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  blue diamond KOREA-US AQUACULTURE -> Main Species->Finfish->Rainbow trout
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Rainbow trout 

Rainbow trout

1. Scientific name: Oncorhynchus mykiss

2. Common name: Rainbow trout
                            Steelhead trout
                            Kamloops trout

3. Distribution

    The rainbow trout is a native to North America, ranging natively from the Kuskokwim River, Alaska, to Rio Presidio and Durango. Now the species extends to all over the world except for tropic area, including eastern coasts of United States, European countries, South America, Japan, New Zealand, South Africa, etc. Even though the species habitats in cold fresh waters, acclimation to marine environments is also possible.

4. Ecology & Habitat

    In spite of its widespread in global sense, rainbows favor cool water with plenty of food. The rainbow is especially limited by water temperature, as it cannot survive in water temperatures over 25℃. The preferred water temperatures remain 10∼20℃. Higher pH and oligotrophic waters appear to be preferred to the rainbow. In Korea, gametes can be obtained in months October to February from adults older than 2∼3 years. Korean populations originate from California population. A total of 10,000 eyed eggs of California population was imported in 1965.

5. Aquaculture

   The site selection for raceway construction is a critical element for rainbow trout aquaculture. The trouts cultured in the raceway require a large quantity of quality-good waters in terms of temperature of around 15℃, dissolved oxygen over 7㎎/ℓ, and pH of 6.7∼8.6, preferably supplied by gravity flow from artesian wells or by pumping flow from underground water. Water flow should be even throughout the raceway to eliminate any locations poorly circulated where waste matters may accumulate in the raceway.

Water temperature is an important factor affecting the growth of the trout in the raceway. The trout fries at 13℃ can grow to 100∼200g in the first year, 600∼1,000g in the second year, and 1,200∼2,000g in the third year.

Getting quality-good eggs is achieved from healthy broodfish, which are cultured separately in the broodstocks raceways. The broodfish of 2 to 3 years old (1.5∼2.0㎏ in body weight) can produce 3,000∼3,500 eggs per female trout. The trout has a specific period of time for spawning. However, a technique of photoperiodic manipulation renders year-round seed production. The following figures show seed production and culture of the species.

Egg collection from female trout.
           Egg collection from female trout.

 

Sperm squeezing into the eggs collected for fertilization. The fertilizing rates can be promoted with an addition of fertilyzing fluid (NaCl 90.4g, CaCl2·2H2O 3.4g, KCl 2.4g in water 10ℓ).
Sperm squeezing into the eggs collected for fertilization. The fertilizing rates can be promoted with an addition of fertilizing fluid (NaCl 90.4g, CaCl2·2H2O 3.4g, KCl 2.4g in water 10ℓ). 

Collection of fertilized eggs into the fertilizing apparatus.  
 Collection of fertilized eggs into the fertilizing apparatus.
 

A type of hatching apparatus for rainbow trout commonly used in Korea.
A type of hatching apparatus for rainbow trout commonly used in Korea.

A type of hatching systems for rainbow trout commonly used in Korea. The optimum water temperature for the hatching of the fertilized eggs is around 10℃ in which the eggs become eyed eggs by day 16, hatch by day 32, and finally reach floating larval stage by day 60. A special care should be given not to exposed to physical shock and light during the hatching period. 
A type of hatching systems for rainbow trout commonly used in Korea. The optimum water temperature for the hatching of the fertilized eggs is around 10℃ in which the eggs become eyed eggs by day 16, hatch by day 32, and finally reach floating larval stage by day 60. A special care should be given not to exposed to physical shock and light during the hatching period.

Larvae of rainbow trout just hatched. Formaldehyde treatement (about 100ppm of Formalin) is suggested to prevent outbreak of aquatic fungi. The dead eggs should be removed regularly from the bottom the hatching tanks.
Larvae of rainbow trout just hatched. Formaldehyde treatment (about 100ppm of Formalin) is suggested to prevent outbreak of aquatic fungi. The dead eggs should be removed regularly from the bottom the hatching tanks.

Fry culture of rainbow trout in the indoor system. 
Fry culture of rainbow trout in the indoor system.

Typical raceway used for the culture of rainbow trout in Korea.
 Typical raceway used for the culture of rainbow trout in Korea.