About Trout

Trout are a member of the Salmon (Salmonidae) family of freshwater fish, which also includes Salmon, Char and Grayling. Salmonids are the only freshwater fish to have an adipose fin, a small extra fin between the dorsal and the tail fin.

Brown Trout

Brown Trout are Europe’s indigenous Trout. They are considered by many to be river trout, but they can also do extremely well in lochs. They have more of a tendency to ‘stay put’ when stocked in rivers and streams. The colour varies, as does the variety of spots, depending upon the habitat. They grow rapidly on natural food but are considered to be the most cannibalistic of all the trout species. They can also be harder to hook because of their cautious nature. Generally they can withstand somewhat warmer temperatures than other trout, even the 21 - 24 degree Celsius ranges, providing the oxygen level is not too low. Brown Trout grow slower than Rainbow Trout. Brown Trout can reach 20 - 24 inches in length and weigh 5 - 8 pounds in trout farm raised conditions. Lengths and weights in the wild however, can be similar. Growth figures of 0.4 inch and 0.6 oz. per month are not uncommon. The average lifespan is about 7 years. The saltwater variety found typically in coastal waters is known as the Sea Trout.

Rainbow Trout

Rainbow Trout are the most popular trout for loch stocking. Native to the lochs and streams of North-West America, they grow rapidly, often gaining an inch per month from spring through to autumn, less during the winter months.  They feed well on natural food. They can withstand temperatures up to 21 - 22 degrees Celsius for brief periods of time, but do best in the 10 to 18 degree Celsius range. They can be stocked with other trout or with coarse fish.  They are moderately cannibalistic.  Trout farm raised Rainbows can reach 23 - 30 inches in length and up to 10 pounds or more in weight. The mean growth rate ranges from 0.35 – 0.62 inches and 0.6 – 1.2 oz. per month. The average lifespan is about 5 years. There is a migratory breed of Rainbow Trout known as the Steelhead. Steelheads are anadromous fish (like the Sea Trout) which means they only visit freshwater from the sea to spawn.

Blue Trout

The Blue Trout is a genetic anomaly, or mutation that occurs in the hatchery production of Rainbow Trout. They are usually separated from the other trout because they are considered to be a weaker fish and do not survive into the second year of the intensive fish farming environment. This genetic glitch can appear in Brown Trout as well as Rainbow Trout. Blue Trout do not reproduce as neither the male nor the female develop mature reproductive organs.
Some scientists consider that Blue Trout probably suffer from a thyroid deficiency. A fish's thyroid gland produces hormones that affect its colouration during all of its life stages therefore; this hormonal anomaly lets these fish form only the bluish pigment.

Tiger Trout

The Tiger Trout is a sterile, hybrid trout produced in fish hatcheries. This is done by combining the female Brown Trout eggs with male American Brook Trout sperm, and then heat shocking the mix. This increases the survival rate from 5% to 85%.  As they are a sterile fish, all their energy goes toward feeding allowing them to grow faster than naturally occurring species. The name Tiger Trout originates from the appearance of the adult fish, which has tiger-like stripes (vermiculation's) that cover most of the body. Usually they are a chocolate golden brown with yellowish vermiculations but coloration can vary. This fish can occasionally occur in the wild, in areas with breeding populations of Brown Trout and Brook Trout sharing the same waters but, it is a rare phenomenon. Tiger Trout are known to be piscivorous (fish eating) and are used as a controlling method against coarse fish and unwanted small fish populations. They are also stocked as a sport fish.

Other Species

Other species of Trout include: American Brook Trout (Salvelinus fontinalis), Golden Trout (Oncorhynchus aguabonita). In addition there are a number of Hybrid varieties such as Leopard Trout and Zebra Trout.

Calculating Weight

Various formulae exist for calculating the weight of fish. The generally accepted formula for trout is: (length x girth²) ÷ 800 = Weight. There is a 5% error factor. Length & girth are measured in inches.

Length is measured from the snout to the fork in the tail (along the lateral line).
Girth is the distance around the body of the fish at its largest point.

800 is the factor for Trout (this number changes with different species of fish).

 
Trout weight = (length x girth x girth) ÷ 800

For example, you catch an 18 inch trout with a 12 inch girth. Using the formula for trout, as above:

(18 x12 x 12) ÷ 800 = 3.24 pounds. Your trout is approximately 3.24 pounds in weight.

Origins of the Species

From the Atlantic Ocean

From the Pacific Ocean

Note: The true origins of some species are obscured by time. For example, the Arctic char's range now spans the entire northern coast of northern North America, from the Pacific to the Atlantic. The lateral range of the lake trout (also a char) is similarly extensive, extending from New England to Alaska.