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Artificial breeding rainbow trout technical points
Rainbow trout, known for its striking brownish-red markings along the sides of its body, is a highly valued fish species in aquaculture. It is praised for its tender, flavorful meat, high nutritional value, and low bone content. Its ease of artificial breeding and management has made it one of the four top freshwater fish species promoted globally by the Food and Agriculture Organization (FAO). In flowing water environments, rainbow trout can yield between 30,000 to 35,000 kilograms of fresh fish per acre, offering substantial economic returns.
This cold-water fish thrives in temperatures ranging from 1°C to 24°C, with the ideal growth range being 14°C to 16°C. It requires dissolved oxygen levels above 5 mg/L and a neutral pH between 7 and 8. Rainbow trout broodstock typically reach sexual maturity between 2 and 3 years of age. Females spawn once annually, laying between 1,000 and 3,000 eggs per spawning event, usually beginning in December.
For breeding, broodstock are kept in tanks with gravel bottoms, 1.5 meters deep, and a flow rate of 0.05 liters per second per 100 square meters. Stocking density ranges from 1 to 3 fish per square meter, with an equal male-to-female ratio. These fish are sensitive to light, so daily exposure is limited to 12 hours. Throughout the year, feed formulations vary depending on the reproductive stage. During egg development, animal-based feed should make up 50% to 60% of the diet, while during other periods, it's around 20% to 30%. The feeding amount is typically 0.5% to 2% of the fish’s body weight.
During spawning, females develop darker coloration and a swollen, soft belly, indicating readiness. Males also show darker coloring and a rougher texture near the vent, with visible white milt when gently pressed. Spawning typically occurs at water temperatures between 1°C and 11°C, with peak activity between 5°C and 9°C. Eggs are collected by gently pressing the female’s abdomen, and sperm is extracted from the male using the same method. The two are mixed with a small amount of water and allowed to incubate for 2 minutes before adding more water and letting it sit for 4 hours. This process must be done in shaded conditions.
For incubation, wooden or plastic troughs measuring 200 cm x 40 cm x 37 cm are used, with hatching trays of 33 cm x 33 cm x 1.6 cm. The trays are placed in the trough, covered with an empty plate and weighted to prevent drifting. The hatching area should remain shaded, with water temperature maintained between 7°C and 13°C, ideally 8°C to 10°C, and a flow rate of 10 to 20 liters per minute. Dead eggs must be removed regularly, and the eggs are disinfected weekly with 1% formalin or 2% saline solution for 30 minutes.