1. Scientific name: Oncorhynchus
2. Common name: Rainbow trout
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
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
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.
collection from female trout.
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.
A type of hatching apparatus for rainbow trout commonly used
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 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.
Typical raceway used for the culture of rainbow trout in Korea.