ABOUT...
ACROSS CANADA
AND...
RESOURCES
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FINFISH SPECIES
RAINBOW TROUT
Introduction
Rainbow trout is the most popular freshwater farmed species in Canada. In 2003, 5,290 tonnes of Rainbow trout were produced in Canada valued at C$21 million. Rainbow trout are commercially raised in British Columbia, Alberta, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia and Prince Edward Island. Rainbow trout is also the predominant species grown in privately-owned U-fish operations (recreational fishing) in most provinces across Canada.
Basic description
 Capable of occupying many different habitats,
Rainbow trout (Onorhynchus mykiss) is well known for its ability to adapt to different conditions. It is a member of the salmon family and native to the eastern Pacific where it is found from Alaska to Mexico. It has a long, slender body, with an iridescent band running along each side from head to tail. The overall body color can range from bluish to yellow-green, brown or black. The flesh is white with a pink tint and it has a mild, delicate and sweet taste.
The marine strain, commonly known as Steelhead trout, is known for its rapid growth and can achieve seven to ten kg within three years. The freshwater strain, Rainbow trout, can only attain 4.5 kg in the same time span. The species can withstand vast ranges of temperature variation (0-27°C), however water temperatures exceeding 20°C may be stressful to the fish.
Background
Since 1874, Rainbow trout has been introduced to waters on all continents except Antarctica, for recreational angling and aquaculture purposes. Production greatly expanded in the 1950s as pelleted feeds were developed for finfish culture.
By 2002, 64 countries were reporting rainbow trout farming production. The primary producing areas are in Europe, North America, Chile, Japan and Australia.
Production cycle
Like salmon species, rainbow trout are raised from broodstock in freshwater, land-based hatcheries. When rainbow trout fry reach 8-10 cm in length, they are moved to outdoor, grow-out facilities. These can comprise concrete raceways, flow-through Danish ponds, or cages. Individual raceways and ponds are typically two to three metres wide, 12 to 30 m long and 1 to 1.2 m deep. Raceways provide well-oxygenated water and water quality can be improved by increasing flow rates; however, the stock is vulnerable to local water quality, and ambient water temperatures can influence growth rates.
Fish are grown to marketable size (30-40 cm), usually within 9 months, although some fish are grown on to larger sizes over 20 months, depending on market demand.
The stock is graded, usually four times (at 2-5 g, 10-20 g, 50-60 g and >100 g) in a production cycle (first year), when the density (the number of fish in an enclosed area) needs to be reduced, thus ensuring fast growth, improving feeding management and creating product uniformity. Fish quantity and size sampling allows the farmer to estimate growth rates, feed conversions, production costs, and carrying capacity; all essential considerations for responsible farm management.
Alternative grow-out systems for rainbow trout include cage culture production systems (6 m x 6 m wide and between 4 to 5 m deep) where fish (up to 100,000) are held in floating cages in freshwater. Rainbow trout fry of about 70 g weight can attain three kg in less than 18 months.
For more information
Freshwater Aquaculture Research Program in Action
- At the Experimental Lakes Area near Kenora, Ontario, Fisheries and Oceans Canada is conducting comprehensive scientific research to understand the effects of freshwater net-cage aquaculture using rainbow trout.
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