by Dan Burden, content specialist, AgMRC, djburden@iastate.edu.

Revised January 2008 by Diane Huntrods, Ag Marketing Resource Center, Iowa State University.


Brook Trout

Brook trout (Salvelinus fontinalis) have a distribution that includes northeastern North America from the Atlantic seaboard south to Cape Cod, the Appalachian Mountains southward to Georgia, west in the upper Mississippi and Great Lakes drainage to Minnesota and north to Hudson Bay. Their natural range has been greatly expanded through artificial propagation.

Brook trout are raised in large quantities by state facilities for stocking into public lakes and streams. They also are cultured in private facilities for both recreational fishing on site and for stocking into private ponds. Additionally they are used by the supermarket and restaurant trade as a food fish. Under culture conditions, brook trout should be maintained at a temperature of about 59°F for optimal growth. The pH should remain close to neutral with an acceptable range of 6.7 to 8.2. As with most salmonid species, dissolved oxygen levels should remain above 5.0 ppm. Generally brook trout spawn before brown trout. 

Brown Trout 
The distribution of brown trout (Salmo trutta) includes Iceland, the British Isles and the Eurasian mainland from Cape Kanin to the Aral Sea and Afghanistan westward throughout Europe. As one of the world’s premier sport fish, brown trout have been widely introduced into many parts of the world. As a result of stocking beginning in the late 1800s, they have been widely established throughout North America.

Brown trout are cultured in large numbers in state facilities for stocking into public waters. Culture also occurs in private facilities mainly for recreational fishing on site and for stocking into private ponds. Under culture conditions, the optimal temperature range for embryo development is 41°F to 55°F. For adults, a temperature range of 54°F to 66°F should be maintained. The pH should remain between 6.8 and 7.8, while dissolved oxygen levels should be above 5.0 ppm. 
 

The habitat requirements for brown trout are essentially the same as those for brook trout. The two frequently coexist, with brown trout slightly more tolerant of higher water temperatures. They have been found to survive in waters as high as 80°F. The diet of young brown trout consists of a wide variety of aquatic and terrestrial insects, their larvae as well as fish and other vertebrates. Larger fish feed mainly during the twilight and nighttime hours with fish and crayfish playing a much more important role in their diet. Brown trout spawn in late autumn to early winter as water temperatures approach 45°F. Natural spawning habitat is essentially the same as for brook trout, namely, shallow gravelly headwaters.

Rainbow Trout 
Originally a Pacific salmonid species, the distribution of rainbow trout (Oncorhynchus mykiss) includes the eastern Pacific Ocean and freshwater west of the Rocky Mountains from northwest Mexico to Alaska. The original source populations in North America were a mixture of stream-living, lake-dwelling and sea-going forms (anadromous steelhead), with most spawned in late winter. As a result of introductions outside its range, rainbow trout are now found throughout North America. 

Rainbow trout are one of the most popular and easily reared aquaculture fish. They are a fast-growing and crowding-tolerant fish, making them well suited to captive breeding. These trout are widely used around the world for fish farming and restocking of angling fisheries. The freshwater forms feed on invertebrates and fish, but reared strains do very well on grain-based artificial diets.

Rainbow trout in common use today come from domestic strains developed to suit intensive fish farming as a food fish for sale as a fresh, fresh-frozen or smoked product to restaurants, supermarkets or consumers. When used for aquaculture meat production, the fish are purchased as fry and reared to marketable size, or are hatched onsite in tanks from eggs and sperm obtained from brood stock. When reared for angling, most are stocked at a harvestable size for rapid removal either to public waters or private ponds. Stocking densities and average weights are dictated by the economics of the angling demand. Due to the widespread use of all-female or sterile triploid strains, spawning is uncommon or nonexistent in some commercial (sterile-hybrid) strains. The diet of young trout consists of a variety of aquatic and terrestrial insects and their larvae as well as fish and other vertebrates. Like all trout, rainbow trout do best in cold, well-oxygenated waters. Like brown trout, however, they are much more tolerant of warmer temperatures than brook trout. They are capable of surviving in waters as high as 85°F, provided the water remains well aerated. Spawning begins in early spring as water temperatures approach 50°F. Eggs numbers may be as high as 12,000 per female. For optimal growth, temperatures should be maintained at about 59°F. The pH should remain close to neutral, with an acceptable range of 6.7 to 8.2. Like most salmonid species, dissolved oxygen levels should remain above 5.0 ppm.

U.S. Production
In 2005 USDA NASS reported that 410 trout-rearing farms were located in the United States with total sales of $79.3 million. The largest number of the trout farms were located in Wisconsin (46), North Carolina (42) and Pennsylvania (40). However, total sales were highest in the states of Idaho ($35.5 million), Washington ($9.1 million), California ($6.9 million) and North Carolina ($6.6 million). Since 1998 the number of trout farms has declined but sales have increased.

The total value of all sales, both fish and eggs, received by trout growers in 20 selected states totaled $74.2 million during 2005, an increase of 4 percent from 2004. For the nation, sales of fish totaled $69.1 million for 2005, while egg sales totaled $5.14 million. Idaho accounted for 51 percent of the total value of fish sold.

Trout distributed in 2005 for restoration, conservation and recreational purposes, primarily by state and Federal hatcheries, included 6.3 million 12-inch or longer fish, 52.0 million 6-inch to 12-inch fish and 52.6 million fingerlings. The estimated value of fish and eggs distributed totaled $74.3 million, up 19 percent from 2004.

The products of trout culture include food products sold in supermarkets and other retail outlets, live fish for the restocking of rivers and lakes for recreational game fisheries, and products from hatcheries whose eggs and juveniles are sold to other farms. Food market fish size can be reached in 9 months, but 'pan-sized' fish, around 1 pound, are harvested after 12 to 18 months. Optimal harvest size in the United States is generally 1.5 pounds. Trout are marketed as fresh or frozen whole fish or fillets (often boneless) and as value-added products, such as smoked trout. 

Production Costs