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Artificial breeding rainbow trout technical points
Rainbow trout is recognized for its distinctive reddish-brown coloration along the sides of its body. This species is highly valued for its flavorful meat, nutritional benefits, and minimal bones, making it an ideal candidate for aquaculture. Due to its ease of breeding in controlled environments, it has been promoted by the Food and Agriculture Organization (FAO) as one of the four key freshwater fish species for global aquaculture development. In flowing water systems, rainbow trout can yield between 30,000 to 35,000 kilograms of fresh fish per acre, offering substantial economic returns.
As a cold-water fish, rainbow trout thrives in temperatures ranging from 1°C to 24°C, with the optimal growth temperature falling between 14°C and 16°C. It requires well-oxygenated water, with dissolved oxygen levels above 5 mg/L, and prefers a pH range of 7 to 8. These environmental conditions are crucial for maintaining healthy growth and reducing disease risk.
Breeding stock typically reaches maturity between two and three years of age. Female rainbow trout spawn once annually, laying between 1,000 to 3,000 eggs per spawning event. Spawning generally begins in December, and the process involves careful management of both the environment and nutrition.
For breeding, broodstock should be kept in tanks with gravel substrates, a water depth of 1.5 meters, and a flow rate of 0.05 liters per second per 100 square meters. Stocking density should be between 1 to 3 fish per square meter, with an equal male-to-female ratio. Rainbow trout are sensitive to light, so daily exposure should be limited to 12 hours. Throughout the year, feed composition changes according to gonadal development stages. Initially, animal-based feed makes up 20% to 30% of the diet, but this increases to 50% to 60% during egg collection and post-spawning phases. The feeding amount should be between 0.5% to 2% of the fish’s body weight.
During oviposition, females develop darker coloration, swollen and soft bellies, and red vents, indicating readiness to spawn. Males also show darker pigmentation and may release white milt when gently pressed. Spawning usually 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 transferring the eggs into a clean container. Male milt is then extracted and mixed with the eggs using a feather for 30 seconds before being diluted with fresh water. After standing for 2 minutes, more water is added, and the mixture is left for 4 hours before being placed in hatching trays. All steps must be performed under shaded conditions to avoid light stress.
For incubation, wooden or plastic troughs measuring 200 cm x 40 cm x 37 cm are used, with hatching trays sized 33 cm x 33 cm x 1.6 cm. The eggs are placed in the trays and covered with an empty plate to prevent floating. The hatchery should remain shaded, with water temperature maintained between 7°C and 13°C, ideally 8°C to 10°C. Water flow should be around 10 to 20 liters per minute. Dead eggs must be removed regularly to prevent contamination. Weekly disinfection with 1% formalin or 2% saline solution for 30 minutes helps maintain hygiene and improve hatching success.