower the dissolved oxygen, the higher the oxygen consumption of the fish, and the higher the safety threshold of dissolved oxygen. Therefore, under high water temperature conditions, it is more likely to occur the dangerous situation of dissolved oxygen falling below the safe threshold. When dissolved oxygen levels are below the safety threshold, the fish's bait efficiency and growth rate drop dramatically and cause death.
When the fish is quieted by blocking out the light and stopping the bait, the oxygen consumption decreases. Under normal feeding conditions, oxygen consumption is equivalent to about 1.1 to 1.2 times that of the quiet state (Table 2-4), and light stimulation can increase oxygen consumption by 20% to 30%. Vibration stimulation increases oxygen consumption by 40% to 50%. Stimulated by changes in water temperature, oxygen consumption increases by 30% to 70%. Compound stimuli caused by factors such as light, vibration and temperature changes can increase oxygen consumption by more than 1x compared to quiet conditions. Eating can also cause an increase in oxygen consumption, which is about twice as high as in an empty stomach state, after 24 hours of fullness. Oxygen consumption is significantly reduced.
Table 2-4 Oxygen consumption per kilogram of rainbow trout per kilogram in quiet conditions (mg)
Water temperature(°C)
Weight (g)
1
2
5
10
25
50
100
200
72.1
66.5
58.8
53.2
45.5
39.9
34.3
28.7
130.9
119.7
105.7
95.2
81.2
70.7
59.5
49.0
15
186.2
171.5
152.6
138.6
91.0
77.0
20
238.0
219.8
196.0
147.8
154.0
135.8
116.2
99.4
The size of the fish body is different, the oxygen consumption per unit weight is also different, and as the fish body grows, the oxygen consumption per unit weight will gradually decrease. The oxygen consumption of a group of juvenile fish is about 2 to 3 times that of adult fish of the same weight.
Dissolved oxygen is an important environmental factor affecting the growth of rainbow trout, and it is the key to ensure the breeding effect to grasp the change of dissolved oxygen in feeding water and adjust it in a timely manner. Saturated dissolved oxygen in freshwater varies depending on the water temperature and altitude. The saturated dissolved oxygen of freshwater listed in Tables 2-5 can be used as a reference for understanding the dissolved oxygen of pool water.
Table 2-5 Saturated dissolved oxygen levels in freshwater (mg/L)
Altitude (m)
400
600
800
1000
4
6
8
12
14
16
18
13.4
12.7
12.1
11.5
10.9
10.4
9.6
9.2
8.9
13.1
12.4
11.8
11.2
10.7
10.2
9.3
9.0
8.6
12.8
9.9
9.5
9.1
8.4
10.1
9.7
8.5
8.2
8.7
8.3
8.8
8.1
7.8
(3) Water quality
The water quality factors that affect the growth of rainbow trout are complex, mainly the acidity and alkalinity (pH) and ammonia nitrogen (NH3) concentration of water. The pH of water depends on the concentration of hydrogen ions (H+) and is usually expressed in pH. The pH value is inversely proportional to the hydrogen ion concentration, the smaller the pH value, the higher the hydrogen ion concentration, the stronger the acidity of the water; the greater the pH, the lower the hydrogen ion concentration, and the stronger the alkalinity of the water. Aquaculture production generally considers water with a pH between 6.5 and 7.5 to be neutral in the aquaculture industry. Rainbow trout tolerate pH in the range of 5.5 to 9.2 and the suitable range is 6.5 to 7.5. Acidic, especially strongly acidic, will have a harmful effect on rainbow trout that inhibits growth, and the causative factor is hydrogen ions. The causative mechanism of hydrogen ions is still unknown, it is generally believed that hydrogen ions stimulate gills, causing hypersecretion of mucus, and excessive mucus deposited on the gills produces a harmful effect of inhibiting breathing. In a weakly acidic water environment, hydrogen ions combine with toxic ammonia nitrogen (NH3) to form NH4, which can weaken its toxic effect.
Nitrogen derived from the non-decompositive state of organic matter such as fish excrement, feces and residual bait, especially ammonia nitrogen and nitrite, is a toxic substance of rainbow trout, which can affect the absorption of oxygen by hemoglobin, weaken the function of hemoglobin to release oxygen to tissues and organs, even if the water contains sufficient dissolved oxygen, it is difficult to be used by the fish body under the influence of ammonia nitrogen and cause the same anorexia symptoms as the hypoxia state. Nitrite is very unstable and generally has very little content in water. The tolerance concentration of ammonia nitrogen in rainbow trout is 0.0125 mg/L. In the running water breeding pond, if the pH is about 7, the tolerance concentration can reach 0.05 to 0.6 mg/l, so in the nearly neutral pool water, ammonia nitrogen generally does not cause great harm. In feed water with low dissolved oxygen and high carbon dioxide, the toxicity of ammonia nitrogen is enhanced. In water with dissolved oxygen of less than 5 mg/L, when the amount of ammonia nitrogen reaches more than 0.5 mg/L, the growth of rainbow trout slows down, the gills are susceptible to damage, and the kidney and liver tissue dysfunction will occur. When the dissolved oxygen content rises to more than 7 mg/L and the ammonia nitrogen amount reaches 0.8 to 0.1 mg/L, there will be no harmful effects after 6 weeks of feeding. The higher the water temperature and the higher the pH, the more toxic the ammonia nitrogen. In addition, turbid water quality can hinder the vision of rainbow trout, affecting feeding and growth.
(4) Reproductive characteristics
The water temperature of rainbow trout spawning is generally 4 ~ 13 °C, and the optimal water temperature is 8 ~ 12 °C. Eggs are laid once a year. The amount of eggs conceived varies according to age and individual size, and the eggs are terminal yellow eggs, round, and dull.
In natural waters, mature broodstock choose riverbeds with gravel substrates, clear water quality and rapid currents as spawning grounds, and females use their tail fins to dig spawning pits and lay eggs in the pits. The male protects against the intrusion of other males, and after the female has laid the eggs, the males then discharge semen, and after the eggs are fertilized, the broodstock are covered with grit with tail fins. The broodstock after reproduction do not die and can proceed to the next reproduction.
The water temperature range for the incubation of fertilized eggs is 2 to 15 °C, and the optimal water temperature is 8 to 10 °C. At water temperature of 9 °C, the incubation period is 36 to 38 days. Hatched fry lie quietly among the dark underwater gravel, in a clustered manner, relying on the yolk to provide nutrients. After 15 to 20 days, when the yolk is absorbed 2/3, the maw begins to inflate and the fry swim towards the upper water layer for food.
The spawning period of rainbow trout varies with region, water temperature and the effects of light. In water bodies with high average water temperatures, the gonads of rainbow trout do not mature on schedule, and after the breeding period, the shortened daily light time can promote the early spawning period. Rainbow trout spawning period in the United States is from September to February of the following year. In Japan, from November to March, from December to January of the following year in France and North Korea, from January to March in Denmark, from February to April in Norway, from March to May in the former Soviet Union, from November to January in Beijing, from December to February of the following year in Taiyuan, Shanxi, and from December to April of the following year at the Bohai Cold-water Fish Test Station of the Heilongjiang Fisheries Research Institute, because the station has five strains of rainbow trout with different geographical populations, and different strains have different breeding periods.
(The author of this article is unknown)
(Note: This article is for reference and communication only!) Most of the content and pictures come from network information, if there is any disagreement, please inform, welcome to correct and leave a message to discuss)
Aquatic practitioners, conspire for the prosperity of the fishery! Please pay attention to the headline number @ fisherman Liu Wenjun, more wonderful content please log on to the Southwest Fishery Network, this article original if you need to reprint please indicate the source, if there are different opinions or content supplements, please share private messages or messages or comments! #Native Fish ##Indigenous Fish##Fish Farming##Fish##水产养殖 #